No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Abstract
Xiaoxinaneha gold-copper deposit occurred in granodiorite-quartz diorite intrusions of Hercynian epoch. The mineralization of it mainly composed of large quartz vein type and fine quartz veinlet type, with molybdenite-quartz veins superimposed only locally. Fluid inclusion study shows that quartz in both of gold-copper ore veins and in molybdenite-quartz veins contain the same kinds of fluid inclusions, which include NaCl daughter mineral-bearing, gaseous and gas-rich as well as aqueous two-phase fluid inclusions. The similarity of homogenization temperature and salinity of the same kind of fluid inclusions reveals that the geochemical nature of ore-forming solutions of gold-copper and molybdenum mineralization have much in common. Hydrogen-oxygen isotopes of fluid inclusions imply they both came from magmatic fluids. Re-Os isotopic dating of molybdenite shows that molybdenum mineralization happened in ca. 109Ma, whereas 40Ar- 39 Ar isotopic dating of quartz in gold-copper veins reveals that gold-copper mineralization happened in 123. 35 ± 0. 8Ma. Combined with the results of chronological study of magmatic intrusions in the mining area, the conclusion were made that the origin of gold-copper mineralization mainly related with fine grained granodiorite intrusion of late phase of Yanshan, while the origin of molybdenum mineralization mainly related with granite porphyry of late phase of Yanshan, which successively emplaced after fine grained granodiorite intrusion in the mining area.
... Both Au-Cu and Mo mineralization are observed in chlorite alteration (Fig. 3f). Previous studies indicated that fluid inclusion homogenization temperatures in this deposit vary widely (120 to 530 • C; Men et al., 2018;Wang et al., 2010;Zhao et al., 2008). The gas composition is dominated by H 2 O, CO 2 , with some CH 4 , similar to the Baogutu reduced porphyry copper deposit (Cao et al., 2014a(Cao et al., , 2014b. ...
... In addition, the Au-Cu mineralization in this deposit is associated with potassic and chlorite alteration (Fig. 3). Previous studies have constrained the age of trace Mo mineralization to ~110 Ma (molybdenite Re-Os dating; Ren et al., 2011;Wang et al., 2010;Zeng et al., 2016;Fig. 10). ...
The Xiaoxi'nancha Au-Cu porphyry deposit, located in the eastern Jilin Province of Northeast China, is characterized by widespread biotite alteration, however, the age of Au-Cu mineralization is not well established. Hydrothermal biotite Ar/Ar dating and chemical composition are widely used to constrain the age and physico-chemical characteristics of hydrothermal fluids. In this paper, microscopy observation, electron microprobe analysis, and ⁴⁰Ar/³⁹Ar dating of hydrothermal biotite from the Xiaoxi'nancha porphyry Au-Cu deposit and zircon U-Pb dating on the ore-bearing granitoids have been carried out to constrain fluid characteristics and the age of mineralization. The zircon crystals from the ore-bearing granitoids display obvious inherited cores and oscillatory rims. A range of ²⁰⁶Pb/²³⁸U age populations were obtained on the cores (e.g., ∼967 Ma, ∼782 Ma, ∼495 Ma, ∼430 Ma, ∼385 Ma, ∼354 Ma, ∼311 Ma) but a young population with a uniform concordia age of 254.4 Ma was determined on the rims. These features indicate the occurrence of xenocrystic zircon in the ore-bearing granitoids, and imply that these rocks were probably derived from partial melting of continental crust with significant crustal contamination. Au-Cu and Mo mineralization are found together and associated with potassic and chlorite alteration. The ⁴⁰Ar/³⁹Ar age of hydrothermal biotite (∼110 Ma) is younger than the zircon U-Pb age (∼255 Ma), but similar to the previously published molybdenite Re-Os age (∼110 Ma). Thus, Au-Cu mineralization is coeval with Mo mineralization and formed at ∼110 Ma, and has no genetic relationship with ore-bearing granitoids. The calculated log(fH2O/fHF) and log(fH2O/fHCl) ratios of hydrothermal fluids are similar to those determined at other major porphyry deposits. However, the log(fHF/fHCl) ratio is lower than that of other porphyry deposits, indicating a relatively Cl-rich hydrothermal system at Xiaoxi'nancha. The Xiaoxi'nancha porphyry Au-Cu deposit is associated with early Cretaceous granitoids, generated during subduction of the Paleo-Pacific Ocean.
... The N isotopic system may potentially provide a detailed record of fluid-rock interaction characteristics and other mixing processes in the crust and mantle 37 . N 2 has been shown to be released during metamorphism and the breakdown of NH 4 + -bearing minerals, such as biotite, cordierite, and white mica 43 . During metamorphism, isotopically "light" N is preferentially fractionated into metamorphic fluids 39,[44][45][46] , and the δ 15 N values of fluid inclusions in quartz veins in low-grade metamorphic rocks yield values ranging from −3 to 5‰ 31 . ...
... Simultaneously (~249 Ma), the circulation of a magmatic-hydrothermal W-mineralizing fluid under high oxygen fugacity conditions transferred heat (~400 °C) to the surrounding metamorphic rock and broke down micas in the host rock 37,51 . Within an oxidizing environment at this temperature range, large amounts of N 2 were released from the NH 4 + -bearing host rocks and stabilized into fluid 43 . The addition of sufficient amounts of N 2 to the mineralizing fluid increased activity coefficients and catalysed the saturation of Ca 2+ and WO 4 2-, greatly decreasing the scheelite solubility and accelerating scheelite precipitation. ...
Nearly pure N2fluid inclusions (Th(L) = -151~-168 °C; Th(V) = ~150.3 °C) were identified in W-mineralized quartz veins from the Yangjingou scheelite deposit, in the eastern Yanbian area, NE China. Other fluid inclusion populations include N2-CO2, NaCl-H2O ± N2and CO2 ± N2-NaCl-H2O, but no hydrocarbons were detected. The host rocks are part of the Wudaogou Group metamorphic series, which mainly consist of Ca-rich mica schist. Subhedral sulfide minerals occur in early disseminated W-mineralized quartz veins, or have partially replaced early scheelite. ThN2and ThN2-H2Oindicate N2fluid-trapping from 315 °C to 410 °C and from 80 MPa to 350 MPa. Oxygen and hydrogen isotopic data (δD = -74.9‰~-77‰, δ18O = 9.6‰~12‰, V-SMOW) suggest that the mineralizing fluids were composed of mixed magmatic and metamorphic water, N2-rich inclusions (δ15N = -0.5‰ to 1.4‰) indicate fluid-rock interaction with metamorphic rocks. The N2-rich fluid was closely associated with scheelite precipitation. During thermal decomposition under high oxygen fugacity conditions, which occurred synchronously with metamorphism and magmatic activity, large amounts of N2were liberated from NH4+-micas, which then accumulated in the parent fluid of the quartz scheelite veins.
... Previous studies show that the intrusions can be divided into three stages (Sun et al., 2008a(Sun et al., , b, 2009Li et al., 2012): the Late Permian quartz diorite (273 Ma, U-Pb age), the Late Triassic granodiorite (205 Ma, U-Pb age) and the Cretaceous granitoids (112-105 Ma, U-Pb age) and dykes (112-102 Ma, U-Pb age). The ore-forming fluid inclusions, H-O isotopic features have also been well performed (Li and Chen, 1995;Zhao et al., 2005Zhao et al., , 2008Sun et al., 2007Sun et al., , 2009Wang et al., 2010). The orebodies are thought to be controlled by the NNW-and S-N-trending faults (Wu, 1986;Liu and Wang, 1987;Li and Chen, 1995;Shi, 1998;Liu et al., 2003Liu et al., , 2006Sun et al., 2009;Cui et al., 2011). ...
... Fluid inclusion study of the quartzes of the stockwork Au-Cu ores from the North Ore Segment shows that fluid inclusions include NaCl daughter mineral-bearing (A-type), gaseous and gas-rich as well as aqueous two-phase fluid inclusions (B-type) (Li and Chen, 1995;Wang et al., 2010). The homogenization temperature and salinity of fluid inclusions (A and B types) from the hydrothermal quartzes of the North Ore Segment change from 242 to 396°C and 27.9 to 56 wt% NaCl eqv. ...
The Xiaoxinancha Au–Cu deposit is located at the eastern segment of the Tianshan–Xingmeng orogenic belt in northeast China. The deposit includes porphyry Au–Cu orebodies, veined Au–Cu orebodies and veined Mo mineralizations. All of them occur within the diorite intrusion. The Late Permian diorite, Late Triassic granodiorite, Early Cretaceous granite and granite porphyry are developed in the ore area. The studies on geological features show that the porphyry Au–Cu mineralization is related to the Late Permian diorite intrusion. New geochronologic data for the Xiaoxinancha porphyry Au–Cu deposit yield Permian crystallization zircon U–Pb age of 257 ± 3 Ma for the diorite that hosts the Au–Cu mineralization. Six molybdenite samples from quartz + molybdenite veins imposed on the porphyry Au–Cu orebodies yield an isochron age of 110.3 ± 1.5 Ma. The ages of the molybdenites coeval to zircon ages of the granite within the errors suggest that the Mo mineralization was genetically related to the Early Cretaceous granite intrusion. The formation of the diorite and the related Au–Cu mineralization were caused by the partial melting of the subduction slab during the Late Palaeozoic palaeo-Asia Ocean tectonic stage. The Re contents and Re–Os isotopic data indicate that the crustal resource is dominated for the Mo mineralization during the Cretaceous extensional setting caused by the roll-back of the palaeo-Pacific plate. Copyright © 2014 John Wiley & Sons, Ltd.
... The Early Cretaceous magmatism, in particular, is space-time related to the regional porphyry-epithermal Au-(Ag) mineralization (ca. 128-97 Ma, Fig. 1c; Han et al., 2013;Zeng et al., 2016;Jia et al., 2012;Huang et al., 2011;Chai et al., 2012;Sun et al., 2008Sun et al., , 2013aJia et al., 2008;Zhao, 2013;Wang et al., 2010). ...
Whether multiple mineralization styles in porphyry deposits are the result of one or multiple pulses of magmatism is unknown. In this paper, we present new age and geochemical data on the Jinchang porphyry gold-copper (Au-Cu) deposit, an important deposit in NE China and in the eastern Central Asian Orogenic Belt (CAOB). Field geological study suggests that both the mineralization and ore-causative magmatism at Jinchang are multiphase. LA-ICP-MS zircon U-Pb dating of the monzogranite ore host yielded 197 ± 1 Ma, which is considerably older than the ore-causative monzonite (115 ± 3 Ma) and granodiorite (107 ± 2 Ma). Molybdenite Re–Os dating on the breccia pipe-hosted Au-Cu ores yielded a well-defined isochron age of 114 ± 3 Ma, coeval to the monzonite emplacement. The Au-Cu mineralization was followed by another phase of crypto-explosive breccia pipe-hosted, disseminated/vein-type Au mineralization. This Au-only mineralization phase was auriferous pyrite Re–Os dated to be 103–101 Ma, coeval to the granodiorite emplacement. Geochemically, the monzonite and granodiorite are enriched in LILEs and LREEs, but depleted in HFSEs and HREEs. The ore-causative rocks are I-type and display continental arc geochemical affinities. We suggest that the monzonite and granodiorite were generated in an intracontinental extensional setting, probably caused by the Early Cretaceous subduction roll-back of the Paleo-Pacific Plate.
... These data lead us to argue that the epithermal gold deposits in the Lesser Xing'an Range and Zhangguangcai Range formed mainly between 124 and 107 Ma (Table 1; Figure 11). The mineralization ages of the epithermal gold deposits in the Zhangguangcai Range are also similar to the porphyry or porphyry-hydrothermal vein Cu-Au deposit at Xiaoxinancha and Nongping in the Zhangguangcai Range (Han, Sun, Bai, et al., 2013;Ouyang et al., 2013;Ren et al., 2015;Shu et al., 2016;Wang et al., 2010;Zeng, Guo, Zhou, & Duan, 2016) which Xiaoxinancha Cu-Au deposit has Molybdenite Re-Os age of (Ren, Wang, Qu, Zhao, & Chu, 2011). Recently, Shu et al. (2016) argued that the Cretaceous porphyry Mo and Cu mineralization and associated magmatism define a southeastward-younging trend, ...
The newly discovered Yongxin Au deposit in the Lesser Xing'an Range of north‐eastern Heilongjiang Province, NE China, has a resource of ~20 t with a grade of 4.1 g/t Au. The deposit is hosted by Carboniferous syenogranite and mylonite, and Cretaceous diorite porphyry and granite porphyry. The syenogranite has a LA‐ICP‐MS ²⁰⁶Pb/²³⁸U zircon age of 316 ± 2 Ma, and both the granite porphyry and diorite porphyry yield an age of 119 ± 1 Ma. The Rb–Sr isochron age of Au‐bearing pyrite from hydrothermal breccia‐type ore is 107 ± 4 Ma, and this is interpreted as the mineralization age of the Yongxin deposit. In combination with published geochronological data, we argue that epithermal Au mineralization in NE China formed during the period ca. 124 to 107 Ma and was produced during rollback of Palaeo‐Pacific oceanic slab. The Cretaceous epithermal Au deposits are distributed in the Erguna Massif, Lesser Xing'an Range, Zhangguangcai Range, and Jiamusi and Nadanhada terranes. In combination with the coeval porphyry Mo deposits present in these areas, we propose that the Erguna Massif, Lesser Xing'an Range, north‐eastern Great Xing'an Range, and eastern Jiamusi and Nadanhada terranes, where only epithermal gold deposits were discovered up to date, might be prospective for concealed porphyry Cu or Mo deposits.
... Tonalite (the shaded areas) associated with mineralization in the Xiaoxinancha deposit is quoted from Li et al. (2012 Ar/ 39 Ar isochron age of 107 ± 6 Ma, with three hydrothermal zircons from a pyrite-phyllic altered porphyritic granodiorite yielding a hydrothermal U-Pb age of 106.8 ± 1.2 Ma, indicating that the Duhuangling gold deposit formed between 108 and 106 Ma, after the emplacement of the porphyritic granodiorite. In addition, a hornblende-granodiorite outside of the ore district yielded a zircon U-Pb age of 111.7 ± 2.8 Ma ( Sun et al. 2008a), molybdenite from the Xiaoxinancha gold-rich porphyry copper deposit yielded a Re-Os isochron age of 111.1 ± 3.1 Ma ( Ren et al. 2011) and a Re-Os model age of 109.4 ± 1.7 Ma ( Wang et al. 2010a), and mineralizationrelated tonalites within the Xiaoxinancha deposit formed at 112 ± 1 Ma ( Li et al. 2012). Chai et al. (2012) determined that the Jiusangou high-sulphidation epithermal gold deposit, some 2 km NW of the Duhuangling gold deposit (Figure 2) was emplaced at 105.8 ± 1.8 Ma, with eight hydrothermal zircons in an adakite-like/adakitic pyrite-phyllic altered quartz diorite yielding an age of 109.3 ± 2.1 Ma. ...
Yanbian area (Northeast China) is part of the Western Pacific porphyry-epithermal gold-copper metallogenic belt. Here, we present the results of a detailed study of Early Cretaceous mineralization-associated magmatic events in this region and, based on the results, identify the geological setting and mineralizing processes involved in mineral deposit formation. We focus on the timing and geodynamic mechanisms of hydrothermal alteration and metallogenesis of the Duhuangling high-sulphidation epithermal gold deposit, located ~15 km NW of the large Xiaoxinancha gold-rich porphyry copper deposit. New data are presented for zircon U-Pb, fluid inclusion Ar-Ar, whole-rock geochemical, and in situ zircon Hf isotopes for igneous rocks of the Duhuangling deposit, and the data - integrated with results of previous research - reveal that Yanbian area epithermal and porphyry Cu-Au deposits are associated with two stages of Early Cretaceous intermediate-felsic magmatism (116-118 and 112-109 Ma), with the later stage of magmatism more closely associated with mineral deposit formation. Our new data constrain the timing of formation of high-sulphidation epithermal gold deposits to 108-106 Ma and the timing of formation of gold-rich porphyry copper deposits to 111-109 Ma. The two stages of magmatism are associated with magmas derived from different sources, with the first-stage magmas potentially derived from partial melting of a depleted mantle wedge that had been metasomatized by subducted slab-derived fluids or melts; these first magmas are also mixed with material derived from the underplated lower crust. Second-stage magmas were probably generated by partial melting of subducting oceanic slab and some oceanic sediments and the interaction of these magmas with melts derived from the overlying lower crust. Most mineralization in the study area is associated with Cu- and Au-rich post-magmatic hydrothermal fluids that were generated during fractionation of hydrous, sulphur-rich, and high oxygen fugacity adakite-like/adakitic mixed magmas. The formation of both igneous rocks and mineral deposits in the study area occurred in a tectonic setting dominated by Late-Early Cretaceous subduction of the Izanagi or Pacific Plate beneath eastern Asia, indicating that the formation of epithermal and porphyry Cu-Au deposits in the Yanbian area involved subduction-derived fluids, melt modification, partial melting, magma mixing, and crystal fractionation.
A wide variety of deposit types formed in the late Palaeozoic-Mesozoic of eastern NE China and adjacent Russian Far East of the eastern Central Asian Orogenic Belt (CAOB). However, outstanding questions remain on the (1) number of magmatic and metallogenic phases, and their respective space–time distribution; (2) geochemical (incl. isotopic) signature and fertility of each magmatic phase; and (3) tectonic link with these magmato-metallogenic events. We present new data (zircon U-Pb dating, geochemistry, and Sr-Nd isotopes) on the Yangjingou W and Xiaoxi’nancha Au-Cu deposits, and compile published data from major ore deposits in the region. We have newly summarized four magmato-mineralization phases: (1) Middle Permian (ca. 273–259 Ma) Cu-Au-Pb-Zn, (2) Latest Permian-Early Triassic (ca. 253–247 Ma) W-Cu-Mo-Au, (3) Earliest-Middle Jurassic (ca. 201–162 Ma) Mo-Au-Fe-W-Pb-Zn, and (4) Cretaceous (ca. 129–83 Ma) W-Sn-Mo-Cu-Au mineralization. Cretaceous ore-causative granitoids are mainly I-type arc-related, whereas those for the three older mineralization phases are largely adakite-like or adakite-normal arc transitional. These granitoids were mostly derived from partial melting of juvenile crust, and to a lesser extent from a mixture of juvenile and ancient crust. We propose that the Middle Permian subduction of the Paleo-Asian and Panthalassa oceans formed the Au/Cu-Pb-Zn skarn and cryptoexplosive breccia-hosted Pb-Zn ± Ag deposits. Subsequently, the latest Permian-Early Triassic Paleo-Asian Ocean closure likely formed the porphyry-skarn Cu-Mo, orogenic Au, and vein-type W deposits in the Songliao and eastern Liaoyuan terranes. In the Early-Middle Jurassic, Paleo-Pacific subduction may have formed the Jiapigou orogenic Au belt and the Fe-polymetallic skarn deposits in the northern Songliao terrane, as well as porphyry Mo deposits along the Mudanjiang fault. Subsequently, Cretaceous W-Sn-Au-Cu metallogeny was controlled by Paleo-Pacific subduction rollback, and in the Russia Far East by partial melting of redox accretionary complexes.
Introduction
The Lakehsiah mining district is hosted in Early Cambrian volcano-sedimentary units (CVSU) of the Kashmar–Kerman zone, Central Iran. The Kashmar-Kerman belt is located between the Yazd block in the west and the Tabas block in the east and it is parallel to the Poshed badam, Tabas and Kalmard faults in the north and Koh Banan and Zarand faults in the south of the area (Ramezani and Tucker, 2003). Compositions of the volcanogenic rocks in this area vary from felsic to mafic and include rhyolitic, rhyodacitic tuff and spilitic lava and diabase. The sedimentary rocks include dolomites, dolomitic limestones and evaporites. Lakehsiah 1 deposit is one of three IOA outcrops in the Lakehsiah district which have been studied in this research.
Materials and Methods
The mineralogical study of alteration zones was carried out by light microscope with transmission light and X-ray diffraction (XRD) analysis, at the Mineralogical Laboratory of Bu-Ali Sina University and Iran Minerals Processing Research Center, respectively. Fluid inclusion and Raman spectroscopy studies were also performed to determine temperature, composition and evolution of the ore-forming fluid at the Institute of Earth Sciences SAS, Slovakia. Stable isotope geochemistry of quartz (O-H) was performed at the Cornell University, USA.
Discussion
Iron deposits hosted in the Tashk Group show hydrothermal alteration. The major minerals of the Sodic-Calcic alteration are the crystals of calcic amphiboles (tremolite-actinolite), pyroxene, calcite, magnetite and apatite. Propylitic alteration (chloritization and epidotization) is very widespread and affects volcanic and intrusive rocks. It consists of chlorite, epidote, calcite, and magnetite with minor amounts of sericite. Silicification alteration, occurs as distal alteration in both hanging wall and footwall host rocks, forming fine-grained to coarse grained quartz aggregates, veins and veinlets. Sericitic-argillic alteration occurs mainly in intrusions. Feldspar (plagioclase and K-feldspar) was altered to sericite and clay minerals. Minor quartz occurs as veinlets in this alteration zone. Na- Ca alteration in volcanic and intrusion rocks is exposed in the center of the area. Amphiboles mainly occur as replacements of plagioclase. Plagioclases were altered to chlorite, epidote, and calcite. Additionally, veinlets of quartz-epidote-chlorite, chlorite-epidote, epidote-quartz, quartz-calcite, calcite, chlorite-calcite, and epidote-calcite are observed. Quartz and carbonates (calcite) are widespread and veins of these minerals crosscut all the rocks described above.
Lakehsiah 1 deposit, hosted within high-silica rhyolitic tuffs and domes, forms a steeply dipping tabular lens and it includes massive magnetite ± apatite ± quartz ± specular hematite ± Fe-Mg silicates.
Fluid inclusion Petrography
Four major types of fluid inclusions are observed based on proportions of vapor, liquid, and solid phases present at room temperature in quartz mineral. They are described as follows:
1-liquid-rich inclusions (L)
2-vapor-rich inclusions (V)
3-Two-phase liquid rich fluid inclusions (L+V)
4-three phase inclusions with halite solid phase as daughter mineral (L+V+H). Study of inclusions petrography shows that most of the inclusions present within this mineral are primary in origin, although secondary or pseudosecondary types have been identified. They have different sizes (typically 5–15 μm). Fluid inclusion shapes are rounded, elliptical, irregular, negative crystal shapes and square.
Results
Microthermometry and Raman spectroscopy
Freezing and heating experiments were performed on Types 3 and 4 fluid inclusions. Stretching of inclusions was noted during heating of large fluid inclusions in quartz from mineralized quartz veins. In such samples, homogenization temperatures range from 217–428 °C for type 3 and 384-467°C for type 4.
Micro-thermometric data were obtained from both Types 3 and 4 inclusions. The data obtained revealed variation in salinity of the trapped fluids. The final ice melting temperature in Types 3 and 4 inclusions varies from −4° to -18 and -9 to -19 °C with a mode at around -12 °C. Final ice-melting temperatures are lowest in the mineralized quartz veins. The first melting temperatures in multiphase Types 3–4 inclusions are also in a similar range which varies from -21 to -34°C. Based on their final ice melting temperatures, it varies between 10 to 27 and 40 to 44 wt. % NaCl equivalent for type 3 and 4 inclusions. T°C vs. salinity plots of inclusions show mixing of magmatic hot fluids with cold meteoric waters. Raman spectroscopy revealed presence of 69 mol % N2 and 31 mol % CO2 and 33 mol % N2 and 67 mol % CO2 in types 3 and 4 inclusions. These gases can be derived from mantle degassing (Wang et al., 2018) and chemical
reactions during ascent of fluids.
H-O isotopes
Isotopic studies are among the most common methods for identifying the primary composition of ore-forming fluids in deposits (Barati and Gholipoor, 2014). In the study area, five quartz samples in quartz grains and veins were used for H-O isotope analyses, with the aim of determining the source(s) of ore-forming fluids. The δDH2O and δ18OH2O values of the ore-forming fluids in quartz samples vary from -60‰ to -80‰, and -4.71‰ to -1.42‰, respectively. The above observations reveal that the early ore-forming fluids are magmatic in origin and is characterized by high temperature and moderate to high salinity, and gradually evolve to low temperature, low salinity meteoric water. The Lakehsiah 1 Fe deposit is associated with the magmatism induced by the protracted subduction. The decrease in temperature, salinity and f(O2), as well as fluid-rock interactions, are the main factors controlling Fe deposition.
References
Barati, M. and Gholipoor, M., 2014. Study of REE behaviors, fluid inclusions, and O, S stable Isotopes in Zafar-abad iron skarn deposit, NW Divandarreh, Kordestan province. Journal of Economic Geology, 6(2): 235–275. (in Persian with English abstract) https://doi.org/10.22067/ECONG.V6I2.20257
Ramezani, J. and Tucker, R.D., 2003. The Saghand region, central Iran: U-Pb geochronology, petrogenesis and implications for Gondwana tectonics. American Journal of Science, 303(7): 622–665. https://doi.org/10.2475/ajs.303.7.622
Wang, Y., Wang, K. and Konare, Y., 2018. N2-rich fluid in the vein-type Yangjingou scheelite deposit, Yanbian, NE China. Scientific Reports, 8(1): 5662. https://doi.org/10.1038/s41598-018-22227-7
The Hongtaiping Cu–Pb–Zn deposit is located in the central part of the Yanbian–Dongning region, NE China, which is the eastern segment of the Central Asian Orogenic Belt. The Cu–Pb–Zn mineralization occurs in the contact zone of the Lower Permian Miaoling and Kedao formations with tuff lavas, tuffs, and marlstones as the principal host rocks. The orebodies are distributed in stratiform, stratiform‐like and lenticular morphologies, consistent with the host strata. Field investigations indicate three ore facies consisting of stringer–stockwork, massive, and laminated ores in the Hongtaiping deposit, which show apparent variation spatially from bottom to top of sulphide types. A lot of liquid‐rich fluid inclusions were identified in mineral crystals from the three types of ore facies with complete homogenization temperatures varying from 162 to 249°C and salinities in the range of 3.3 to 9.6 wt% NaCl equiv. The δD and values of calcite samples from the stringer or stockwork ores range from −82.0 to −75.1‰ and 3.3 to 3.7‰, respectively, lower than those (δD values of −64.1 to −38.8‰, values of −0.9 to 2.2‰) of the massive and laminated ores. In addition, the calcite samples show restricted δ13C values from −6.8 to −4.0‰. These fluid inclusions and H–O–C isotope geochemistry suggest that ore‐forming fluids of the Hongtaiping deposit were mainly sourced from heated seawater or brine derived, with the carbon from marine carbonates by water–rock interaction. The δ34S values of sulphide separates from the stringer–stockwork, massive and laminated ores range from −15.2 to −9.2‰ with an average value of −12.3‰. The sulphide minerals yield 206Pb/204Pb ratios from 18.025 to 19.758, 207Pb/204Pb ratios from 15.601 to 15.795, and 208Pb/204Pb ratios from 37.202 to 39.305. These S and Pb isotope compositions indicate that the sulphur had an origin in seawater sulphates from which sulphur was most possibly transformed into sulphide by thermochemical reduction, while the lead in ores originated mainly from the Miaoling Formation, with small amounts directly derived from the subvolcanic intrusion. Taken together, the Hongtaiping deposit can be classified as a volcanogenic massive sulphide (VMS) deposit, for which the possible mineralization process is interpreted in terms of a long‐lived convective circulation of mobile heated seawater mixed with some magmatic fluids along submarine faults and fissures during the Early Permian. The metals were migrated and subsequently enriched in the hydrothermal circulation system by being leached from the underlying volcanic rocks, with the metal‐rich ore‐forming fluids combined with contributions of water–rock reaction, thermochemical sulphate reduction and temperature change leading to the precipitation of polymetallic sulphides.
The Chiweigou gold deposit is located in the eastern Jilin and Heilongjiang provinces at the junction of the Paleo-Asian Ocean and Circum-Pacific metallogenic domains, where was affected by the events that marked the transition between these two domains. The gold orebodies in the Chiweigou deposit are hosted in three calcite veins controlled by compressional-shearing faults, which cut across Early Cretaceous intermediate–acidic volcaniclastic rocks. The Au-bearing calcite veins have low metal sulfide contents (<1%), and the main ore deposits display disseminated, brecciated, comb, and miarolitic structures. The minerals vary from euhedral to anhedral. In addition to the main carriers of the Au and Ag are native gold, calaverite, hessite, and aurotellurite, and the gold-carrying minerals coexist closely with other common minerals in the carbonatite veins such as calcite, quartz, apatite, and magnetite, implying genetic relationships among them. The main type of wall-rock alteration is carbonatization, and alkali metasomatism, including fenitization, is widespread. The SiO2 contents of the Au-bearing calcite veins show very large variations (0.87–53.9 wt%), and the veins have high contents of CaO (24.4–54.9 wt%) and low contents of MgO (0.06–0.13 wt%) and (Na2O + K2O) (0.10–0.39 wt%). The main oxide contents show good linear relationships with SiO2 on Harker diagrams, and this indicates that differentiation took place between the siliceous and carbonate components during the formation of the calcite veins. The LREE contents of the calcite veins are higher than the HREE contents (LREE/HREE ratios range from 10.7 to 15.8), and the normalized distribution patterns slope towards the HREE end. Eu and Ce show positive anomalies. The calcite veins are enriched in incompatible elements (Rb, Sr, Hf, and Ta) and depleted in K. The trace element ratios of the samples plot in the CHARAC field, indicating an igneous origin. In the εNd(t) vs. (⁸⁷Sr/⁸⁶Sr)i diagram the Chiweigou carbonatite plots close to Mesozoic carbonatites from the adjacent NCC, and the evolutionary trend is from primary mantle to an enriched mantle I-type. Based on our analytical results, and taking into account previous research, we conclude that the Chiweigou calcite veins are carbonatites, that were derived from an end-member EMI-type mantle source that had been metasomatized by highly differentiated C–H–O supercritical fluids. The Au was probably dispersed by and precipitated from colloidal Au–Si complexes (AuH3SiO4). The geochemical characteristics of the contemporary andesitic tuffs and diorite porphyrite indicate that the formation of the Chiweigou Au-bearing calcite veins resulted from extensional tectonics related to Early Cretaceous subduction of the Pacific Plate. During the early stages of intense extension (140 Ma), the carbonatite magmas ascended rapidly along extensional faults, and when they arrived in the shallow crust they mixed with meteoric water to produce the alkali metasomatism (fenitization) and the precipitation of Au as temperatures and pressures fell, thus forming the Au-bearing calcite veins and related mineralization of the Chiweigou deposit.
Numberous endogenetic gold deposits are found in the epicontinental region in Northeast China, and they have attracted more attention and research efforts from both domestic and international economic geologists. These deposits are featured by the characteristic of complex and obviously multistage mineralization. Based on systematic study on geological features and metallogenic epoch of these endogenetic gold deposits in the area, the present paper has divided the gold deposits into four main types: mesothermal, contact-metamorphic, porphyry gold-copper and epithermal gold deposits. They were formed in three important ore-forming epochs at 170-160 Ma, 130-110 Ma and 110-90 Ma. Based on isotope geochemistry, we concluded that that the metallogenic material of the mesothermal gold deposit was derived from the lower crustal source and its mineralization was closely related to lithospheric thinning and delamination of the continental margin, a processes triggered by the subduction of the Paleo-Pacific plate in the Early Mesozoic Yanshanian orogeny. The metallogenic material of the contact-metamorphic gold deposit was derived from the younger crust and the mineralization was relevant to contact metasomatism of magmatic process under extensional setting of the lithospheric thinning and delamination, which caused by the subduction of Paleo-Pacific plate. However, metallogenic material of porphyry gold-copper deposit and epithermal gold deposit manifested as crust-mantle mixture. Their mineralization occurred in the tectonic transition period from Asian continent subducted by the Paleo-Pacific plate towards the due north to the Izanagi-Farallon plate subduction toward west.
Jinchang gold deposit is a superlarge one with three different kinds of mineralization, which are cryptoexplosive breccia pipe type, bedded micro-fine vein disseminated type as well as fault-controlled quartz-vein and altered rock type respectively. This paper carried out a comparative study on fluid inclusions occurred in quartz of the three-type ores from petrography, microthermometry, compositional and hydrogen-oxygen isotope analyses as well as SEM/EDS analysis of daughter minerals etc. aspects, the results show that the ore-forming fluids of the three-type mineralization posed different geochemical features. The ore-forming fluids of the cryptoexplosive pipe type mineralization belong to magmatic-hydrothermal transitional fluids: that of the micro-fine vein disseminated type mineralization belong to highly saline solutions with a complex composition: whereas the ore-forming fluids of the fault-controlled quartz-vein and altered rock type mineralization belong to highly saline NaCl-H 2O solutions. The composition of hydrogen-oxygen isotopes of fluid inclusions reveal that they all came from magmatic activities. Combined with the occurrences of ore bodies and geochronological data existed, the conclusion was made that the metallogenic evolution sequence in the mining district is cryptoexplosive breccia pipe type→ bedded micro-fine vein disseminated type→ fault-controlled quartz-vein and altered rock type and Jinchang gold deposit is the result of superimposition of mimeralization of magmatic fluids at different phases.
Daheishan molybdenum deposit is a superlarge porphyry type deposit that occurred in granodiorite-granodiorite porphyry complex of Early Yanshanian Period. Based on mineral assemblages, the mineralization can be classified into four stages, which are I disseminated pvrite ± molybdenite-quartz, II molvbdenite-quartz. III pyrite ± chalcopyrite-quartz and IV sulfide-poor quartz respectively. Fluid inclusion study showed that there are halite-bearing three-phase, vapor-rich as well as aqueous two-phase three types of fluid inclusions developed in quartz of mineralization stage I and II , the ore-forming fluids are of medium to high temperature, high salinity NaCl-H 20 type hvdrothermal solutions correspondingly and mainly came from ore-bearing granodiorite porphyry. Only aqueous two-phase type of fluid inclusions were observed in quartz of mineralization stage III and IV , which corresponds to low to medium temperature, low salinity NaCl-H2O type hvdrothermal solutions and mainly derived from ore-bearing granodiorite porphyry and meteoric water. The geochemical features of ore-forming fluids of Daheishan molybdenum deposit is very different from the NaCl-CO2 - H 2O type ore-forming fluids of the inner continental porphyry type molybdenum deposit, which implies that Daheishan molybdenum deposit was not formed in inner continental environment, but in active continental margin or arc environment instead.
Hongling lead-zinc deposit is one of the representative large deposits in southeastern Inner Mongolia. Presently, there's very little research on geochemical characteristics and evolution of ore-form fluids, and ore genesis. The fluid inclusions are systemly researched in this paper, The results show that there are three types of primary fluid inclusions in garnet of garnet-skarn stage (I) including halite-bearing three-phase, aqueous two-phase as well as vapor-rich two-phase; there are two types of primary fluid inclusions in quartz of stage (II) including aqueous two-phase as well as vapor-rich two-phase. It is found in our microthermometric study that the ore-forming fluid is of high temperature, high salinity and immiscible NaCl-H2O type solutions and the boiling process plays important role in the precipitation of Pb, Zn, and Cu. Quartz of mineralization stage III to IV of quartz-sulfide epochs contains only aqueous two-phase of fluid inclusions. The homogenization temperature of this type of fluid inclusions is obviously lower than that of skarn epoch, while the salinity does not obviously change. The homogenization temperatures of fluid inclusions show a rising trend with salinities displaying a dropping trend of stage IV, and it may be caused by adding of high temperature, low salinity type fluid. The dropping of homogenization temperatures and salinities of ore-forming fluids from mineralization stages V to VI suggests that meteoric water continuously joining into the ore-forming fluid. Overall, the ore-forming fluids of quartz-sulfide epoch is of medium-low temperature and low salinity NaCl-H2O type solutions. C, H, O isotope study of fluid inclusions shows that the ore-forming fluids of skarn epoch mainly came from magmatic water and that of quartz-sulfide epoch came from mixed magmatic water and meteoric water, whereas at the latest stage of mineralization, the ore-forming fluids mainly came from meteoric water. The study of S, Pb isotopes implies that the ore-forming materials posed a deep source feature.
To obtain the exact metallogenic age of Xiaoxi nancha copper gold deposit, the quartz-molybdenite vein newly discovered in the Beishan ore block is studied and dated by Re-Os isotopic dating of molybdenite. The quartz molybdenite vein is parallel to adjacent lode copper gold ore bodies, which indicates that both are controlled by the common structure system. The dominant metal minerals in molybdenum ore is molybdenite which is occasionally cut by later pyrite and chalcopyrite. Due to the intergrowth of different metal minerals, the lode molybdenum mineralization in Xiaoxi nancha deposit is clearly earlier than major copper gold metallogenic stage. Accordingly, it can be concluded that the lode molybdenum mineralization belongs to early metallogenic stage of copper gold mineralization. Six samples of molybdenite for Re-Os isotopic dating are analyzed. The model ages vary from 109.2±3.4 Ma to 110.8±4.0 Ma, average 109.9±3.9 Ma, and a good isochron age of 111.1±3.1 Ma. These results are consistent with new isotopic dating of granitic intrusions related to copper gold mineralization in this deposit. It indicates that the large copper gold mineralization took place in late Yanshanian periods and both the granites and copper gold mineralization were generated under extensive active continental margin resulted from the obliquely subduction of Pacific Ocean slab. Moreover, petrological & geochemical characters, isotopic dating of ore forming intrusions as well as low content of Re in molybdenite demonstrate that granitic intrusions and copper gold mineralization were derived from deep source, mainly upper mantle.
a b s t r a c t North-eastern China and surrounding regions host some of the best examples of Phanerozoic juvenile crust on the globe. However, the Mesozoic tectonic setting and geodynamic processes in this region remain debated. Here we attempt a systematic analysis of the spatio-temporal distribution patterns of ore deposits in NE China and surrounding regions to constrain the geodynamic milieu. From an evalua-tion of the available geochronological data, we identify five distinct stages of ore formation: magmatism and associated mineralisation occurred during in a post-collisional tectonic setting involving the closure of the Paleo-Asian Ocean. The Early-Mid Jurassic (190–165 Ma) events are related to the subduction of the Paleo-Pacific Ocean in the eastern Asian continental margin, whereas in the Erguna block, these are associated with the subduction of the Mongol–Okhotsk Ocean. From 155 to 120 Ma, large-scale con-tinental extension occurred in NE China and surrounding regions. However, the Late Jurassic magmatism and mineralisation events in these areas evolved in a post-orogenic extensional environment of the Mon-gol–Okhotsk Ocean subduction system. The early stage of the Early Cretaceous events occurred under the combined effects of the closure of the Mongol–Okhotsk Ocean and the subduction of the Paleo-Pacific Ocean. The widespread extension ceased during the late phase of Early Cretaceous (115–100 Ma), follow-ing the rapid tectonic changes resulting from the Paleo-Pacific Oceanic plate reconfiguration.
Zircon SHRIMP and LA-ICP-MS U-Pb dating was performed on diabase gabbro of premineralization stage and dioritic porphyrite dykes of mineralization stage, collected from the Xiaoxinancha Au- and Cu-rich deposit, both of which have closely relation in spatial distribution. The results show that five sets of concordant ages for 16 zircon grains or spots from diabase-gabbro are obtained, i. e. 387.0±11.8Ma, 292. 0-251.1Ma (Mean=270 ±14Ma, n=10), 129.8±2.6 Ma, 107.0-95.6Ma (Mean= 103±13Ma,n=3) and 46.8±2.6Ma; whereas one set of concordant ages ranging from 108-98Ma (Mean=102.1±2.2Ma,) for 11 zircon grains and 12 spots from diorite porphyrite are obtained. Combined with the features of CL images, it was suggested that the premineralization diabase-gabbro was formed in the late Early Permian epoch and trapped some detrital zircons during magma ascending (intruding) and subsequently experienced thermal modifications in the early Cretaceous and middle Eocene time. Diorite porphyrite was formed in the late Early Cretaceous. Considering the match of the age of diorite porphyrite with age 107.0-95.4Ma of the diabase gabbro, the ages of hydrothermal zircons from the diabase gabbro range between 103-95. 4Ma, which further indicates that thermal event of the gold-copper mineralization took place in 108-98Ma and the mineralization occurred during the late stage of middle/late Mesozoic when the crust experienced intensive extension and thinning. Then, the gold- and copper-rich deposit was exposed to the present surface due to uplifting and denudation processes during the late Cretaceous Paleocene period. In general, the mineralization was 10Ma behind the large-scale magmatic-hydrothermal gold mineralization (120Ma) in East China during the late Mesozoic.