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An exploration model for Jiama copper polymetallic deposit in Maizhokunggar County, Tibet
... Within the Jiama Cu-polymetallic deposit in Tibet, previous studies focused on element zonation based on lithogeochemical data for surface samples and those from orebodies to build an exploration model for deep mineral resources [22][23][24][25][26][27][28][29]. Primary geochemical zonation and elemental distributions have thus been proved to be valid methods for estimating mineral resources at Jiama. ...
... Geological Setting. The Jiama deposit is one of the most economically significant Cu deposits in Tibet and lies in the Gangdese metallogenic belt within the eastern Tethyan metallogenic domain [24,28,29,57] (Figure 1). Collision of the India-Asia plates during the Paleocene and ensuing post-collisional magmatism during the Miocene caused the formation of the Gangdese belt, which hosts several giant porphyry Cu deposits [57][58][59][60][61][62] and is highly prospective for Cu-polymetallic deposits, containing >18 Mt of Cu resources [35,59]. ...
... Skarn mineralization at 4200-4700 m corresponds to orebody I. Molybdenite mineralization below 4700 m includes skarn, hornfels, and porphyry mineralization, which are related to orebodiesI, III, and IV, respectively. Lead and Zn mineralization occurs within Cu mineralization, mainly in the upper skarn orebody I. Au and Ag are hosted mainly within Cu mineralization as by-products of Cu extraction in the skarn orebody I [22][23][24][27][28][29] (Figures 4 and 5). ...
The identification of primary geochemical haloes can be used to predict mineral resources in deep-seated orebodies through the delineation of element distributions. The Jiama deposits a typical skarn–porphyry Cu–polymetallic deposit in the Gangdese metallogenic belt of Tibet. The Cu–polymetallic skarn, Cu–Mo hornfels, and Mo ± Cu porphyry mineralization there exhibit superimposed geochemical haloes at depth. Three-dimensional (3D) primary geochemical halo modeling was undertaken for the deposit with the aim of providing geochemical data to describe element distributions in 3D space. An overall geochemical zonation of Zn(Pb) → Au → Cu(Ag) → Mo gained from geochemical cross-sections, together with dip-direction skarn zonation Pb–Zn(Cu) → Cu(Au–Ag–Mo) → Mo(Cu) → Cu–Mo(Au–Ag) and vertical zonation Cu–(Pb–Zn) → Mo–(Cu) → Mo–Cu–(Ag–Au–Pb–Zn) → Mo in the #24 exploration profile, indicates potential mineralization at depth. Integrated geochemical anomalies were extracted by kernel principal component analysis, which has the advantage of accommodating nonlinear data. A maximum-entropy model was constructed for deep mineral resources of uncertainty prediction. Three potential deep mineral targets are proposed on the basis of the obtained geochemical information and background.
... The ore hosting strata are sandy slate and hornfels of Linbuzong Formation (K1l) and marble and limestone of Duodigou Formation (J3d) (Tang et al., 2010(Tang et al., , 2011Zheng, 2012). ...
... The As, Sb and Hg anomalies point to the extensive distribution of pyrite in hornfels, representing the outer alteration zone of porphyry metallogenic system. Based on the regional geological setting and the characteristics of the Jiama deposit, Tang et al., (2011) and Zheng (2012) have summarized the targeting elements in the Jiama area ( Table 1). Note that all of the targeting elements in Table 1 are related to trapping mechanisms at the deposit scale, and at this scale source and transportation pathways are irrelevant (Zhai, 1999;McCuaig et al., 2010). ...
... The orebodies are steeper in the west where they dip 60°, but are shallower towards east dipping at ~10° (Fig. 4b). This result is consistent with the previous findings of Zheng (2011Zheng ( , 2012 who reported that the spatial pattern of element distribution at the Jiama deposit is Mo→Cu+Mo→Cu→Pb+Zn from northeast to southwest and from deeper to near-surface levels, which reflects the zonation seen from close the source (Mo) to relatively distal from the source (Pb+Zn) (Zeng, 1981;Chang, 2011). ...
This paper reports a deposit-scale GIS-based 3D mineral potential assessment of the Jiama copper-polymetallic deposit in Tibet, China. The assessment was achieved through a sequential implementation of metallogenic modelling and 3D modelling of geology, geochemistry and prospectivity. A metallogenic model for the Jiama deposit and 3D modelling workflow were used to construct multiple 3D layers of volumetric and triangular mesh models to represent geology, geochemistry and ore-controlling features in the study area. A GIS-based 3D weights-of-evidence analysis was then used to estimate the subsurface prospectivity for Cu (Mo) orebodies in the area, which led to the identification of three prospective deep-seated exploration targets. Additionally, the geochemical modelling indicates three potential fluid flow pathways based on the 3D zonation of major geochemical elements and their ratios, particularly the Zn/Pb ratios, which support the results of the weights of evidence model.
... The Tibetan Plateau is the youngest orogen and underwent amalgamation of several blocks during the evolution of the Jinsha–Honghe, Bangong–Nujiang, and Indus–Yarlung–Zangbo oceanic basins (cf.Dewey et al., 1988;Yin and Harrison, 2000;Xu et al., 2006), and therefore can be regarded as a suitable region for investigating the metallogenesis related to accretionary and collisional orogenesis. Previous studies have focused on the individual and typical ore deposits and also, to a lesser extent, on the regional metallogenesis in the Tibetan Plateau (Meng et al., 2003;Zheng et al., 2004Zheng et al., , 2007Zheng et al., , 2014aZheng et al., , 2014bQin et al., 2008;Yang et al., 2009;Tang et al., 2010Tang et al., , 2011).Hou and Cook (2009)studied the metallogenesis in the Tibetan Plateau, but emphasized only the mineralization generated in the Cenozoic corresponding to the collisional environment. Recently, many types of deposits, such as the porphyry–skarn Mo(–W) and skarn Fe(–Cu), have been recognized but were not included in the classification of collision-related deposits byHou and Cook (2009). ...
... molybdenite + chalcopyrite ? molybdenite (Tang et al., 2011). ...
... A Re–Os isotopic data of the molybdenite from quartz– molybdenite vein indicates that the porphyry-type Mo mineralization took place at 65.0 ± 1.9 Ma (Gao et al., 2011). In addition to these skarn Pb–Zn(–Ag) deposits, certain skarn-type Pb–Zn ore veins are present at the periphery of the porphyry orebodies, such as those in the Jiama and Bangpu deposits (Tang et al., 2011;Zhao et al., 2014a,b). ...
... The rocks at Jiama consists of limestone and marble assigned to the Late Jurassic Duodigou Formation (J3d), and sandstone, siltstone and shale assigned to the overlying Early Cretaceous Linbuzong Formation (K1l) (Fig. 4). The main types of mineralization at Jiama are hornfels-and skarn-types hosted by sandy slate and hornfels of the Linbuzong Formation and marble and limestone of the Duodigou Formation (Tang et al., 2010(Tang et al., , 2011Zheng, 2012). Obviously, the hornfels-type of mineralization is hosted by hornfels that form favourable traps for magmatichydrothermal mineralization in the area, and the skarn-type mineralization is hosted by interlayered hornfels and marble (Fig. 11). ...
... The magmatism in SG can be generally divided into four phases, including the Lower Jurassic arc volcanic rocks and arc granites of the Yeba Formation, granites that are related to Late Cretaceous subduction, volcanic rocks from the Linzizong Group and coeval collision-type granites that date from the Paleocene to the Eocene, and porphyries and granites that are associated with large-scale porphyry Cu deposits from the Oligocene and Miocene ( Geng et al., 2005;Zheng et al., 2004Zheng et al., , 2014Wu et al., 2016). The Gangdese porphyry copper belt is the largest copper belt in China that has been found thus far, where more than 10 large and super-large ore deposits have been discovered, including the Qulong porphyry Cu-Mo deposit (approximately 10 Mt. of Cu and 0.44 Mt. of Mo metal; Zheng et al., 2013), the Zhunuo porphyry Cu-Mo-(Au) deposit (approximately 2.3 Mt. of Cu metal; Zheng et al., 2015), and the Jiama porphyry − skarn Cu-Mo-Au-Ag-Pb-Zn deposit (approximately 5 Mt. of Cu, 0.55 Mt. of Mo, 105 t of Au, 7000 t of Ag, and 0.56 Mt. of Pb + Zn metal; Tang et al., 2011) ( Fig. 1c). ...
The Zhibula Cu skarn deposit contains 0.32Mt. Cu metal with an average grade of 1.64% and is located in the Gangdese porphyry copper belt in southern Tibet. The deposit is a typical metasomatic skarn that is related to the interaction of magmatic-hydrothermal fluids and calcareous host rock. Stratiform skarn orebodies occur at the contact between tuff and marble in the Lower Jurassic Yeba Formation. Alteration zones generally grade from a fresh tuff to a garnet-bearing tuff, a garnet pyroxene skarn, and finally to a wollastonite marble. Minor endoskarn alteration zonations are also observed in the causative intrusion, which grade from a fresh granodiorite to a weakly chlorite-altered granodiorite, a green diopside-bearing granodiorite, and to a dark red-brown garnet-bearing granodiorite. Prograde minerals, which were identified by electron probe microanalysis include andradite-grossularite of various colors (e.g., red, green, and yellow) and green diopside. Retrograde metamorphic minerals overprint the prograde skarn, and are mainly composed of epidote, quartz, and chlorite. The ore minerals consist of chalcopyrite and bornite, followed by magnetite, molybdenite, pyrite, pyrrhotite, galena, and sphalerite. Three types of fluid inclusions are recognized in the Zhibula deposit, including liquid-rich two-phase inclusions (type L), vapor-rich two-phase inclusions (type V), and daughter mineral-bearing three-phase inclusions (type S). As the skarn formation evolved from prograde (stage I) to early retrograde (stage II) and later retrograde (stage III), the ore-forming fluids correspondingly evolved from high temperature (405-667°C), high salinity (up to 44.0wt.% NaCl equiv.), and high pressure (500-600bar) to low-moderate temperature (194-420°C), moderate-high salinity (10.1-18.3 and 30.0-44.2wt.% NaCl equiv.), and low-moderate pressure (250-350bar). Isotopic data of δ34S (-0.1‰ to -6.8‰, estimated δ34Sfluids=-0.7‰), δDH2O (-91‰ to -159‰), and δ18OH2O (1.5‰ to 9.2‰) suggest that the ore-forming fluid and material came from magmatic-hydrothermal fluids that were associated with Miocene Zhibula intrusions. Fluid immiscibility likely occurred at the stage I and stage II during the formation of the skarn and mineralization. Fluid boiling occurred during the stage III, which is the most important Cu deposition mechanism for the Zhibula deposit.
The Jiama deposit, a significant porphyry‐skarn‐type copper polymetallic deposit located within the Gangdese metallogenic belt in Tibet, China, exemplifies a typical porphyry metallogenic system. However, the mineral chemistry of its accessory minerals remains under‐examined, posing challenges for resource assessment and ore prospecting. Utilizing electron microprobe analysis and LA‐ICP‐MS analysis, this study investigated the geochemical characteristics of apatite in ore‐bearing granite and monzogranite porphyries, as well as granodiorite, quartz diorite, and dark diorite porphyries in the deposit. It also delved into the diagenetic and metallogenic information from these geochemical signatures. Key findings include: (1) The SiO 2 content, rare earth element (REE) contents, and REE partition coefficients of apatite indicate that the dark diorite porphyry possibly does not share a cogenetic magma source with the other four types of porphyries; (2) The volatile F and Cl contents in apatite, along with their ratio, indicate the Jiama deposit, formed in a collisional setting, demonstrates lower Cl/F ratios in apatite than the same type of deposits formed in a subduction environment; (3) Compared to non‐ore‐bearing rock bodies in other deposits formed in a collisional setting, apatite in the Jiama deposit exhibits lower Ce and Ga contents. This might indicate that rock bodies in the Jiama deposit have higher oxygen fugacity. Nevertheless, the marginal variation in oxygen fugacity between ore‐bearing and non‐ore‐bearing rock bodies within the deposit suggests oxygen fugacity may not serve as the decisive factor in the ore‐hosting potential of rock bodies in the Jiama deposit.
Jiama is a giant, high‐grade porphyry copper system in the Gangdese metallogenic belt, Tibet. Multistage intermediate‐felsic porphyries intruded in this deposit, some of which are strongly associated with copper–polymetallic mineralization. These ore‐bearing porphyries include monzogranite, granodiorite, and quartz diorite porphyries. A new granite aplite dyke was found in the south of Jiama. Its age, genesis, and relationship with ore‐related magmatism are obscure. Here, its emplacement age and petrogenesis were determined using mineralogy, zircon U–Pb dating, geochemistry, and Sr–Nd–Pb isotope studies. The zircon LA–ICP–MS U–Pb age of the aplite dyke is 16.66 ± 0.21 Ma (n = 14, MSWD = 0.66), earlier than that of the ore‐bearing porphyries (∼15 Ma) in Jiama. Furthermore, the aplite exhibits high amounts of silicon (SiO2 = 73.39%–74.74%), potassium (K2O = 5.12%–6.61%), aluminum (Al2O3 = 14.25%–14.69%), and light/heavy rare earth elements (LREE/HREE = 12.12–16.19) as well as negative europium (δEu = 0.47–0.72) and weak negative cerium anomalies (δCe = 0.84–0.93). The aplite dyke is characteristic of metaluminous–peraluminous I‐type granite, which is rich in large‐ion lithophile elements (Rb, Ba, Th, and U) and depleted in high‐field‐strength elements (Nb, P, and Ti). The aplite dyke and ore‐bearing porphyries in the Jiama deposit are the results of a partial melting of the juvenile lower crust, according to whole‐rock geochemistry and Sr–Nd–Pb isotope data, but the dyke and ore‐bearing porphyries were emplaced from the same magma chamber at different times. Thus, the aplite dyke shows the composition of the early evolution stage of shallow magma in the Jiama deposit and is the product of rapid condensation and crystallization.
Whole-rock geochemical data and compositional balance analysis (CoBA), combined with a magnetic susceptibility model obtained from a high-precision magnetic survey, are useful exploration tools in the Jiama porphyry–skarn deposit, southern Tibet, China. In this paper, three innovative aspects of the model are described that have assisted exploration of the Jiama deposit: an improved geological understanding of a thrust–nappe structure, hydrothermal fluid pathways, and magma mixing; data- and knowledge-driven compositional balance analysis of whole-rock geochemistry; and a high-precision magnetic survey of the deposit. The local strata provided the materials and natural trap for skarn formation, and a site for fluid circulation and porphyry ore precipitation. An interlayer detachment zone, gliding nappe structure, and cylindrical fissure system provided channels for fluid migration, and the Niumatang Anticline provided the accommodation space for the porphyry system. Miocene magma mixing and crustal contamination led to the development of complex mineralization in the Jiama area. The geochemical signatures obtained from CoBA, and the spatial distribution of the strata, structures, igneous rocks, alteration, mineralization, and degree of erosion enable integration of the geochemical and geological data. The “demagnetization skylight” identified by magnetic anomalies and a magnetic susceptibility model obtained with UBCmag3D software revealed the location of a concealed porphyry system. A magnetic susceptibility of 0.014–0.016 was found to identify the location of an interlayer skarn. Our exploration indicators of the Jiama porphyry–skarn deposit can be used to guide ore exploration throughout the region.
With the increasing demand for copper resources, exploration methods based on the discovered porphyry Cu deposits (PCDs) to target concealed orebodies are of greater importance. Single parameter is no longer sufficiently effective against concealed deposit exploration, and different combinations of survey techniques are required. The Qulong porphyry Cu-Mo deposit is the largest collisional PCD found in China. Here we evaluated the relationship between variations in multiple parameters and alteration to define exploration footprints around the porphyry Cu centers. In order to improve the exploration efficiency and accuracy, we combined geophysical (magnetic susceptibility and resistivity) and popular geochemical exploration methods (i.e., short wavelength infrared spectroscopy- SWIR, portable X-ray fluorescence- pXRF, and indicator minerals) to the drill hole ZK005 of Qulong PCD in southern Tibet seeking for a firm interpretation. Four orebody indicators were established in study of Qulong deposit, which are: (i) the fluctuations of Ca/K, Mg/Fe, Sr/Ti, and Si/Al ratios, (ii) long-wavelength white mica (2207–2214nm) and short-wavelength chlorite (2247–2253nm), (iii) sub-high magnetic susceptibility and (iv) low resistivity. Multi-scale prospecting methods can effectively improve prospecting efficiency and narrow down the target area. Based on the local environment, selecting an appropriate combination of methods can improve exploration efficiency in the brownfields at a lower cost.
With the decrease in surface and shallow ore deposits, mineral exploration has focused on deeply buried ore bodies, and large-scale metallogenic prediction presents new opportunities and challenges. This paper adopts the predictive thinking method in this era of big data combined with specific research on the special exploration and exploitation of deep-earth resources. Four basic theoretical models of large-scale deep mineralization prediction and evaluation are explored: mineral prediction geological model theory, multidisciplinary information correlation theory, mineral regional trend analysis theory, and mineral prediction geological differentiation theory. The main workflow of large-scale deep resource prediction in the digital and information age is summarized, including construction of ore prospecting models of metallogenic systems, multiscale 3D geological modeling, and 3D quantitative prediction of deep resources. Taking the Lala copper mine in Sichuan Province as an example, this paper carries out deep 3D quantitative prediction of mineral resources and makes a positive contribution to the future prediction and evaluation of mineral resources.
The giant Jiama polymetallic ore deposit is a porphyry–skarn system in the eastern Gangdese porphyry belt of the Tibetan Plateau. Steeply dipping high-grade massive sulfide veins are classified as lode-type high-sulfidation (HS) mineralization comprising mainly Cu-sulfosalts in Au-poor and Au-rich veins. Au-poor veins contain an As-rich pyrite–enargite–tennantite assemblage, whereas Au-rich veins contain an Sb-rich enargite–luzonite–tetrahedrite–chalcostibite–watanabeite assemblage. The coexistence of pyrite, dendritic muscovite, and euhedral quartz in the Cu-sulfosalts indicates slightly acidic or near-neutral formation conditions. Most Au- and Ag-bearing minerals are inclusions of tellurides (hessite, sylvanite, and petzite) in tennantite–tetrahedrite, and watanabeite. Au and Ag concentrations in tennantite–tetrahedrite, watanabeite, and chalcostibite are much higher than in enargite and luzonite, confirming that they were controlled by intermediate-sulfidation state Cu–As–Sb–S solid solutions, with Au tending to be enriched in Sb-rich minerals compared with As-rich solid solutions. The HS veins overlying the known porphyry intrusion and cutting skarn orebodies in the Jiama deposit constitute a porphyry–skarn–high sulfidation system. The occurrence of HS veins suggests that channels in paleo-fumaroles and the mineralization that resulted may be ascribed to expansion of magmatic vapor. HS veins close to the porphyry intrusion exposed at the surface indicate that shallow epithermal disseminated mineralization was likely removed by rapid regional uplift and erosion of the Gangdese porphyry belt.
China has widely distributed silver deposits, and is rich in silver resources. Although silver deposits are mainly associated with Pb-Zn deposits, a number of independent silver deposits have also been discovered in recent years. Silver deposits include different types, such as submarine volcanism and continental volcanism related type, intrusion related type, and sedimentary related type. This study summarized the metallogenic regularity of China's silver deposits systematically based mainly on the data from 490 silver deposits. It is shown that submarine volcanic sedimentary type, continental volcanic or sub-volcanic type, skarn type, hydrothermal type (including vein type and stratabound type), sedimentary metamorphic type, sedimentary type and regolith type should be regarded as the most important prediction types of silver deposit. A total of 32 silver mineralization belts and 111 silver concentration areas have been delineated. The map of "Spatial distribution of silver mineralization belts in China" and other series of maps finished in this study may provide a theoretical basis for the evaluation and prognosis of silver resources potential in China.
Copper resources in China are rich, but imported copper products are still required. Researches on metallogenic regularity of major types of copper deposits by geologists have involved in worldwide classification, significant copper belts, representative copper deposits, etc. Studies on metallogenic regularity of copper deposits in China also have made achievements with a long-term work. Combined with latest exploration advances obtained in recent ten years, this review aims to conclude the achievements of researches on copper metallogenic regularity in China. Based on data of 814 copper deposits and other ore (mineralized) occurrences, ten prediction types of copper deposits have been suggested. Porphyry and skarn copper ores are taken as the key targets. Porphyry copper deposits are the most important one which concentrate in Gangdese, Changdu-Sanjiang, Dexing and East Tianshan. The Cenozoic and Mesozoic are the major metallogenic epochs. Four main metallogenic epochs are been studied based on the copper ore geochronological data including Precambrian Era (Archean and Proterozoic), Paleozoic Era, Mesozoic Era and Cenozoic Era. Based on the study of metallogenic series of ore deposits in China, twenty-seven metallogenic series of copper deposits are proposed. This is suggested to deepen the study of metallogenic regularity of copper ore and provide the theory guide for copper resources prediction in China.
The Jiama copper deposit is one of the largest deposits recently found in Tibet and is composed of three types of mineralization including skarn, hornfels and porphyry. To investigate the relationship between mineralization, structure and alteration, we report new zircon U–Pb age and present field observations on the deformation characteritics associated with the copper mineralization in Jiama. Two main periods of deformation were identified, represented by D1 and D2 in Jiama. The first deformation (D1) occurred around 50 Ma, whereas the second deformation (D2) that was closely related to mineralization occurred later. Previous zircon U–Pb and molybnite Re–Os dating results indicate that the mineralizatoin occurred at ∼15 Ma and thus the D1 regional deformation significantly occurred before the mineralization time, although the D1 deformation probably provided important space for the development of significant copper deposition. Our new mapping and observations on the D2 deformation demonstrate that the mineralization was closely coeval with or slightly later than the time of D2 deformation. The new U–Pb zircon age further indicates that the aplite formed in ∼17.0 Ma and thus the D2 deformation happened later than this time because the D2 deformation cut across the aplite, which is proposed to be the key control for copper mineralization. Altered laminated hornfels including three types of alteration (A-, K- and S-type) were found spatially associated with the D2 deformation. The type-A is mainly silicification, with fine sericite or chlorite, as well as abundant disseminated sulphides on fracture surfaces; the type-S is mainly fine-grained silicification with patches of chlorite, epidote and common sulphides; the type-K (potassic alteration) appears to be fine-grained biotite. Such types of alteration indicate the presence of skarns at depth where ore shoots are located. Taken together, the multiple structural-magmatic-mineralization events contributed to the formation of the supergiant Jiama porphyry copper deposit in Tibet. The results have general implication for regional exploration.
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