青海省柴北缘独树沟金矿床成矿流体特征及矿床成因
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摘要
独树沟金矿床成矿过程由早至晚主要分为3个阶段:黄铁矿-石英阶段(Ⅰ)、石英-黄铁矿-多金属硫化物阶段(Ⅱ)和含黄铁矿-石英-碳酸盐阶段(Ⅲ)。其中,成矿Ⅱ阶段为主成矿阶段。成矿流体主要有富液相、富气相和含CO_2三相包裹体。成矿流体均一温度为134. 8℃～310. 2℃,盐度为1. 39%～12. 31%NaCleqv,密度为0. 77～0. 99 g/cm~3,显示为中低温、低盐度、低密度的特点,成矿流体属于含CO_2的中温、低盐度的NaCl-H_2O热液体系。综合矿床地质特征和成矿流体特征,确定矿床成因类型为中温热液脉型金矿床,估算矿床成矿深度为1. 5～2. 3 km,成矿与海西期中酸性侵入岩有关。
The ore-forming process of Dushugou Gold Deposit is mainly divided into three mineralization stages:pyrite-quartz stage(Ⅰ),quartz-pyrite-polymetallic sulphide stage(Ⅱ) and pyrite-quartz-carbonate containing stage(Ⅲ),of which stage Ⅱ is the main metallogenic stage. The ore-forming fluids are mainly composed of liquid-rich phase,gas-rich phase,CO_2-containing three-phase inclusions. The homogeneous temperature of the ore-forming fluids ranges 134. 8 ℃-310. 2 ℃,the salinity of the fluids ranges 1. 39 %-12. 31 % and the density ranges 0. 77-0. 99 g/cm3 mainly indicative of the characteristics of medium temperature,low salinity and low density. The ore-forming fluids belong to a medium-temperature low-salinity CO_2-containing NaCl-H2 O hydrothermal system. Based on comprehensive analysis of the characteristics of deposit geology and ore-forming fluids,it is determined that the genetic type of the deposit is mesothermal vein-type gold deposit with the estimated mineralization depth 1. 5-2. 3 km and the mineralization should be related to the intermediate-acid intrusions of the Hercynian period.
The ore-forming process of Dushugou Gold Deposit is mainly divided into three mineralization stages:pyrite-quartz stage(Ⅰ),quartz-pyrite-polymetallic sulphide stage(Ⅱ) and pyrite-quartz-carbonate containing stage(Ⅲ),of which stage Ⅱ is the main metallogenic stage. The ore-forming fluids are mainly composed of liquid-rich phase,gas-rich phase,CO_2-containing three-phase inclusions. The homogeneous temperature of the ore-forming fluids ranges 134. 8 ℃-310. 2 ℃,the salinity of the fluids ranges 1. 39 %-12. 31 % and the density ranges 0. 77-0. 99 g/cm3 mainly indicative of the characteristics of medium temperature,low salinity and low density. The ore-forming fluids belong to a medium-temperature low-salinity CO_2-containing NaCl-H2 O hydrothermal system. Based on comprehensive analysis of the characteristics of deposit geology and ore-forming fluids,it is determined that the genetic type of the deposit is mesothermal vein-type gold deposit with the estimated mineralization depth 1. 5-2. 3 km and the mineralization should be related to the intermediate-acid intrusions of the Hercynian period.
引文
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[4]郝国杰,陆松年,王惠初,等.柴达木盆地北缘前泥盆纪构造格架及欧龙布鲁克古陆块地质演化[J].地学前缘,2004,11(3):115-122.
[5]杨佰慧,李碧乐,金烨,等.青海锡铁山地区二长花岗岩U-Pb年代学、地球化学、Hf同位素研究及其地质意义[J].黄金,2018,39(4):7-14.
[6]青海省第一地质矿产勘查院.青海省滩间山地区金矿整装勘查找矿部署研究成果报告[R].海东:青海省第一地质矿产勘查院,2017.
[7]刘延和.青海省大柴旦镇独树沟地区金矿地质特征及找矿前景分析[D].北京:中国地质大学(北京),2015.
[8] POTTER R WⅡ,CIYNNE M A. Solubility of highly soluble salts in aqueous media:part 1,Na Cl,KCl,CaCl2,Na2SO4and K2SO4solubilities to 100℃[J]. Journal of Research of the United States Geological Survey,1978,6:701-705.
[9]刘斌,沈昆.流体包裹体热力学[M].北京:地质出版社,1999.
[10]邵洁涟.金矿找矿矿物学[M].北京:中国地质大学出版社,1988.
[11]孙丰月,金巍,李碧乐,等.关于脉状热液金矿床成矿深度的思考[J].长春科技大学学报,2000,30(增刊1):27-30.
[12]卢焕章,池国祥,朱笑青,等.造山型金矿的地质特征和成矿流体[J].大地构造与成矿学,2018,42(2):244-265.
[13] CHEN Y J,PIRAJNO F,QI J P,et al. Ore geology,fluid geochemistry and genesis of the Shanggong gold deposit,eastern Qinling Orogen,China[J]. Resource Geology,2006,56(2):99-116.
[14] PHILLIPS G N,EVANS K A. Role of CO2in the formation of gold deposits[J]. Nature,2004,429:860-863.
[15] HAGEMANN S G,LUDERS V. P-T-X conditions of hydrothermal fluids and precipitation mechanism of stibnite-gold mineralization at the Wiluna lode-gold deposits,Western Australia:conventional and infrared microthermometric constraints[J]. Mineralium Deposita,2003,38(8):936-952.
[16] MERNAGH T P,BASTRAKOV E N,ZAW K,et al. Comparison of fluid inclusion data and minerxlization processes for Australian orogenic gold and intrusion-related gold systems[J]. Acta Petrologicx Sinicx,2007,23(1):21-32.
[17]李甘甜,王力,宁传奇,等.延边地区沙金沟金矿床流体地球化学特征及矿床成因研究[J].黄金,2017,38(7):10-17.
[18]吴锁平.柴北缘古生代花岗岩类成因及其造山响应[D].北京:中国地质科学院,2008.