地质通报2025，Vol.44Issue(2)：459-476,18.DOI:10.12097/gbc.2022.11.030
阿拉善地块北缘雅干中酸性火山岩LA-ICP-MS年龄、地球化学特征及其对区域构造演化的制约
The Zircon LA-ICP-MS U-Pb dating and geochemistry of the Yagan intermediate-acid volcanics in the northern margin of the Alxa block:Constraints on regional tectonic evolution
摘要
Abstract
[Objective]The northern Alxa block is the key area for studying the closing of the Paleo-Asian Ocean.Since the Permian volcanics have been rarely investigated in the Yagan area,the tectonic evolution of the Yagan Fault in the Paleozoic remains uncertaintu;and more importantly,the closing timing of the Paleo-Asian Ocean in northern Alxa block is restricted.[Methods]In this paper,we carried out a systematic study of the petrography,geochemistry,zircon U-Pb dating for the intermediate-acid volcanics,which are located in the south of the Yagan Fault.[Results]The intermediate-acid volcanics in the Yagan region are mainly composed of andesite,rhyolite,dacite,rhyolitic crystal tuff and dacitic crystal tuff.The zircon LA-MC-ICP-MS U-Pb dating results show that the rhyolite and dacite were formed during the Early Permian at 278±2 Ma,279±2 Ma,and 283±1 Ma.The Yagan intermediate-acid volcanics are characterized by high K calc-alkaline or calc-alkaline feature,relative enrichment in large ion lithophile elements,such as Rb,U and Th,and depleted in high field strength elements,such as Nb,Ta,P and Ti.They show right-leaning chondrite-normalized patterns,which indicate enrichment in LREE and depletion in HREE,and exhibit relatively moderate-strong negative Eu anomalies(average value of δEu is 0.42～0.67).[Conclusions]Based on the formation age and geochemical characteristics,it is concluded that the Yagan intermediate-acid volcanics were likely formed in a continental margin arc setting as products of the subduction of the Paleo-Asian ocean during Early Permian.Combined with regional geological background,it is inferred that the closure of the Paleo-Asian ocean in the northern margin of the Alxa block should postdate the late period of the Early Permian.关键词
阿拉善地块/雅干断裂/LA-ICP-MS锆石U-Pb年龄/早二叠世/陆缘弧环境Key words
northern margin of the Alxa block/Yagan Fault/LA-ICP-MS zircon U-Pb dating/Early Permian/continental arc分类
地质学引用本文复制引用
雷聪聪,高琪,王文宝,李卫星,马军,闫振军..阿拉善地块北缘雅干中酸性火山岩LA-ICP-MS年龄、地球化学特征及其对区域构造演化的制约[J].地质通报,2025,44(2):459-476,18.基金项目
中国地质调查局项目《内蒙古自治区额济纳旗辉森乌拉等三幅 1∶5 万区域地质调查》(编号:DD20230252)及《内蒙古自治区额济纳旗克克桃勒盖等4幅区域地质调查》(编号:DD20220503) （编号:DD20230252）
