地质通报2024，Vol.43Issue(7)：1104-1119,16.DOI:10.12097/gbc.2023.02.009
柴北缘茶卡北山伟晶岩型锂铍矿变质围岩时代及原岩特征
Age and protolith characteristics of metamorphic surrounding rock of Chakabeishan pegmatitic lithium-beryllium ore in the northern margin of Qaidam
摘要
Abstract
The Chakabeishan lithium beryllium deposit is located in the west of Nanshan,Qinghai Province.The region is tectonically located in the eastern segment of the Zongwulong Mountain continental margin rift belt.The orebody occurs in the granite pegmatite dike,and the surrounding rock is metamorphic rock assemblage of low amphibole-high green schist facies.The study value of this set of metamorphic rocks as the surrounding rock of lithium beryllium ore body is of great significance for discussing the regularity and prediction of lithium beryllium mineralization in the northern margin of Qaidam.Based on the rock assemblages,the schist formation was identified as the Chakabeishan Schist Formation.Based on zircon cathodoluminescence image characteristics and zircon U-Pb(LA-ICP-MS)dating tests,the formation age was determined to be Nanhuaian—Ordovician.Zircon Hf isotope analysis shows that the εHf(t)values range from-19.62 to-3.07,indicating that the rocks in the source area were partially melted from paleoproterozoic to Neoarchean upper crust.The contents of SiO2,FeO,TFe2O3,and MgO in schist Formation are 61.33%～70.57%,3.58%～5.13%,5.2%～7.95%and 1.89%～4.95%respectively.The REE partition curve of chondrites is right-leaning,and the REE curve tends to be flat,with weak europium deficit and light REE enrichment characteristics.High field strength elements such as Th,U,Nd,Zr,Hf,Nb and Ti are enriched in trace elements,while lithophilic elements such as Ba and Sr are depleted.Based on the chronology and geochemistry,the author believes that the Chakabeishan schist was formed in the Neoproterozoic and Early Paleozoic back-arc basin environment.The protolith suffered from weak weathering and denudation,and the chemical composition is stable.It is determined to be argillaceous sandstone,whose material is mainly derived from felsic igneous rocks in the island arc environment.The tectonic setting is a continental island arc,which is consistent with the source area of pegmatite dikes containing lithium beryllium ore.关键词
茶卡北山/片岩/碎屑锆石/锆石U-Pb定年/南华纪—奥陶纪/构造环境Key words
Chakabeishan/schist/detrital zircon/zircon U-Pb dating/Nanhuaian—Ordovician period/tectonic environment分类
天文与地球科学引用本文复制引用
郑英,李五福,张小永,韩杰,靳旭亮,缑明亮..柴北缘茶卡北山伟晶岩型锂铍矿变质围岩时代及原岩特征[J].地质通报,2024,43(7):1104-1119,16.基金项目
青海省地质调查局项目《青海省天峻县贡卡休玛地区1∶2.5万区域地质矿产调查项目》(编号:2019048021jc013)和中国科学院广州地球化学研究所项目(第二次青藏高原综合科学考察研究项目)(编号:2019QZKK0702) （编号:2019048021jc013）
