西藏乃东县雄嘎晚白垩世石英二长岩地球化学特征及成因探讨  

GEOCHEMICAL CHARACTERISTICS AND GENESIS OF LATE CRETACEOUS QUARTZ MONZONITE IN XIONGGA,NAIDOGN COUNTY,TIBET,CHINA

作　　者：佘小龙 王滔 张志平 汪宏涛 马涛 SHE Xiao-long;WANG Tao;ZHANG Zhi-ping;WANG Hong-tao;MA Tao(The Second Institute of Geology and Mineral Exploration,Gansu Provincial Bureau of Geology and Mineral Exploration and Development,Lanzhou 730020,China;Engineering Technology Research Center for Exploration and Comprehensive Utilization of Metal and Precious Metal Mineral Resources of Gansu Province,The Third Institute of Geology and Minerals Exploration,Gansu Provincial Bureau of Geology and Mineral Exploration and Development,Lanzhou 730050,China)

机构地区：[1]甘肃省地矿局第二地勘院,甘肃兰州730020 [2]甘肃省金属贵金属矿产资源勘查与综合利用工程技术研究中心,甘肃省地矿局第三地勘院,甘肃兰州730050

出　　处：《甘肃地质》2023年第2期6-14,共9页Gansu Geology

基　　金：甘肃省科技计划(22YF7GA050);甘肃省青年人才项目(2020RCXM152);中国地调查局“西藏乃东县地区1∶5万区域地质调查”项目(121201010000150014-46)资助。

摘　　要：拉萨地块南部的冈底斯岩浆岩带,保存了新特提斯洋俯冲消减、印度板块与欧亚板块碰撞、板内俯冲等一系列地质过程的重要岩石学记录,对冈底斯岩浆岩带进行深入研究不仅对阐明青藏高原南部造山带的形成演化具有重要意义,也对岩浆作用与成矿作用之间的关系有着指导作用。通过岩石学、岩石地球化学等方法对西藏乃东县雄嘎地区石英二长岩进行研究,结果显示,雄嘎石英二长岩具有富硅、高铝、富钾、低钛、准铝质—过铝质等特征,属钙碱性I型花岗岩;岩石具轻稀土富集、重稀土亏损,具明显的负Eu异常;微量元素表现为相对富集Rb、K、Th、U等大离子亲石元素,显著亏损Nb、P、Ti等高场强元素。认为雄嘎石英二长岩是晚白垩世新特提斯洋向北俯冲形成的岛弧环境下上地壳基性熔岩部分熔融的产物。Gangdise magmatite belt in the south of Lhasa block has preserved a series of important petrological records,including subduction of Neo-Tethys Sea,collision of Indian plate and Eurasian plate,and intraplate subduction.So,an in-depth study of the Gangdise magmatite belt is of great significance to clarify the formation and evolution of the mountain forming belt in the south of Qinghai Tibet Plateau,and it has played a guiding role in identifying the relationship between magmatism and mineralization,as well.This paper has studied the quartz monzonite in Xiongga area,Naidong Country,Tibet from petrology and petrochemistry perspective.The results show that the quartz monzonite in this area is characterized by rich silicon,aluminum,and potassium,short of titanium,quasi aluminum peraluminous,belonging to I-type calc-alkaline granite.The rocks are high in light rare earth,deficient in heavy rare earth,with obvious negative Eu anomaly.Trace elements are relatively rich in large-ion lithophile elements like Rb,K,Th,and U,and significantly lack high field-strength elements such as Nb,P,Ti,etc.Xionga quartz monzonite is the product of partial melting of basic lava in the upper crust under the island arc environment formed by the northward subduction of Neo-Tethys Sea in the late Cretaceous.

关 键 词：西藏雄嘎 石英二长岩 岩石地球化学 I型花岗岩 成因 

分 类 号：P584[天文地球—岩石学] P597[天文地球—地质学]