西藏拿若斑岩型铜(金)矿床黄铁矿、黄铜矿原位硫同位素特征及其地质意义
In-situ sulfur isotope characteristics of pyrite and chalcopyrite from the Naruo porphyry Cu(Au)deposit in Xizang:Implications for geological significance
李发桥 1唐菊兴 1王立强 1宋扬 1李社 2林彬 1李海峰 3杨欢欢 1孙豪 1旦增宗追 4郭朵朵 4李彦波 5李建力5
作者信息
- 1. 中国地质科学院矿产资源研究所,北京 100037
- 2. 西藏金龙矿业股份有限公司,西藏 阿里 859200
- 3. 中国十九冶集团有限公司,四川 成都 610031
- 4. 西藏大学,西藏 拉萨 850000
- 5. 西藏自治区地质矿产勘查开发局第五地质大队,青海 格尔木 816099
- 折叠
摘要
拿若矿床是目前西藏多龙矿集区内第三大斑岩型铜(金)矿床,前人针对成岩成矿地质年代学、成矿地质背景等开展了大量研究,但对于其成矿物质硫的来源等成矿机制尚不明确.本文针对拿若矿床中广泛发育的黄铁矿和黄铜矿,利用镜下鉴定、LA-MC-ICP-MS同位素测试分析等方法,开展了矿相学特征和同位素地球化学研究,以期查明其原位硫同位素特征,揭示其矿床成因并指示找矿勘查.研究结果显示,黄铁矿主要分为三类,从早到晚分别为:Py-Ⅰ→Py-Ⅲ→Py-Ⅱ→Py-Ⅲ,除Py-Ⅰ外,其他均与黄铜矿的形成密切相关.黄铁矿δ34S值介于-4.05‰～3.49‰(均值为-0.2‰,n=53),黄铜矿表现出更小的δ34S值特征,即δ34S=-7.24‰～0.32‰(均值为-2.44‰,n=24),测试结果与矿集区内其他矿床数值相近.计算所得成矿流体总硫值(δ34SΣ)为-3.06‰,表明硫的来源主要与岩浆硫有关.硫同位素黄铁矿-黄铜矿矿物对显示成矿温度介于 255℃～590℃之间,成矿中心温度为 320℃,证实了中温成矿环境.硫同位素空间分布特征表明,从矿化中心到外围,δ34S值呈逐渐降低的趋势,这与某些碱性斑岩型矿床明显不同.本次研究认为,拿若矿床的成矿主要与中温环境和远端SO2 的脱气作用有关,该特征可作为拿若矿床重要的找矿勘查指示标志.本次研究丰富了对于拿若矿床硫的来源和成矿温度等成矿机制的认识,为下一步成矿理论和找矿勘查研究奠定了基础.
Abstract
The Naruo deposit is the third largest porphyry Cu(Au)deposit within the Duolong ore district in Xizang.Previous studies have extensively investigated the petrogenesis,metallogenetic geological chronology,and metallogenic geological background.However,the ore-forming mechanism,including the source of sulfur,remains unclear.This study focuses on the widespread occurrence of pyrite and chalcopyrite in the Naruo ore deposit.Through methods such as optical microscopy identification and LA-MC-ICP-MS isotopic analysis,mineralogical characteristics and isotopic geochemistry were investigated.The aim is to elucidate the in-situ sulfur isotope characteristics,reveal the ore genesis of the deposit,and provide guidance for mineral exploration.Based on microscopic observations,three types of pyrite are categorized,from earlier to later:Py-Ⅰ→Py-Ⅲ→Py-Ⅱ→Py-Ⅲ.Except for Py-Ⅰ,all others are closely associated with the occurrence of chalcopyrite.Pyrite exhibits δ34S values ranging from-4.05‰ to 3.49‰(with a mean of-0.2 ‰,n=53),while chalcopyrite demonstrates smaller δ34S values,ranging from-7.24‰ to 0.32‰(with a mean of-2.44‰,n=24).These test results closely approximate values found in other deposits within the ore cluster.The total sulfur value of the ore-forming fluid(δ34SΣ)is-3.06‰,indicating that the source of sulfur is primarily associated with magmatic sulfur.The sulfur isotope mineral pairs of pyrite-chalcopyrite indicate ore-forming temperatures ranging from 255℃to 590℃,with a central ore-forming temperature of 320℃,revealing a mesothermal ore-forming environment in the ore deposit center.The spatial distribution patterns of sulfur isotopes indicate a gradual decrease in δ34S values from the mineralization center to the periphery,which is notably different from some alkaline porphyry-type deposits.This study suggests that such variation is attributed mainly to ore formation in a mesothermal environment and the degassing of remote SO2,thus serving as crucial exploration indicators for the Naruo deposit.This study has enriched our understanding of the sources of sulfur and ore-forming temperatures,among other ore-forming mechanisms,in the Naruo ore deposit.It lays the foundation for further research in ore-forming theories and mineral exploration.
关键词
黄铁矿/黄铜矿/原位硫同位素/拿若矿床/多龙矿集区/西藏Key words
pyrite/chalcopyrite/in-situ S isotope/Naruo deposit/Duolong ore district/Xizang引用本文复制引用
出版年
2024
国家科技期刊平台
NSTL
万方数据