Article

Classification, Genesis, and Exploration Guides for Nonsulfide Zinc Deposits

June 2003
Economic Geology 98(4):685-714

June 2003
98(4):685-714

DOI:10.2113/gsecongeo.98.4.685

Authors:

Murray Hitzman

Colorado School of Mines

Neal Anthony Reynolds

CSA Global

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Nonsulfide zinc deposits, popularly but incorrectly termed "zinc oxide" deposits, are becoming attractive exploration targets owing to new developments in hydrometallurgy. They are divided into two major geologic types-supergene and hypogene deposits. Supergene deposits are the most common type of nonsulfide zinc deposit and are distributed worldwide. The vast majority occur in carbonate host rocks owing to the high reactivity of carbonate minerals with the acidic, oxidized, zinc-rich fluids derived from the oxidative destruction of sphalerite-bearing sulfide bodies. Formation of these deposits depends upon the size and mineralogy of the preexisting zinc occurrence, vertical displacement of the water table, rate of water table descent through tectonic uplift and/or arid climatic conditions, wall-rock fracture density, and a suitable neutralizing trap site. Weathering of Mississippi Valley-type and high-temperature carbonate replacement-type zinc deposits may generate significant supergene nonsulfide zinc deposits, but the weathering of pyrite-rich, sedimentary exhalative, and volcanogenic massive sulfide deposits is much less likely to form economic supergene zinc deposits. Three subtypes of supergene nonsulfide zinc deposits are recognized-direct replacement, wall-rock replacement, and residual and karst-fill deposits. Hypogene nonsulfide zinc deposits are more poorly known owing to the paucity of examples; however, two major subtypes are recognized: structurally controlled, replacement bodies and manganese-rich, exhalative(?) stratiform bodies. The structurally controlled bodies contain willemite and variable amounts of sphalerite, are hematitic, and are generally associated with hydrothermal dolomitization. Stratiform, manganese-rich, nonsulfide zinc deposits appear to be end members of a spectrum of deposits that include base metal-poor stratiform manganese deposits and sulfide-dominant Broken Hill-type deposits. Hypogene nonsulfide zinc deposits appear to have formed owing to the mixing of a reduced, low- to moderate-temperature (80°-200°C), zinc-rich, sulfur-poor fluid with an oxidized, sulfur-poor fluid.

Spatial distribution of rock uplift in the Bongarà district (Peruvian Andes) and implications for the genesis of supergene ore deposits

Article

Aug 2023
GEOMORPHOLOGY

Genesis of the Florida Canyon Nonsulfide Zn Ores (Northern Peru): New Insights Into the Supergene Mineralizing Events of the Bongará District

Article

Apr 2022

The Florida Canyon Zn deposit in the Bongará Province of northern Peru consists of sulfide and nonsulfide mineralizations within dolomitized strata of the Triassic Chambará Formation, a member of the Triassic-Jurassic Pucará Group. The nonsulfide mineralization, which represents one third of the total resource, formed by supergene alteration of Mississippi Valley-type sulfide bodies. The nonsulfide assemblages occur in stratabound or fault-related, discordant zones that mimic the shapes of the former sulfide zones. Two nonsulfide facies can be distinguished: facies 1 – red zinc ores, which are characterized by smithsonite, or hemimorphite-dominant bodies that formed by direct replacement of primary sulfide assemblages, and facies 2 – white zinc ores, which are characterized by masses of colloform smithsonite formed by replacement of wall rock. The facies are distinct in bulk chemical composition and stable isotope geochemistry. Facies 1 shows high concentrations of Zn, Pb, Fe, Ge, Mn, and As, whereas facies 2 shows only high Zn and Cd concentrations. Enrichments in Ge, which have been reported in other Zn deposits of the Bongará Province, are associated with hemimorphite, Fe hydroxides, and remnant sphalerite in facies 1. The δ13C and δ18O signatures of smithsonite in both facies suggest that meteoric waters infiltrating the precursor sulfide bodies were affected by kinetic fractionation and originated from multiple sources at different altitude.

Zn-clays in the Kihabe and Nxuu prospects (Aha Hills, Botswana): a XRD and TEM study

Article

Feb 2022

Zinc clays are commonly found in oxidized Zn deposits and, even though they rarely represent the main target of the ore exploitation, they can be used as a proxy to restore the genetic conditions during ore-forming processes. This work sheds light on the micro-to nano-mineralogy and on the genesis of Zn-clays in the Kihabe and Nxuu prospects (located in the Aha Hills district, Northern Botswana), through an integrated XRD and TEM study of the mineralized facies occurring in the mineralized system. The Kihabe and Nxuu ores are hosted in a Neoproterozoic metamorphozed quartzwacke unconformably covered by the recent sedimentary rocks, also containing calcretes, of the Kalahari Group. In the analyzed samples, four distinct mineralogical facies have been recognized: i. vanadate calcrete facies, poor of Zn-clays; ii. low Zn-clay facies, characterized mostly by clays showing low Zn concentrations; iii. Zn-clay facies, containing proper Zn clay minerals; iv. sulfide facies, devoid of Zn-clays. In all the facies detrital dioctahedral mica (muscovite and illite) is interstratified with smectite in the form of random (R0) to short-range ordered (R1) I/S, which locally shows significant Zn concentrations. In the sulfide facies kaolinite overgrowing onto mica packets has been detected. The low Zn-clay facies is dominated by Zn-bearing beidellite, with minor kaolinite and fraipontite. The Zn-clay facies consists mostly of a random (R0) interstratified clay between a 7-Å phase corresponding to fraipontite, and a 2:1 swelling clay component identifiable with the dioctahedral smectite, with minor sauconite. The micro-to nanoscale paragenetic study performed by TEM indicates that the above-mentioned clays formed through a multistage process, eventually ending with the genesis of Zn-bearing phyllosilicates assemblages. The main steps were: i. alteration of detrital mica and dissolution of feldspar clasts, which led to the formation of epitaxial kaolinite and replacive beidellite; ii. fertilization of barren clays and formation of replacive to epitaxial fraipontite/smectite and of Zn-bearing mica, through input of Zn2+ deriving from sphalerite or willemite dissolution by mixed meteoric-hydrothermal fluids; iii. formation of low tetrahedral charge sauconite, either in pores or as replacement of K-feldspars under surficial hypersaline conditions, possibly also linked to the establishment of the arid climate in region. These processes provide insights into genesis of Zn-Pb-V ore deposits in northwest Botswana. Furthermore, the identification of a Zn-smectite species having a stevensite-like stoichiometry is valuable for future studies dealing with the systematics of clay minerals.

Lufilian copper–gold mineralization in the Mkushi District, Zambia: regional metallogenic implications

Article

Full-text available

Oct 2022
MINER DEPOSITA

The copper–gold mineralization in the Mkushi district of central Zambia is hosted by Paleoproterozoic metamorphic rocks of the Mkushi gneiss (~ 2040 Ma) and Mesoproterozoic intrusions of the Irumide Belt (~ 1020 Ma). Mineralization is associated with a series of northeast-trending felsic intrusions of aplite, microgranite, and pegmatite defining a ~ 15-km-long mineralized corridor (Mtuga line), alongside the Mtuga shear zone. Foliated dolerite dikes attest to mafic magmatic input along the trend. Re–Os analyses of molybdenite intergrown with chalcopyrite at two deposits along the Mtuga line yielded ages of 530.4 ± 2.9 and 516.7 ± 2.2 Ma, thus effectively dating the copper–gold mineralization. A third prospect in the district returned an age of 485.6 ± 2.1 Ma. Although the molybdenite in this latter sample is not observed to be in direct contact with chalcopyrite, the similarity of mineralization style and host geology suggest that the age also has metallogenic significance. The geologic relationships and molybdenite dates confirm that most magmatic-hydrothermal copper–gold mineralization in the district occurred during peak periods of deformation and metamorphism of the Lufilian Orogeny between 530 and 517 Ma, and formed synchronously with much of the sediment-hosted copper mineralization in the Central African Copperbelt and the copper-dominant IOCG mineralization of the synorogenic Hook Batholith. The copper metallogeny in central Zambia is, therefore, inferred to be an integral part of the evolution of the large Kuunga Orogen that resulted from wholesale Pan-African collision of major cratonic elements during final consolidation of Gondwana.

C-O Stable Isotope Geochemistry of Carbonate Minerals in the Nonsulfide Zinc Deposits of the Middle East: A Review

Article

Full-text available

Nov 2017

Zinc nonsulfides are well represented in the Middle East, with occurrences in Turkey, Iran, and Yemen. Their genesis can be constrained by using carbon and oxygen isotope systematics applied to carbonate minerals. The δ 13 C ratios of smithsonite and hydrozincite in Iran and Turkey are comprised in the typical interval of supergene Zn carbonates (−0.4 and −7.1 V-PDB). The oxygen isotope geochemistry is more complex. Oxygen isotope compositions of smithsonite of the Hakkari deposit (Turkey) (δ 18 O from 24.2 to 25.6 V-SMOW) point to precipitation temperatures between~4 and~18 • C, corresponding to a normal weathering environment at these latitudes, whereas δ 18 O of smithsonite from other Middle East deposits (Angouran in Iran, Jabali in Yemen) point to the precipitation from low-to medium-temperature hydrothermal fluids. The CO isotopic compositions of hydrozincite from the Mehdi Abad, Irankuh, and Chah-Talkh deposits can be only partially compared with those of smithsonite, because the oxygen isotopes fractionation equation for hydrozincite-water is not known. A comparison between the geochemical characteristics of all Zn-nonsulfide ores in the Middle East indicates that, even though several mineral deposits are derived from supergene weathering processes, other ones have been deposited from fluids associated with magmatic activity (Angouran, Iran) or with hydrothermal systems (Jabali, Yemen). This suggests that it is not possible to apply a common interpretative model to the genesis of all nonsulfide deposits in the Middle East.

The Cristal Zn prospect (Amazonas region, Northern Peru). Part II: An example of supergene enrichments in tropical areas

Article

Sep 2021

The Cristal Zn prospect is located in the northernmost part of a wide mining district corresponding to the "Charlotte Bongará Zinc Project", which covers an area of approximately 110 km 2 in the Amazonas region in northern Peru. The mineralized area consists of many Zn occurrences that contain mixed sulfide and nonsulfide mineralizations. The nonsulfide ores are interpreted to be the product of weathering of primary MVT sulfide bodies. The Zn concentrations of the Cristal prospect are hosted by platform carbonates of the Condorsinga Formation (Early Jurassic), which belongs to the Pucará Group. The prospect extends over an area of approximately 2 × 1 km, with nearly continuous zones of Zn enrichment that has been detected in soil and rock samples. The nonsulfide mineralization consists mainly of semi-amorphous orange to brown zinc "oxides" that include hemimorphite, smithsonite and Fe-(hydr)oxides. The most important mineralized areas are the Esperanza and Yolanda occurrences, which were also most intensively explored. In both occurrences, the su-pergene Zn-carbonates and silicates infill solution cavities, or replace the carbonate host rocks and/or the primary sulfides, forming smithsonite-and hemimorphite-rich mineralizations. The analyzed drill core samples have on average 20 wt% Zn and maximum Ge concentrations of 200 ppm. The Bongará area experienced a prolonged phase of weathering from Miocene to Recent under tropical climatic conditions. In these conditions, the weathering processes affected many pre-existing sulfide deposits (e.g. Cristal, Florida Canyon, Mina Grande), where supergene profiles were developed under locally different settings that are defined primarily on the basis of mineralogical and geochemical data. Contrary to the Mina Grande deposit, at Cristal, the development of a karst network was minor due to limited uplift, and supergene alteration did not completely obliterate the roots of the original sulfide orebody. The mineralogy and geochemistry of Bongará nonsulfides is dependent on two main factors at the local scale: (1) uplift rates, and (2) host rock composition. The latter may have favored the development of more (e.g. Mina Grande) or less (e.g. Cristal) alkaline supergene environments. Uplift was controlled by the activity of local faults, which allowed the exposure of sulfide protores at variable elevations in different periods of time and hydrological settings. Such different settings resulted in the precipitation of isotopically different supergene carbonates (e.g. smithsonites and calcites at Mina Grande and Cristal).

Critical elements in non-sulfide Zn deposits: a reanalysis of the Kabwe Zn-Pb ores (central Zambia)

Article

Sep 2021

The Kabwe Zn-Pb deposit (central Zambia) consists of a cluster of mixed sulfide and non-sulfide orebodies. The sulfide ores comprise sphalerite, galena, pyrite, chalcopyrite and accessory Ge-sulfides (±Ga and In). The non-sulfide ores comprise: (1) willemite-dominated zones encasing massive sulfide orebodies and (2) oxide-dominated alteration bands, overlying both the sulfide and Zn-silicate orebodies. This study focuses on the Ge, In and Ga distribution in the non-sulfide mineralization, and was carried out on a suite of Kabwe specimens, housed in the Natural History Museum Ore Collection (London). Petrography confirmed that the original sulfides were overprinted by at least two contrasting oxidation stages dominated by the formation of willemite (W1 and W2), and a further event characterized by weathering-related processes. Oxygen isotopic analyses have shown that W1 and W2 are unrelated genetically and furthermore not related to supergene Zn-Pb-carbonates in the oxide-dominated assemblage. The δ 18 O composition of 13.9-15.7‰ V-SMOW strongly supports a hydrothermal origin for W1. The δ 18 O composition of W2 (−3.0‰ to 0‰ V-SMOW) indicates that it precipitated from groundwaters of meteoric origin in either a supergene or a low-T hydrothermal environment. Gallium and Ge show a diversity of distribution among the range of Zn-bearing minerals. Gallium has been detected at the ppm level in W1, sphalerite, goethite and hematite. Germanium occurs at ppm levels in W1 and W2, and in scarcely detectable amounts in hemimorphite, goethite and hematite. Indium has low concentrations in goethite and hematite. These different deportments among the various phases are probably due to the different initial Ga, In and Ge abundances in the mineralization, to the different solubilities of the three elements at different temperatures and pH values, and finally to their variable affinities with the various minerals formed.

Influence of Genetic Processes on Geochemistry of Fe-oxy-Hydroxides in SupergeneZnNon-SulfideDeposits

Article

Full-text available

Jan 2020

Origin of the Moroccan Touissit-Bou Beker and Jbel Bou Dahar Supergene Non-Sulfide Biomineralization and Its Relevance to Microbiological Activity, Late Miocene Uplift and Climate Changes

Article

Full-text available

Apr 2021

Through integration of Pb-Zn ± Cu non-sulfide mineralogy, texture, and stable isotope (C, O, S) geochemistry, the world-class Touissit- Bou Beker and Jbel Bou Dahar Mississippi Valley-type dis-tricts of the Moroccan Atlasic system have been investigated in order to gain insights into the origin and processes that contributed to the formation of the base metal non-sulfide mineralization. In both districts, direct replacement (“red calamine”) and wallrock replacement (“white calamine”) ores are observed. Based on the mineral assemblages, ore textures, and crosscutting relations, three distinct mineralizing stages are recognized. The earliest, pre-non-sulfide gossanous stage was a prerequisite for the following supergene stages and constituted the driving force that ultimately promoted the leaching of most base metals such as Zn and Cu and alkalis from their rock sources. The following two stages, referred to as the main supergene “red calamine” and late “white calamine” ore stages, generated the bulk of mineable “calamine” ores in the Touissit-Bou Beker and Jbel Bou Dahar dis-tricts. Stable isotope compositions (13CV-PDB, 18OV-SMOW, 34SCDT) support a three-stage model whereby metals were released by supergene acidic fluids and then precipitated by bacteria and archaea-mediated metal-rich meteoric fluids due to a decrease in temperature and/or increase of fO2. Oxygen isotope thermometry indicates decreasing precipitation temperatures with advancing paragenetic sequence from 33° to 18 °C, with wet to semi-arid to arid climatic conditions. The close spatial relationships between coexisting sulfide and non-sulfide mineralization along with stable isotope constraints suggest that the oxidation of sulfides occurred concurrently after the main stage of the Alpine orogeny between 15 Ma and the present. More importantly, the current data show for the first time the involvement of biologically controlled activity as the major driving process that triggered both oxidation and deposition of supergene mineralization at Jbel Bou Dahar and Touissit-Bou Beker districts. Conclusions drawn from this study therefore have implications for supergene Mississippi Valley-type (MVT) -derived non-sulfide deposits worldwide and account for the prominent role of biological processes in the genesis of this category of ore deposits.

CHARACTERIZATION AND GRAVITY SEPARATION OF NONSULFIDE ZINC DEPOSITS FROM UM GHEIG MINE, RED SEA COAST, EGYPT

Article

Full-text available

Jan 2011

Musings on Future Exploration Targets and Strategies in the Andes

Chapter

Jan 2005

Richard H Sillitoe

A variety of metals and deposit types define the metallogeny of the Andes from Colombia through Ecuador, Peru, and Bolivia to Argentina and Chile, although porphyry copper and epithermal gold deposits undoubtedly predominate and will continue to do so. Discoveries over the last 30 yrs or so, predominantly in the central Andes and especially Chile, have been made using routine, field-based geologic and complementary geochemical methods, a situation that is considered unlikely to change radically in the foreseeable future. The only clearcut evolutionary change is the increased number of deposits being discovered beneath pre- and postmineral cover. The predictive capacity of conceptual geology has had minimal impact on the Andean discovery record but is thought to offer much promise for the future. This introductory article selects mineralization styles and relationships as well as some broader metallogenic parameters as simple examples of geologic concepts that may assist exploration. Emphasis is placed on porphyry copper ± molybdenum ± gold and high-, intermediate-, and lowsulfidation epithermal gold ± silver deposits, although reference is also made to several carbonate rock-hosted precious and base metal deposit types and styles as well as subvolcanic tin, volcanogenic massive sulfide, and slate-belt and intrusion-related gold deposits. Particular emphasis is placed on the potential for exceptionally high grade porphyry copper, porphyry gold, epithermal gold, and subvolcanic tin deposits. Deposits resulting from the oxidation, enrichment, and chemical transport of copper and zinc and mechanical transport of gold and silver during supergene weathering are also briefly highlighted. Si bien la metalogenia de los Andes de Colombia, Ecuador, Perú, Bolivia y Chile se encuentra definida por una gama de metales y estilos de mineralización, son los depósitos tipo pórfido de cobre y epitermal de oro los que dominan en el presente y continuarán prevaleciendo en el futuro. Los descubrimientos de los últimos 30 años, predominantemente en los Andes centrales y especialmente en Chile, han sido realizados mediante métodos geológicos rutinarios de campo, generalmente complementados satisfactoriamente por métodos geoquímicos. Se estima que esta situación difícilmente experimentará variaciones radicales en un futuro cercano. El único cambio destacable en esta historia evolutiva está dado por el aumento apreciable de descubrimientos de depósitos cubiertos, bajo cobertura pre o postmineral. A nivel andino, la capacidad predictiva de la geología conceptual ha tenido un impacto mínimo en el número total de descubrimientos, aunque se piensa que su uso debiera garantizar buenas perspectivas futuras. El presente artículo

Reverse flotation separation of calcite/dolomite from hemimorphite based on their surface sulphophile and oxyphile affinity differences

Article

Dec 2023
COLLOID SURFACE A

This study attempts to selectively inhibit hemimorphite flotation using sodium sulphide and uncover the mechanisms behind it. With the use of a fatty acid collector, the flotation test results showed that sodium sulphide had a strong inhibition performance on hemimorphite flotation while having no adverse impact on calcite and dolomite flotation, which were consistent with the contact angle measurement results. According to the results of attenuated total reflectance-Fourier transform infrared spectroscopy and adsorption proportion measurement of sodium oleate, sodium sulphide can inhibit sodium oleate binding on hemimorphite surfaces while having no effect on calcite and dolomite surfaces. The sulphide species exhibited an extremely high binding affinity for the hemimorphite surface but not for the surfaces of the calcium/magnesium-bearing gangue minerals, as demonstrated by the X-ray photoelectron spectroscopy measurements. Because of the strong sulphophile affinity of zinc, when the sodium sulphide concentration was sufficiently high, an interface boundary layer of a liquid solution with the remaining sulphide species formed on the hemimorphite surface, preventing sodium oleate from binding on the hemimorphite surfaces and thus selectively inhibiting the hemimorphite flotation.

Pb-Zn Deposits in Ruchun-Mazar Region, Kerman Province: Geology, Alteration and Mineralization ARTICLE INFO ABSTRACT

Article

Full-text available

Jan 2023

Ruchun-Mazar region is located in southern Sanandaj-Sirjan Zone, southwest of Baft city in Kerman province, Iran. Seh Chah, Chah Sorbi, Chah Nar, Zardbazi Dar, and Chah Sorbi Arjmand Pb-Zn deposits located in this region were investigated. The most outcrops of the geological units in the area include the Paleozoic metamorphic complexes of Gol Ghohar (amphibolite, gneiss and micaschist), Ruchun (schist, marble, calcschist, black chert, slate and phyllite), and Khabar (marble, calcschist). Microdioritic, monzodioritic and diabasic dykes have intruded into the metamorphic units. Dolomitic and calcitic marble of Ruchun complex is the host rock for Pb-Zn mineralization. Primary mineralization in Seh Chah, Chah Sorbi, and Chah Nar deposits includes galena, sphalerite, and pyrite ± chalcopyrite along with quartz, calcite, and dolomite ± barite. Vein-veinlet, open space filling, brecciated ± disseminated ± laminate structures and textures can be seen in these deposits. The most important alterations in these deposits are silicification and carbonitization (calcitic and dolomitic alterations). Primary sulfide ore in Zardbazi Dar and Chah Sorbi Arjmand deposits has been weathered and mining has been carried out on nonsulfide ore (supergene ore). The nonsulfide ore formed at the expense of sulfides, and mainly consists of smithsonite, hydrozincite, hemimorphite, and cerussite. It seems that these deposits belong to the direct replacement and, to a lesser extent, wall rock replacement nonsulfide zinc deposits. Based on the geological, mineralogical and alteration evidence, the primary mineralization in the region can be divided into two groups of SEDEX type (Chah Sorbi deposit) and vein type (Chah Nar and Seh Chah deposits). It was concluded that under supergene conditions in some deposits, nonsulfide ore was also formed. Moreover, the deposits of this region can be categorized into primary sulfide (hydrothermal) and nonsulfide (supergene).

Willemita y otros minerales de las canteras de Sant Fost de Campsentelles, Vallès Oriental, Barcelona, Cataluña. Paragénesis. Revista de Mineralogía; vol. 3, núm. 1 (2021-1), pp. 3-46.

Article

Full-text available

May 2021

RESUMEN En el término municipal de Sant Fost de Campsentelles, Barcelona, casi en el límite con el de Montcada i Reixac, se ubican las canteras de Can Rovira y de Can Donadéu. Ambas explotan el zócalo granodiorítico de la sierra de Marina. Durante los últimos seis años hemos podido visitar, con autorización de la empresa PROMSA, la cantera de Can Rovira. La de Can Donadéu no ha sido posible estudiarla in situ. El estudio de los filones encajados en la granodiorita nos ha permitido conocer una interesante asociación mineral en estas canteras, con: arsenopirita, barita, calcita, calcopirita, cuarzo, esfalerita, fluorita, galena y pirita. Como minerales secundarios hemos encontrado: azurita, brochantita, cerusita, epidota, eritrita, malaquita, mimetita (y su variedad cálcica), posnjakita, surita, willemita y wulfenita. Dos de estas especies, surita y willemita, así como la variedad cálcica de mimetita, han requerido estudios analíticos más exhaustivos. En el caso de la mimetita cálcica, para determinar si se trataba de esta variedad o de hedifana. La surita es la primera cita en la Europa continental, mientras que la willemita lo es en Cataluña.

Genesis of the Giant Huoshaoyun Non-Sulfide Zinc–Lead Deposit in Karakoram, Xinjiang: Constraints from Mineralogy and Trace Element Geochemistry

Article

Full-text available

Jun 2023

The Huoshaoyun zinc–lead deposit, a giant non-sulfide deposit in Xinjiang, is one of the most significant discoveries of zinc–lead deposit in China and globally in recent years. The deposit is dominated by zinc–lead non-sulfides, with minor occurrences of sulfides such as sphalerite, galena, and pyrite. The non-sulfide minerals include smithsonite, cerussite, anglesite, and Fe-oxide. This study focuses on the mineralogical characteristics of sulfide and non-sulfide ores, as well as the trace element characteristics of sphalerite, smithsonite, and Fe-oxide. Mineralogical analysis reveals that smithsonite is derived from the oxidation of primary sulfide minerals and can be classified into three types that are generated during different stages of supergene oxidation. The three types of smithsonite are formed through replacing the sphalerite and host limestone, as well as directly precipitating in the fissures and vugs. Trace element analysis of sphalerite indicates that it is rich in Cd, Tl, and Ge, but poor in Fe and Mn. The ore-forming temperature, calculated using the GGIMFis geothermometer, is mostly within the range of 100~150 °C. Moreover, the trace element characteristics, ore-forming temperature, and S and Pb isotope compositions of the sulfide ores of the Huoshaoyun deposit are similar to those of the Jinding and Duocaima MVT lead–zinc deposits, which are also located in the Eastern Tethyan zinc–lead belt. This suggests that the sulfide orebody in the Huoshaoyun Zn-Pb deposit could also be the MVT deposit. Study of the trace element of the non-sulfide minerals shows that the Mn and Cd are relatively enriched in smithsonite, while Ga, Ge, and Pb are enriched in Fe-oxide. This can be attributed to distinct geochemical properties of the trace elements in the non-sulfide minerals of the Huoshaoyun deposit and is consistent with those of the other oxidized MVT deposits, thus indicating the supergene oxidation process of this deposit.

Zinc Isotope Constraints on the Formation of Sedimentary Exhalative (SEDEX) ore deposits: New Evidence from the Franklin, NJ Mining District

Article

Jun 2022
ORE GEOL REV

We report δ⁶⁶Zn for the high temperature metamorphic zinc oxide and silicate minerals franklinite (Fr) (Zn²⁺Fe³⁺2O4), zincite (Zc) (ZnO) and willemite (Wlm) (Zn2SiO4) from the Franklin, NJ, historic mining district. With reference to the JMC-Lyon standard, δ⁶⁶Zn franklinite ranges from -0.10 to 0.48‰ with an average of 0.20 ±0.17‰ (n=22). δ⁶⁶Zn willemite ranges from 0.23 to 0.48‰ with an average of 0.37 ±0.09‰ (n=7). δ⁶⁶Zn zincite ranges from 0.29 to 0.60‰ with an average of 0.47±0.12‰ (n=9). These data suggest that the analyzed phases fractionate heavy zinc in the order Fr<Wlm<Zc. Taken as a group, these minerals have an average δ⁶⁶Zn of 0.30 ±0.19‰. This is 0.16‰ heavier than an estimated global mean δ⁶⁶Zn for sphalerite (ZnS) of 0.14 ±0.16‰ for seafloor zinc deposits. Our results are consistent with fractionation factors that predict that Zn oxides and silicates (protoliths of these ores) should be isotopically heavier than sphalerite when precipitated from fluids of the same temperature with similar zinc isotope compositions. Our samples from Sterling Hill are taken from two short transects across the orebody. Calcite (Cal) (CaCO3) from the same samples has δ¹³C from -0.54 to 1.46‰ with an average of 0.79±0.51‰ (VPDB), while δ¹⁸O ranges from 9.72 to 15.12‰ with an average of 12.42±1.35‰ (VSMOW; n=30). Results for these two isotope systems are consistent with earlier studies. δ¹³C decreases smoothly with distance towards the west along both transects; δ¹⁸O in contrast stays very close to its mean on the longer, southern transect but increases with distance to the west along the shorter, northern transect. There is no apparent covariation between δ⁶⁶Zn and either of the other isotopic ratios measured.

Crystal growth, structure and thermal properties of anhydrous zinc carbonate (ZnCO3)

Article

Nov 2021
J ALLOY COMPD

Carbonate materials have been increasingly favoured in terms of the development of flame retardants because of the eternal subject of inorganic carbon sequestration. In this regard, anhydrous zinc carbonate (ZnCO3) has been deemed as suitable candidate thanks to its excellent flame retardancy compared to traditional hydroxid flame retardant. However, the single crystals growth, accurate characterizations of structural and thermal properties are still not entirely clear from previous studies. With this in mind, ZnCO3 single crystals were synthesized under high-pressure-temperature conditions (high P-T; 3 GPa and 973 K). The crystal structure of impurity-free ZnCO3 was determined by means of single crystal X-ray diffraction (XRD). The symmetry was identified as R3¯c, while the unit cell parameters were a=4.6463(3) Å and c=15.0015(11) Å with a final R value of 0.0229. The quantitative analyses of Raman spectrum and infrared absorption indicate that the as-synthesized ZnCO3 is anhydrous phase. Using Thermogravimetric (TG) / Differential Scanning Calorimeter (DSC) measurements, ZnCO3 was decomposed in the temperature range of 593-773 K, whereas the heat capacity and the endothermic peak were determined. According to the single crystal XRD from 150 K to 383 K, the thermal expansion coefficients were quantified as αa=7.90×10⁻⁶ K⁻¹ and αc=22.8×10–6 K⁻¹, as well as αVunit cell=38.8×10–6 K⁻¹. These findings provide a precise characterisation and obtain important thermal parameters for the evaluation of its flame retardant properties.

Analysis of fracturing and installation of hydrothermal vein mineralization in the Mesozoic cover of the Tazekka Paleozoic inlier, Morocco

Article

Full-text available

Aug 2021

The present paper is to characterize the geological setting of vein-type mineralization at the Mesozoic cover of Tazekka Variscan massif, constituted by sedimentary and volcanic rocks and is located in the NE of the Middle Atlas. The main objectives are based on the tectonic analysis of fracturing in the Mesozoic cover (Triassic-Liassic), and its relationship with open space-filling deposits include mineralized veins which show before, contemporaneous, and posterior striations, of which their tectonic and structural study makes it possible to identify the relationship between mineralizations, stress fields, and associated tectonic structures and determine the relative age of the vein-type mineralization. These are based mainly on the automatic processing of tectonic measurement of striated fault planes determined by inversion of fault-slip data. The mineralization is controlled by three events of main compressive deformations: (i) sub-meridian trending σ1 axis associated with sub-equatorial extensional trending σ3 axis characterized by N30-70 sinistral strike-slip faults with a reverse component and N120-140 dextral strike-slip faults. This phase caused the formation of the anticlinal ridges and contain lead-zinc, iron nodules, and white and pink barite mineralization; (ii) NE-SW trending σ1 axis and NW-SE trending σ3 axis materialized by N10-40 dextral and N60-80 sinistral strike-slip faults and N140-160 reverse faults. These N140-160 trending faults accommodate the thrusting of the Variscan basement on the Upper Triassic argillites. These faults show planes filled by white calcite mineralization (iii) WNW-ESE trending σ1 axis and NNE-SSW trending σ3 axis materialized by N70-80 dextral and N150-170 sinistral strike-slip faults, comprising a lead-zinc and white barite mineralization. The three hydrothermal and mineralizing events occur successively from the post-Bathonian and ante-Barremian, Oligocene–Middle-Lower Miocene, and Vallesian or Miocene-Pliocene age. These tectonic and mineralization events are associated in parallel with Mississippi Valley–type deposits (MVT) karst cavities dissolution structures in the Liassic carbonates and percolation of hydrothermal fluid along the major North Middle Atlas Fault.

Metallogenic age of the world‐class giant huoshaoyun non‐sulphide Zn–Pb deposit in Karakoram Area, Xinjiang, Northwest China

Article

Jun 2024

Metallogenic geochronology plays a crucial role in the study of ore genesis and mineralization evolution. Unfortunately, accurately determining the metallogenic age of the non‐sulphide Zn–Pb deposits is difficult. Herein, we employed Rb–Sr dating of smithsonite and Sm–Nd dating of coexisting calcite to explore the mineralization ages of the Huoshaoyun Zn–Pb deposit. The Rb–Sr and Sm–Nd isotopic ratios yield isochron ages of 26.6 ± 1.7 and 27.5 ± 7.6 Ma, respectively. These obtained ages are identified as the metallogenic age of the Huoshaoyun deposit. Moreover, investigations into carbonate‐hosted Zn–Pb deposits in the East Tethys Metallogenic belt suggest they have formed in similar tectonic settings and yielded consistent Cenozoic ages. In sum, our research indicates that carbonate‐hosted Pb–Zn metallogenic ages in the East Tethys Metallogenic belt are principally concentrated in the late Palaeogene, and directly related to the collisional orogeny of the Tibetan Plateau during 40–26 Ma.

Tracing the Eh–pH evolution of Cu–Pb–As–Zn supergene mineralization using detailed petrography in the Cap Garonne mineral deposit (Provence, France)

Article

Full-text available

Apr 2024
MINER DEPOSITA

The supergene zone of the Cap Garonne mineral deposit (Provence, France) hosts one of the most remarkable mineralogy in the world with no less than 150 minerals, 16 of which are type locality. Such mineral diversity offers a detailed view of mineral and geochemical changes during weathering processes. The stratabound epigenetic primary mineralization occurs within a few meters-thick fluvial conglomerates resting above the Permian–Triassic transition and is probably related to Late Triassic–Early Jurassic hydrothermal events. The Cu–As mineralization in the lower part of the conglomerates is locally overlapped by a thin Pb–Zn-rich layer in the northern mine. The results show that the weathered part is significantly enriched in Cu, Pb, As, Zn, Ag, Ba, Sb, and Bi. The evolution of the supergene fluid is traced in an Eh–pH diagram by the succession of sulfides I (tennantite, galena), sulfides II (covellite), arsenates (olivenite), sulfates and sulfo-arsenates (brochantite, anglesite), and carbonates (malachite, azurite, cerussite). The primary sulfide oxidation acidified the host conglomerate and enabled the crystallization of secondary sulfides and arsenates. Efficient and rapid neutralization by the calcite cement of the host conglomerate and chlorite in the matrix caused successive precipitation of arsenates, sulfates, and carbonates. The supergene processes could be related to major periods of weathering in Western Europe (Early Cretaceous–Late Oligocene/Early Miocene). Erosion-prone periods may have contributed to the stripping of the Pb–Zn-rich layer in the southern mine.

The important role of fluid chemistry in the hydrothermal alteration of ordinary chondrites: Insights from halite and sphalerite in the Sidi El Habib 001 (H5) meteorite

Article

Sep 2023
EARTH PLANET SC LETT

The important role that aqueous fluids played during the evolution of carbonaceous chondrites (CCs) and the carbonaceous asteroids that they derive from is well documented. In comparison, our understanding of how such fluids affected ordinary chondrites (OCs) and their S-type asteroid parent bodies is less mature in part due to the intense thermal metamorphism that overprinted the records of alteration. Further, that only a small suite of unequilibrated OCs shows evidence of hydration hinders our understanding of the role that fluids played in the evolution of OCs and S-type asteroids. Here we report a microstructural analysis on halite (NaCl) and sphalerite (ZnS) in Sidi El Habib 001 (SEH 001), a H5 OC that provides new insights into the role of fluids on the OC parent bodies. Our data reveal that halite contains alteration relicts of submicron silicates, and that widespread sphalerite spatially correlates with halite. This relationship suggests that sphalerite formed from the same hydrothermal fluid that precipitated halite, consistent with experimental and theoretical work showing that Cl-rich fluids induce complexation of Zn and significantly enhance its mobility. We hypothesize that Cl-rich hydrothermal fluids resulted from melting of locally concentrated HCl hydrate, which produced acidic fluids capable of dissolving chondritic mineral phases. The pH of the fluid presumably varied on a micrometer scale due to different rates of hydrolysis reactions as a function of grain size, as illustrated by the absence of halite in SEH 001 chondrules. Such a fluid-alteration model is attractive because it offers a reasonable explanation for the limited and heterogeneous alteration effects in OCs.

Zinc incorporation into carbonate minerals from the Selac area, Kosovo

Conference Paper

Full-text available

Aug 2023

Chemical composition of carbonate minerals from the Selac area in Kosovo was studied. Samples from three sampling areas were analysed by using transmitted-light microscopy and electron microprobe. The main hydrothermal vein mineral is dolomite, which is characterized by enrichments in ZnO (up to 7.2 wt.%) and FeO (up to 12.78 wt.%). Another carbonate minerals found in veins: calcite, magnesite, and siderite are also characterized by zinc incorporation. Two substitutional trends are observed in the Selac dolomites: Fe+Mn enrichment as well as Zn enrichment both substituting Mg.

Vanished evaporites, halokinetic structure, and Zn-Pb mineralization in the world-class Angouran deposit, northwestern Iran

Article

Aug 2023

The Angouran deposit (19.3 Mt at 23.4% Zn and 4% Pb) is the second-largest Zn-Pb deposit in Iran. The deposit is hosted in a Neoproterozoic−Cambrian marble-schist sequence within a breccia pipe in a domal structure, with sulfide mineralization under low-temperature hydrothermal conditions (<200 ºC). The features of the ore-hosting breccias are similar to known halokinetic diapir breccias in the world but evaporite minerals are subtle. The common types of breccia clasts in the Angouran breccia pipe include a matrix-supported angular clast (float breccia) with highly variable sizes and orientations and exotic volcanic clasts. The volcanic clasts were derived from the underlying Miocene volcanic rocks, evidenced by the consistent petrography and zircon U-Pb ages dated at 20−19 Ma. Abundant smithsonite pseudomorphs after anhydrite and anhydrite inclusions within sphalerite and pre-ore marcasite in the breccia matrix indicate that the breccia pipe contains abundant anhydrite prior to the Zn-Pb mineralization. The enrichment of evaporite is also supported by the occurrence of considerable double-terminated quartz crystals that contain spherical and tabular carbonate inclusions and anomalously high Li, Na, and K concentrations, relatively high B concentration, and high δ18O values (up to 28.3‰). These observations suggest the Angouran deposit formed in a former halokinetic diapir breccia pipe. The halokinetic diapirism was possibly triggered by thrust loading of the marble-schist sequence over the Miocene evaporite beds during the Arabia-Eurasia continental collision. Halokinetic structures elsewhere in the Angouran region warrant this consideration. Most of the evaporite minerals in the breccia pipe were dissolved and replaced before and/or during subsequent Zn-Pb sulfide and smithsonite mineralization events. This study provides a good example for the identification of vanished evaporites, halokinetic structure, and associated Mississippi Valley-type mineralization.

Zinc speciation and desorption kinetics in a mining waste impacted tropical soil amended with phosphate

Article

Dec 2022
SCI TOTAL ENVIRON

Mining is an important component of the Brazilian economy. However, it may also contribute to environmental problems such as the pollution of soils with zinc and other potentially toxic metals. Our objective was to evaluate changes in the chemical speciation and mobility of Zn in a soil amended with phosphate. Soil samples were collected from a deactivated mining area in the state of Minas Gerais, Brazil, and amended with NH4H2PO4 saturated with deionized water to 70 % of maximum water retention and incubated at 25 ± 2 °C in open containers for 60 days. The soil was chemically and mineralogically characterized, and sequential extraction, desorption kinetics, and speciation were carried out using synchrotron bulk-sample and micro–X-ray Absorption Near-Edge Structure (XANES/μ-XANES) spectroscopy at the Zn K-edge, and X-ray fluorescence microprobe analysis (μ-XRF). The combination of μ-XRF and μ-XANES techniques made it possible to identify Zn hotspots in the main species formed after phosphate remediation. The best fit combination for bulk XANES and μ-XANES was observed in Zn-montmorillonite, Zn-kerolite, Zn-ferrihydrite, and gahnite. In the course of phosphate treatment, gahnite, Zn layered double hydroxides (Zn-LDH), Zn3(PO4), and ZnO were identified by bulk XANES, while Zn-ferrihydrite, Zn-montmorillonite, and scholzite were identified by μ-XANES. Zinc in the phosphate-amended soil had the strongest partial correlations (r′ > 0.05) with Ni, Co, Fe, Cr, Mn, Si, P, Cd, Pb, and Cd, while the unamended soil showed the strongest correlation with Cu, Pb, Fe, and Si. The application of NH4H2PO4 altered Zn speciation and favored an increase in Zn desorption. The most available Zn contents after phosphate amendment were correlated with the release of exchangeable Zn fractions, associated with carbonate and organic matter.

Mapping hydrothermal and supergene alteration zones associated with carbonate-hosted Zn-Pb deposits by using PRISMA satellite imagery supported by field-based hyperspectral data, mineralogical and geochemical analysis

Article

Dec 2022
ORE GEOL REV

Delineating hydrothermal alteration and supergene caps is fundamental for mineral exploration of sulfide ores. The aim of this study is to apply a multi-scale workflow based on hyperspectral remote and proximal sensing data in order to delineate hydrothermal dolomitization and supergene alteration associated with the Mississippi Valley-Type Zn-Pb(-Ag) deposit of Jabali (Western Yemen). The area was investigated through hyperspectral images derived from the new launched Italian Space Agency’s PRISMA satellite, which has a higher spectral resolution compared to multispectral sensors and covers the mineral-diagnostic wavelength regions (such as the 2100 nm to 2300 nm range) with a Signal to Noise Ratio (SNR) ≥100. Spectral mineral maps were produced through the band ratios method using specific feature extraction indices applied to the hyperspectral satellite data. The results were validated by using Visible Near InfraRed (VNIR) to Short Wave InfraRed (SWIR) reflectance spectra, mineralogical (XRPD) and geochemical (ICP-ES/MS) analyses on rock samples collected in the Jabali area. The dolomites footprint was mapped using a PRISMA Level 2C image, by enhancing the spectral differences between limestones and dolomites in the SWIR-2 region (major features centered at 2340 nm and 2320 nm, respectively). Gossans were detected due to the Fe³⁺ absorption band in the VNIR region at 900 nm. The Zn-Pb mineralized area, extended for approximately 25 km², was thus identified by recognizing gossan occurrences in dolomites. The study demonstrates that the PRISMA satellite is effective in identifying Zn-Pb mineralized outcrops in sedimentary basins.

Vanadium as a critical material: economic geology with emphasis on market and the main deposit types

Article

Full-text available

Aug 2022
B Appl Earth Sci

Vanadium is currently considered a critical material in the European Union, the U.S.A., and other jurisdictions. The vanadium mine production for 2021 is estimated at more than 120 000 tonnes; however, the market base is expected to grow rapidly due to the increase in the use of vanadium for redox flow batteries. Currently, worldwide , many projects are in the advanced stages of exploration and development. In the longer term, should vanadium cease to be a critical material and the law of supply and demand applies, the marginal mines will be decommissioned, and the best deposits will remain economic. Depending on the prevailing regulations in specific jurisdictions, geological settings, and the most up-to-date metallurgical research results, the main vanadium deposit types that could be considered as potential exploration and development targets are the vanadiferous titanomagnetite deposits, sandstone-hosted uranium-vanadium deposits (Salt Wash category), shale-hosted vanadium deposits, and base metal-related vanadate deposits. However, placer deposits, surficial uranium-vanadium type mineralisation, and the Minas Ragra type patrónite deposits should also be considered. ARTICLE HISTORY

New Models to Aid Discovery of CRM Deposits for the Green Stone Age

Article

Full-text available

May 2022

Critical raw materials (CRMs) will be crucial for the delivery of the technologies society requires to meet its decarbonization goals and successfully address the current climate crisis. Although there are a number of well-established ore deposit models, few have been developed for CRMs. History demonstrates that ore deposit models are commonly developed to explain new discoveries. However, it is also possible to develop new ore deposit models based solely on basic geochemical and geological principles. We review the development of several ore deposit models, suggest some deposits for which models have not yet been developed, and utilise the specific example of hydrothermal nickel deposits in the Central African Copperbelt to illustrate how new ore deposit models for CRM deposits may be formulated. The current impetus to discover new resources of what have been up to the present elemental curiosities should spur significant research including work to determine the geochemical behaviour of CRMs across a range of physio-chemical conditions. There is no reason to believe that economically significant concentrations of any of the newly critical elements do not exist in nature. Imagination should make the future of CRM discovery in the Green Stone age bright.

Ammonia pretreatment for enhancement of Pb ions adsorption on smithsonite surface and its flotation performance

Article

Mar 2022
APPL SURF SCI

The surface modification of smithsonite with Pb ions is an effective method to improve the sulfidization-xanthate flotation process. In the present study, NH3·H2O was employed to enhance Pb ion adsorption on the smithsonite surface, thus improving its flotation performance. The time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy analyses showed that the main species of Pb adsorbed were Pb(OH)2 and Pb3(CO3)2(OH)2 precipitates. Adsorption of the main Pb species increased by 35.29% (TOF-SIMS) on the smithsonite surface at an appropriate NH3·H2O concentration. Analysis of the chemical reactions in the aqueous solution indicated that the aqueous NH3 interacted with the smithsonite surface, and more uncoordinated carbonate ions and hydroxyl ions were produced. The uncoordinated sites further combined with free Pb3(OH)4²⁺ and PbOH⁺ in solution, forming more Pb precipitates on the smithsonite surface during Pb ion adsorption. As a result, the recovery of NH3·H2O-pretreated smithsonite was increased by approximately 10% in a Pb ion-modified sulfidization–xanthate flotation system.

Alteration of High Alkaline and Alkaline Basaltic Rocks: Parent Rocks in the Lava Durian Orchard, Sisaket Province, NE Thailand

Article

Full-text available

Dec 2021

Lava Durian Sisaket is the first geographically identified (GI) fruit related to the volcano in Thailand and distributed in three districts of Sisaket Province, the southernmost edge of the Khorat Plateau. The parent rocks of orchards are important for the description of soil and rock relation with respect to mineralogical and geochemical characteristics. This work aims to study lithology, mineralogy, and geochemistry of basaltic rocks, parent rocks of in situ soil in these orchards, and delineate the existing basaltic soil models. The several orchards are covered by reddish-brown to brown in situ soils, weathered from mafic volcanic rocks: porphyritic olivine basalt, vesicular olivine basalt, and nephelinite. The microscopic image analysis, XRD, and MiniSEM-EDS are used to classify mineralogy, while XRF and analysis of large and rare elements in ICP-MS/ICP-OES were used to determine parental rocks geochemistry and alteration. The olivine basalts comprise forsterite microphenocrysts associated with bytownite, diopside, augite, pigeonite, and ilmenite groundmass, while nephelinite is composed of nepheline groundmass and bytownite-labradorite, diopside, augite, pigeonite, and ilmenite crystals. In addition, these basalts display high alteration rates, especially olivine highly altered to iddingsite. According to the geochemical data, Sisaket’s basalts were identified as alkali basalt and nepheline basanite with high LILEs and LREEs (La, Nd, Pr, Gd, Eu). The kaolinite, smectite, and illite are altered from felsic minerals, while the chlorite and iddingsite are from mafic minerals. The mineralogical analyses classified secondary phyllosilicates related to low-moderate temperature hydrothermal fluid, very high cation exchange capacity (H+ , K+ , Ca2+ , Mg2+ ), and tropical weathering. The alkaline and high alkaline basalts, presenting as parent rocks, are one of the parameters that produced good nitisal soil of Sisaket’s agricultural areas.

From peridotite to fuchsite bearing quartzite via carbonation and weathering: with implications for the Pb budget of continental crust

Article

Full-text available

Nov 2021
CONTRIB MINERAL PETR

Extensive carbonation of peridotite results in listvenite, a rock composed of magnesite and quartz. At Gråberget, Røros, SE-Norway, a variably serpentinized peridotite body, surrounded by the Røros schists, a former abyssal sediment displays all stages of transformation of peridotite to quartzite. In this paper we record the sequence of steps in this process by combining the observation of mineral assemblages, textural relationships and geochemistry, and variations in Pb isotopic compositions. Initial serpentinization, a stage that also involved an enrichment in fluid-mobile elements (Pb, Sb and As), was followed by carbonation through CO2 fluids that formed soapstone, and eventually listvenite. The listvenite grades by decreasing amounts of carbonates into fuchsite bearing quartzite. The carbonates dissolved during supergene alteration and formed pores coated with oxides of Fe, Mn and Ni resulting in a brown rock color. The quartzite displays porous stylolites enriched in Pb, As and Sb and fuchsite with porous chromite grains as the only relicts of the original mineralogy in the peridotite. The dissolution of the carbonate occurred at oxidizing conditions at temperatures below 150 °C, where the solubility of magnesite is higher than that of quartz. Formation of quartzite from peridotite is supported by low REE contents and lack of zircons in the two rock types. The transformation involved enrichment of Pb, coupled with the elimination of Mg and enrichment of Si. This chemical fractionation and selective transfer of elements to the continents is an important mechanism and needs to be taken into account in models of continental evolution.

Trace element geochemistry of iron-(oxy)-hydroxides in Ni(Co)-laterites: Review, new data and implications for ore forming processes

Article

Sep 2021
ORE GEOL REV

Iron-(oxy)-hydroxide (FeO/OH) phases are abundant in all supergene ore deposits. The most common FeO/OH phase in supergene environments is goethite, although hematite, lepidocrocite, ferrihydrite, and maghemite can also occur. Natural FeO/OHs are rarely chemically pure, as a range of metal cations can be readily incorporated into their mineral structure. Although an extensive body of literature exists on the scavenging action of synthetic FeO/OHs, there is a general lack of studies of natural systems and, more specifically, of studies dealing with the geochemistry of trace elements in FeO/OHs associated with supergene ores. Furthermore, although it is known that FeO/OHs in supergene ore systems typically contain elevated levels of useful metals like REE, Sc, V, Co, Mn, Cr, and Ni, in most cases, these phases are considered as gangue and hence, the metals are not recovered. Only in the case of Ni(Co)-laterite deposits the FeO/OHs are often exploited for Ni and Co, and sometimes for Sc. Most previous works on Ni(Co)-laterite deposits have focused on the lateritization process of the parent rocks and the mineralogy of the resulting Ni(Co)-bearing minerals. Only rarely have published studies focused on REE, V, Sc, and PGE deportment within FeO/OHs. In this study, we describe new mineralogical and chemical data (XRPD, SEM-EDS, EPMA, ICP-AES, LA-ICP-MS, and TEM-HRTEM) obtained from a range of natural FeO/OH samples collected from four important Ni(Co)-laterite deposits, namely Wingellina (Western Australia), Piauí (Brazil), Karaçam and Çaldağ (Turkey). In the course of this study, we investigated the geochemistry of goethite and hematite within the oxidation zone of the respective laterite profiles, evaluating the deportment of minor metals such as Ti, Sc, Cr, Ni, Co, V, Zn, and Mn. Although derived from different parent rocks located in different geographic areas, the FeO/OH samples collected share a number of common features. In particular, there are commonalities in ore textures, mineralogy, and metal deportment. Based on multivariate statistical analysis, the chemistry of the studied FeO/OHs define three major elemental associations: i) Mn–Al–Ti–Sc–V as evident in goethite samples from Wingellina; ii) Mg–Ni–Si–Zn as exemplified by samples from Karaçam and Piauí, and iii) Cr–V as illustrated by the Çaldağ samples. These contrasting geochemical footprints can be explained in terms of first- and second-order controls with the chemical composition of the parent rock representing the first-order, and favorable pH conditions for the fixation of trace elements within FeO/OHs representing the second-order control. Seasonality and maturation may be additional factors influencing FeO/OHs mineralogy, as periods of arid climate may have favored the dehydration of some FeO/OHs to form more stable species (such as goethite to hematite) over time. In summary, our observations have helped to better understand the ore deposition model relating to surficial weathering systems and have also established the parameters that control the distribution of economically relevant by-product metals in FeO/OHs in diverse conditions during the formation of Ni(Co)-laterites.

Zinc oxide with various surface characteristics and its role on mechanical properties, cure-characteristics, and morphological analysis of natural rubber/carbon black composites

Article

May 2021

Owing to the ecological concern about the ZnO release and its toxicity towards the marine environment leads to the minimization of ZnO amount in rubber compounding. The present study explores and optimizes the amount of various ZnOs used in rubber compounding. It is carried out by investigating the impact of various ZnOs such as conventional ZnO, active ZnO and nano ZnO on Natural Rubber matrix filled with Carbon Black filler. The whole study is conducted without any processing aid, and ZnOs are characterized by using SEM, TGA and XRD. The prepared composites are evaluated for their rheo-characteristics, physical properties and morphologies. The study concludes that 1.5 phr of nano ZnO and 3 phr of active ZnO offers equivalent performance to 5 phr conventional ZnO in the Natural Rubber matrix giving excellent properties with a reduction of about 70 and 40% usage of ZnO respectively in the formulation of elastomeric product.

The Hypogene Emplacement and Supergene Modification History of the Angouran Zinc Deposit, NW-Iran - a Holistic Approach

Book

Full-text available

Jan 2009

n.b. correct list of authors is: Farahnaz Daliran, Gregor Borg, Richard Armstrong, Johannes Walther, Torsten Vennemann, Kurt Friese, Mohammad Sadeghi, Jonathan D. Woodhead - - - The Angouran Zn-Pb sulphide-nonsulphide deposit is located in NW Iran and hosts an unusually high-grade zinc ore deposit (2.9 Mt sulphide ore @ 28% Zn and 2% Pb, 14.6 Mt nonsulphide ore @ 22.6% Zn and 4.6 %Pb and 1.8 Mt “mixed ore” @ 27% Zn and 3% Pb). The deposit is situated in a prominent topographic ridge in a mountainous region and is currently mined in an open pit. The country rocks comprise a range of meta-igneous and metasedimentary lithotypes, which are of Palaeozoic (to possibly Mesozoic) ages and which document the regional effects of Alpine metamorphism in SHRIMP data from overgrown and metamorphically grown zircons. Young magmatic activity, related to the subduction of the Arabian Plate underneath the Iranian Plate, is documented at Angouran by Tertiary (Burdigalian) rhyolitic tuff, extruded at 18.42 ± 0.18 Ma and subsequently intruded in turn by even younger basaltic dykes. The Angouran deposit is hosted by a conspicuous breccia at the lithological contact between footwall quartz-sericite schist and hangingwall graphitic marble in the nose of an open, concentric antiform. The entire anticlinal host rock package represents an allochthonous nappe sheet, which has been thrusted over the Tertiary rhyolitic tuff. Previous scholars have proposed a wide range of metallogenic models and ages of formation for the Angouran deposit, ranging from Proterozoic SEDEX and VMS to epigenetic MVT to distal intrusion-related ore systems. The present study incorporates from geological, structural, textural, ore mineralogical, alteration paragenetical, geochemical and stable and radiogenic isotope studies, which allow establishing a holistic metallogenic model, which involves two mineralisation stages, distinctly separate in time. Hypogene ore formation comprised early sphalerite-galena and late smithsonite precipitation during multiple stages of hydraulic brecciation of wall rocks and ore. The emplacement of the hypogene ore has been tectonically, thrust-controlled with ascending (overpressured) ore fluids being pushed episodically along the thrust plane by seismic pumping. Fluid pressure has built up repeatedly and has resulted in several hydraulic fracturing and brecciation events. While the initial rock failure brecciated only schist and marble wall rocks, subsequent brecciation affected also the sulphide ore, formed during the earlier stages. Brecciation was predominantly extensional and shearing or mylonitisation in these breccias are conspicuously absent. The hypogene ore fluids have been of moderate temperatures (<160°C), evolved from Fe-rich to Fe-poor compositions and became rapidly impoverished in sulphur towards the final stage of the hypogene process. The final, smithsonite-precipitating hypogene ore fluids have been cooler (110°C) and of low salinity, possibly indicting mixing with deep meteoric fluids. Stable isotope data suggest a fluid source that has tapped a mixed sedimentary-metamorphic reservoir and a magmatic origin can be excluded for the hypogene ore fluids. The supergene ore at Angouran has formed much later (< 3 Ma) in an oxidising near-surface environment, when abundant descending meteoric fluids oxidised and partly dissolved hangingwall marble and the contained hypogene sulphide-nonsulphide ore body. The supergene ore formation has also been accompanied by repeated brecciation, although at this stage due to dissolution collapse and possibly minor normal faulting. The dissolution, remobilisation and reprecipitation of nonsulphide minerals have caused a minor degree of systematic metal fractionation. During this process, Fe became particularly immobilised due to oxidation and subsequent smithsonite attained a higher degree of purity and thus maturity. The final stages of ore formation have been dominated by intensified dissolution, particularly in the uppermost, near-surface portions of the supergene ore body. Eventually, this dissolution would have led to the partial or total chemical erosion and loss of the ore body. Whereas the onset of supergene metallogeny is loosely constrained by the regional exhumation age of 3 Ma, the process is not finished yet and continues to the present day. The supergene ores have formed from the oxidation of the Angouran hypogene ores by meteoric fluids without any significant involvement of hydrothermal processes. The remobilisation or “loss” of metals such as Zn, Pb, Ni and As, together with Ca, S and Cl from the ore body has formed a significant geochemical halo, locally in footwall schists and particularly in the travertine terrace below the deposit. Consequently, the Angouran travertines are “metal contaminated” but otherwise normal precipitates, formed where the groundwater table intersected the topography. These travertines contrast both morphologically and geochemically with hydrothermal travertines of the wider Takhab region towards the west. Especially anomalous concentrations of Zn and Ni within the Angouran travertine suggest that travertine can be used as a regionally easily accessible sampling medium in geochemical exploration for supergene base metal deposits. Whereas the hypogene metallogenesis has been largely tectonically and subordinately rheologically and lithologically controlled, the supergene ore formation has been predominantly controlled by solubility, permeability and reactivity of ores and wall rocks.

Um Samra-Um Bakra Shear Zone, Central Eastern Desert, Egypt: Example of Vein -Type Base Metal Mineralization

Article

Full-text available

Jan 2017

Minerals of Berg Aukas, Otavi Mountainland, Namibia

Article

Mar 2021

Bruce Cairncross

Enhancing Zn-bearing gossans from GeoEye-1 and Landsat 8 OLI data for non-sulphide Zn deposit exploration

Article

Mar 2024

Ore deposits formed in the Critical Zone: Laterite Ni, Co, REE, Nb and supergene Cu

Article

Feb 2024

Critical Zone processes can mobilize metals from bedrock, or pre-existing ore bodies, to form regolith-hosted (laterites) and supergene deposits of copper, nickel, cobalt, rare earth elements and niobium. Other critical elements such as the platinum group elements and scandium are also an exploration target. Many deposits form under particular climatic and geomorphic conditions in the Cenozoic from coupled physical-chemical-biological processes, however, older examples can be preserved in the rock record. This chapter focusses on economic ore deposits that are formed in the Critical Zone, and specifically, two distinct types of deposits that originate from contrasting parent rocks in diverse tectonic, climatic, biological, and hydrological environments: laterite (Ni, Co, REE, Nb) and supergene (Cu) deposits. We present an overview on a suite of currently economic laterite deposits worldwide, and then we focus on supergene Cu deposits in the Andean Cordillera of South America as a key locality to understand supergene Cu upgrading. These systems exemplify two endmembers that illustrate the range of processes that can lead to metal enrichment in the Earth’s surface, and offer the opportunity to assess the nature of element cycles and the effects of changing climate on interactions in the Critical Zone.

Geochemistry, mineralogy, and development constraints of the Changarzeh non-sulfide ore, southern Natanz: Implications on tracing of carbonate rock-hosted supergene Pb-Zn deposits

Article

Jan 2024

Ebrahim Tale Fazel

Fluid inclusion, mineralogical, geochemical, and isotopic (O, S) evidence for the genesis of the Khan-Khatun Zn-Pb deposit, Tabas Block, Iran

Article

Apr 2024

Effect of the pulp potential on galena flotation with amyl xanthate as the collector

Article

Full-text available

Mar 2024

Mineralization and genesis of the Pb-Zn(-Cu) non-sulfide ore in Chah Mileh deposit (NE Anarak), Central Iran

Article

May 2023

Integrated Geology, Mineralogy, Element and C–O–S–Pb Isotopes Characteristics Elucidate Ore Genesis of the World-Class Huoshaoyun Zn–Pb Deposit in Karakoram Area, Xinjiang, Northwest China

Article

Jul 2023
ORE GEOL REV

Response to: Discussion on “Syn-metamorphic sulfidation of the Gamsberg zinc deposit, South Africa” by Stefan Höhn, Hartwig E. Frimmel, and Westley Price

Article

Full-text available

Apr 2023

Cawood et al. (this issue) critize our hypothesis of a pre-Klondikean weathering/oxidation event having affected the Aggeneys-Gamsberg ore district. Instead, they reinforce the long-held view that the sulfide deposits of the ore district with its pronounced metal zonation, its unusually high mineralogical variability and numerous geochemical anomalies are the product of amphibolite- to granulite-facies metamorphic overprint of originally syn-sedimentary exhalative deposits. Here we gladly use the opportunity to counter all issues raised and explain further our evidence of oxidation and subsequent re-sulfidation of the original synsedimentary deposits.

Zinc Speciation and Desorption Kinetics in a Mining Waste Impacted Tropical Soil Amended with Phosphate

Article

Jan 2022

Germanium re distribution during weathering of Zn mine wastes: Implications for environmental mobility and recovery of a critical mineral

Article

May 2022
APPL GEOCHEM

Germanium (Ge) is a metal used in emerging energy technologies, communications, and defense, and has been deemed critical by the United States due to its essential applications and scarce supply. Germanium is recovered as a byproduct of zinc (Zn) sulfides, and mining and processing of these materials lead to waste that could act both as a source of extractable Ge and a source for exposure to humans and ecosystems. Yet the distribution, speciation, and mineral hosts of Ge in mining-impacted areas are poorly understood. The Tar Creek Superfund Site, a former Zn mining area and Ge producer, is a natural laboratory to understand the environmental behavior and economic implications of Ge in mine wastes. We studied the distribution and behavior of Ge in solid wastes at the Tar Creek Superfund Site using bulk and microanalytical techniques. In wastes at this site we find that Ge has been redistributed from its original host, sphalerite (ZnS), to the fine-grained weathering product hemimorphite (Zn4Si2O7(OH)2·H2O), which impacts germanium's mobility, bioaccessibility, and potential for recovery. We provide chemical and mineralogical evidence of this redistribution, along with an evaluation of the oxidation state and molecular-scale substitution of Ge into sphalerite, hemimorphite, and quartz. Geochemical modeling shows that hemimorphite is more stable than sphalerite in waste piles and provides a stable secondary repository for Ge. However, hemimorphite is fine-grained, and if ingested or inhaled is readily soluble, with the potential to release Ge. Lastly, we discuss other sites internationally where similar behavior may be important. This study shows that weathering can have a significant impact on the distribution, speciation, and mineral hosts of Ge in mine wastes; directly influence mobilization from waste piles and subsequent availability to humans and ecosystems; and dictate metallurgical strategies to target Ge for recovery.

Deposit classification scheme for the Critical Minerals Mapping Initiative Global Geochemical Database: U.S. Geological Survey Open-File Report 2021–1049, 60 p.

Technical Report

Jun 2021

A challenge for the global economy is to meet the growing demand for commodities used in today’s advanced technologies. Critical minerals are commodities (for example, elements, compounds, minerals) deemed vital to the economic and national security of individual countries that are vulnerable to supply disruption. The national geological agencies of Australia, Canada, and the United States recently joined forces to advance understanding and foster development of critical mineral resources in their respective countries through the Critical Minerals Mapping Initiative (CMMI). An initial goal of the CMMI is to fill the knowledge gap on the abundance of critical minerals in ores. To do this, the CMMI compiled modern multielement geochemical data generated by each agency on ore samples collected from historical and active mines and prospects from around the world. To identify relationships between critical minerals, deposit types, deposit environments, and mineral systems, a unified deposit classification scheme was needed. This report describes the scheme developed by the CMMI to classify the initial release of geochemical data. In 2021, the resulting database—along with basic query, statistical analysis, and display tools—will be served to the public through a web-based portal managed by Geoscience Australia. The database will enable users to trace critical minerals through mineral systems and identify individual deposits or deposit types that are potential sources of critical minerals.

Combining zinc desorption with EXAFS speciation analysis to understand Zn mobility in mining and smelting affected soils in Minas Gerais, Brazil

Article

Feb 2021
SCI TOTAL ENVIRON

Zinc contents exceeding regulatory levels have been documented in several areas in Brazil and elsewhere, especially in sites surrounding mining and smelting sites. Studies involving Zn release and speciation are keys to assess the mobility and bioavailability and thus the potential ecological risk of this element. This study evaluated Zn desorption and speciation from soils affected by mining (soils from a mine area, classified as Technosols) and smelting (mine tailing) activities in Brazil with high total Zn contents, ranging from 1.8 to 8.2%, using a stirred-flow approach and synchrotron-based X-ray absorption spectroscopy (XAS), in order to better assess Zn availability and mobility in these environments. The exchangeable fraction, extracted by 0.1 M CaCl2 solution, represented only a small (<0.5%) portion of the total Zn from soils of the mining site, while accounting for ~80% from tailings of the smelting site. In the mine area, X-ray absorption fine structure (XAFS) showed that Zn was associated with hemimorphite, Zn-ferrihydrite, Zn-phyllosilicates (Zn-kerolite), and Zn-layered double hydroxides (Zn-LDH); this is the first time these Zn precipitate/sorbed forms have been detected in Brazilian mining soils, which have been exposed to tropical conditions. The formation of these insoluble phases of Zn could explain the low Zn desorption from these soils, taking into consideration that Zn-ferrihydrite, Zn-kerolite, and Zn-LDH can lead to a significant decrease of the exchangeable/mobile fraction of Zn in soils. The higher amount of Zn desorbed (⁓80%) from the tailing material located in the smelting site could be attributed to the predominance of weakly bound forms of Zn (~70%). These findings were also seen by analyzing the Fourier Transform (FT) and Wavelet Transform (WT). This study has shown that combining EXAFS analyses with desorption extraction is relevant to better understand Zn mobility and how it is related to Zn speciation.

The genesis of the Jurassic-hosted Mississippi Valley-Type Pb-Zn ore deposit, Tigrinine-Taabast district (Central High Atlas, Morocco): Insights from fluid inclusion and C-O-S-Pb isotopes studies

Article

Feb 2021
J Afr Earth Sci

Larbi Rddad

The Mississippi Valley-type Pb-Zn ore deposit of the Tigrinine-Taabast ore district, located in the southern border of the Moroccan Central High Atlas, is hosted in hydrothermally dolomitized Hettangian-Sinumerian carbonates. The mineralogical paragenetic sequence is simple: Quartz-dolomite-pyrite-galena-sphalerite. Fluid inclusions carried out on sphalerite reveal that sulfide ore precipitated from a NaCl-CaCl2-MgCl2 basin-derived warm (78° - 168°C) and saline (21 - 36 wt.% NaCl equiv.) brine. The carbon and oxygen isotopes of the ore-related calcite (Cal-1) suggests an equilibrium between the calcite-forming fluid and carbonates. The late post-ore calcite (Cal-2) reveals the influx of isotopically light meteoric fluid during the precipitation of this calcite. The δ34S values range from 6.6 to 9.4‰ and from 12.7 to 13.0‰ for galena and sphalerite, respectively. Sulfur derived from dissolved Triassic-Jurassic sulfates and/or coeval seawater pore sulfates primarily through thermochemical sulfate reduction and possibly bacterial sulfate reduction. Galena samples have a homogeneous Pb isotopic composition with 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios ranging from 18.229 to 18.236, 15.643 to 15.655, and 38.448 to 38.527, respectively. This uniform Pb isotope composition suggests that Pb and by inference other metals derived primarily from the Paleozoic rocks. During the African-European Cenozoic collision, the metal-bearing fluid was remobilized and migrated through the major faults and mixed with a shallow, diluted, cooler fluid, leading to the precipitation of ore sulfides.

‫Mineralogy and Geochemistry of Pb-Zn mineralization in the Nesar area, West of Khomein, Central Iran

Conference Paper

Full-text available

Nov 2020

Mohammad Yazdi

Abstract Nesar Pb-Zn deposit is located in the south of Lakan village. This vaillage is located in the Markazi province, central Iran. The exploration area of Nesar is situated in NW of Lakan village. The area is located in the middle part of the Sanandaj-Sirjan geotectonic Zone. The main faults of the area are in the main trend of this zone (NW - SE). The local faults of the area are in the trend of W-E. The major rock units of the area include phyllite and schist (Triassic age), metamorphosed sandstone, phyllite and schist (Jurassic age), yellow sandy-dolomite, massive gray limestone, interlayers of calcareous shale (Cretaceous) and Quaternary alluvium. The northern part of the area is mainly composed of gray massive limestone, calcareous marl, yellow sandy-dolomite (Lower Cretaceous) and Jurassic sandstones. The major ore minerals in the host rocks are galena, sphalerite, hematite and goethite. Minor ore minerals are cerusite, chalcopyrite, pyrite and malachite. The mineralization is mainly vein type and is associated with different facies of limestones. The main alteration is silicification and rarely dolomitization. The mineralization is mainly associated with silicification. The geochemical analyses of the 116 samples show that the Zn, Pb and Ag are the most anomalous elements. The average concentration is for Zn (4%), Pb (1.3%) and Ag (10ppm). The data show that the Zn has enough cat of grad for mining. The structural and textural evidences such as vein and veinlet mineralization, and solid solution,… show that the mineralization is epigenetic type. Geological, petrographic, mineralogical, geochemical and host rocks data show that the mineralization in the Nesar area is Irish type. Keywords: Pb-Zn mineralization, Irish type, Nesar, Khomein, Central Iran

Genesis of As-Pb-Rich Supergene Mineralization: The Tazalaght and Agoujgal Cu Deposits (Moroccan Anti-Atlas Copperbelt)

Article

Full-text available

Dec 2020

In the Moroccan Anti-Atlas, sulfide deposits hosted by Neoproterozoic to Cambrian formations underwent significant weathering, leading to the formation of supergene profiles. In the Tazalaght Cu-As deposit, three mineralogical steps are distinguished: (1) the replacement of hypogene sulfides (chalcopyrite, pyrite, tennantite) by supergene sulfides (bornite, chalcocite) in the large cementation zone; (2) the formation of oxidized minerals (malachite, azurite, olivenite, and chenevixite, mainly) in a more oxidizing and neutral environment; and (3) the precipitation of goethite, hematite, and quartz in the gossan. In the Cu-As-Pb-V deposit of Agoujgal, the mineralogical units are spatially less confined than at Tazalaght. The narrow cementation zone hosts chalcocite, resulting from the weathering of hypogene chalcopyrite, pyrite, tennantite and galena, while the much more extended and diversified oxidized zone is rich in Cu and Pb carbonates, arsenates, sulfates, phosphates, vanadates, and oxides. Goethite, hematite, mottramite, and late calcite occur in the gossan. Both deposits are characterized by As-rich secondary ores that were formed through similar processes, despite some mineralogical and chemical variations highlighting the influence of the host rocks on weathering. The restricted oxidized mineralization at Tazalaght and the Agoujgal cementation zone most likely arise from the contrasting omnipresence of quartzite at Tazalaght that could not enable a fast and effective neutralization of the fluid’s acidity, and the large amounts of dolomitic host rocks that could be dissolved at Agoujgal. At both sites, the weathering of tennantite through a boxwork texture records the transition from the cementation zone (chalcocite), the oxidized zone (arsenates), and the gossan, and reflects the fluids evolution with time.

A review of the geological setting of the Tynagh orebody, Co. Galway.

Article

Full-text available

Jan 1986

The local stratigraphy and structure are described, followed by mineralogical and textural descriptions of the Tynagh Zn-Pb-Cu-Ag ores. Four stages of sulphide mineralization are distinguished: 1) early diagenetic sulphides as rim cements and linings to stromotactis cavities, 2) sulphide infills and geopetal sediments in dilatant fracture/breccia systems associated with the main mineralization phase, 3) epigenetic Cu-Pb-Ba mineralization as vein infills and replacements, 4) post-ore carbonate infills and replacements. Various genetic theories are discussed. -R.E.

Sulfide-carbonate relationships in Upper Silesian Zn-Pb deposits (Mississippi Valley type), Poland, and their genesis.

Article

Full-text available

Jan 1984

The contact zone between the ore-bearing dolomite of these deposits in the Orzel Bialy mine and both tiny open cracks and small veinlets of sphalerite, galena and pyrite, consists mainly of ferroan dolomite, zincian dolomite and minor plumbian dolomite; the contents of Fe, Zn and Pb decrease towards the ore-bearing dolomite. The zone between the ore-bearing dolomite and massive, layered sphalerite consists of smithsonite, ferroan smithsonite, zincian dolomite and ferroan dolomite; it also contains numerous cracks and micro-cavities and examples of sulphides replacing Zn and Fe carbonates, giving a volume decrease. Layers of different generations within the layered sphalerite are separated by microscopically thin carbonate layers containing minute ZnCO3 relics and numerous empty cracks in a pattern recalling the cleavage of rhombohedral carbonates. This is the result of replacement of layered sphalerite by sphalerite which reduces the volume by 16.1%. A significant amount of Zn and minor Pb was primarily accumulated in carbonate form and later transformed to Zn and Pb sulphides, resulting in volume decrease and brecciation in the ore-zone.- R.A.H.

Isotopic studies of epigenetic features in metalliferous sediment, Atlantis II Deep, Red Sea

Article

Full-text available

Sep 1988

Robert A. Zierenberg

The unique depositional environment of the Atlantis II Deep brine pool in the Red Sea produces a stratiform metalliferous deposit of greater areal extent than deposits formed by buoyant-plume systems typical of the midocean ridges because of much more efficient metal entrapment. Isotopic analyses of strontium, sulfur, carbon, and oxygen from the metalliferous sediments indicate that three major sources contribute dissolved components to the hydrothermal system: seawater, Miocene evaporites, and rift-zone basalt. An areally restricted magnetite-hematite-pyroxene assemblage formed at high temperatures, possibly in response to hydrothermal convection initiated by intrusion of basalt into the metalliferous sediment. A correlation between smectite Fe/(Fe+Mg) ratios and oxygen isotope temperatures suggests that smectite is a potentially important chemical geothermometer, and confirms geochemical calculations indicating that Mg-rich smectite is more stable than Fe-rich smectite at elevated temperatures.

Genthelvite and Willemite, Zinc Minerals Associated with Alkaline Magmatism from the Motzfeldt Centre, South Greenland

Article

Full-text available

Sep 1990

Adrian A. Finch

Two new occurrences of Zn-rich minerals are described from the SM6 lujavrite unit of the Motzfeldt alkaline centre, South Greenland. Zinc and beryllium complexes in the magma gave rise to the formation of interstitial grains of genthelvite (Zn4Be3Si3012S), identified in samples by strong green cathodoluminescence. It is suggested that subsequent metasomatism leached Be from the genthelvite, giving rise to the formation of associated willemite (Zn2SiO4).

Iron-Manganese-Barium Deposit from the Northern Afar Rift (Ethiopia)

Article

Full-text available

Oct 1972

Geochemistry and genesis, submarine hydrothermal activity followed by fractional precipitation of elements, similarity to hot-brine metalliferous deposits from the Red Sea and to deposits from active oceanic rifts

The Kuh-e-Surmeh mineralization, a carbonate-hosted Zn-Pb deposit in the Simply Folded Belt of the Zagros Mountains, SW Iran

Article

Full-text available

Jan 2000

The Kuh-e-Surmeh carbonate-hosted zinc-lead deposit, located within the Simply Folded Belt of the Zagros Mountains in southwestern Iran, is an orogen-related Mississippi Valley type deposit originally formed in the foreland Thrust Belt of the Zagros Mountains. Structural and textural observations indicate that ore deposition took place as open-space fillings in brecciated carbonate rock and as internal sediments consisting of fine-grained ore minerals interlayered with carbonates. The preferred genetic model for the concentration of the ore metals is that of dewatering of the Zard-Kuh basin due to regional tectonic compaction tectonism and expulsion of basin-derived fluids into the highly porous and brecciated dolomitized rocks of the Dalan Formation. The metals precipitated from dense basinal brine (15 wt% equiv. NaCl) at low temperatures (less than 200 °C), typically within strata of a Late Paleozoic carbonate platform.

Chapter II.1. The Mechanisms of Sulphide Oxidation and Gossan Formation

Article

Dec 1992

General geology and mines of the East-Tintic mining district, Utah and Juab counties, Utah.

Article

Jan 1979

The East Tintic mountains consist of the eroded flank of a composite volcano, which during the Oligocene, buried a preexisting mountain range. During this volcanic episode hydrothermal solutions which eventually deposited large replacement ore bodies and veins that occur almost exclusively in the sedimentary rocks beneath the hydrothermally altered lavas. Metalliferous ores include Pb, Zn, Ag, Au, Cu, Cd and Mn. 2743, Paleozoic sedimentary rocks exposed range from L.Cambrian to U. Mississippian. No rocks of Mesozoic age are exposed. -from AuthorsEnglish

The tectono-stratigraphic controls to mineralisation in the Silvermines area, County Tipperary, Ireland.

Article

Jan 1986

C.J. Andrew

Zn-Pb-Ba mineralization occurs in Courceyan transgressive siliciclastic rocks and overlying carbonates within the Silvermines fault zone, which was active during sedimentation and mineralization. Mineralization occurs in hydraulic fracture zones and as epigenetic replacements within Lower Palaeozoic greywackes and basal Carboniferous clastics. The upper orebody is a tabular, stratiform, irregular lens of massive baryte, siderite, marcasite and pyrite with variable amounts of base-metal sulphides of syngenetic character. Genetically the Silvermines deposits are of sedimentary exhalative origin. Convective mineralizing fluids were derived from the Lower Palaeozoic basement at approx 220oC and at salinities of 10-15 wt.% NaCl equiv. At high levels these were mixed with formational waters (20oC, 25 wt.% NaCl equiv.) derived from Carboniferous sea-water. Mixing led to rapid and sometimes explosive boiling, followed by precipitation of the lower, epigenetic orebodies. The upper orebody was due to debouching of the mixed brines onto the seafloor, followed by lateral migration to palaeotopographic lows between Waulsortian mudbanks.-R.E.

Supergene mineral deposits and physiographic development in southwest Sardinia, Italy

Article

Jan 1972

J.M. Moore

The Reading Prong of New Jersey and eastern Pennsylvania: An appraisal of rock relations and chemistry of a major Proterozoic terrane in the Appalachians

Chapter

Jan 1984

Avery Ala Drake

The Proterozoic Y terrane of the Reading Prong of eastern Pennsylvania and New Jersey consists of light-colored, sodic-rich rocks containing intercalated amphibolite, the Losee Metamorphic Suite, calcarerous and quartzofeldspathic metasedimentary rocks, the intrusive Hexenkopf Complex, the Byram Intrusive Suite, and quartz-poor monzonite, syenite, and related pyroxene granite. The Losee consists of oligoclase-quartz gneiss and amphibolite that in places has been partly mobilized to form venite and albite oligoclase granite. Rocks of charnockitic affinity may be a partial melt of an amphbiolite-rich phase of the Losee. The Losee is thought to be metamorphosed quartz keratophyre and related sodic basalt. It is probably basement to the calcareous and quartzofeldspathic metasedimentary rocks. The calcareous rocks are mostly marble, amphibolite, pyroxene gneiss, and epidoteand scapolite-bearing gneisses. They are interlayered with quartzofeldspathic gneiss of two general types: biotite-quartz-feldspar gneiss and potassic feldspar gneiss. At places, the potassic feldspar gneiss has melted and has formed small bodies and layers of potassium-rich granite. The quartzofeldspathic rocks are of continental margin type and are thought to be a clastic wedge containing layers and lenses of calcareous rocks. The source of the clastic material was probably a granitic terrane because of the large amount of potassic feldspar. Some volcanic material may be present in this sequence, but the evidence is equivocal. The Hexenkopf Complex consists of severely altered mafic plutonic rock. It appears to lie beneath the Losee, and if so, is the oldest known rock in this part of the Reading Prong. The Byram Intrusive Suite consists of hornblende granite and alaskite that form syntectonic and conformable sheets within the metamorphic rocks, as well as scattered small bodies of biotite granite that resulted from the granitization of biotite-quartzfeldspar gneiss. Byram leucosome forms arterites from both biotite-quartz feldspar gneiss and amphibolite. The Byram probably results from the anatectic melting of older rocks, but at the present level of erosion, there is no evidence that this has taken place. The Byram probably had its origin in the source terrane of the quartzofeldspathic gneiss. The quartz-poor monzonite, syenite, and related pyroxene granite are not well understood. These rocks form syntectonic conformable sheets like the rocks of the Byram Intrusive Suite, with one exception, in which a sheet of quartz syenite appears to cut across the structure of hornblende granite. These rocks are also probably anatectic, perhaps originating at a lower level than the Byram. This place of origin is not certain, however, because the relation of the quartz-poor rocks to the Byram is not really known. The rocks in eastern Pennsylvania and New Jersey were metamorphosed in at least upper amphibolite facies, and most were probably metamorphosed in hornblende granulite facies. There is some evidence of polymetamorphism in northeasternmost New Jersey, but that concept needs further evaluation. The metamorphic, intrusive, and deformational event in the Reading Prong can be dated at about 1 b.y. ago, so it is clearly Grenvillian. The rocks in the Reading Prong are very much like those of the Adirondacks and probably like those of the Honey Brook Upland. They have similarities to rocks of the Green Mountains, Berkshires, and basement massifs of western Connecticut. They are not at all like the rocks of Avondale- West Chester Massif, the Baltimore Gneiss, or the rocks of the northern and southern Blue Ridge. In a few small areas, the Proterozoic Y rocks are overlain by a sequence of interlayered metasedimentary and metavolcanic rocks that are named the Chestnut Hill Formation. These rocks are at a lower metamorphic grade and are much less homogenized than the Proterozoic Y rocks and are thought to be of probable Proterozoic Z age.

Poland.

Article

Jan 1986

R. Osika

The territory of Poland can be divided into seven tectonic-metallogenic regions: 1) Gory Swietokrzyskie (Holy Cross Mountains), 2) Lower Silesia, 3) Upper Silesia, 4) Carpathians, 5) Carpathian foredeep, 6) Precambrian platform, and 7) Palaeozoic platform. Poland possesses Fe, Cu, Zn and Pb, and As ores and also, in smaller quantities, ores of Sn, Ni, Al, Cr and other metals. The most important are the magmatic-type iron ores that occur in the Suwalki region and the Dogger sedimentary iron ore deposits in the Zarki-Czestochowa-Klobuck region. Of considerable importance are the Zechstein deposits of Cu ores in the Fore-Sudetic monocline and Zn-Pb ores in the sediments of the Silesian Triassic. -J.M.H.

The Morro Agudo Zn-Pb deposit, Minas Gerais, Brazil: A Proterozoic Irish-type carbonate hosted sedex replacement deposit

Article

Jan 1995

The mineral resources of Burma

Article

Jan 1956

S. Griffith

The mineralogy and genesis of the lead-zinc-vanadium deposit of Abenab West in the Otavi Mountains, South West Africa

Article

Jan 1957

W.J. Verwoerd

Geochemistry of the Furnace Magnetite Bed, Franklin, NewJersey, and the Relationship between Stratiform Iron Oxide Ores and StratiformZinc Oxide-Silicate Ores in the New Jersey Highlands

Article

Jun 2003

The New Jersey Highlands terrace, which is an exposure of the Middle Proterozoic Grenville orogenic belt located in northeastern United States, contains stratiform zinc oxide-silicate deposits at Franklin and Sterling Hill and numerous massive magnetite deposits. The origins of the zinc and magnetite deposits have rarely been considered together, but a genetic link is suggested by the occurrence of the Furnace magnetite bed and small magnetite lenses immediately beneath the Franklin zinc deposit. The Furnace bed was metamorphosed and deformed along with its enclosing rocks during the Grenvillian orogeny, obscuring the original mineralogy and obliterating the original rock fabrics. The present mineralogy is manganiferous magnetite plus calcite. Trace hydrous silicates, some coexisting with fluorite, have fluorine contents that are among the highest ever observed in natural assemblages. Furnace bed calcite has δ 13C values of -5 ± 1 per mil relative to Peedee belemnite (PDB) and δ 18O values of 11 to 20 per mil relative to Vienna-standard mean ocean water (VSMOW). The isotopic compositions do not vary as expected for an original siderite layer that decarbonated during metamorphism, but they are consistent with nearly isochemical metamorphism of an iron oxide + calcite protolith that is chemically and minerlogically similar to iron-rich sediments found near the Red Sea brine pools and isotopically similar to Superior-type banded iron formations. Other magniferous magnite + calcite bodies occur at approximately the same stratigraphic position as far 50 km from the zinc deposits. A model is presented in which the iron and zinc deposits formed along the western edge of a Middle Proterozoic marine basin. Zinc was transported by sulfate-stable brines and was precipitated under sulfate-stable conditions as zincian carbonates and Fe-Mn-Zn oxides and silicates. Whether the zincian assemblages settled from the water column or formed by replacement reactions in shallowly buried sediments is uncertain. The iron deposits formed at interfaces between anoxic and oxygenated waters. The Furnace magnetite bed resulted from seawater oxidation of hydrothermally transported iron near a brine conduit. Iron deposits also formed regionally on the basin floor at the interface betveen anoxic deep waters and oxygenated shallower waters. These deposits include not only manganiferous magnetite + calcite bodies similar to the Furnace magnetite bed but also silicate-facies deposits that formed by iron oxide accumulation where detrital sediment was abundant. A basin margin model can be extended to Grenvillian stratiform deposits in the northwest Adirondacks of New York and the Mont Laurier basin of Quebec. In these areas iron deposits (pyrite or magnetite) are found basinward of marble-hosted sphalerite deposits, such as those in the Balmat-Edwards district. Whether the iron and zinc precipitated as sulfide assemblages or carbonate-oxide-silicate assemblages depended on whether sufficient organic matter or other reductants were available in local sediments or bottom waters to stabilize H 2S.

The Padaeng Supergene Nonsulfide Zinc Deposit, Mae Sod, Thailand

Article

Jun 2003

The Padaeng deposit near Mae Sod in western Thailand was the first supergene nonsulfide zinc deposit in the world to be developed as a large modern mining operation. The mine and associated zinc smelter, operated by Padaeng Industry Public Company Ltd. since 1984, went into production with reserves of 4.59 Mt at a grade of 28.9 percent zinc with it 10 percent zinc cutoff. Current resources are 5.14 Mt at a grade of 12.0 percent zinc with a 3 percent zinc cutoff. The Padaeng deposit is hosted by a mixed carbonate-clastic sequence of Middle Jurassic age. The deposit occurs in the hanging wall of the Padaeng fault, a major northwest-trending structure that was active through Cretaceous and Tertiary tectonism and uplift. Nonsulfide zinc ore comprises dominant hemimorphite with minor smithsonite and hydrozincite. Strata-bound ore zones occur within a northwest-dipping, deeply weathered, dolomitic sandstone; steeply dipping and irregular karstic zones in underlying massive, silty dolomite are controlled by north-trending fracture zones. Sulfide zinc-lead mineralization of Mississippi Valley type occured extensively in the vicinity of the Padaeng mine, most notably the small resources at Pha De and Hua Lon. Mineral deposits are typically sphalerite rich with minor galena and pyrite, forming small-scale open-space fillings, veins, and replacements within hydrothermal dolomite. Mineralization is dominantly strata bound within a horizon of intense hydrothermal dolomitization that forms the stratigraphic hanging wall to the nonsulfide ore zones at Padaeng. The only significant sulfide at the Padaeng mine is within this unit. Only trace sulfide occurs peripheral to, or down dip of, strata-bound or steeply dipping, nonsulfide orebodies. Sulfide mineralization is believed to have accompanied Cretaceous uplift and deformation, related to the onset of oblique subduction beneath the western margin of the Shan-Thai terrane. The nonsulfide deposit is believed to have formed when a substantial body of sulfide ore was uplifted on the margin of the Mae Sod Tertiary intermontane basin, commencing in the middle to late Miocene. Zinc-bearing acidic supergene fluids, generated by oxidation of the precursor sulfide body, reacted with carbonate in the underlying stratigraphic section to precipitate hemimorphite and smithsonite. Fluids were channeled by permeable dolomitic sandstones and by steep fracture and fault zones. Acidic fluids promoted deep weathering and karst formation, allowing mineralization to extend down dip in sandstone units for at least 150 m and vertically for it similar distance in steep structural zones. Transport of zinc out of the precursor sulfide body was facilitated by a falling water table, owing to uplift of the Padaeng fault block and a change from wet tropical to monsoonal or semi-arid climatic conditions. There is no evidence for significant in situ replacement of sulfide deposits, and the leached remnants of the precursor sulfide body have been removed by erosion. The supergene process of dissolution and reprecipitation of zinc in the host rocks increased zinc grades and separation of zinc from lead, producing an economically attractive deposit. Successful exploration for this type of deposit requires a good understanding of the controls on primary sulfide mineralization and a good knowledge of local neotectonism, uplift history, hydrogeology, climatic evolution, and weathering history.

The Shaimerden Supergene Zinc Deposit, Kazakhstan: APreliminary Examination

Article

Jun 2003

The Shaimerden supergene zinc deposit in the southern Urals Mountains is located in the province of Kostanai in northwest Kazakhstan. It lies at the southern end of the Kostanai megasyncline, a north-northeast-trending, structurally controlled area of lower Paleozoic clastic and carbonate sedimentary rocks and volcanic rocks. A zinc-lead resource estimated at 4,645,100 tonnes at 21.06 percent Zn has been defined. The deposit is hosted within a sequence of intertidal to open-marine carbonates and evaporites of Viséan (Early Carboniferous) age. Although drilling to date has not intersected a fault, significant faulting in the area is suggested by the presence of polymict debris flows comprising a wide range of carbonate facies and by large variations in micropaleontologic dates. Sulfide deposits replaced hydrothermally dolomitized carbonates and were subsequently reworked into polymict conglomerates of probable Carboniferous age that were deposited in a marine environment. Weathering of the sulfide mineral deposits took place during the Triassic Period, following uplift during the late Paleozoic. The weathering occurred in situ, and small intervals of relict sulfides were preserved in the center of the deposit. The degree of weathering increases outward from the center of the deposit, which passes from massive sulfide to massive hemimorphite-smithsonite to weathered clays with hemimorphite-smithsonite fragments. The supergene minerals are overlain by bauxitic clays of Cretaceous age and Quaternary silty soils and sands.

A Holocene zinc orebody formed by supergene replacement of mosses

Article

Oct 1983
J GEOCHEM EXPLOR

An extensive deposit of secondary zinc minerals has been formed at Howard's Pass, Yukon by replacement of mosses and as a cement within talus. The deposits are of Holocene age (younger than 9610 yr. B.P.) and occur in blanket peat bogs percolated by zinc-rich springwaters. Buried moss strata undergo cell by cell replacement forming zincian clacite, smithsonite and hemimorphite. The last is the most important secondary mineral in both mosses and talus.

Supergene process in zinc-lead-silver sulfide ores in carbonates.

Article

Oct 1983

The distribution and stabilities of mineral assemblages formed during supergene alteration of polymetallic sulphide ores in carbonate rocks were evaluated thermodynamically. In this study, the chemistry of supergene alteration has been approximated for three Zn-Pb-Ag deposits. In each instance, the distribution of alteration assemblages is controlled primarily by the initial mineralogy, the composition and flow rates of groundwater, and rock permeability. The Burgin mine, East Tintic district, Utah, displays a simple vertical zonation of supergene alteration products. This is caused by the alteration of primary minerals, at pH's fixed by carbonate buffering and at irregular Eh conditions which generally decrease with depth. Beginning at the top of the zone of oxidation, Mn-Fe oxides, oxidized Pb-Zn-Ag ores, incipiently altered primary ore, and finally unaltered primary ore are encountered. At the Tynagh mine, Co. Galway, Ireland, the complexly zoned assemblages are the result of oxidation of Cu-poor, pyrite-rich Zn-Pb-Ag ores in less permeable rocks. Oxidation of primary sulphides occurs at variable Eh-pH conditions but at pH's higher than when buffered by carbonate. Alteration assemblages are characterized either by relatively more oxidized minerals (carbonates, sulphates) or by more reduced products including supergene Pb- and Cu-sulphides (due to sulphate-reducing bacteria). The complexly zoned assemblages at the Matagente mine, Cerro de Pasco, Peru, are produced by oxidation of primary ore in less-permeable host rocks at generally low Eh values but at pH values that are more alkaline than if buffered by carbonate. The variation in pH is due to irregular distribution of pyrite in the primary ores. Characteristic alteration products include carbonates and sulphates. Use of such thermodynamic data permit a comparison of the alteration history of Zn-Pb-Ag sulphide deposits.-J.E.S.

The formation of goethite, jarosite, and alunite during the weathering of sulfide-bearing felsic rocks

Article

Feb 1982

Kenneth W. Bladh

Quantities of goethite and jarosite produced by weathering correlate with abundance and composition of sulfide minerals originally in rocks. To characterize processes forming these minerals, chemical weathering of sulfide-bearing rocks was simulated using differential equations which describe mass transfer between aqueous solutions and minerals (Helgeson, 1968).Goethite begins precipitating during reaction between meteoric water (f (sub O 2 ) = 10 (super -06) atm) and sulfides after dissolution of 6.7 X 10 (super -9) g pyrite or 6.0 X 10 (super -9) g chalcopyrite per 1,000 g H 2 O. Reaction of the oxygen dissolved in 1,000 g water that is initially saturated with the atmospheric abundance of oxygen consumes 0.0085 g pyrite or 0.013 g chalcopyrite. Goethite is the only reaction product. The calculations predict that weathering produces jarosite or alunite after goethite when >0.04 moles of oxygen have been consumed per 1,000 g H 2 O and where rates of oxygen replenishment approximately equal or exceed consumption. Simultaneous reactions between K-feldspar, an aqueous solution, and pyrite or chalcopyrite produce alunite and goethite if the irreversible molar flux of Fe/Al is less than 0.5. Reactions with fluxes of Fe/Al between 0.5 and 1.0 produce alunite, goethite, and jarosite; those with Fe/Al fluxes greater than 1.0 generate only jarosite after goethite.Following saturation of the solution with jarosite, the mass ratio, goethite/(goethite + jarosite) decreases smoothly from 1.0 to 0.0 accompanying continuous dissolution of pyrite and chalcopyrite. The interval of reaction progress over which goethite and jarosite coexist increases, relative to pyrite and K-feldspar reactions, when weathering involves muscovite or chalcopyrite. In simulations whose sulfides have been totally oxidized, this ratio varies antithetically with the volume percent sulfide and/or ratio of pyrite/(pyrite + chalcopyrite) initially present, a prediction consistent with geologic observations.

The Pb-Zn deposit of Rosh Pinah Mine, South West Africa

Article

Feb 1976

A stratabound and stratiform lead-zinc sulfide deposit, confined to the rocks of the upper volcanoclastic portion of the Precambrian Kapok Formation, was discovered in 1963 in the south of South West Africa.The ore horizon consists of a well-bedded sedimentary sequence comprising presumably biologically and chemically precipitated sediments, namely microquartzite (a carbonaceous chert), carbonates, sugary quartz, and massive sulfides with intercalated detrital quartzite and argillite. Carbon- and barium-bearing minerals are ubiquitous in all the rocks of the ore horizon as well as in the footwall and hanging wall. The latter, which is not mineralized, is composed of arkosic quartzite and grits and has a fairly sharp contact with the ore horizon. The footwall, consisting of an arkosic quartzite, is featured by brecciation and disseminated sulfides and stringer ore in interfragmental dolomite veins. The brecciation and mineralization of the footwall rocks probably took place contemporaneously with the deposition of the orebody and is not considered to be genetically related to later deformation. Silicification of the footwall is in evidence. The sediments are all characterized by sedimentary slumping, facies changes over short distances, and even local unconformities.All the presently known orebodies are characterized by intricate structures which can be ascribed to at least two periods of tectonic deformation, i.e., folding and refolding.It is proposed that the ore is genetically related to volcanogenic massive sulfide deposits.

Lead-Zinc Mineralization in Carbonate Rocks, Central Guatemala

Article

Dec 1973

Stephen E. Kesler

Lead-zinc-(silver) mineralization is widespread in carbonate rocks of the Permian Chochal and Cretaceous Coban-Ixcoy formations in a 250 X 50 km zone elongated east-west across central Guatemala. Massive galena-sphalerite-pyrite-quartz mineralization is concentrated along bedding planes and fault surfaces in areas up to 1,500 X 100 m. Minor barite, chalcopyrite, and pyrargyrite are present locally and the silver content of galena increases southward across part of the mineralized zone. Most mineralization is near the base of the lowest carbonate unit in the local stratigraphic section and does not appear to be related, in surface outcrop, to the depositional and collapse breccias that are widespread throughout the Chochal and Coban-Ixcoy carbonate rocks. Mineralization appears to be late Cretaceous in age.delta S ³⁴ values for sulfides in the mineralized area exhibit a spread of 25 per mil, do not center on zero, and are similar to those of many Mississippi Valley deposits. Lead isotope values are only slightly radiogenic, however, and show greater similarities to magmatic-hydrothermal lead-zinc deposits. Limited sulfur isotope and fluid inclusion data suggest that mineralization took place below 250 degrees C. Sulfides with the observed variation in delta S ³⁴ values could have been deposited below 250 degrees C under a small range of f (sub O 2 ) and pH if the bulk isotopic composition of the ore-forming sulfur was +18 to +26 per mil. The lower part of this range coincides with estimates of delta S ³⁴ for Jurassic-Cretaceous sea water, which is widespread in the mineralized zone as the gypsum facies of a large evaporite basin that occupied northern Central America during Jurassic-Cretaceous time.

The Geology of the Beltana Willemite Deposits

Article

Dec 1972

D. W. Muller

Intrusive sedimentary breccias in Archaeocyatha limestone (Cambrian), diapirism, faults, hydrogeologic controls, Ordovician Delemarian Orogeny mesothermal ores, enrichment, mobility of ions, evolution, changes

Genesis of the Franklin-Sterling, New Jersey, orebodies

Article

Sep 1966

William H. Callahan

The volcanic-sedimentary origin of modern Red Sea muds rich in iron, zinc, manganese and other metals 'suggests a possible environment and process for deposition of. . . strata-bound oxide-silicate minerals of Fe, Zn, and Mn that characterize the Franklin-Sterling ore deposits.'

Supergene alteration of zinc and lead deposits in limestone

Article

Sep 1960

Taro Takahashi

An attempt is made here to describe occurrences and paragenetic sequences of the supergene zinc and lead minerals in three districts representing varying mean temperatures and humidities. The facts observed in field and laboratory are interpreted in the light of physical chemistry, assuming equilibrium conditions. The stability relationships between smithsonite, hydrozincite and zinc hydroxide are defined in terms of pH and total carbon dioxide concentrations in the aqueous solution system, or of the partial pressure of carbon dioxide in the dry system. The stability fields of hemimorphite and willemite are also discussed. The study explains the common occurrence of hydrozincite in arid regions, and the scarcity of this mineral in humid regions. The common occurrences of smithsonite and hemimorphite in the Southern Appalachian district, and the predominance of smithsonite over hydrozincite and hemimorphite in the Upper Mississippi Valley district can be explained by the pH of the ground waters and soils. The stability fields of supergene lead oxide minerals, wulfenite, cerussite, anglesite, and cadmium minerals are calculated in terms of pH, Eh and total sulfur concentration or total carbon dioxide concentration in solution. The para-genesis of the lead minerals and the mobilization of molybdate and cadmium ions are discussed. The results of the spectrochemical analyses indicate that molybdenum and arsenic in the supergene facies were derived from galena, whereas vanadium and phosphorus were derived from the limestones and shales.

The geochemistry of the ores of Franklin, New Jersey

Article

Mar 1952

John Drew Ridge

It is suggested that the ores at Franklin and Sterling are pyrometasomatic deposits formed in the Franklin Limestone, at some distance from the unknown igneous source of the ore-forming fluid. The general classes of skarn minerals developed by contact metamorphism (contact metasomatism in Barrell's sense of the term)--spinels, garnets, pyroxenes, epidotes, micas, olivines, and melilites--all are present in the deposits. These minerals are, however, unique in their high content of Mn (super +2) and Zn (super +2) and their relatively small amounts of Fe (super +2) and Mg (super +2) . The explanation advanced for this peculiar situation is that, in the source magma of the ore-forming fluid involved, an unusual abundance of Mn (super +3) resulted in the oxidation of most of the Fe (super +2) , which normally would have entered the ore fluid in that form, to Fe (super +3) and the concomitant reduction of much Mn (super +3) to Mn (super +2) . This oxidation of ferrous to ferric ion resulted in an uncommonly high acceptance of magnesium ion in the dark silicates of the crystallizing source magma and almost entirely eliminated Mg (super +2) from the ore fluid. The unusual scarcity of ferrous and magnesium ions in the ore fluid forced Zn (super +2) and Mn (super +2) to neutralize in large part those various contact mineral anions which are found in normal contact deposits combined with Fe (super +2) and Mg (super +2) . The lack of Cu (super +2) is thought to have been caused by its proxying for ferrous iron in the minerals of the original source magma and the paucity of Pb (super +2) by the difficulty of the large lead ion in entering and neutralizing any of the variety of anions available.

Stability of minerals in the system ZnO-SiO 2 -H 2 O

Article

Aug 1956

An experimental study of the phase equilibria in the system ZnO-SiOa-H2O has been made at elevated temperatures in the range 130° C to 780° C employing water vapor pressures from 500 to 40,000 pounds per square inch. Stability regions were established for several minerals in this system, which occur naturally in the oxidized zones of lead and zinc deposits. Hemimorphite was found to be stable up to about 250° C at 20,000 psi., while above this temperature, willemite plus water are in equilibrium. With suitable qualifications this temperature may be taken as the maximum temperature of formation and stability of hemimorphite as well as the minimum for willemite. The pure zinc oxide-silica end member of the montmorillonoid-type mineral, sauconite, was found to be stable up to 210° C, although natural sauconite, containing alumina is stable to approximately 125° C higher. Uncertainties still remain in the determination of the Zn(OH) 2ZnO + H2O equilibrium, and for that reason studies of the reaction ZnCOa ZnO + CO2 may prove to be more significant in determining the minimum temperature of zincite formation.

Geochemistry of the Sterling Hill Zinc deposit, Sussex County, New Jersey

Article

Jan 1958

The Sterling Hill ore body is mineralogically similar to its neighbor to the north in Franklin, N. J. It is an intricately folded, steeply plunging body in Precambrian graphitic, sparsely silicated, coarsely crystalline white marble. The marble is graphite-free within 5 feet of ore. The ore is wrapped around a central core of graphitic marble and an annular gneissic cylinder of mica, feldspar, hornblende, pyroxene, and garnet composition. Ore minerals are willemite, franklinite, and zincite. Franklinite, tephroite, pyroxene, and biotite compose the leanly mineralized areas. The mineral distribution is zoned. Black willemite with magnetic franklinite forms a band of varying thickness that follows closely the convolutions of the upper surface of the brown willemite-franklinite body. Ore textures are identical with those of the areas of lean mineralization, and the transition is not sharply defined. A thin band of rhodonite is found at this boundary between pyroxenes and willemite. Paragenetically, it appears that of the ore minerals, willemite formed first in the sequence, with tephroite, zincite, and franklinite following in undetermined order; tephroite and zincite may have been emplaced at the same time. There is abundant evidence of later generations of willemite, franklinite and zincite. Primary zincite has been observed only in the presence of tephroite. There is evidence that tephroite has replaced willemite. Manganese solutions possibly replaced the zinc in willemite to form tephroite and may have resulted in the formation of zincite. The rock core of the ore body is altered to zinciferous clayey mud, locally containing hemimorphite. This alteration extends from the surface to a depth of 680 feet. The variation in willemite color is due to color differences in <10 micron franklinite inclusions. Red franklinite is nonmagnetic with a unit cell dimension of nearly 8.51 Å. Black franklinite is magnetic with a unit cell dimension of about 8.42 Å. Macroscopic franklinite cell dimensions are intermediate. Origin of franklinite inclusions is attributed to willemite serpentinization, similar to that commonly observed in magnetite formation by serpentinization of olivine.

The willemite-hemimorphite relationship

Article

Jun 1960

N. L. Markham

Discusses factors accounting for the preferential development of willemite (rather than hemimorphite) in the oxidized zone of certain sphalerite-bearing ore deposits in South-West Africa in the light of recently published investigations of the stability of minerals in the ZnO-SiO 2 - H 2 O system.

Geology and structure of the Franklin-Sterling area, New Jersey

Article

Jan 1956

The Franklin-Sterling area is located in Sussex County, New Jersey, and Orange County, New York, along the western border of the New Jersey Highlands. A geologic study of the Precambrian rocks of the area which include metasedimentary, igneous, and probable metavolcanic types was undertaken by geologists of The New Jersey Zinc Company. The marble and paragneisses have been divided into stratigraphic units which are, from oldest to youngest, the Hamburgh Mountain gneisses, the Franklin marble band, the Cork Hill gneiss zone, the Wildcat marble band, and the Pochuck Mountain gneiss series. Some of the Precambrian igneous rocks were probably intruded during deformation as sills and phacoliths, whereas the granites and pegmatites were intruded as discordant bodies during or after the last stages of deformation. The Precambrian rocks have been metamorphosed to a high grade but show signs of subsequent hydrothermal metamorphism. The major structures in the area are isoclinal, overturned synclines and anticlines formed during Precambrian time. Two sets of minor cross-folds were superimposed on the major folds. Paleozoic folding is apparent only in the Paleozoic rocks. The most recent fault movements were post-Ordovician but may have been controlled by Precambrian faulting. Two sets of cross-faults are associated with the major faults.

Classification, Genesis, and Exploration Guides for Nonsulfide Zinc Deposits

Abstract

No full-text available

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