东秦岭官坡地区稀有金属伟晶岩成矿机制  

Metallogenic mechanism of the rare-element pegmatite dykes in Guanpo area from the East Qinling Orogen

作　　者：周起凤 秦克章[4,5] 唐冬梅 马留锁[6] ZHOU QiFeng;QIN KeZhang;TANG DongMei;MA LiuSuo(China Institute of Disaster Prevention,Sanhe 065201,China;Hebei Key Laboratory of Earthquake Dynamics,Sanhe 065201,China;Institute of Mineral Resources Research,China Metallurgical Geology Bureau,Beijing 101300,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;Bureau of Natural Resources of Lushi County,Sanmenxia 472200,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]中国冶金地质总局矿产资源研究院,北京101300 [4]中国科学院地质与地球物理研究所,岩石圈演化与环境演变全国重点实验室,北京100029 [5]中国科学院大学地球与行星科学学院,北京100049 [6]卢氏县自然资源局,三门峡472200

出　　处：《岩石学报》2024年第9期2729-2752,共24页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(42272101)资助.

摘　　要：东秦岭伟晶岩区是我国著名稀有金属产地,是秦岭造山带规模最大、稀有金属矿化最丰富的伟晶岩区。官坡地区以伟晶岩脉数量多、含矿伟晶岩脉占比高、稀有金属矿化类型全(锂、铍、铌、钽、铯)、产出具有一定规模的锂矿化伟晶岩和多种稀有金属矿物为特色,是东秦岭伟晶岩区最具代表性和典型性的伟晶岩密集区。官坡地区由北西至南东依次产出火炎沟锡铌钽矿、南阳山、七里沟-前台和蔡家沟锂矿。稀有金属伟晶岩内部结构分带型式多样,呈弱分带(均一结构和分层结构)和复杂分带(主要为对称分带);伟晶岩类型主要是复杂型锂辉石亚型,少量为复杂型锂云母亚型和钠长石-锂辉石型;总体具有高硅、富碱、过铝质特征,富集大离子亲石元素(Rb、K)和高场强元素(Nb、Ta、Hf),亏损Ba和Ti,具有低的Nb/Ta值,稀土元素四分组效应明显,显示伟晶岩岩浆高度分异演化特征。矿物学研究结果表明,与火炎沟含锡伟晶岩相比,南阳山、七里沟和蔡家沟稀有金属伟晶岩(主要是锂矿化伟晶岩)岩浆具有更高的分异演化程度。官坡地区存在晚奥陶世-早志留世伟晶岩岩浆活动,稀有金属伟晶岩主要成岩成矿峰期为晚志留世-早泥盆世(424~408Ma)和早-中泥盆世(399~384Ma)。官坡稀有金属伟晶岩形成于北秦岭碰撞阶段、汇聚减弱-地壳抬升背景和造山后伸展阶段,集中于造山作用晚期。电气石B同位素和锆石Hf同位素组成显示官坡稀有金属伟晶岩来自元古宙陆壳变质沉积岩。官坡稀有金属伟晶岩与区域上出露的花岗岩不具有明显的成因联系,可能为北秦岭单元熔融产物。弱分带火炎沟锡铌钽矿化伟晶岩岩浆就位后未经历明显的分异作用;弱分带锂矿化伟晶岩岩浆是富锂岩浆在其就位后未经历明显的结晶分异即达到锂饱和的沉淀锂矿物,在该体系进入流体阶段后继续沉淀锂矿物完成稀有�The East Qinling pegmatite district is a famous rare-metal production area,and it is the largest pegmatite district hosting abundant rare element(REL)in the Qinling orogenic belt.The Guanpo area,as the most representative and typical pegmatite high-density area in East Qinling,is featured by a large number of pegmatite dykes,high proportion of REL-mineralized pegmatites,multi types of REL mineralization involved in Li,Be,Nb,Ta and Cs,large lithium-mineralized pegmatite dykes,and various REL minerals.From northwest to southeast,this area developed the Huoyangou Sn-Nb-Ta deposit,Nanyangshan,Qiligou-Qiantai and Caijiagou lithium deposits.The internal structures include weakly zoned pegmatites which are homogeneous and layered,and complexly zoned pegmatites.The REL pegmatite dykes belong to spodumene subtype in complex type dominantly,accompanied with lepidolite subtype in complex type and albite-spodumene type.The REL pegmatite magmas are peraluminous with high contents of Si and alkalis,and they are enriched in large ion lithophile elements(Rb,K)and high field strength elements(Nb,Ta,Hf),and poor in Ba and Ti with low Nb/Ta ratios and strong REE tetrad effects.Thus,the REL pegmatite magmas are highly fractionated and evolved.The mineralogical studies show that the Nanyangshan,Qiligou-Qiantai and Caijiagou REL pegmatites have high degrees of evolution compared with tin-bearing pegmatites in Huoyangou deposit.There is a Late Ordovician-Early Silurian pegmatite magma activity in Guanpo area and the main ore forming times are Late Silurian-Early Devonian(424~408Ma)and Early-Middle Devonian(399~384Ma).The Guanpo REL pegmatite dykes formed in collision,weakening convergence with crust uplift and post-orogenic extension settings,and mainly concentrate in late orogeny.The tourmaline B isotopes and zircon Hf isotopes indicate that the Guanpo REL pegmatite dykes are derived from Proterozoic crustal materials,mainly metasedimentary rocks.There is no genetic correlation between REL pegmatites and granites exposed in this regio

关 键 词：稀有金属伟晶岩 岩浆-热液演化过程 伟晶岩岩浆来源 成矿机制 东秦岭 

分 类 号：P588.131[天文地球—岩石学] P618.6[天文地球—地质学]