西藏斯弄多低硫化型浅成低温热液Ag-Pb-Zn矿床:Si-H-O同位素的示踪应用

发布时间：2018-02-09 11:31

  本文关键词： 林子宗群陆相火山岩 Ag-Pb-Zn矿 Si-H-O同位素 古热泉喷口 低硫化浅成低温热液型Au-Ag矿　出处：《地质学报》2017年04期 　论文类型：期刊论文

【摘要】：拉萨地块南木林盆地林子宗群火山机构内发育有斯弄多隐爆角砾岩型、热液脉型Ag-Pb-Zn矿床,该矿床金属矿物为闪锌矿、方铅矿,少量黄铜矿和辉银矿,蚀变矿物为绢云母、伊利石、玉髓、蒙脱石、碧玉、方解石、菱锰矿和菱铁矿,符合低硫型浅成低温热液矿床的基本特征。本次研究对陆相火山岩中热泉喷口的硅质条带及穿切矿体石英脉进行了Si、H、O同位素测试,结果表明:(1)硅质条带的石英单矿物δ~(30)Si_(NBS-28)为-1.2‰~-0.4‰,记录有热水沉积Si同位素地球化学特征,为古热泉硅华成因;(2)受后期火山热液作用改造的热水沉积硅质条带全岩δ~(30)Si_(NBS-28)为-0.2‰~+0.3‰,显示火山岩与热水沉积岩混合特征;(3)穿切矿体石英脉δ~(30) Si_(NBS-28)值为-0.8‰~-0.1‰,与热水沉积硅质条带石英单矿物Si同位素组成一致,显示低温成因高Δ30Si同位素分馏值特征;(4)石英脉和硅质条带全岩的流体包裹体氢氧同位素特征显示大气水与火山岩发生了水-岩交换作用的"氧同位素漂移"现象,说明成矿流体在火山岩地层中经历了长期的循环作用。因此,Si-H-O稳定同位素指示:矿区内仍保留有古热泉喷口,表明矿区自古新世火山岩喷发和成矿后,剥蚀程度低,"缺位"寻找低硫化浅成低温热液型Au-Ag矿床的勘查潜力较大,低δ~(30)Si_(NBS-28)值石英脉和硅化是重要找矿标志。
[Abstract]:In the volcanic mechanism of Linzizong Group in the South Mulin Basin of Lhasa block, there are Ag-Pb-Zn deposits of the Srundo cryptoexplosive breccia type and hydrothermal vein type. The metallic minerals of the deposit are sphalerite, galena, a small amount of chalcopyrite and pyroxene, and the altered minerals are sericite. Illite, chalcedony, montmorillonite, Jasper, calcite, rhodochrosite and siderite, In accordance with the basic characteristics of low-sulfur type epithermal hydrothermal deposits, the siliceous bands of hot spring vents in continental volcanic rocks and the quartz veins of penetrating orebodies have been measured by Si-H _ 2O isotopic measurements. The results show that the quartz monomineral 未 ~ (30) S _ (S _ (28)) of the siliceous belt is -1.2 鈥，

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