摘要
特提斯喜马拉雅带地处青藏高原南部,是产于青藏高原大陆碰撞背景的新生代金成矿省,然而其赋存的造山型金矿床分布零散,且不同构造层次造山型金矿床(如中成、浅成)的蚀变矿化、流体组成和成矿过程缺乏系统对比。本文通过详细对比特提斯喜马拉雅东段中成明赛金矿和浅成马扎拉金(锑)矿床蚀变矿化、硫化物结构、原位微量元素和硫同位素组成,探讨其成矿过程、成矿流体组成及控制因素。两矿床均赋存于侏罗系板岩和凝灰岩夹层中,板岩中蚀变弱,沿层理发育浸染状黄铁矿-铁白云石-绢云母-石英;而凝灰岩夹层蚀变强,长石和黑云母等矿物已蚀变为铁白云石、绿泥石和绢云母等,并发育大量浸染状自形-半自形黄铁矿和毒砂。板岩中黄铁矿(明赛:Py sa;马扎拉:Py sb)结构均较为均一,且Au(平均为0.33×10^(-6))等微量元素含量低,δ^(34)S值变化较大(Py sa:8.12‰~15.6‰;Py sb:-24.3‰~3.36‰)且与侏罗系地层δ^(34)S值相吻合。明赛凝灰岩中黄铁矿(Py va)发育富砷同心环带,具较高的Au(平均含量为14.3×10-6)、As含量,而马扎拉凝灰岩中黄铁矿(Py vb)发育不规则核-边结构且富Au(平均含量为3.8×10-6)、Cu、Pb、Sb。两矿床凝灰岩中黄铁矿和毒砂的δ^(34)S值相似(Py va平均值为2.7‰、毒砂为2.4‰;Py vb平均值为3.2‰、毒砂为3.2‰),与藏南造山型金矿中黄铁矿δ^(34)S值一致。上述两个矿床板岩中黄铁矿贫金且硫同位素组成差异较大,可能为成矿流体与含不同沉积黄铁矿围岩反应所致;而凝灰岩中的黄铁矿富金且与毒砂具有相似的硫同位素组成,可归因于同源流体与相同围岩发生均一化水岩反应。本次研究表明藏南地区广泛分布的凝灰岩是形成造山型金矿的有利岩性,研究区不同构造层次的造山型金矿具相似物质源区,成矿系统差异性受控于不同水岩反应过程。
Tethyan Himalaya is a famous Cenozoic gold metallogenic province formed by continental collision in southern Tibet.However,gold deposits are distributed sporadically,and systematic comparison of alteration,fluid composition,and mineralization process between those deposits at different tectonic levels(like mesozonal and epizonal ones)are absent.In this study,detailed comparisons between the hydrothermal alteration,sulfide textures,in-situ trace elements,and sulfur isotope compositions of the Mingsai Au deposit with the Mazhala Au-Sb deposit in the eastern part of Tethyan Himalaya to probe the mineralization process,ore-forming fluid composition,and controls on the genesis.Both deposits occur in Jurassic slate and tuff interlayer.Among them,the weakly altered slates comprise disseminated pyrite-ankerite-sericite-quartz along the bedding,while the tuff interlays are characterized by intense alterations of replacing feldspar,biotite,and other minerals with ankerite-chlorite-sericite and developing a large amount of euhedral to subhedral pyrite and arsenopyrite.Slate-host pyrites(Py sa in Mingsai and Py sb in Mazhala)with a homogeneous texture have low contents of Au(averaged at 0.33×10-6)and other trace elements,and a broad range ofδ^(34)S value(Py sa:8.12‰~15.6‰;Py sb:-24.3‰~3.36‰),which is consistent with theδ^(34)S value of regional Jurassic strata.Meanwhile,pyrites within the tuff interlayer of the Mingsai deposit(Py va)have a concentric ring texture with highest Au(averaged at 14.3×10-6)and As,while pyrites within the tuff interlayer of the Mazhala deposit(Py vb)have an irregular core-rim texture and high contents of Au(averaged at 3.8×10-6),Cu,Pb,and Sb.The tuff-host pyrites have similarδ^(34)S values with the arsenopyrites(averaged at 2.7‰of Py va and 2.4‰of arsenopyrite in Mingsai;3.2‰both for Py vb and arsenopyrite in Mazhala),which is comparable with theδ^(34)S value of pyrite in other orogenic gold deposits in southern Tibet.The significant variance of sulfur isotope composition in th
作者
翁玮俊
李华健
杨林
董超一
王庆飞
WENG WeiJun;LI HuaJian;YANG Lin;DONG ChaoYi;WANG QingFei(State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences(Beijing),Beijing 100083,China;Frontiers Science Center for Deep-time Digital Earth,China University of Geosciences(Beijing),Beijing 100083,China;State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,China)
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2024年第6期1733-1747,共15页
Acta Petrologica Sinica
基金
国家重点研发计划(2022YFF0800903)
国家自然科学青年基金项目(4210021270)
中央高校科技领军人才团队项目(2652023001)
高等学校学科创新引智计划(BP0719021)联合资助.
关键词
硫化物原位微量元素
硫同位素
水岩反应
造山型金矿
青藏高原
In-situ sulfide trace elements
Sulfur isotope
Fluid-rock interaction
Orogenic gold deposit
Tibet Plateau
