安徽天井山金矿成矿流体特征及成矿过程初探
摘要
本文在矿床地质调研的基础上,通过主要矿石和蚀变岩石的岩矿相、SEM/EDS、流体包裹体岩相学、显微测温和成分分析,对天井山金矿成矿流体特征、流体来源及成矿过程进行了研究。结果表明,金矿化主要发育于石英脉中,少数产于蚀变围岩中,矿区蚀变以硅化、绢云母化最为发育,另发育含铁碳酸盐化、绿泥石化、黄铁矿化、黄铜矿化、方铅矿化、闪锌矿化等。金矿化发生于石英脉形成后的脆性变形阶段,与之相关的蚀变以绢云母化为主,其次为含铁碳酸盐化和硫化物矿化。金主要以自然金的形式与绢云母共生于石英脉的裂隙中或蚀变围岩中。通过与绢云母同期的流体包裹体研究表明,与金矿化有关的成矿流体为富水、含CO2的中高温(286~380℃)、低盐度流体(3·0%~5·1%,NaCleq,质量分数),单个流体包裹体的LA-ICP-MS成分分析表明,成矿流体中富含Pb、Zn、Cu、Bi、Mo、Sb等金属元素。综合流体包裹体中水的H同位素组成和流体成分特征,成矿流体主要为岩浆水的贡献。含CO2的岩浆流体沿活化的先期断裂上升并发生流体沸腾,在流体沸腾过程中CO2进入气相而改变了流体的pH值,造成金和其它金属硫化物的沉淀,同时形成石英裂隙中和围岩中的绢云母化、含铁碳酸盐化等蚀变。
Based onfield survey,petrographic,ore microscopic and SEM/EDS analyses of ores and altered wall rocks as well as petrographic,microthermometric,LRMand LA-ICP-MS analyses of fluid inclusions in quartz,this paper deals withthe characteristics and origin of ore-formingfluid andthe metallogenic process in the Tianjingshan gold deposit.The results showthat gold mineralization occurs dominantly in quartz veins and subordinately in altered wall rocks andis related mainly to sericitization and Fe-bearing carbonization and subordinately to chloritization,pyritization,chalcopyritization,galenitization and sphaleritization.Gold mineralization took place after the formation of quartz veins and took place during the brittle deformation stage of quartz.Native gold has beenfoundtogether withsericite asinfillingsin quartz fractures or as cement of quartz breccia.Fluidinclusion analysesindicate that the ore-forming fluidis a water-rich and CO2-bearing fluid characterized by middlehigh temperature(286 ~380℃) and lowsalinity(3·0 %~5·1 %Nacleq).The LA-ICP-MSanalyses of fluid inclusionsin quartz reveal high Pb,Zn,Cu,Bi,Mo and Sbin the fluid.The Hisotope measurements together with the enrichment of polymetallic components in ore-formingfluidi mply an obvious magmatic origin.The upward migration of the magmatic fluid along the reactivated fault and the decreasing of temperature and pressure caused the boiling of the fluid.Duringthe boiling process,the CO2preferentially went intothe vapor phase and resulted in pHchange of the ore-forming fluid.The change of pHcaused the precipitation of gold and sulfides and also generated sericitization and Fe-carbonation.
Based onfield survey,petrographic,ore microscopic and SEM/EDS analyses of ores and altered wall rocks as well as petrographic,microthermometric,LRMand LA-ICP-MS analyses of fluid inclusions in quartz,this paper deals withthe characteristics and origin of ore-formingfluid andthe metallogenic process in the Tianjingshan gold deposit.The results showthat gold mineralization occurs dominantly in quartz veins and subordinately in altered wall rocks andis related mainly to sericitization and Fe-bearing carbonization and subordinately to chloritization,pyritization,chalcopyritization,galenitization and sphaleritization.Gold mineralization took place after the formation of quartz veins and took place during the brittle deformation stage of quartz.Native gold has beenfoundtogether withsericite asinfillingsin quartz fractures or as cement of quartz breccia.Fluidinclusion analysesindicate that the ore-forming fluidis a water-rich and CO2-bearing fluid characterized by middlehigh temperature(286 ~380℃) and lowsalinity(3·0 %~5·1 %Nacleq).The LA-ICP-MSanalyses of fluid inclusionsin quartz reveal high Pb,Zn,Cu,Bi,Mo and Sbin the fluid.The Hisotope measurements together with the enrichment of polymetallic components in ore-formingfluidi mply an obvious magmatic origin.The upward migration of the magmatic fluid along the reactivated fault and the decreasing of temperature and pressure caused the boiling of the fluid.Duringthe boiling process,the CO2preferentially went intothe vapor phase and resulted in pHchange of the ore-forming fluid.The change of pHcaused the precipitation of gold and sulfides and also generated sericitization and Fe-carbonation.
引文
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Xu Youhua,Wu Xinhua and Lou Fasheng.2008.Division and correla-tion of the Middle Proterozoic strata in Jiangnan Old Land[J].Re-sources Survery&Environment,29(1):1～11(in Chinese withEnglish abstract).
Yang Minggui and Mei Yongwen.1997.Characteristics of geology andmetatllizationin the Qinzhou-Hangzhou Paleoplate Juncture[J].Ge-ology and Mineral Resources of South China,(3):52～59(in Chi-nese with English abstract).
Yu Xinqi,Zhang Da,Wang Longwu,et al.2006.Features of Caledo-nian tectonic deformation in the Zhejiang-Anhui-Jiangxi border re-gion,China[J].Geological Bulletin of China,25(6):676～684(inChinese with English abstract).
Zheng Xinjian,Cheng Jinhua,Hu Wenhua,et al.2006.Initial analysisof geological and geochemical features of the deposit of arsenopyrite-polymetals and associated gold and gold-prospecting potential in Xiao-he,Xiuning County,Anhui Province[J].Geology of Anhui,16(3):185～189(in Chinese with English abstract).
段留安,杨晓勇,孙卫东,等.2011.皖南天井山金矿床地质-地球化学特征及找矿前景[J].地质学报,85(6):965～978.
侯明兰,蒋少涌,沈昆,等.2007.胶东蓬莱金矿区流体包裹体和氢氧同位素地球化学研究[J].岩石学报,23:2241～2256.
李治平,杨文思,王郁,等.1989.皖南岩浆作用及其与金矿化的关系[J].地质找矿论丛,4(2):42～53.
吴建阳,张均.2010.从天井山金矿和金山金矿的成矿特征对比谈天井山金矿的找矿前景及突破方向[J].矿床地质,(29):1003～1004.
徐有华,吴新华,楼法生.2008.江南古陆中元古代地层的划分与对比[J].资源调查与环境,29(1):1～11.
杨明桂,梅勇文.1997.钦-杭古板块结合带与成矿带的主要特征[J].华南地质与矿产,(3):52～59.
余心起,张达,汪隆武,等.2006.浙皖赣相邻区加里东期构造变形特征[J].地质通报,25(6):676～684.
郑新建,程金华,胡文华,等.2006.安徽省休宁县小贺毒砂-多金属伴生金矿地质地化特征及找金前景浅析[J].安徽地质,16(3):185～189.
Duan Liu’an,Yang Xiaoyong,Sun Weidong,et al.2011.Geochemical characteristics and prospecting in the Tianjingshan Gold Deposit,South Anhui[J].Acta Geologica Sinica,85(6):965～978(in Chi-nese with English abstract).
Hall D L,Sterner MS and Bodnar RJ.1988.Freezing point depressionof NaCI-KCI-H2Osolutions[J].Economic Geology,83:197～202.
Hou Minglan,Jiang Shaoyong,Shen Kun,et al.2007.Fluidinclusion and H-Oisotope study of gold mineralizationinthe Penglai goldfield,Eastern Shandong[J].Acta Petrologica Sinica,23(9):2241～2256(in Chinese with English abstract).
Li Zhiping,Yang Wensi,Wang Yu,et al.1989.Relation between magamatismand gold mineralization in South Anhui Province[J].Contributions to Geology and Mineral Resources Research,4(2):42～53(in Chinese with English abstract).
Phillips G Nand Evans K A.2004.Role of CO2inthe formation of golddeposits[J].Nature,429:860～863.
Wu Jianyang and Zhang Jun.2010.Study Prospecting potential andbreakthrough direction of the Tianjingshan Gold Deposit based oncomparing with the metallogenic characteristics of the TianjingshanGold Deposit and the Jinshan Gold Deposit[J].Mineral Deposits,(29):1003～1004(in Chinese).
Xu Youhua,Wu Xinhua and Lou Fasheng.2008.Division and correla-tion of the Middle Proterozoic strata in Jiangnan Old Land[J].Re-sources Survery&Environment,29(1):1～11(in Chinese withEnglish abstract).
Yang Minggui and Mei Yongwen.1997.Characteristics of geology andmetatllizationin the Qinzhou-Hangzhou Paleoplate Juncture[J].Ge-ology and Mineral Resources of South China,(3):52～59(in Chi-nese with English abstract).
Yu Xinqi,Zhang Da,Wang Longwu,et al.2006.Features of Caledo-nian tectonic deformation in the Zhejiang-Anhui-Jiangxi border re-gion,China[J].Geological Bulletin of China,25(6):676～684(inChinese with English abstract).
Zheng Xinjian,Cheng Jinhua,Hu Wenhua,et al.2006.Initial analysisof geological and geochemical features of the deposit of arsenopyrite-polymetals and associated gold and gold-prospecting potential in Xiao-he,Xiuning County,Anhui Province[J].Geology of Anhui,16(3):185～189(in Chinese with English abstract).
段留安,杨晓勇,孙卫东,等.2011.皖南天井山金矿床地质-地球化学特征及找矿前景[J].地质学报,85(6):965～978.
侯明兰,蒋少涌,沈昆,等.2007.胶东蓬莱金矿区流体包裹体和氢氧同位素地球化学研究[J].岩石学报,23:2241～2256.
李治平,杨文思,王郁,等.1989.皖南岩浆作用及其与金矿化的关系[J].地质找矿论丛,4(2):42～53.
吴建阳,张均.2010.从天井山金矿和金山金矿的成矿特征对比谈天井山金矿的找矿前景及突破方向[J].矿床地质,(29):1003～1004.
徐有华,吴新华,楼法生.2008.江南古陆中元古代地层的划分与对比[J].资源调查与环境,29(1):1～11.
杨明桂,梅勇文.1997.钦-杭古板块结合带与成矿带的主要特征[J].华南地质与矿产,(3):52～59.
余心起,张达,汪隆武,等.2006.浙皖赣相邻区加里东期构造变形特征[J].地质通报,25(6):676～684.
郑新建,程金华,胡文华,等.2006.安徽省休宁县小贺毒砂-多金属伴生金矿地质地化特征及找金前景浅析[J].安徽地质,16(3):185～189.
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