喜马拉雅东段库曲伟晶岩铁电气石-锂电气石-钙锂电气石系列及其指示意义  

Tourmaline of the schorl-elbaite-liddicoatite series from the Kuqu pegmatite in the East Himalaya,Tibet,and its implication.

作　　者：周起凤 秦克章[3,4] 刘宇超 何畅通 曹明坚 赵俊兴 施睿哲[3,4] ZHOU QiFeng;QIN KeZhang;LIU YuChao;HE ChangTong;CAO MingJian;ZHAO JunXing;SHI RuiZhe(China Institute of Disaster Prevention,Sanhe 065201,China;Hebei Key Laboratory of Earthquake Dynamics,Sanhe 065201,China;State Key Laboratory of Lithospheric and Environmental Coevolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]防灾科技学院,三河065201 [2]河北省地震动力学重点实验室,三河065201 [3]岩石圈演化与环境演变全国重点实验室,中国科学院地质与地球物理研究所,北京100029 [4]中国科学院大学地球与行星科学学院,北京100049

出　　处：《岩石学报》2025年第3期837-858,共22页Acta Petrologica Sinica

基　　金：国家重点研发计划青年科学家项目(2023YFC2908400);第二次青藏高原综合科学考察研究项目(2019QZKK0802、2019QZKK0806);国家自然科学基金项目(42272101)联合资助.

摘　　要：电气石是花岗伟晶岩中常见的副矿物。喜马拉雅花岗岩-伟晶岩系统以普遍产出电气石为重要地质特征。喜马拉雅东段库曲岩体产出含锂辉石伟晶岩脉,发育复杂稀有金属矿化。本文调查了库曲岩体桑玉村南侧的绿色电气石伟晶岩,其由墨绿色电气石-钠长石-微斜长石-石英-云母集合体、少量黄绿色电气石-钠长石-微斜长石-石英-云母集合体和无色电气石-钠长石-石英-云母集合体组成,产出绿柱石、锂云母、铌铁矿族矿物、细晶石、萤石等矿物。电气石属于碱基-钙基系列,包括铁电气石、锂电气石、F-锂电气石和F-钙锂电气石。锂电气石分为富铁锂电气石(FeO=3.36%~7.17%)和贫铁锂电气石(FeO=0.12%~2.70%)。与贫铁锂电气石相比,富铁锂电气石富Fe、贫Al、Li和Na,F-锂电气石富Ca和F、贫Na。F-钙锂电气石的SiO_(2)和Al_(2)O_(3)含量分别为36.35%~38.17%和39.78%~41.81%,Li_(2)O^(*)、CaO和F含量高(2.27%~2.59%、2.37%~3.48%和0.99%~1.26%),FeO和Na_(2)O含量低(0.13%~1.87%和0.90%~1.41%)。其中,最富Ca的F-钙锂电气石分子式是(Ca_(0.55)Na_(0.30)□_(0.16))(Li_(1.60)Al_(1.34)Mn_(0.02)Fe_(0.02))Al_(6)(Si_(5.85)Al_(0.15))O_(18)(BO_(3))_(3)(OH)_(3)(F_(0.61)OH_(0.39))。在背散射图像下,电气石具有均一、核-(幔)-边、不规则分带和补丁结构。墨绿色电气石(Type I)由铁电气石核、铁电气石或富铁锂电气石幔/补丁、以及富铁锂电气石边组成,偶见F-钙锂电气石边。黄绿色电气石(TypeⅡ)主要由富铁锂电气石核和贫铁锂电气石、F-锂电气石或F-钙锂电气石幔/边组成(TypeⅡa),或呈具有不规则分带的富铁锂电气石细脉(TypeⅡb)。无色电气石(TypeⅢ)的内部结构分带多样,其中,TypeⅢa呈均一结构,为贫铁锂电气石、F-锂电气石或F-钙锂电气石颗粒;TypeⅢb由贫铁锂电气石核/幔与贫铁锂电气石、F-锂电气石或F-钙锂电气石边组成,偶见F-锂电气石或F-钙锂电气石核/幔;TypeTourmaline is a common associate mineral in granitic pegmatites.Most of granite-pegmatite systems in Himalaya are characterized by widespread occurrence of tourmaline.The Kuqu intrusion hosts several spodumene-bearing pegmatite dykes and develops complex rare-element mineralization types.In this study,a green tourmaline-bearing pegmatite located at the Sangyu village has been identified in the Kuqu intrusion.This tourmaline-bearing pegmatite is composed of dark green tourmaline-albite-K-feldspar-quartz-mica assemblage,yellowish green tourmaline-albite-K-feldspar-quartz-mica assemblage and colorless tourmaline-albite-quartz-mica assemblage,with occurrences of beryl,lepidolite,columbite-group mineral,microlite and fluorite.Tourmalines belong to alkali and calcic groups,including schorl,elbaite,fluor-elbaite and fluor-liddicoatite.Elbaite is divided into Fe-rich elbaite(FeO=3.36%~7.17%)and Fe-poor elbaite(FeO=0.12%~2.70%).Compared with Fe-poor elbaite,Fe-rich elbaite is rich in Fe and poor in Al,Li and Na,while F-elbaite is rich in Ca and F and poor in Na.Fluor-liddicoatite has the SiO_(2) and Al_(2)O_(3) content ranges of 36.35%~38.17%and 39.78%~41.81%with high contents of Li_(2)O^(*),CaO and F(2.27%~2.59%,2.37%~3.48%and 0.99%~1.26%)and low contents of Fe and Na(0.13%~1.87%and 0.90%~1.41%).The most calcic composition of fluor-liddicoatite corresponds to(Ca_(0.55) Na_(0.30)□0.16)(Li _(1.60) Al_(1.34) Mn_(0.02) Fe_(0.02))Al_(6)(Si_(5.85) Al_(0.15))O_(18)(BO_(3))_(3)(OH_(3.39) F_(0.61)).The BSE images show that tourmalines are homogeneous,core-(mantle)-rim,irregular-zoned and patchy.The dark green tourmaline crystals(Type Ⅰ)are composed of schorl core,schorl/Fe-rich elbaite mantle/patch,and Fe-rich elbaite rim or occasionally fluor-liddicoatite rim.The yellowish green tourmaline grains(Type Ⅱ)are crystals composed of Fe-rich elbaite core and Fe-poor elbaite/fluor-elbaite/fluor-liddicoatite mantle/rim(Type Ⅱa),or appear as irregular-zoned Fe-rich elbaite veinlets(Type Ⅱb).The colorless tourmaline crystals(Typ

关 键 词：铁电气石-锂电气石-钙锂电气石 白云母-铁锂云母-锂云母 岩浆分异演化 富锂伟晶岩 喜马拉雅 

分 类 号：P578.953[天文地球—矿物学] P588.131[天文地球—地质学]