西秦岭温泉钼矿区含钼花岗斑岩锆石U-Pb年龄、Hf同位素组成及岩浆物质来源讨论  

Zircon U-Pb age,Hf isotope composition,and magma source of Mo-bearing granite porphyry in the Wenquan Mo deposit from West Qinling

作　　者：吴纪修[1,2] 王文 黄增保 王晓赛[1] 薛倩冰 苏新[2] WU Jixiu;WANG Wen;HUANG Zengbao;WANG Xiaosai;XUE Qianbing;SU Xin(Institute of exploration techniques,CAGS,Langfang 065000,Hebei,China;China University of Geosciences,Beijing 100083,China;Geological Survey Institute of Gansu Province,Lanzhou 735000,Gansu,China)

机构地区：[1]中国地质科学院勘探技术研究所,河北廊坊065000 [2]中国地质大学(北京),北京100083 [3]甘肃省地质调查院,甘肃兰州730000

出　　处：《中国地质》2021年第5期1596-1608,共13页Geology in China

基　　金：中国地质调查局项目“共和—略阳地区区域地质调查”(DD20190072)资助。

摘　　要：温泉钼矿床位于西秦岭造山带北缘,是西秦岭地区唯一斑岩型钼矿床。矿体产于花岗斑岩体及其与围岩接触带内。对温泉钼矿含矿花岗斑岩开展锆石U-Pb年代学与原位Hf同位素研究,有助于精确约束含钼花岗斑岩时代,揭示岩浆演化信息,深化温泉钼矿床成因的认识。本文利用LA-ICPMS锆石U-Pb定年方法,对温泉钼矿区含钼岩体进行精确同位素定年。结果表明:花岗斑岩的锆石环带结构明显,Th/U比值较大(0.41~0.88),为典型的岩浆锆石,含钼花岗斑岩侵位年龄为212.43~213.4 Ma,其侵入的似斑状二长花岗岩年龄(围岩)则为219.9 Ma,均属晚三叠世岩浆活动的产物。温泉矿区花岗斑岩锆石Hf同位素组成较为一致,ε_(Hf)(t)值均为负值,介于-1.89~-0.63,平均-1.59,在ε_(Hf)(t)-t图解中,样点集中分布于球粒陨石以及亏损地幔线之下,暗示其岩浆源区较单一,应为经改造过的地壳物质部分熔融的产物。二阶段模式年龄(T_(DM2))主要集中在1291~1408 Ma,表明中元古代地壳物质可能为岩体主要来源。The Wenquan Mo ore deposit,the only one porphyry-type Mo deposit in the West Qinling,is located on the northern margin of the West Qinling orogenic belt.The ore bodies are mainly distributed within the granite porphyry and the contact zone between the granite porphyry and its surrounding rocks.The zircon U-Pb dating and Hf isotope studying of the ore deposit have great significance to define the forming age of the granite porphyry,reveal the evolution of the magma,and furthermore to clarify genesis of the ore deposit.The zircon LA-ICP MS U-Pb dating method was used to constrain the forming age of Mo-bearing granite porphyry in the Wenquan mine.Zircons from the granite porphyry have clear zonal texture and large value of Th/U ratio(0.41~0.88).The LA-ICPMS U-Pb dating of zircons from the Mo-bearing granite porphyry and its intruding porphyritic monzogranite yield ages of 212.43~213.4Ma and 219.9Ma respectively,indicating Late Triassic magmatic product.The hafnium isotope of the granite porphyry has a negative value between-1.89 and-1.63,with an average value of-1.59.On theε_(Hf)(t)-t diagram,the sampling points are plotted below the chondrite and the deficit mantle line,which indicates a unitary magmatic source.This source is the partially melting product of the modified earth crust.The age of the second stage(T_(DM2))model ranges from 1291 to 1408 Ma,which indicates that the magma was probably derived from the partiall melting of Mesoproterozoic earth crust.

关 键 词：锆石U-PB年龄 LA-ICP MS HF同位素 温泉钼矿 西秦岭 地质调查工程 

分 类 号：P597[天文地球—地球化学] P588.121[天文地球—地质学]