西藏中南部格达乡地区典中组岩石地球化学特征及成因分析

詹纯; ZHAN Chun; 杨虎; YANG Hu; 孟繁华; MENG Fanhua; 王嘉; WANG Jia; 何涛; HE Tao; 张明圆; ZHANG Mingyuan; 梁军; LIANG Jun; 张滔; ZHANG Tao

doi:10.48014/cesr.20231009001

西藏中南部格达乡地区典中组岩石地球化学特征及成因分析

Geochemical Characterization and Genetic Analysis of Rocks of the Dianzhong Formation in Geda Township Area,South-Central Tibet

中国地球科学评论 2024年第3卷第1期页码[30-40] 下载全文[4.7MB] [HTML]

摘要

西藏中南部白垩-古近纪典中组火山岩成因和地球化学特征研究对于工作区内岩浆演化序列的建立具有重要意义。格达地区典中组火山岩大致分为英安岩、安山岩, 流纹岩类, 锆石U-Pb同位素定年结果显示, 少斑流纹岩和安山岩岩样品的Pb206/U238加权平均年龄分别为65. 5±2. 3Ma (MSWD=2. 0) 和68. 7±3. 1Ma (MSWD=2. 0) , 说明典中组中酸性火山岩喷发于晚白垩世至古新世。岩石地球化学分析表明, 典中组中酸性火山岩为一套偏铝质-过铝质钙碱性安山岩-英安岩-流纹岩岩石组合。大离子亲石元素及轻稀土元素较为富集, 亏损高场强元素。在岩浆演化过程中, 经历了斜长石的大量结晶析出或者大量斜长石难熔残留, 并且典中组火山岩中含有大量大陆地壳物质。综合分析认为典中组火山岩具有陆缘弧火山岩化学特征, 可能为从俯冲机制向陆陆碰撞机制转换阶段岩浆产物。以格达地区典中组中酸性火山岩作为讨论对象, 进行锆石U-Pb定年、锆石原位Lu-Hf同位素和全岩主微量分析, 目的在于研究该区岩石地球化学特征及其演化成因。为讨论研究区侏罗纪以来的构造演化阶段划分提供地球化学数据支撑。

Abstract

The study on the genetic and geochemical characteristics of volcanic rocks of the Cretaceous-Paleogene Dienzhong Formation in central and southern Tibet is of great significance for the establishment of magma evolution sequence in the working area. The volcanic rocks of Dianzhong Formation in Geda area can be roughly divided into dite, andesite and rhyolite. Zircon U-Pb isotopic dating results show that the weighted average age of Pb206/U238 of oligopleural rhyolite and Andesite samples is 65. 5±2. 3Ma (MSWD=2. 0) and 68. 7±3. 1Ma (MSWD=2. 0) , respectively. This indicates that the middle acid volcanic rocks of Dianzhong Formation erupted from Late Cretaceous to Paleocene. Geochemical analysis of rocks shows that the acidic volcanic rocks in Dianzhong Formation are a set of meta-aluminous-peraluminouscalc- alkaline andesite-dacite-rhyolite rock assemblages. Large ion lithophile elements and light rare earth elements are enriched, and high field strength elements are deficient. In the process of magmatic evolution, there is a large amount of crystallization of plagiase or a large amount of refractory residue of plagiase, and there are a lot of continental crust materials in the volcanic rocks of the Dian Zhong Formation. Comprehensive analysis shows that the volcanic rocks of Dianzhong Formation have the chemical characteristics of continental arc volcanic rocks, and may be magmatic products in the transition stage from subduction mechanism to continental collision mechanism. Zircon U-Pb dating, in situ Lu-Hf isotope and whole rock principal and trace analysis were carried out on the acidic volcanic rocks in Dianzhong Formation, Geda Area. The aim is to study the geochemical characteristics and evolutionary origin of rocks in this area. It provides the geochemical data support for the discussion on the division of tectonic evolution stages in the study area since Jurassic.

DOI

10.48014/cesr.20231009001

文章类型

研究性论文

收稿日期

2023-10-09

接收日期

2023-12-06

出版日期

2024-03-28

关键词

U-Pb定年, 地球化学, 成因, 典中组, 西藏中南部

Keywords

U-Pb dating, geochemistry, cause of formation, Dianzhong Group, central and southern Xizang

作者

詹纯, 杨虎^*, 孟繁华, 王嘉, 何涛, 张明圆, 梁军, 张滔

Author

ZHAN Chun, YANG Hu^*, MENG Fanhua, WANG Jia, HE Tao, ZHANG Mingyuan, LIANG Jun, ZHANG Tao

所在单位

中国地质调查局军民融合地质调查中心, 成都 610036

Company

Civil-Military Integration Center, China Geological Survey, Chengdu 610036, China

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433

下载量

212

参考文献

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引用本文

詹纯, 杨虎, 孟繁华, 等. 西藏中南部格达乡地区典中组岩石地球化学特征及成因分析[J]. 中国地球科学评论, 2024, 3(1): 30-40.

Citation

ZHAN Chun, YANG Hu, MENG Fanhua, et al. Geochemical characterization and genetic analysis of rocks of the Dianzhong Formation in Geda Township area, south-central Tibet[J]. Chinese Earth Sciences Review, 2024, 3(1): 30-40.