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引用本文:吴纪修,王文,黄增保,王晓赛,薛倩冰,苏新. 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[J]. 中国地质, 2021, 48(5): 1596-1608.
WU Jixiu,WANG Wen,HUANG Zengbao,WANG Xiaosai,XUE Qianbing,SU Xin. Zircon U-Pb age, Hf isotope composition, and magma source of Mo-bearing granite porphyry in the Wenquan Mo deposit from West Qinling[J]. Geology in China, 2021, 48(5): 1596-1608(in Chinese with English abstract).
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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
吴纪修1,2, 王文1, 黄增保3, 王晓赛1, 薛倩冰1, 苏新2
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
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,εHft)值均为负值,介于-1.89~-0.63,平均-1.59,在εHft)-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(TDM2)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。
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
DOI:10.12029/gc20210520
分类号:P597;P588.12+1
基金项目:中国地质调查局项目“共和—略阳地区区域地质调查”(DD20190072)资助。
Zircon U-Pb age, Hf isotope composition, and magma source of Mo-bearing granite porphyry in the Wenquan Mo deposit from West Qinling
WU Jixiu1,2, WANG Wen1, HUANG Zengbao3, WANG Xiaosai1, XUE Qianbing1, SU Xin2
1.Institute of exploration techniques, CAGS, Langfang 065000, Hebei, China;2.China University of Geosciences, Beijing 100083, China;3.Geological Survey Institute of Gansu Province, Lanzhou 735000, Gansu, China
Abstract:
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 the εHf(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 (TDM2) model ranges from 1291 to 1408 Ma, which indicates that the magma was probably derived from the partiall melting of Mesoproterozoic earth crust.
Key words:  zircon U-Pb age  LA-ICP MS  Hf isotope  Wenquan Mo deposit  West Qinling  geological survey engineering