The Jizhong-Yanbian Cu-Mo-Au-Pb-Zn polymetallic metallogenic belt is a major nonferrous and precious metal resource base in Northeastern China.The genesis of ore deposits in this district has remained controversial.To...The Jizhong-Yanbian Cu-Mo-Au-Pb-Zn polymetallic metallogenic belt is a major nonferrous and precious metal resource base in Northeastern China.The genesis of ore deposits in this district has remained controversial.To constrain ore genetic models and provide information for exploration,we conducted precise Zn-Cd isotopic measurements on sphalerite and galena.Theδ^(66)Zn_(AA-ETH)values of galena and sphalerite range from−0.07‰to 0.03‰and−0.68‰to−0.12‰,respectively;and theirδ^(114/110)Cd_(NIST SRM 3108)values vary from−0.96‰to 3.83‰and−0.63‰to 0.77‰,respectively.Our study suggests that the Xiaohongshilazi Pb-Zn-(Ag)deposit should be classified as a Mississippi Valley Type(MVT)-like deposit,because both its geological,sulfide trace elemental,and S-Pb-Fe-Zn-Cd isotopic characteristics are similar to those of the typical MVT deposit,except for the differences of the wall rocks.Rayleigh fractionation during sphalerite precipitation is identified as the primary mechanism for Zn-Cd isotopic variations,which is validated by the Zn-Cd fractionation models from 100℃to 250℃.Finally,we propose an ore prospecting model based on migration pathways of ore-forming fluid and the Zn isotopic fractionation model of sphalerite under 100℃.This model indicates potential resources undiscovered at shallow/peripheral and deep zones of current mining level in both the Eastern and Western Ore Block,with parts of the potential resources having been corroborated by recent drilling.Despite the complexity of mineralization,processes,this study provides new insights into the application of Zn-Cd isotopes in understanding ore genesis and guiding mineral exploration in similar contexts.展开更多
The Maoping Pb-Zn deposit(~3 Mt Pb+Zn reserves with grades of 12-30 wt%)is one of the largest Pb-Zn deposits in the Sichuan-Yunnan-Guizhou(SYG)metallogenic province,which has contributed a tremendous amount of lead an...The Maoping Pb-Zn deposit(~3 Mt Pb+Zn reserves with grades of 12-30 wt%)is one of the largest Pb-Zn deposits in the Sichuan-Yunnan-Guizhou(SYG)metallogenic province,which has contributed a tremendous amount of lead and zinc resources for China.To obtain a further understanding of the sources of ore-forming materials and ore genesis of the deposit,S-Pb isotopes of sulfides and C-O isotopes of ore-stage calcites were systematically collected from representative orebodies at different elevations with a Finnigan MAT-253 mass spectrometer.The calcites separated from the sulfides of the NoⅠand NoⅡorebodies shared identical b13 CPDB values(-5.3 to-0.8‰)andδ18OSMOW values(+14.5 to+21.8‰)with those of the calcites in the SYG region,suggesting that CO2 in regional ore-forming fluids possibly had a homologous C-O source that originated from a ternary mixture of the dissolution of marine carbonate rocks,degassing process of the Emeishan mantle plume,and dehydroxylation of sedimentary organic matter.The No.Ⅰ-1 and No.Ⅰ-2 orebody was hosted in the same strata,but the sulfur source of No.Ⅰ-1 orebody(+13.1 to+19.0‰)with equilibrated sulfur fractionation(δ34Sspbaierite-<δ34Sgalena)and No.Ⅰ-2 orebody(+18.0 to+21.8‰)with sulfur equilibrium fractionation(δ34Sspnaierite>δ34-Sgalena)were different.They were derived from the allopatry thermochemical sulfate reduction(TSR)of overlying Carboniferous sulfates in the ore-hosting strata and local TSR of sulfates in the ore-bearing Upper Devonian Zaige Formation,respectively.The narrow and uniform Pb isotopic ratios of single galena grains collected from sulfides with 206Pb/204Pb of 18.713-18.759,207Pb/204Pb of 15.772-15.776 and 208Pb/204Pb of39.383-39.467 indicate a well-mixed metal source(s)that consist of Proterozoic Kunyang and Huili Group basement rocks and Devonian to Middle Permian ore-hosting sedimentary rocks.Besides,the late Permian Emeishan basalts are difficult to contribute metals for regional Pb-Zn mineralization despite a closely spatial relationship with the distribution of the Pb-Zn deposit.This is supported by Pb isotopic ratios plotting above the average upper crustal Pb evolution curves and staying far away from that of the agecorrected Emeishan basalts.Hence,taking into account of the similarities in tectonic setting,ore-hosting rock,ore assemblage,wall rock alteration,ore-controlling structure,and ore-forming materials and the differences in relationship with regional magmatism,fluid inclusion characteristic and ore grade between the Maoping deposit and typical MVT Pb-Zn deposit,the ore genesis of the Maoping deposit should be an MVT like Pb-Zn deposit.展开更多
基金supported by the Open Research Project from the Young Elite Scientists Sponsorship Program by BAST(No.BYESS2023411)the State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences(GPMR202407)the Enterprise Authorized Item from Jilin Sanhe Mining Development Co.LTD(3-4-2021-120).
文摘The Jizhong-Yanbian Cu-Mo-Au-Pb-Zn polymetallic metallogenic belt is a major nonferrous and precious metal resource base in Northeastern China.The genesis of ore deposits in this district has remained controversial.To constrain ore genetic models and provide information for exploration,we conducted precise Zn-Cd isotopic measurements on sphalerite and galena.Theδ^(66)Zn_(AA-ETH)values of galena and sphalerite range from−0.07‰to 0.03‰and−0.68‰to−0.12‰,respectively;and theirδ^(114/110)Cd_(NIST SRM 3108)values vary from−0.96‰to 3.83‰and−0.63‰to 0.77‰,respectively.Our study suggests that the Xiaohongshilazi Pb-Zn-(Ag)deposit should be classified as a Mississippi Valley Type(MVT)-like deposit,because both its geological,sulfide trace elemental,and S-Pb-Fe-Zn-Cd isotopic characteristics are similar to those of the typical MVT deposit,except for the differences of the wall rocks.Rayleigh fractionation during sphalerite precipitation is identified as the primary mechanism for Zn-Cd isotopic variations,which is validated by the Zn-Cd fractionation models from 100℃to 250℃.Finally,we propose an ore prospecting model based on migration pathways of ore-forming fluid and the Zn isotopic fractionation model of sphalerite under 100℃.This model indicates potential resources undiscovered at shallow/peripheral and deep zones of current mining level in both the Eastern and Western Ore Block,with parts of the potential resources having been corroborated by recent drilling.Despite the complexity of mineralization,processes,this study provides new insights into the application of Zn-Cd isotopes in understanding ore genesis and guiding mineral exploration in similar contexts.
基金supported by the National Natural Science Foundation of China(Grant Nos.U1812402 and 41673056)。
文摘The Maoping Pb-Zn deposit(~3 Mt Pb+Zn reserves with grades of 12-30 wt%)is one of the largest Pb-Zn deposits in the Sichuan-Yunnan-Guizhou(SYG)metallogenic province,which has contributed a tremendous amount of lead and zinc resources for China.To obtain a further understanding of the sources of ore-forming materials and ore genesis of the deposit,S-Pb isotopes of sulfides and C-O isotopes of ore-stage calcites were systematically collected from representative orebodies at different elevations with a Finnigan MAT-253 mass spectrometer.The calcites separated from the sulfides of the NoⅠand NoⅡorebodies shared identical b13 CPDB values(-5.3 to-0.8‰)andδ18OSMOW values(+14.5 to+21.8‰)with those of the calcites in the SYG region,suggesting that CO2 in regional ore-forming fluids possibly had a homologous C-O source that originated from a ternary mixture of the dissolution of marine carbonate rocks,degassing process of the Emeishan mantle plume,and dehydroxylation of sedimentary organic matter.The No.Ⅰ-1 and No.Ⅰ-2 orebody was hosted in the same strata,but the sulfur source of No.Ⅰ-1 orebody(+13.1 to+19.0‰)with equilibrated sulfur fractionation(δ34Sspbaierite-<δ34Sgalena)and No.Ⅰ-2 orebody(+18.0 to+21.8‰)with sulfur equilibrium fractionation(δ34Sspnaierite>δ34-Sgalena)were different.They were derived from the allopatry thermochemical sulfate reduction(TSR)of overlying Carboniferous sulfates in the ore-hosting strata and local TSR of sulfates in the ore-bearing Upper Devonian Zaige Formation,respectively.The narrow and uniform Pb isotopic ratios of single galena grains collected from sulfides with 206Pb/204Pb of 18.713-18.759,207Pb/204Pb of 15.772-15.776 and 208Pb/204Pb of39.383-39.467 indicate a well-mixed metal source(s)that consist of Proterozoic Kunyang and Huili Group basement rocks and Devonian to Middle Permian ore-hosting sedimentary rocks.Besides,the late Permian Emeishan basalts are difficult to contribute metals for regional Pb-Zn mineralization despite a closely spatial relationship with the distribution of the Pb-Zn deposit.This is supported by Pb isotopic ratios plotting above the average upper crustal Pb evolution curves and staying far away from that of the agecorrected Emeishan basalts.Hence,taking into account of the similarities in tectonic setting,ore-hosting rock,ore assemblage,wall rock alteration,ore-controlling structure,and ore-forming materials and the differences in relationship with regional magmatism,fluid inclusion characteristic and ore grade between the Maoping deposit and typical MVT Pb-Zn deposit,the ore genesis of the Maoping deposit should be an MVT like Pb-Zn deposit.
