【作者】 张玙；

【导师】 邓军；

【作者基本信息】 中国地质大学（北京） ， 矿物学、岩石学、矿床学， 2011， 硕士

【摘要】 本文从区域地质背景和矿床地质特征入手,通过流体包裹体地球化学、岩矿石和黄铁矿主微量元素、稳定同位素及铅同位素研究,判别成矿流体和成矿物质来源,并类比同产于结合带的丘洛金矿带,总结结合带内类卡林型金矿形成机理。流体包裹体仅发育H2O-NaCl体系的水溶液包裹体,低温(Th=120～215℃)、低盐度(0.18～5.26 wNaCl %);包裹体成分气相以H2O为主(91.80%～97.63%),其次为CO2(2.015%～7.297%),液相以Na+、K+和SO42-为主;流体氧同位素组成(δ18O水)-0.36‰～1.91‰,氢同位素组成(δD)-124.243‰～-114.968‰,变化范围窄。表明成矿流体为浅部循环后的大气降水。岩矿石和2类黄铁矿(成岩黄铁矿和矿化期黄铁矿)的稀土配分曲线一致(微右倾,弱Eu负异常),只是黄铁矿的总稀土(ΣREE)略低;2类黄铁矿微量元素组成一致;岩矿石硫化物硫同位素组成(δ34S)一致,均具有较大负值(-13.249‰～-8.091‰);铅同位素组成靠近Zartman图解的上地壳增长曲线。表明成矿物质来源于围岩,S来自形成于开放火山-沉积体系的早期成岩硫化物和围岩有机物还原。流体碳同位素组成(δ14C=-4.693‰～8.644‰)及烯烃气体的存在指示碳来源于海相碳酸盐岩去碳酸盐化,并部分为围岩有机碳。流体密度(ρ)0.859～0.968 g/cm3,包裹体捕获压力(p)2.21～19.62 bar。研究认为印支末期洋壳俯冲形成具高金背景值的矿源层,燕山期弧—陆碰撞及喜山期陆内转换作用为成矿提供热动力,促使大气降水在浅部萃取围岩中的有用物质并发生同位素交换形成含矿热液,之后沿日则—萨马隆洼壳层断裂运移上升并在形成于喜山期的孔隙度及渗透率高的阿加隆洼次级断裂破碎带与早期成岩黄铁矿或其他含铁矿物反应卸载沉淀,形成元素组合为Au、As、Sb、W、B、Hg的浅成低温低盐度微细浸染状类卡林型金矿床。同丘洛金矿带,早期成岩硫化物非喷流沉积成因,低的硫化物含量不足以形成同生沉积矿床,热液期成矿流体也低H2S含量,导致金的搬运介质以硫砷络合物为主,而区别于以硫氢络合物为主的盆地(类)卡林型金矿。更多还原

【Abstract】 In order to realize origins of ore-forming fluids and materials of Ajialongwa gold deposit, based on regional geology settings and characteristics of the deoposit, this thesis made research on: geochemistry of fluid inclusions; major and trace elements of host/ore rocks and pyrites; stable and Pb isotope compositions. In addition, comparing it with Qiuluo gold belt, which deposited in suture zone as well, this article summa- rized the metallogenic mechanism of Carlin-like gold deposits located in suture zones. There were only H2O-NaCl aqueous ore-forming fluid inclusions, which were low in homogenous temperature (Th=120～215℃) and salinity (0.18～5.26 wNaCl%); the gas phase composition of fluid inclusions gave priority to H2O (91.80%～97.63%), and CO2 (2.015%～7.297%) secondaryly, while Na+, K+ and SO42- as the main liquid phase composition; theδ18O values of ore-forming fluid ranged from -0.36‰to 1.91‰, and theδD from -124.243‰to -114.968‰, which variation ranges were narrow. It showed that ore-forming fluids were meteoric water, having taken circulation at shallow depth. Except pyrites’ΣREEs were lower, chondrite normalized rare earth element patterns for host/ore rocks and pyrites of two types (pyrites of mineralization period and diagenetic pyrites) were consistent, which were right deviation slightly and had weakly negative anomaly for Eu; there were consistant trace element composition,δ34S and Pb isotope composition for pyrites of the two types, that theδ34S values ranged from -13.249‰to -8.091‰and the composi- tion of Pb isotope was near to the growth curve of upper crust in Zartman graphic. It proved that ore materials were sourced from host rocks, while the sulfur derived from diagenetic sulfides which formed in an open volcanic-sedimentary system and the reduction of organic compounds. That theδ14C values were -4.693‰～8.644‰and the existence of olefin gas for ore fluid inclusions, indicated the carbon derived mainly from marine carbonate dissolution and partly organic matter. Fluids density (ρ) was 0.859～0.968 g/cm3, and trapping pressure of inclusions (p) 2.21～19.62 bar. The study holded that oceanic crust subduction at late Indosinian epoch produced gold rich ore source bed, then arc-continent collision at early Yanshan stage and inner continent conversion at Himalayan stage provided the tectonic thermal dynamic condition for the deposit, which precipitated meteoric water to leach ore materials from the surrounding rocks and exchange isotopes with them to form ore-forming fluids at shallow depth, then fluids raised through Rize-Samalongwa basement fault, and via interact with diagenetic sulfides or other ferroan minerals, deposited in secondary fracture zone of Ajialongwa that developed at Himalayan stage and had high degree of porosity and permeability, hence Au, As, Sb, W, B, Hg assembled, low temperature and salinity, disseminated Carlin-like gold deposit formed. In common with Qiuluo gold belt, diagenetic sulfides were not generated in exhalative sedimentary condition, low sulfide content was not enough to form syngenetic deposit, and also very limited H2S in ore fluids of the later hydrothermal system. As a result, it’s sulfur-arsenic complexes that transported gold rather than sulfhydryl complexes, which differred from Carlin-type/like gold deposits located in basins.更多还原