高校地质学报2023，Vol.29Issue(6)：847-861,15.DOI:10.16108/j.issn1006-7493.2022006
喜马拉雅东部拉隆岩体伟晶岩中的铌铁矿族矿物特征及两期铌钽成矿作用
Columbite-group Minerals from the Pegmatite in the Lalong Pluton,Eastern Himalaya and the Two-staged Nb-Ta Mineralization
摘要
Abstract
Leucogranites are widely distributed in the Himalayan orogenic belt and are closely related to rare-metal mineralization.This study focuses on the Nb and Ta mineralization and columbite-group minerals(CGMs)from the granitic pegmatite in the Lalong pluton,eastern Himalayas.Three zones(i.e.,wall zone,intermediate zone,and core zone)can be identified from the Lalong pegmatite based on their lithology.The CGMs mainly exist in the intermediate zone(quartz-feldspar-muscovite zone).Major element,trace element,and U-Pb isotopic compositions of CGMs were systemically analyzed.Two types of CGMs are distinguished by occurrences and chemical compositions.Type Ⅰ CGMs have euhedral occurence and uniform chemical compositions with low Ta#[Ta/(Nb+Ta)]ranging from 0.08 to 0.34.Type Ⅱ CGMs mainly distribute around crystals of the type Ⅰ CGMs or as tiny veins cutting through the type Ⅰ CGMs with higher Ta#ranging from 0.45 to 0.60.Several structures(i.e.,oscillatory structure,metasomatic structure,fissure-filling,and porous)are well developed in the type Ⅱ CGMs.The normalized REE patterns of these CGMs are similar,showing a strong negative Eu anomaly with δEu ranging from 0.001 to 0.020.The LREE/HREE ratio of CGMs ranges from 0.016 to 0.044.Our results indicate a two-staged Nb-Ta mineralization in the Lalong pluton.The first-staged mineralization is related to the magmatic process with the crystallization of the type Ⅰ CGMs,while the second-staged process is late-staged hydrothermal fluid-rich magmatism with the formation of the type Ⅱ CGMs.The REE pattern of the type Ⅱ CGMs,however,is not convincing enough to indicate the magmatic-hydrothermal mineralization.The CGMs U-Pb isotopic analysis reveals the age of Nb-Ta mineralization at 22.3±0.3Ma,implying a rare-metal resource potential of the leucogranites formed in the Neohimalayan period(25-14 Ma).关键词
拉隆淡色花岗岩/稀有金属成矿作用/高喜马拉雅/洛扎Key words
Lalong leucogranite/rare-metal mineralization/Higher Himalaya/Lhozhag分类
地质学引用本文复制引用
李雪姣..喜马拉雅东部拉隆岩体伟晶岩中的铌铁矿族矿物特征及两期铌钽成矿作用[J].高校地质学报,2023,29(6):847-861,15.基金项目
本文受国家自然科学基金项目(91855209)和第二次青藏高原综合科学考察研究(2019QZKK0802)联合资助 （91855209）
