珠峰西北侧尼布晓巴锂辉石伟晶岩的识别及指示意义  

Identification of the Nibuxiaoba spodumene-bearing pegmatite in the northwest side of Mount Qomolangma and its implication

作　　者：刘海永 王雨 杨浩[3] 张旭东 付德钰 王艳 郝建亭 LIU HaiYong;WANG Yu;YANG Hao;ZHANG XuDong;FU DeYu;WANG Yan;HAO JianTing(Tibet Geological Survey,Lhasa 850000,China;The Second Geological Party,Tibet Bureau of Geological and Mineral Exploration and Development,Lhasa 850000,China;College of Earth Sciences,Jilin University,Changchun 130061,China)

机构地区：[1]西藏自治区地质调查院,拉萨850000 [2]西藏地勘局第二地质大队,拉萨850000 [3]吉林大学地球科学学院,长春130061

出　　处：《岩石学报》2025年第3期789-803,共15页Acta Petrologica Sinica

基　　金：第二次青藏高原综合科学考察专题(2019QZKK0806-02)资助.

摘　　要：喜马拉雅稀有金属成矿带是我国地质学者和地矿工作者新近提出的一条重要的稀有金属成矿带,近年来在伟晶岩型锂资源方面取得重大突破。其中珠峰地区(包括普士拉、琼嘉岗、热曲、前进沟等)是锂辉石伟晶岩发育最为集中的区域。本文报道了热曲-琼嘉岗之间新识别的锂辉石伟晶岩和伴生绿柱石伟晶岩-淡色花岗岩,发现地位于尼布晓巴东西两侧,近水平呈岩席或透镜体侵位于肉切村群中,发育绿柱石-铌钽铁矿-锂辉石等稀有金属矿物。独居石-铌钽铁矿U-Pb定年结果显示淡粉红色锂辉石伟晶岩形成于23.5±0.8Ma,淡绿色锂辉石伟晶岩形成于21.0±0.5Ma,含绿柱石伟晶岩形成于21.4±1.3Ma,含绿柱石电气石白云母花岗岩形成于15.9±0.1Ma,指示珠峰地区稀有金属成矿时代集中于新喜马拉雅阶段。尼布晓巴含绿柱石-锂辉石淡色花岗岩-伟晶岩具有显著低的∑REE、Zr/Hf、Nb/Ta,以及高的Rb/Sr和TE_(1,3)(>1.0),表明其经历了高度的结晶分异和强烈的熔流体相互作用。尼布晓巴地区达到工业品位的锂辉石伟晶岩集中分布在其东侧海拔5500~6000m范围,而尼布晓巴西侧海拔5500~5200m主要发育绿柱石淡色花岗岩-伟晶岩。本文及前人资料显示,岩浆分异程度和稀有金属含量和出露高度有较为明显的正相关关系,反映其受控于藏南拆离系的构造驱动成矿的地球动力机制。本研究所揭示的尼布晓巴成矿时代和成矿特征对于理解喜马拉雅稀有金属成矿作用与找矿具有借鉴意义。The Himalayan rare metal metallogenic belt is an important metallogenic belt recently proposed by geologists in China.In recent years,great breakthroughs have been made in pegmatite-type lithium resources.Among them,the Qomolangma region(including Pusi La,Qongjiagang,Ra Chu,Qianjingou,etc.)is the most spodumene-bearing pegmatites concentrated area.This paper reports the newly identified spodumene-bearing pegmatite and associated beryl-bearing pegmatite-leucogranite in the Ra Chu-Qongjiagang transition area.They were found on both the east and west sides of Nibuxiaoba,invading into the Rouqiecun Group as near-horizontal sheets or lenses.The monazite-niobium-tantalite U-Pb dating results show that the light pink,the light green and the beryl-bearing pegmatite spodumene pegmatites were formed at 23.5±0.8Ma,21.0±0.5Ma and 21.4±1.3Ma,respectively,while the beryl-bearing tourmaline muscovite granite was formed at 15.9±0.1Ma,indicating that the metallogenic age of rare metals in the Qomolangma area is concentrated in the Neo-Himalayan stage.The Nibuxiaoba rare metal leucogranites and pegmatites have significantly low∑REE,Zr/Hf,Nb/Ta,and high Rb/Sr and TE_(1,3)(>1.0)values,indicating that they have experienced high degree of crystallization differentiation and strong fluid-melt interaction.The industrial grade spodumene pegmatite in the Nibuxiaoba area is concentrated in the east of Nibuxiaoba at an altitude of 5500~6000m,whereas the west of Nibuxiaoba mainly develops beryl-bearing granites-pegmatites at an altitude of 5500~5200m.This paper and the previous data show that the degree of magmatic differentiation and the content of rare metals are positively correlated with the height of outcrops,which reflects the geodynamic mechanism of metallogenic driven by the activities of the Southern Tibet Detachment System.Our research on the metallogenic age and characteristics at Nibuxiaoba have important reference significance for understanding the mineralization and prospecting of rare metals in the Himalaya belt.

关 键 词：喜马拉雅 尼布晓巴 锂辉石伟晶岩 肉切村群 稀有金属成矿 

分 类 号：P588.131[天文地球—岩石学] P597.3[天文地球—地质学] P618.71