内蒙古白乃庙铜-金-钼矿床成矿机制——来自流体包裹体和He-Ar同位素的证据

发布时间：2018-04-28 22:17

本文选题：He-Ar同位素 + 还原性流体　；参考：《地质学报》2017年03期

【摘要】：白乃庙铜-金-钼矿是华北板块北缘中段一个重要矿床,其矿化特征既显示斑岩型蚀变特征,同时又表现出明显的后期造山作用改造的特点。本次研究通过系统的流体包裹体显微测温、激光拉曼和气液相色谱分析揭示其成矿流体为中—低温、中低盐度的CO_2(CO)-H_2O-CH_4(C_2H_2+C_2H_4)-NaCl-CaCl_2体系,流体混合作用和CO_2逃逸为成矿主要因素。富还原性流体的存在可能促使气相流体携带大量的Cu、Au等成矿元素迁移至较远点的白乃庙群地层,沿着片理或裂隙沉淀成矿。对不同成矿阶段矿石中黄铁矿的He-Ar同位素组成测试结果显示白乃庙矿床黄铁矿流体包裹体的~3He/~4He比值在0.06~0.71Ra之间,~(40)Ar/~(36)Ar比值为375.5~1436.3,指示成矿体系由不同性质和组成的两个端元流体混合而成,即混入了类似于MORB型地幔端元的高温高盐度流体和富含地壳放射成因氦但具有空气氩同位素组成特征的低温大气降水。白乃庙矿床属受后期造山作用改造的斑岩型铜-金-钼矿床,形成于古亚洲洋板块持续向南俯冲背景。
[Abstract]:The Bainaimiao copper-gold-molybdenum deposit is an important ore deposit in the northern margin of the North China plate. Its mineralization features not only show porphyry alteration characteristics, but also show obvious characteristics of late orogenic transformation. In this study, the microthermometry of fluid inclusions, laser Raman and gas liquid chromatography analysis revealed that the ore-forming fluid is a medium-low temperature, low-salinity CO_2(CO)-H_2O-CH_4(C_2H_2 C_2H_4)-NaCl-CaCl_2 system, fluid mixing and CO_2 escape are the main metallogenic factors. The existence of rich reductive fluids may cause the gas phase fluid to carry a large amount of copper au and other metallogenic elements to the far point of the Bainaimiao formation and precipitate the mineralization along the lithology or fissures. The He-Ar isotopic compositions of pyrite in the ore at different metallogenic stages show that the ratio of 3 he / 4 he in the fluid inclusions of pyrite in the Bainaimiao deposit is 375.5% 1436.3 between 0.06~0.71Ra, indicating that the ore-forming system is composed of two ends with different properties and compositions. The meta-fluid is mixed, In other words, a high temperature and high salinity fluid similar to the MORB type mantle end element and a low temperature precipitation rich in radiogenic helium in the crust but characterized by argon isotopic composition of air are mixed in. The Bainaimiao deposit is a porphyry copper-gold-molybdenum deposit modified by late orogeny.
【作者单位】：中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室;中国地质大学(北京)地球科学与资源学院;
【基金】：中央级公益性科研院所基本科研业务费项目(编号K1314) 中国地质大调查项目(编号12120113093600) 国家自然科学基金项目(编号41302061)资助的成果
【分类号】：P618.41;P618.51;P618.65

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