青藏高原东北部玉树地区尕朵-扎朵早侏罗世含(绿柱石-锂云母)锂辉石伟晶岩的发现及成矿意义  

Discovery and Mineralization Significance of Early Jurassic(Beryl-and Lepidolite-) Spodumene-bearing Pegmatites in the Gaduo-Zaduo Area of the Yushu Region, Northeastern Tibet

作　　者：李五福[1] 刘金恒 李善平[1] 贾春兴[1] 王成武 周金胜 王春涛[1] 许传兵 谈生祥[1] 胡继春[1] 章荣清[3] 龚林 王秉璋[1] 王强[2] LI Wufu;LIU Jinheng;LI Shanping;JIA Chunxing;WANG Chengwu;ZHOU Jinsheng;WANG Chuntao;XU Chuanbing;TAN Shengxiang;HU Jichun;ZHANG Rongqing;GONG Lin;WANG Bingzhang;WANG Qiang(Key Laboratory of the Northern Qinghai-Tibet Plateau Geological Processes and Mineral Resources,Qinghai Geological Survey Institute,Xining 810012,Qinghai,China;State Key Laboratory of Isotope Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Guangdong,China;State Key Laboratory for Mineral Deposits Research,School of Earth Sciences and Engineering,Nanjing University,Nanjing 210023,Jiangsu,China)

机构地区：[1]青海省地质调查院,青海省青藏高原北部地质过程与矿产资源重点实验室,青海西宁810012 [2]中国科学院广州地球化学研究所,同位素地球化学国家重点实验室,广东广州510640 [3]内生金属矿床成矿机制研究国家重点实验室,南京大学地球科学与工程学院,江苏南京210023

出　　处：《大地构造与成矿学》2022年第5期924-950,共27页Geotectonica et Metallogenia

基　　金：第二次青藏高原综合科学考察研究(STEP)项目(2019QZKK0702);青海省地质矿产勘查开发局项目(青地矿科[2021]59号)联合资助。

摘　　要：三江北段青海草陇、川西扎乌龙(或卡亚吉)伟晶岩型锂铍矿床与西部的喀喇昆仑白龙山、大红柳滩、肖尔布隆锂铍矿床以及东部的川西甲基卡、可尔因、雪宝顶等锂铍矿床,一起构成了青藏高原北缘一条近东西向的古特提斯巨型锂成矿带。但在草陇(青海南部玉树)以西到喀喇昆仑白龙山(新疆南部)之间一直还没有其他锂铍矿的报道。本次研究在青海省玉树地区草陇锂铍矿床以西72 km的尕朵‒扎朵地区发现了92条花岗伟晶岩,其中22条含(绿柱石‒锂云母)锂辉石花岗伟晶岩脉含矿性较好,另有不含矿伟晶岩脉15条,含矿性不明伟晶岩55条。本文对尕朵‒扎朵地区新发现的含(绿柱石‒锂云母)锂辉石花岗伟晶岩(含矿)和白云母花岗伟晶岩(不含矿)开展了系统的岩石学、地球化学及年代学研究。结果显示,含矿伟晶岩具有高SiO_(2)(72.87%~75.01%)、Al2O3(14.81%~17.18%)含量,低MgO(0.02%~0.03%)、CaO(0.32%~0.48%)、TiO_(2)(0.001%~0.007%)、P_(2)O_(5)(0.30%~0.42%)含量,及富钠( Na_(2)O/K_(2)O=2.05~12.92)的地球化学特征;白云母花岗伟晶岩(不含矿)亦具有高SiO_(2)(69.97%~73.75%)、Al_(2)O_(3)(15.18%~16.18%)含量,低MgO(0.01%~0.02%)、CaO(0.22%~0.38%)、TiO_(2)(0.001%~0.003%)、P_(2)O_(5)(0.35%~0.46%)含量,及变化的 Na_(2)O/K_(2)O值(0.35~2.04,平均1.0)。含矿和不含矿花岗伟晶岩的微量元素均富集大离子亲石元素Rb、K和高场强元素Nb、Ta、Hf,亏损Ba、Nd、Zr、Ti和稀土元素,且Zr/Hf值(7.85~18.44)低和Rb/Sr值(2.98~74.21)高;稀土元素总量较低,轻稀土元素富集,轻、重稀土元素分馏弱,发育负Ce异常,正‒负Eu异常,显示出岩浆演化晚期高度分异特性。含矿伟晶岩Li_(2)O品位为0.18%~2.33%,平均品位0.76%;BeO品位为0.04%~0.05%,平均品位0.043%,显示了良好的含矿性。年代学研究显示,含矿和不含矿伟晶岩的铌钽铁矿和锡石U-Pb年龄分布在194~178 Ma区间内,代表岩浆结晶和成矿时代The Caolong and Zawulong lithium-beryllium mineralized pegmatites in the northern section of the Sanjiang River Tectonic Zone,together with the Bailongshan,Dahongliu,Xiaoerbulong lithium-beryllium deposits of the Karakoram area in the west and the Jiajika,Keeryin,Xuebaoding deposits of west Sichuan in the east,constitute an approximately west-east trending giant lithium belt of Paleo-Tethys Suture in the northern Tibet Pateau.However,no Li-Be-rich pegmatite has been reported between the Caolong(Yushu of southern Qinghai)and Bailongshan(Karakoram area of southern Xinjiang)pegmatites.This study reports newly discovered more than 92 pegmatite dikes to the west of the Caolong pegmatites(about 72 km)in the Yushu Regions,southern Qinghai province.There are more than 22 pegmatite dikes containing spodumene,lepidolite or beryl,15 ore-free pegmatite dikes,and 55 pegmatite dikes of unknown ore-bearing potential.In this paper,a systematic study on petrology,geochemistry and chronology has been carried out on the(lepidolite or beryl)spodumene(ore-bearing)and muscovite(ore-free)granitic pegmatites newly discovered in the Gado-Zaduo area of the Yushu region in the middle part of the Paleo-Tethys metallogenic belt.The ore-bearing pegmatites have high contents of SiO_(2)(72.87%–75.01%)and Al_(2)O_(3)(14.81%–17.18%),and low MgO(0.02%–0.03%),CaO(0.32%–0.48%),TiO_(2)(0.001%–0.007%),and P_(2)O_(5)(0.30%–0.42%)with high Na_(2)O/K_(2)O ratios ranging from 2.05 to 12.92,indicating sodium-rich geochemical characteristics.The ore-free muscovite pegmatites have similar high contents of SiO_(2)(69.97%–73.75%)and Al_(2)O_(3)(15.18%–16.18%),and low MgO(0.01%–0.02%),CaO(0.22%–0.38%),TiO_(2)(0.001%–0.003%),and P_(2)O_(5)(0.35%–0.46%),but exhibt varible Na_(2)O/K_(2)O ratios ranging from 0.35 to 2.04.The trace elements of ore-bearing or-free granitic pegomatites show the enrichment of large ion lithophile elements Rb,K and high field strength elements Nb,Ta,and Hf,while the depletion of Ba,Nd,Zr,Ti and rare earth element

关 键 词：含(绿柱石-锂云母)锂辉石伟晶岩 锂铍成矿 成矿时代 尕朵-扎朵 草陇-尕朵矿集区 青海玉树 青藏北部 

分 类 号：P587[天文地球—岩石学] P595[天文地球—地质学] P597