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Rongqing Zhang - One of the best experts on this subject based on the ideXlab platform.
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in situ la icp ms trace element analyses of Scheelite and wolframite constraints on the genesis of veinlet disseminated and vein type tungsten deposits south china
Ore Geology Reviews, 2018Co-Authors: Qiang Zhang, Rongqing Zhang, Jianjun Lu, Jinwei WuAbstract:Abstract Veinlet-disseminated and vein-type tungsten deposits are important tungsten resources in South China and show remarkable diversity in dominant tungsten minerals. To better understand their genesis, Scheelite from the Shimensi veinlet-disseminated deposit and wolframite from the Xihuashan and Piaotang vein-type deposits were selected to conduct in-situ laser ablation-inductively coupled plasma-mass spectrometry trace element analyses. The Shimensi tungsten mineralization occurs in intensively altered granitic rocks and is characterized by Scheelite. Two generations of Scheelite in a single grain can be identified by cathodoluminescence (CL) imaging. The early Scheelite (dark domains in CL images) is characterized by nearly flat chondrite-normalized REE (REE N ) patterns with significantly negative Eu anomalies, whereas the late one (bright domains in CL images) shows light rare earth element (LREE)-enriched REE N patterns and obviously positive Eu anomalies. The former has higher REE, Na, Nb and Ta and lower Sr contents than the latter. The Xihuashan and Piaotang wolframite-quartz veins are developed in greisenized granite (type I) and metasedimentary rocks (type II). Both types of wolframite show LREE-depleted patterns, but type I exhibits strongly negative Eu anomalies and type II positive Eu anomalies. Type I contains higher REE, Nb and Ta concentrations, and lower FeO/MnO ratios than type II. Variations of Eu anomalies and trace element compositions in both Scheelite and wolframite can be used to decipher the origin and processes of tungsten mineralization. Both the early Scheelite and wolframite (type I) display significantly negative Eu anomalies and have high REE, Nb and Ta contents, suggesting that the initial ore-forming fluids were of magmatic origin. Precipitation of tungsten minerals and alteration would effectively modify the composition of ore-forming fluids. Deposition of the early tungsten minerals would lower REE, Nb and Ta in the mineralizing fluids, leading to depletion of these elements in the late ones. Although both the type I and II wolframite have different REE contents and Eu anomalies, they show similar left-dipped REE N patterns, implying that compositional variation of fluids is likely driven by crystallization of wolframite during the processes of fluid evolution. In contrast, the elevated LREE/HREE (heavy rare earth element) ratios, δEu (Eu N /Eu N ∗ ) values and Sr abundances in the late Scheelite are possibly caused by the decomposition of plagioclase and K-feldspar. Alteration plays an important role in the formation of veinlet-disseminated Scheelite deposits. It can be concluded that vein-type wolframite mineralization is mainly formed by filling and that veinlet-disseminated Scheelite mineralization is associated with metasomatism.
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origin of the muguayuan veinlet disseminated tungsten deposit south china constraints from in situ trace element analyses of Scheelite
Ore Geology Reviews, 2018Co-Authors: Jianfeng Gao, Rongqing Zhang, Wenhui ChenAbstract:Abstract The Late Triassic Muguayuan W deposit is located in the middle of the Jiangnan Orogen, South China. This deposit is characterized by veinlet-disseminated W mineralization that developed in the Sanxianba granitic porphyry stock. The ore minerals are mainly Scheelite with minor molybdenite and wolframite. Scheelite mineralization was closely related to greisenization and phyllic alteration, and took place in two stages. Stage I involved Scheelite ± wolframite ± molybdenite + quartz veinlet and disseminated mineralization, whereas Stage II resulted in Scheelite + quartz + sericite veinlet mineralization. Sulfide and quartz + calcite ± pyrite veinlets formed during the post-ore stage. Scheelites from the two mineralization stages have different textures and compositions. Cathodoluminescence (CL) images of Stage I Scheelites reveal two generations of growth (I-a and I-b). Stage I-a Scheelite is dark under CL with oscillatory zoning, and has light rare earth element (LREE)-enriched chondrite-normalized patterns, negative Eu anomalies, and high total REE contents. Stage I-b Scheelite forms rim overgrowths on Stage I-a Scheelite, is bright under CL, and shows positive Eu anomalies and relatively low REE contents. Although Stage II Scheelites are nearly uniform under CL, they can be subdivided into two generations according to their REE systematics. Stage II-a Scheelite yields middle REE (MREE)-enriched chondrite-normalized patterns, with negative Eu anomalies, whereas Stage II-b Scheelite has MREE-depleted patterns with positive Eu anomalies. Minor amounts of apatite formed in both stages of mineralization. Stage I apatite contains 1370–1930 ppm Mn and 97.7–127 ppm Sr, whereas Stage II apatite has lower Mn (111–158 ppm) and higher Sr (2170–4690 ppm) concentrations. The distinct trace elements compositions of the Scheelite and apatite from the two stages identify two ore-forming fluids that had different origins and compositions. The ore-forming fluids in Stage I-a were relatively reduced magma-derived fluids with high Mo, Mn, Nb, and Ta, and low Sr. Fluid modeling shows that the initial fluids of Stage I-a were LREE-enriched with negative Eu anomalies, similar to the Sanxianba granitic porphyry. Precipitation of early apatite and Scheelite, as well as plagioclase decomposition, altered the fluid composition and led to relative depletions in REE, Nb, and Ta, and increases of Eu and Sr in the Stage I-b fluids. Cooling of these fluids and the addition of recycled meteoric water led the fluids to become relatively oxidized and Sr-rich; Stage II Scheelite precipitated from these fluids. Precipitation of Stage II-a Scheelite resulted in the Stage II-b fluids becoming progressively MREE-depleted. Extensive alteration, especially greisenization and phyllic alteration, led to plagioclase decomposition, which provided the Ca necessary for Scheelite mineralization. This process was important in generating the W mineralization in the Muguayuan deposit, and perhaps for other granite-hosted, veinlet-disseminated Scheelite deposits in the Jiangnan Orogen.
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garnet and Scheelite as indicators of multi stage tungsten mineralization in the huangshaping deposit southern hunan province china
Ore Geology Reviews, 2018Co-Authors: Rongqing Zhang, Teng DingAbstract:Abstract The Huangshaping W–Mo–Pb–Zn deposit in southern Hunan province, south China, contains multiple generations of garnet and Scheelite in skarn and sulfide–carbonate altered rocks. Optical characteristics and chondrite-normalized rare earth element (REEN) patterns obtained by in situ laser ablation–inductively coupled plasma–mass spectrometry analysis were used to distinguish different generations of garnet and Scheelite. These data show a clear correspondence of garnet REEN patterns to major element zonation, with HREEs (e.g., Gd–Lu) being depleted overall. Coarse-grained garnets in the Huangshaping deposit have extreme HREE depletions and significant LREE (e.g., La–Eu) enrichment, particularly for Ce, Pr, and Nd. This indicates that REEs in these garnets are the result of coupled substitutions: [Ca2+]VIII− 1[REE3+]VIII+1 and [Fe2+]IV +1[Al3+]IV − 1. Medium-grained garnets have REEN patterns showing significant LREE enrichment and depleted HREEs, with high Sn contents. This suggests that substitution of REEs in these garnets occurs as [Ca2+]VIII−1[REE3+]VIII+1[Sn4+]IV−1[Al3+]IV+1. The fact that medium-grained garnets have high Sn contents indicates mineralizing fluids were oxidizing, which is consistent with significant positive Eu anomalies. However, hump-shaped REEN patterns for garnet rims suggest substitution by: [Ca2+]VIII−2[Na+]VIII+1[REE3+]VIII+1, where Nd–Tb are preferentially incorporated into the garnet lattice over other REEs. Group-1a Scheelite has black cores in cathodoluminescence images, and REEN patterns showing extreme LREE enrichment and HREE depletion. Group-1b Scheelite has cores with fine oscillatory zoning and enriched LREEs with depleted HREEs, similar to the REEN patterns of Group-2a Scheelite that occur as rims with bright CL surrounding both Group-1a and 1b Scheelite. The substitution mechanism for REEs in these three types of Scheelite is: [Ca2+]VIII−3[ ]VIII+1[REE3+]VIII+2, with [ ] being a Ca site vacancy. The influence of REE speciation in the hydrothermal fluid dominates the REEN patterns of these types of Scheelite. However, for Group-2b bright rims of Scheelite, REEs are incorporated as: [Ca2+]VIII−2[Na+]VIII+1[REE3+]VIII+1, similar to the garnet rims. Finally, Scheelite Mo contents and δEu values that decrease from Group-1a to 2b support a temporal decrease in oxygen fugacity of the mineralizing fluids. Ratios of Y/Ho and Mo contents that decrease from Group-1a and 1b to Group-2a and 2b Scheelites are similar to those in porphyry-related skarn W (Mo) and quartz vein Au–W deposits, respectively. Our studies also suggest that all these Scheelites in this deposit formed from magmatic fluids. At the Huangshaping deposit, medium-grained garnets associated with Group-1a Scheelite precipitated from evolved magmatic fluids during prograde metamorphism, as indicated by their complementary Y/Ho ratios. Paragentically younger Scheelite, particularly Group-2b, may have formed from dilute magmatic fluids that underwent large-scale hydrothermal circulation. The characteristics of Group-1b and 2a Scheelite likely reflect a transitional environment and fluid mixing during tungsten mineralization in the polymetallic Huangshaping deposit.
Zheng Zhao - One of the best experts on this subject based on the ideXlab platform.
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comparative geochemical study of Scheelite from the shizhuyuan and xianglushan tungsten skarn deposits south china implications for Scheelite mineralization
Ore Geology Reviews, 2019Co-Authors: Jingwen Mao, Zheng Zhao, Trevor Ireland, Fojun Yao, Yuping Yang, Weidong SunAbstract:Abstract Scheelite has been analyzed from the Shizhuyuan and the Xianglushan world-class W deposits from the Nanling W–Sn region and Jiangnan W belt, respectively. The Shizhuyuan deposit consists of proximal skarn and greisen W–Sn–Mo–Bi and distal Pb–Zn–Ag veins. The Xianglushan deposit, contains layer-like sulfide–Scheelite and skarn W orebodies on granite cupolas overprinted by W greisen veins. Scheelite in skarn ores from the Shizhuyuan contains higher concentrations of Mo than those in the sulfide–Scheelite and skarn ores from the Xianglushan deposit, reflecting differences between oxidizing and reducing magmatic-hydrothermal fluids. Under oxidizing conditions, W is accompanied by Mo partitions into exsolved fluids to form W–Mo garnet skarns, whereas under reducing conditions, little Mo is carried by exsolved fluids to form W pyroxene skarns. Trace element patterns of Scheelite from both deposits show negative Ba, Sr, Zr, and Ti, and positive Ta anomalies. Rare earth element (REE) patterns of Scheelite within skarns from the Shizhuyuan deposit have negatively inclined and flat M-type tetrad patterns, and Scheelite from the greisens displays flat and positively inclined M-type tetrad patterns. We infer that the fluids formed Scheelite within the W skarns and greisens inherited parental magma trace element and REE characteristics (depleted Ba, Sr, Zr, and Ti, enriched Ta, negative Eu anomalies, and tetrad effects). Whereas, Scheelite from sulfide–Scheelite veins and skarns of the Xianglushan deposit also has W- and MW-type tetrad REE patterns. The W-type tetrad REE patterns are complementary to REE patterns from the Renjiashan granite, and the MW-type tetrad REE patterns occur during a single evolutionary stage within a complex hydrothermal environment. Sulfide mineralization can form after or before W skarns (the former like Shizhuyuan deposit and the latter like Xianglushan deposit). The formation conditions of the latter included reducing conditions and sulfide firstly supersaturated in the melt, resulting in sulfide drops which carried W aggregated on the cupolas. W skarns and greisens in both deposits underwent generally successive processes related to water supersaturation in the melt. Following a temperature decrease and crystallization, bubbles carried material changing from Si and metal to Si oxide complexes.
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constraints on the uptake of ree by Scheelite in the baoshan tungsten skarn deposit south china
Chemical Geology, 2018Co-Authors: Wen Winston Zhao, Meifu Zhou, Anthony E Williamsjones, Zheng ZhaoAbstract:Abstract Scheelite is the main ore mineral in skarn-type tungsten deposits, and a common accessory mineral in a variety of rock-types. The Baoshan deposit in South China is one of the most important polymetallic Scheelite skarn deposits in China, hosting 40,000 t of WO3 with economic concentrations of Zn, Cu, and Ag. It is hosted by a calcic skarn that is zoned outwards mineralogically from garnet-clinopyroxene, through clinopyroxene-garnet, to wollastonite, and overprinted by retrograde minerals. Scheelite occurs in both the prograde and retrograde skarns, and is complexly zoned. On the basis of its textures, the Scheelite was classified into three types. Scheelite I and II belong to the early and late prograde stages, respectively, and Scheelite III precipitated during the retrograde stage. The molybdenum (Mo) content of these Scheelite types ranges from 54 ppm to 24 wt%, and the total rare earth element content ranges from 12 to 321 ppm. Rare earth element (REE) concentrations and chondrite-normalized REE profiles vary with the distribution of major elements. The profiles indicate variable degrees of REE enrichment, which correlates negatively with the Mo content. Molybdenum-rich Scheelite displays a negative Eu anomaly, and Mo-poor Scheelite a positive Eu anomaly. Crystal structure provided the first-order control on the minor and trace element composition of the Scheelite. Incorporation of REE3 + into Scheelite was controlled partly by a coupled substitution involving Mo. The lattice strain model was used to estimate Scheelite-fluid partition coefficients for the REE from the contents of these elements in the Scheelite and to predict the relative distributions of the REE in the ore-forming fluids. It is proposed that conditions were initially oxidizing, leading to strong incorporation of Mo in Scheelite I, that they became more reducing with the crystallization of Scheelite II containing lesser Mo, and that during retrograde skarn formation there was a return to oxidizing conditions due to an influx of meteoric waters, which altered Scheelite II giving rise to the formation of Scheelite III. The study shows that the composition of Scheelite recorded the history of the Baoshan hydrothermal system, and that the behaviour of the REE could be used to quantitatively reconstruct the changing physicochemical conditions during ore formation.
Jingwen Mao - One of the best experts on this subject based on the ideXlab platform.
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comparative geochemical study of Scheelite from the shizhuyuan and xianglushan tungsten skarn deposits south china implications for Scheelite mineralization
Ore Geology Reviews, 2019Co-Authors: Jingwen Mao, Zheng Zhao, Trevor Ireland, Fojun Yao, Yuping Yang, Weidong SunAbstract:Abstract Scheelite has been analyzed from the Shizhuyuan and the Xianglushan world-class W deposits from the Nanling W–Sn region and Jiangnan W belt, respectively. The Shizhuyuan deposit consists of proximal skarn and greisen W–Sn–Mo–Bi and distal Pb–Zn–Ag veins. The Xianglushan deposit, contains layer-like sulfide–Scheelite and skarn W orebodies on granite cupolas overprinted by W greisen veins. Scheelite in skarn ores from the Shizhuyuan contains higher concentrations of Mo than those in the sulfide–Scheelite and skarn ores from the Xianglushan deposit, reflecting differences between oxidizing and reducing magmatic-hydrothermal fluids. Under oxidizing conditions, W is accompanied by Mo partitions into exsolved fluids to form W–Mo garnet skarns, whereas under reducing conditions, little Mo is carried by exsolved fluids to form W pyroxene skarns. Trace element patterns of Scheelite from both deposits show negative Ba, Sr, Zr, and Ti, and positive Ta anomalies. Rare earth element (REE) patterns of Scheelite within skarns from the Shizhuyuan deposit have negatively inclined and flat M-type tetrad patterns, and Scheelite from the greisens displays flat and positively inclined M-type tetrad patterns. We infer that the fluids formed Scheelite within the W skarns and greisens inherited parental magma trace element and REE characteristics (depleted Ba, Sr, Zr, and Ti, enriched Ta, negative Eu anomalies, and tetrad effects). Whereas, Scheelite from sulfide–Scheelite veins and skarns of the Xianglushan deposit also has W- and MW-type tetrad REE patterns. The W-type tetrad REE patterns are complementary to REE patterns from the Renjiashan granite, and the MW-type tetrad REE patterns occur during a single evolutionary stage within a complex hydrothermal environment. Sulfide mineralization can form after or before W skarns (the former like Shizhuyuan deposit and the latter like Xianglushan deposit). The formation conditions of the latter included reducing conditions and sulfide firstly supersaturated in the melt, resulting in sulfide drops which carried W aggregated on the cupolas. W skarns and greisens in both deposits underwent generally successive processes related to water supersaturation in the melt. Following a temperature decrease and crystallization, bubbles carried material changing from Si and metal to Si oxide complexes.
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the formation of the world class zhuxi Scheelite skarn deposit implications from the petrogenesis of Scheelite bearing anorthosite
Lithos, 2018Co-Authors: Shiwei Song, Jingwen Mao, Guiqing Xie, Zaiyu Yao, Guohua Chen, Jianfeng Rao, Yongpeng OuyangAbstract:Abstract A quartz-free Scheelite-bearing fine- to medium-grained anorthosite occurs as a dike in the world-class Zhuxi Scheelite skarn deposit of South China. The anorthosite mainly comprises An-rich plagioclase (Anavg = 91, ~90 vol%) + Scheelite (~3 vol%) + apatite (~2.5 vol%) + ilmenite (~1.5 vol%) + titanite (~1 vol%), as well as minor (~2 vol%) fluorite, prehnite, chalcopyrite, pyrrhotite, pyrite, sphalerite, rutile, and uraninite. This paper reports the first occurrence of Scheelite-bearing anorthosite of hydrothermal origin in a W deposit. Field, textural, mineralogical, and geochemical evidence suggest a hydrothermal genesis for the Scheelite-bearing anorthosite in the Zhuxi deposit. The Scheelite-bearing anorthosite formed when the Al-, Si-, P-, W-, and F-rich residual magma (fluid) was contaminated by pure limestone in a reducing environment. The formation of the Scheelite-bearing anorthosite requires fertile (W-rich) metasedimentary rocks as a magmatic source, which formed granitic magma emplaced at a great depth that emanated W-enriched magmatic hydrothermal fluids during the latest stage of magma crystallization, thus producing the large-scale tungsten mineralization in the Zhuxi mine.
Anthony E Williamsjones - One of the best experts on this subject based on the ideXlab platform.
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constraints on the uptake of ree by Scheelite in the baoshan tungsten skarn deposit south china
Chemical Geology, 2018Co-Authors: Wen Winston Zhao, Meifu Zhou, Anthony E Williamsjones, Zheng ZhaoAbstract:Abstract Scheelite is the main ore mineral in skarn-type tungsten deposits, and a common accessory mineral in a variety of rock-types. The Baoshan deposit in South China is one of the most important polymetallic Scheelite skarn deposits in China, hosting 40,000 t of WO3 with economic concentrations of Zn, Cu, and Ag. It is hosted by a calcic skarn that is zoned outwards mineralogically from garnet-clinopyroxene, through clinopyroxene-garnet, to wollastonite, and overprinted by retrograde minerals. Scheelite occurs in both the prograde and retrograde skarns, and is complexly zoned. On the basis of its textures, the Scheelite was classified into three types. Scheelite I and II belong to the early and late prograde stages, respectively, and Scheelite III precipitated during the retrograde stage. The molybdenum (Mo) content of these Scheelite types ranges from 54 ppm to 24 wt%, and the total rare earth element content ranges from 12 to 321 ppm. Rare earth element (REE) concentrations and chondrite-normalized REE profiles vary with the distribution of major elements. The profiles indicate variable degrees of REE enrichment, which correlates negatively with the Mo content. Molybdenum-rich Scheelite displays a negative Eu anomaly, and Mo-poor Scheelite a positive Eu anomaly. Crystal structure provided the first-order control on the minor and trace element composition of the Scheelite. Incorporation of REE3 + into Scheelite was controlled partly by a coupled substitution involving Mo. The lattice strain model was used to estimate Scheelite-fluid partition coefficients for the REE from the contents of these elements in the Scheelite and to predict the relative distributions of the REE in the ore-forming fluids. It is proposed that conditions were initially oxidizing, leading to strong incorporation of Mo in Scheelite I, that they became more reducing with the crystallization of Scheelite II containing lesser Mo, and that during retrograde skarn formation there was a return to oxidizing conditions due to an influx of meteoric waters, which altered Scheelite II giving rise to the formation of Scheelite III. The study shows that the composition of Scheelite recorded the history of the Baoshan hydrothermal system, and that the behaviour of the REE could be used to quantitatively reconstruct the changing physicochemical conditions during ore formation.
Bin Chen - One of the best experts on this subject based on the ideXlab platform.
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trace elements and sr nd isotopes of Scheelite implications for the w cu mo polymetallic mineralization of the shimensi deposit south china
American Mineralogist, 2017Co-Authors: Keke Sun, Bin ChenAbstract:The Shimensi deposit (South China) is a newly discovered W-Cu-Mo polymetallic deposit with a reserve of 0.76 million tones WO 3 , one of the largest tungsten deposits in the world. We report elemental and Sr-Nd isotopic data for Scheelites from the giant deposit, to determine the source region and genesis of the deposit. Scheelite is the most important ore mineral in the Shimensi deposit. Trace elements (including REEs) and Nd-Sr isotopic compositions of Scheelites were used to constrain the origin of the mineralizing fluids and metals. Our data reveal that the REEs of Scheelite are mainly controlled by the substitution mechanism 3Ca 2+ = 2REE 3+ + □ Ca, where □ Ca is a Ca-site vacancy. Scheelites from the Shimensi deposit show negative Eu anomalies in some samples, but positive Eu anomalies in others in the chondrite-normalized REE patterns. The variation of Eu anomalies recorded the ore-forming processes. Considering the close spatial and temporal relationship between the mineralization and porphyritic granite, we think the negative Eu anomalies were inherited from the porphyritic granite and the positive ones from destruction of plagioclase of country rock during fluid-rock interaction. The variation of cathodeluminescence (CL) color of a single Scheelite from red to blue and to yellow was likely associated with the increase of REE contents. The Scheelites hosted in the Mesozoic porphyritic granite with negative Eu anomalies formed in a primitive ore-forming fluid, whereas the Scheelites hosted in Neoproterozoic granite with positive Eu anomalies precipitated in an evolved ore-forming fluid. The high Nb, Ta, LREE contents, and LREE-enriched REE patterns of Scheelites from the Shimensi deposit reveal a close relationship with magmatic hydrothermal fluids. The Scheelites from the Shimensi deposit are characterized by low e Nd (t) values (−6.1 ≈ −8.1) and unusually high and varied initial 87 Sr/ 86 Sr ratios (0.7230~0.7657). The e Nd (t) values of Scheelites are consistent with those of the Mesozoic porphyritic granite, but the Sr isotopic ratios are significantly higher than those of the granites, and importantly, beyond the Sr isotopic range of normal granites. This suggests that the ore-forming fluids and metals cannot be attributed to the Mesozoic porphyritic granites alone, the local Neoproterozoic Shuangqiaoshan Group schists/gneisses with high Rb/Sr ratios and thus radiogenic Sr isotopic compositions should have contributed to the ore-forming fluids and metals, particularly, in a later stage of ore-forming process, by intense fluid-rock interaction. This is different from a commonly accepted model that the ore-forming fluids and metals were exsolved exclusively from the granite plutons.
