| 摘要: |
| 拉隆穹隆出露于西藏北喜马拉雅带的东段，位于康马穹隆和错那洞穹隆之间。通过1∶5万矿产地质填图和精细剖面测量，在拉隆穹隆核部和围绕穹隆核部呈环状发育的滑脱系中发现一套含Be、Nb、Ta等稀有金属的钠长石花岗岩。拉隆花岗岩由内向外呈现出规律性的岩性变化，依次为二云母花岗岩、白云母花岗岩、伟晶质花岗岩、钠长石花岗岩、伟晶岩及石英壳，表明其是一套岩浆分异程度极高的花岗岩。岩相学研究显示，拉隆钠长石花岗岩的矿物成分以钠长石、石英、钾长石和白云母为主，含少量石榴石，可见少量绿柱石和铌钽族矿物。岩石化学分析表明，该钠长石花岗岩以富含Be、Nb、Ta、Li、Rb、Cs等稀有金属元素及富含H2O、P、F和B等挥发分为典型特征，其中稀有金属Be、Nb、Ta的含量均已达到工业品位，构成了Be-Nb-Ta稀有金属矿体。本文对拉隆穹隆核部的钠长石花岗岩进行独居石U-Pb测年分析，获得21.3 Ma的独居石结晶年龄，与区域上的淡色花岗岩的侵位年龄基本一致。拉隆含Be-Nb-Ta稀有金属钠长石花岗岩的发现，丰富了北喜马拉雅带稀有金属成矿作用类型，对在北喜马拉雅地区寻找钠长石花岗岩型Be-Nb-Ta稀有金属矿具有重要意义。 |
| 关键词: 独居石 Be-Nb-Ta稀有金属 钠长石花岗岩 拉隆穹隆 北喜马拉雅 |
| DOI：10.19826/j.cnki.1009-3850.(2020)02-0091-13 |
| 附件 |
| 投稿时间：2020-03-16修订日期：2020-05-19 |
| 基金项目:中国地质调查局二级项目西藏山南地区铍锡多金属矿调查评价（DD20190147）、国家自然科学基金项目（91955208，41602214）、科学技术部“青藏高原典型矿集区透明化与矿体定位预测”（2016YFC060308）、“青藏高原重要矿产资源基地成矿系统深部探测技术与勘查增储示范”（2018YFC0604103）项目联合资助 |
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| Identification and its significances of the Lalong Be-Nb-Ta-bearing albite granite in the Northern Himalaya, Tibet |
| FU Jiangang, LI Guangming, DONG Suiliang, ZHANG Hai, GUO Weikang, ZHANG Linkui, JIAO Yanjie, ZHANG Xiaoqiong |
(1. Chengdu Center, China Geological Survey, Chengdu 610081, Sichuan, China;
2. The bureau of natural resources and planning, Ya'an 625000, Sichuan, China) |
| Abstract: |
| The Lalong dome is one of the North Himalayan Gneiss Domes (NHGD), located between the well-studied Kangmar dome and the Cuonadong dome. On the basis of 1:50,000 geological survey for minerals, 1:10,000 geological mapping, detailed measured profiles and monazite U-Pb dating, a set of Be-Nb-Ta-bearing rare metal albite granite was first discovered and identified in the Lalong dome. The Lalong Be-Nb-Ta-bearing albite granite shows continuous zonings of granitic magma evolution. From inside out, two mica granite, white mica granite, pegmatitic granite, albite granite, and pegmatite were observed. The albite granite is characterized by high contents of Be, Nb, Ta, Li, Rb and Cs, and it is also rich in volatiles such as H2O, P, F and B. A 21.3 Ma age was obtained by U-Pb dating for the monazite in the albite granite, which represented the crystallizing ager of the Lalong Be-Nb-Ta-bearing albite granite, implying an extensively magmatic activity in the northern Himalaya at that time. The identification of the Be-Nb-Ta rare metal albite granite in the Lalong dome not only opened an important prospecting prelude of albite granite type Be-Nb-Ta rare metal deposits, but vastly enriched metallogenic types of rare metals in the northern Himalaya. |
| Key words: monazite Be-Nb-Ta rare metal albite granite Lalong dome Northern Himalaya |
