摘要
东昆仑西段拖拖拉林一带首次发现早三叠世花岗岩(体),其岩石组合为黑云母花岗闪长岩+黑云母二长花岗岩+正长花岗岩。岩石地球化学特征显示具有高硅、富钾、贫钙的特征,属高钾钙碱性花岗岩类(KCG),为弱过铝质花岗岩,稀土和微量元素含量变化范围大,LREE富集,轻重稀土分馏明显,负Eu异常明显,稀土配分模式显向右倾斜的"V"字形,明显富集Rb、K、Th等大离子亲石元素,相对富集Zr、Hf等高场强元素,相对亏损Sr、P、Ti等。采用LA-MC-ICPMS锆石U-Pb定年方法,获得黑云母二长花岗岩的206Pb/2 38U年龄为248.7±1.6Ma(NSWD=2.9),属早三叠世。结合岩石学、岩石地球化学特征、构造特征和区域地质背景认为,该套花岗岩体其物源为壳幔混合源,为洋-陆俯冲阶段的产物。
Early Triassic granites are firstly found in the west of East Kunlun, the granite pluton is made of biotite granodior- ite granite, biotite monzogranite and syenogranite. The granites are mainly high SiO2 content, high- potassium, poor-calcium, which belong to peraluminous high-potassium calc-alkaline series. The granite features wide-range variance in contents of REE and trace element, enriched LREE and evidently fractionation of LREE and HREE, negative Eu content. The LEE distribution pattern demonstrates a right-inclined ＂V＂ type, relatively enriched in large ion lithophile elements （Rb ,K ,Th） and less enriched high field strength elements （Zr and Hf） and depleted in elements （such as Sr,P,Ti）. LA-MC-ICPMS zircon U-Pb age determination shows that biotite monzogranite206pb/238 U ages is 248.7± 1.6Ma（ NSWD = 2.9） , so the granite pluton is formed in Early Triassic. Analysis on petrography, geochemistry, tectonition and regional geology, indicates that the granites are the product of mixed source of crust and mantle, the product of the ocean continent subduction stage.
出处
《甘肃冶金》
2016年第4期48-54,共7页
Gansu Metallurgy
作者简介
陈光庭（1988-），男，助理工程师。从事区域地质矿产调查工作。
