内蒙古林西地区小北沟萤石矿床成矿流体特征及矿床成因探讨
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摘要
小北沟萤石矿床矿体赋存于中生代中酸性火山-沉积岩中,主要受近SN向、NNE向断裂破碎带控制。流体包裹体显微测温和激光拉曼分析结果表明:各成矿阶段主要发育气液两相H_2O包裹体,包裹体均一温度集中分布在160~200℃,盐度(w(NaCl_(eqv)))集中分布在0.2%~1.4%,流体密度0.77~0.93 g/cm~3;包裹体成分以H_2O为主,含少量C_3H_6等有机组分,成矿流体属于中-低温、低盐度、低密度NaCl-H_2O流体体系。野外地质特征及显微测温结果均表明,流体弱沸腾导致早阶段石英沉淀,水/岩反应是萤石的主要沉淀机制。小北沟萤石矿属于中低温热液充填型脉状矿床,成矿流体主要来源于被加热的大气降水和地层水。
The Xiaobeigou fluorite deposit is a newly discovered hydrothermal deposit in Linxi area,Inner Mongolia. The ore bodies are hosted in the Mesozoic intermediate-acid volcanic-sedimentary rocks and are mainly controlled by the nearby SN and NNE trending faults. The results of microthermometry and laser Raman analysis of fluid inclusions show that the fluid inclusions in different stages of mineralization are predominantly gas-liquid two-phase H_2O fluid inclusions with a homogenization temperature of 160-200 ℃,a salinity of 0. 2%~-1. 4%NaCl_(eqv),and a density of 0. 77-0. 93 g/cm~3. The compositions of fluid inclusions are predominantly H_2O and minor organic components,such as C_3H_6. The ore-forming fluid belongs to NaCl-H_2O fluid system,which is characterized by medium-low temperature,low salinity and low density. The geological features and microthermometry results suggest that the quartz precipitation is due to the weak fluid boiling process. The water/rock reaction is one of the potential causes for the precipitation of fluorite. Hence,it can be inferred that the ore-forming fluid was mainly sourced from meteoric water and formation water,and the Xiaobeigou fluorite deposit is considered to be a medium to low-temperature hydrothermal,vein-type deposit.
The Xiaobeigou fluorite deposit is a newly discovered hydrothermal deposit in Linxi area,Inner Mongolia. The ore bodies are hosted in the Mesozoic intermediate-acid volcanic-sedimentary rocks and are mainly controlled by the nearby SN and NNE trending faults. The results of microthermometry and laser Raman analysis of fluid inclusions show that the fluid inclusions in different stages of mineralization are predominantly gas-liquid two-phase H_2O fluid inclusions with a homogenization temperature of 160-200 ℃,a salinity of 0. 2%~-1. 4%NaCl_(eqv),and a density of 0. 77-0. 93 g/cm~3. The compositions of fluid inclusions are predominantly H_2O and minor organic components,such as C_3H_6. The ore-forming fluid belongs to NaCl-H_2O fluid system,which is characterized by medium-low temperature,low salinity and low density. The geological features and microthermometry results suggest that the quartz precipitation is due to the weak fluid boiling process. The water/rock reaction is one of the potential causes for the precipitation of fluorite. Hence,it can be inferred that the ore-forming fluid was mainly sourced from meteoric water and formation water,and the Xiaobeigou fluorite deposit is considered to be a medium to low-temperature hydrothermal,vein-type deposit.
引文
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[2]许东青.内蒙古苏莫查干敖包超大型萤石矿化区形成环境、地质特征及成矿机理研究[D].北京:中国地质科学院,2009.
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[4]孙祥,杨子荣,王永春,等.辽西义县萤石矿床Sr同位素组成及成因[J].地质科技情报,2009,28(1):82-86.
[5]Pei Q M,Zhang S T,Santosh M,et al.Geochronology,geochemistry,fluid inclusion and C,O and Hf isotope compositions of the Shuitou fluorite deposit,Inner Mongolia,China[J].Ore Geology Reviews,2017,83:174-190.
[6]曹华文,张寿庭,高永璋,等.内蒙古林西萤石矿床稀土元素地球化学特征及其指示意义[J].地球化学,2014,43(2):131-140.
[7]曹华文,张寿庭,邹灏,等.内蒙古林西萤石矿床石英ESR年龄及其地质意义[J].现代地质,2013,27(4):888-894.
[8]方乙,邹灏,王光凯,等.甚低频电磁法在萤石矿床勘查中的应用——以内蒙古林西俄力木台萤石矿为例[J].桂林理工大学学报,2013,33(2):246-251.
[9]夏炳卫,曹华文,裴秋明,等.VLF-EM和EH4在浅覆盖区萤石矿床勘查中的应用——以林西水头萤石矿区为例[J].桂林理工大学学报,2016,36(2):228-233.
[10]许东青,聂凤军,钱明平,等.苏莫查干敖包超大型萤石矿床的稀土元素地球化学特征及其成因意义[J].矿床地质,2009,28(1):29-41.
[11]陈敏.赤峰地区萤石矿成矿特征及综合信息成矿预测研究[D].北京:中国地质大学(北京),2011.
[12]曾昭法,曹华文,高峰,等.内蒙古林西地区萤石矿床流体包裹体研究[J].地球化学,2013,42(1):73-81.
[13]裴秋明,张寿庭,曹华文,等.内蒙古林西地区小北沟萤石矿床地质特征及找矿潜力分析[J].桂林理工大学学报,2016,36(3):426-434.
[14]曹俊臣.热液脉型萤石矿床萤石气液包裹体氢、氧同位素特征[J].地质与勘探,1994,30(4):28-29.
[15]卢焕章.流体包裹体[M]:北京:科学出版社,2004.
[16]李双林,欧阳自远.兴蒙造山带及邻区的构造格局与构造演化[J].海洋地质与第四纪地质,1998,18(3):45-54.
[17]Wu F Y,Sun D Y,Ge W C,et al.Geochronology of the Phanerozoic granitoids in northeastern China[J].Journal of Asian Earth Sciences,2011,41:1-30.
[18]Wu F Y,Sun D Y,Li H M,et al.A-type granites in northeastern China:age and geochemical constraints on their petrogenesis[J].Chemical Geology,2002,187:143-173.
[19]肖文交,舒良树,高俊,等.中亚造山带大陆动力学过程与成矿作用[J].中国基础科学,2009(3):14-19.
[20]薛怀民,郭利军,侯增谦,等.中亚-蒙古造山带东段的锡林郭勒杂岩:早华力西期造山作用的产物而非古老陆块?——锆石SHRIMP U-Pb年代学证据[J].岩石学报,2009,25(8):2001-2010.
[21]邵济安,张履桥,牟保磊.中亚造山带东段铀、钼矿床分布与中间地块的关系[J].吉林大学学报(地球科学版),2011,41(6):1667-1675.
[22]陈衍景,翟明国,蒋少涌.华北大陆边缘造山过程与成矿研究的重要进展和问题[J].岩石学报,2009,25(11):2695-2726.
[23]翟明国,朱日祥,刘建明,等.华北东部中生代构造体制转折的关键时限[J].中国科学(地球科学),2003,33(10):913-920.
[24]Chen B,Jahn B M,Tian W.Evolution of the Solonker suture zone:constraints from zircon U-Pb ages,Hf isotopic ratios and whole-rock Nd-Sr isotope compositions of subductionand collision-related magmas and forearc sediments[J].Journal of Asian Earth Sciences,2009,34:245-257.
[25]陈慧军.内蒙古林西地区萤石矿床矿石组分分异特征及其影响因素[D].北京:中国地质大学(北京),2014.
[26]陈衍景,倪培,范宏瑞,等.不同类型热液金矿系统的流体包裹体特征[J].岩石学报,2007,23(9):2085-2108.
[27]Moncada D,Mutchler S,Nieto A,et al.Mineral textures and fluid inclusion petrography of the epithermal Ag-Au deposits at Guanajuato,Mexico:application to exploration[J].Journal of Geochemical Exploration,2012,114:20-35.
[28]Moncada D,Bodnar R J.Gangue mineral textures and fluid inclusion characteristics of the Santa Margarita Vein in the Guanajuato Mining District,Mexico[J].Central European Journal of Geosciences,2012,4(2):300-309.
[29]Moncada de la Rosa J D.Application of fluid inclusions and mineral textures in exploration for epithermal precious metals deposits[D].Blacksburg:Virginia Polytechnic Institute and State University,2008.
[30]Wilkins R W T.The mechanisms of stretching and leaking of fluid inclusions in fluorite[J].Economic Geology,1986,81:1003-1008.
[31]Capitani G C,Mellini M.The crystallisation sequence of the Campiglia Marittima skarn[J].Neues Jahrbuch Für Mineralogie-Monatshefte,2000,3(3):97-115.
[32]Bodnar R J,Bethke P M.Systematics of stretching of fluid inclusions I:fluorite and sphalerite at 1 atmosphere confining pressure[J].Economic Geology,1984,79:141-161.
[33]张寿庭,李忠权,徐旃章.浙江武义盆地中段萤石矿体垂向分带特征与规律[J].西南工学院学报,1997,12(4):52-59.
[34]张振亮,王秀林,吕新彪,等.流体沸腾机制探讨及在石油地质中的可能性——来自合成流体包裹体的证据[J].地质学报,2007,81(5):695-700.
[35]张俊武,邹华耀,李平平,等.含烃盐水包裹体PVT模拟新方法及其在气藏古压力恢复中的应用[J].石油实验地质,2015,37(1):102-108.
[36]史宇文,刘学成,刘俊吉,等.加压下液体过热的亚稳态[J].高校化学工程学报,1995,9(1):75-79.
[37]杨子荣,吴晓娲,程琳,等.辽宁义县地区萤石矿床流体包裹体研究[C]//全国成矿理论与深部找矿新方法及勘查开发关键技术交流研讨会论文集,2011:72-76.
[38]刘斌,段光贤.Na Cl-H2O溶液包裹体的密度式和等容式及其应用[J].矿物学报,1987,7(4):345-352.
[39]Bischoff J L.Densities of liquids and vapors in boiling Na Cl-H2O solutions:a PVTx summary from 300℃to 500℃[J].American Journal of Science,1991,291:309-338.
[40]张惠芬,曹俊臣,谢先德.天然萤石的喇曼光谱和发光谱研究[J].矿物学报,1996,16(4):394-402.
[41]龙腾,王国芝,李娜,等.四川盆地米仓山南缘新立萤石矿床成矿流体研究[J].矿物岩石地球化学通报,2016,35(3):552-558.
[42]马承安.武义萤石矿床矿物包裹体研究[J].中国地质科学院南京地质矿产研究所所刊,1990,11(3):13-24.
[43]张兴阳,顾家裕,罗平,等.塔里木盆地奥陶系萤石成因及其油气地质意义[J].岩石学报,2006,22(8):2220-2228.
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