东昆仑昆仑河泥盆纪过铝质花岗岩成因和找矿意义  

Genesis and prospecting significance of Caledonian peraluminous granite in Kunlunhe area,East Kunlun

作　　者：王涛[1] 王秉璋[1] 陈静 张金明[1] 何皎[1] 金婷婷[1] 李五福[1] WANG Tao;WANG BingZhang;CHEN Jing;ZHANG JinMing;HE Jiao;JING TingTing;LI WuFu(Qinghai Geological Survey Institute,Key Laboratory of the Northern Qinghai-Tibet Plateau Geological Processes and Mineral Resources,Engineering and Technology Center of Remote Sensing Big Data in Qinghai Province,Xining 810012,China;College of Geography Science,Qinghai Normal University,Xining 810000,China)

机构地区：[1]青海省地质调查院,青藏高原北部地质过程与矿产资源重点实验室,青海省遥感大数据工程技术研究中心,西宁810012 [2]青海师范大学地理科学学院,西宁810000

出　　处：《岩石学报》2024年第2期571-590,共20页Acta Petrologica Sinica

基　　金：第二次青藏高原综合科学考察研究项目(2019QZKK0806);国家重点研发计划项目(2021YFC2901902);国家自然科学基金项目(41762006、42262027);青海省地质矿产勘查开发局项目(青地矿61号)联合资助。

摘　　要：昆仑河地区是东昆仑造山带过铝质花岗岩分布相对集中的地区,昆仑河过铝质花岗岩分布区形成了Li、Be、Sn等元素高背景区,部分地区具明显的异常,可为东昆仑造山带古生代碰撞造山过程的研究和相关稀有金属矿产成矿预测提供重要的依据。本文通过对昆仑河地区花岗岩岩相学、地球化学、同位素年代学及Hf、Sr同位素研究发现:昆仑河地区新发现的花岗岩形成时代为早泥盆世(418~416Ma),其岩性为黑云母花岗闪长岩、二云母花岗闪长岩和二云母花岗岩,暗色矿物均为黑云母(≤5vol%);为富钠弱过铝高钾钙碱性系列,Na_(2)O/K_(2)O平均值是1.13,A/CNK为1.03~1.10,富集LREE,(La/Yb)_(N)为9.7~28.1,重稀土弱亏损,Y为8.69×10^(-6)~23.4×10^(-6),Yb为0.67×10^(-6)~2.43×10^(-6);Eu具较明显的负异常(Eu/Eu^(*)=0.48~0.86),Rb/Sr比值(0.34~1.12)和Rb/Ba比值(0.18~0.32)较低;(^(87)Sr/^(86)Sr)_(i)为0.7045~0.7083,ε_(Nd)(t)为-4.94~-1.64,t_(DM2)为1.56~1.29Ga;锆石ε_(Hf)(t)值分布在-3.3~2.7之间,t_(DM2)为1.61~1.28Ga;岩浆源于古老元古代地壳的部分熔融,源区有地幔物质或源于地幔的新生地壳物质的参与。结合以往研究成果,昆仑河地区存在晚志留世(425~422Ma)和早泥盆世(418~416Ma)两期过铝质花岗岩,两者与东昆仑加里东期碰撞造山带俯冲岩石圈板片断离、幔源岩浆底侵引发的地壳熔融相关。根据1/25万化探数据做概要分析,该花岗岩分布区显示了较好的Li、Be、Sn等矿的找矿前景。The Early Paleozoic peraluminous granites in the Kunlunhe area can provide important constraints on the Paleozoic collisional process and rare metal metallogenic genesis of the East Kunlun Orogenic Belt.This paper introduces the newly discovered Early Devonian(418~416Ma) peraluminous granite in the Kunlunhe area,whose lithology is biotite granodiorite,two-mica granodiorite and two-mica granite with its dark minerals all composed of biotite(≤5vol%).The peraluminous granites belong to a sodium-rich,weak peraluminous,high potassium and calc-alkaline series.These granite samples have averaged Na_(2)O/K_(2)O=1.13,and varied values of A/CNK=1.03~1.10,(La/Yb)_N=9.7~28,Y=8.69×10^(-6)~23.4×10^(-6) and Yb=0.67×10^(-6)~2.43×10^(-6) with enrichment of LREE and weak depletion of HREE.They also have obvious Eu negative anomaly(Eu/Eu^(*)=0.48~0.86),with relatively lower Rb/Sr(0.34~1.12) and Rb/Ba(0.18~0.32) ratios.Their(^(87)Sr/^(86)Sr)_(i),ε_(Nd)(t) and t_(DM2) values are 0.7045~0.7083,-4.94~-1.64 and 1.56~1.29Ga,respectively.Their measured zircon ε_(Hf)(t) and t_(DM2) are-3.3~2.7 and 1.61~1.28Ga,respectively.Its magma is originated from the partial melting of the ancient Proterozoic crust with the participation of mantle material or new crustal material from mantle.Combined with previous researches,there are two peraluminous granites series in the Kunlunhe area:the Late Silurian(425~422Ma) series and the Early Devonian(418~416Ma) series.Both of them are related to the melting of crust caused by subduction lithospheric slab break-off and mantle magma penetration in the Caledonian collision orogenic belt of East Kunlun.There is high Li,Be and Sn backgrounds with some obvious anomalies in the peraluminous granites distributed area,showing a good prospecting potential in the Kunlunhe area.

关 键 词：过铝花岗岩 加里东期 东昆仑 昆仑河 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]