西藏日土县奴雷地区古近纪火山岩新发现及构造意义  

New Discovery and Tectonic Significance of Paleogene Volcanic Rocks in Nulei Area, Ritu County, Tibet

作　　者：肖业斌[1] 凌国卿 高原 

机构地区：[1]江西省地质调查研究院,江西 南昌 [2]江西省地质矿产开发局赣东北大队,江西 上饶

出　　处：《地球科学前沿（汉斯）》2019年第10期996-1005,共10页Advances in Geosciences

基　　金：中国地质调查局工作项目(编号1212011121249)。

摘　　要：日土县奴雷地区火山岩岩石类型为粗安岩,属于次铝的或偏铝的火山岩,高钾钙碱性系列。稀土配分显示属轻稀土富集型,重稀土平坦,δCe=0.89,δEuN=0.90~0.92,以弱铕负异常为特征,分配曲线为右倾型。火山岩喷发方式为裂隙中心式,以喷溢相为主,喷发的火山岩成分以安山质岩浆为主,获得粗安岩LA-ICP-MS锆石U-Pb年龄为34.7 ±0.5Ma,形成时代属古近纪始新世。从岩石地球化学特征来看,火山岩原始岩浆来源于青藏高原加厚陆壳之下与岩石圈地幔之上的特殊壳幔过渡带,岩石形成环境为板内初始裂谷环境,兼具了板块边缘造山带的岩石地球化学性质,是青藏高原汇聚隆升演化阶段陆内俯冲成因机制的产物。The volcanic rocks in Nulei area of Ritu County belong to coarse andesite, subaluminium or me-taaluminium volcanic rocks and high potassium calc-alkaline series. Rare earth partition shows that it belongs to light rare earth enrichment type with flat heavy rare earth, δCe=0.89, δEuN=0.90-0.92. It is characterized by weak negative Europium anomaly and its distribution curve is right-leaning. The volcanic rocks erupt mainly in the form of fissure-centered facies, and the vol-canic rocks erupt mainly in andesite magma. The LA-ICP-MS zircon U-Pb age of the trachyandesite is 34.7 ±0.5Ma, which belongs to the Paleogene Eocene. According to the geochemical characteristics of the rocks, the original magma of the volcanic rocks originated from the special crust-mantle transition zone beneath the thickened continental crust and above the lithospheric mantle of the Qinghai-Tibet Plateau. The formation environment of the rocks is the initial intraplate rift environment, which possesses both the lithogeochemical properties of the orogenic belt on the plate margin and is the continental land in the convergence and uplift evolution stage of the product of the genetic mechanism of internal subduction.

关 键 词：构造意义 古近纪火山岩 奴雷地区 西藏日土县 

分 类 号：P61[天文地球—矿床学]