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甘肃马坞金矿成矿流体特征及地质意义

ISSN号：1000-3657
期刊名称：《中国地质》
时间：0
分类：P611[天文地球—矿床学;天文地球—地质学] P618.51[天文地球—矿床学;天文地球—地质学]
作者机构：[1]地质过程与矿产资源国家重点实验室中国地质大学地球科学与资源学院,北京100083, [2]河南省地质调查院,河南郑州450001, [3]中国人民武装警察部队黄金第五支队,陕西西安710100
相关基金：国家自然科学重点基金（41030423）、中国地质调查局地质调查工作项目（1212011220805,1212011220924）、中国人民武装警察部队武警黄金地质研究所项目（WHY（05）-03）、高等学校学科创新引智计划（B07011）联合资助.

作者：刘坤[1,2], 刘家军[1], 吴杰[1], 杨尚松[1], 辛晓军[3], 李渊[3]

关键词：金矿, 流体包裹体, 氢氧同位素, 马坞, 甘肃, gold deposit, fluid inclusion, hydrogen and oxygen isotopes, Mawu, Gansu

中文摘要：

位于西秦岭岷（县）—礼（县）成矿带西段的马坞金矿床,是近年发现的一个中型卡林型金矿床。矿体产出受NWW向断裂构造控制,其赋矿围岩为中泥盆统的千枚岩与灰岩。矿床流体包裹体研究表明,脉石矿物中主要发育CO2-H2O型和H2O溶液型包裹体;均一温度为135～389℃,盐度为4.4%～15.9%,为中-低温、中-低盐度流体;流体成矿压力为34.6～219.8 MPa,成矿深度为1.3～8.1 km。流体包裹体气相成分以H2O、N2为主,其次为CO2、O2,并含有少量CH4、CO等还原性气体;液相成分中阳离子以Ca^2＋、Na^＋为主,阴离子以C^l-和SO4^2-占主导地位,成矿流体为N2-H2O-Ca^2＋-Cl^-体系。氢氧同位素测试结果表明,成矿流体的δ^18O水为5.3‰～10.5‰,δD为-123‰～-93‰,成矿流体主要为热卤水。从流体性质及其演化来看,构造体制的转换使流体稳定体系发生改变与沸腾作用是造成金富集成矿的主要因素。

英文摘要：

Located in the western part of the Min-Li metallogenic belt within the West Qinling Mountains, the Mawu gold deposit is a medium Carlin-type disseminated gold deposit discovered in recent years. The orebody is controlled by the NW-trending faults and hosted in the Devonian phyllite and limestone. Two main types of fluid inclusions, i.e., CO2-H20 inclusions and aqueous fluid inclusions, are trapped in the gangue minerals. The homogenization temperatures range from 135℃ to 389 ℃, while the salinities range from 4.4% to 15.9%, indicating medium-low temperature and medium-low salinity. The trapping pressures are 34.6 MPa to 219.8 MPa. The gold mineralization occurred at the depths of 1.3 km to 8.1 kin. Fluid inclusion analyses show that the gas phase is mainly composed of H20 and N2, with minor CO2 and 02, while the liquid phase is mainly composed of Ca^2＋, Na^＋, Cl^- and SO4^2-. The ore- forming fluid belongs to the N2- H20- Ca^2＋- Cl^- system. The hydrogen and oxygen isotopic compositions of fluid inclusions show that δ^18O_H2O values range from 5.3‰ to 10.5‰, while 6 D values range from -123‰ to -93‰. The ore-forming fluid came from the geothermal brine. An analysis of the fluid evolution shows that the variation of the stability of the fluid system caused by the structural transition and the boiling action played vital roles in the precipitation of gold.

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