摘要
那更银矿床位于东昆仑造山带东段,矿区出露大量斜长花岗岩,这些岩石的成因和构造背景能为揭示该地区构造演化过程提供新的证据。对出露于矿区中部的斜长花岗岩开展了岩石学、地球化学及锆石U-Pb年代学等研究。结果表明,那更斜长花岗岩LA-ICP-MS锆石U-Pb年龄为(425.1±4.6)Ma,形成于中志留世。岩石地球化学特征显示,那更斜长花岗岩的w(SiO_(2))为71.16%~71.32%,w(K_(2)O)/w(Na_(2)O)值为0.29~0.35,且铝饱和指数A/CNK(1.09~1.30)显示出过铝质的特征,里特曼指数(δ)介于1.33和1.48之间,说明那更斜长花岗岩属于钙碱性过铝质I型花岗岩。稀土总量ΣREE为54.12×10^(-6)~55.90×10^(-6),且具有轻稀土元素强烈富集,重稀土元素亏损的特点;微量元素蛛网图显示,那更斜长花岗岩具有高场强元素相对亏损,大离子亲石元素和不相容元素(如U)相对富集的特征。那更斜长花岗岩的的岩石地球化学特征结合已有的关于东昆仑构造演化的研究资料指示它们可能是玄武质洋壳在原特提斯洋向北俯冲过程中发生部分熔融并混入壳源物质形成的。
The Nageng silver deposit is located in the eastern segment of the East Kunlun orogenic belt.A large number of plagiogranite are exposed in the mining area.The genesis and tectonic background of these rocks can provide new evidence for revealing the tectonic evolution process of the region.Therefore,here,we present detailed petrological,geochemical and zircon U-Pb geochronological analyses of plagiogranite exposed in the middle of the mining area.LA-ICP-MS zircon U-Pb age of the Nageng plagiogranite is(425.1±4.6)Ma,suggesting they are formed in the middle Silurian.Their SiO_(2)contents and w(K_(2)O)/w(Na_(2)O)ratios are 71.16%-71.32%and 0.29-0.35,respectively,with aluminum saturation index(A/CNK)ranging from 1.09 to 1.30,resembling to that of typical peraluminous.Their ritmann indexs(δ)are 1.33-1.48,belonging to the I-type peraluminous granite with calc-alkaline content.REE of the plagiogranite(ΣREE=54.12-55.90 ppm)is characterized by strong enrichment of LREE.They showrelative depletion of high field strength elements but enrichment of large ion lithophile elements and incompatible elements(such as U)in Primitive mantle-normalized trace element patterns.The above petrogeochemical characteristics of the Nageng plagiogranite combined with previous research data on the tectonic evolution of the East Kunlun,suggest that they may be formed by the partial melting of the basaltic oceanic crust and input of crustal materials during the northward subduction of the original Tethys ocean.
作者
赵云川
胡俊
周洪兵
何志威
ZHAO Yun-chuan;HU Jun;ZHOU Hong-bing;HE Zhi-wei(Sichuan Institute of Metal Geologic Survey,Chengdu 611730,China;Contemporary Amperex Technology Co.,Limited,Guiyang 550081,China;College of Earth Sciences,Chengdu University of Technology,Chengdu 610059,China)
出处
《矿物学报》
CAS
CSCD
北大核心
2023年第5期640-652,共13页
Acta Mineralogica Sinica
基金
青海省地质勘查基金项目(编号:2019048120kc062)。
