金川铜镍硫化物矿床晚中生代以来抬升冷却事件的磷灰石裂变径迹约束  

Apitite Fission Track Constraints on the Late Mesozoic Uplift and Cooling Events of the Jinchuan Cu-Ni Sulfide Deposit

作　　者：刘健[1] 于强[1,2,3] 王猛 焦建刚[1,2,3] 陈长发[5] 马云飞 LIU Jian;YU Qiang;WANG Meng;JIAO Jiangang;CHEN Changfa;MA Yunfei(School of Earth Science and Resources,Chang’an University,Xi’an 710054,Shaanxi,China;MOE Key Laboratory of Western China’s Mineral Resources and Geological Engineering,Xi’an 710054,Shaanxi,China;Xi’an Key Laboratory for Mineralization and Efficient Utilization of Critical Metals,Xi’an 710054,Shaanxi,China;Northwest Bureau of China Metallurgical Geology Bureau,Xi’an 710119,Shaanxi,China;Xi’an Yuanfengcheng Engineering Consulting Co.,Ltd,Xi’an 710018,Shaanxi,China)

机构地区：[1]长安大学地球科学与资源学院,陕西西安710054 [2]西部矿产资源与地质工程教育部重点实验室,陕西西安710054 [3]西安市关键金属成矿与高效利用重点实验室,陕西西安710054 [4]中国冶金地质总局西北局,陕西西安710119 [5]西安源丰诚工程咨询有限公司,陕西西安710018

出　　处：《大地构造与成矿学》2023年第3期618-630,共13页Geotectonica et Metallogenia

基　　金：国家自然科学基金项目(92162213);长安大学中央高校基本科研业务费专项资金(300102272205、300102272808);长安大学研究生教学改革项目(300103102762)和长安大学大学生创新创业训练计划项目(202110710060)联合资助。

摘　　要：金川铜镍硫化物矿床位于阿拉善地块西南缘的龙首山隆起,大地构造位置属于华北板块西南边缘。该矿床形成后的保存与变化过程认识不足,尤其是其抬升冷却历史尚未明确。明确金川铜镍硫化物矿床自晚中生代以来抬升冷却时期及速率,为提高对其成矿动力学过程的认识及今后深部找矿工作提供依据。本文结合区域热年代学数据,采用基于LA-ICP-MS的磷灰石裂变径迹分析和热史反演模拟,综合讨论了金川矿区晚中生代以来的抬升和冷却过程。金川铜镍硫化物矿区南部白家嘴子组的3个混合岩样品产生的裂变径迹池年龄依次为40.8±5.4 Ma、30.8±10.4 Ma和50.9±4.6 Ma。利用磷灰石裂变径迹数据及反演模拟热史结果,揭示金川岩体及围岩晚白垩世以来(~100 Ma)经历了两个构造抬升阶段:①晚白垩世‒晚中新世时期岩体相对缓慢抬升,②晚中新世以来,岩体快速冷却并被抬升至地表。金川地区晚中新世(~8 Ma)发生的快速抬升是对区域构造演化(喜马拉雅运动Ⅱ)的响应,其动力学环境为南、北双向构造挤压力作用之下,印度板块向北挤压俯冲楔入到青藏高原之下,导致青藏高原不断向北楔入,同时位于祁连山地体之下的阿拉善地块岩石圈地幔向南楔入(被动俯冲)于青藏高原东北部之下,形成一种双向挤压对冲模式,使得金川岩体在这一时期发生了快速冷却抬升事件。The Jinchuan Cu-Ni sulfide deposit is located in the Longshoushan terrane on the southwest margin of the Alxa Block,geotectonically belonging to the southwest edge of the North China Craton.The preservation and exhumation processes of the Jinchuan deposit have not been well documented,its uplift and cooling history,in particular,is still not clear.The aims of this study are to clarify the uplifting-cooling episodes and rate of the deposit since the late Mesozoic,and provide constraints on the metallogenic dynamic process and guides on the deep prospection in the future.LA-ICP-MS apatite fission track ages of three migmatite samples from the Baijiazuizi Formation in the south of the mining area are 40.8±5.4 Ma,30.8±10.4 Ma,and 50.9±4.6 Ma,respectively.Apatite fission track results and inversion simulation of the thermal history reveal that the Jinchuan intrusion and its surrounding rocks underwent two stages of uplifting and cooling since the late Cretaceous(~100 Ma):(1)From the Late Cretaceous to late Miocene(~8 Ma),the intrusion was relatively slowly uplifted and cooled,with an average cooling rate of about 0.8℃/Ma;(2)Since the Late Miocene,the intrusion was uplifted to the surface and cooled rapidly,with an average cooling rate of about 7.4℃/Ma.The rapid uplifting and cooling of the Jinchuan area in the Late Miocene(~8 Ma)is a response to the regional tectonic evolution(Himalayan movementⅡ).Under the south-north tectonic compression,the Indian plate compressed and subducted northward and wedged under the Qinghai-Tibet Plateau,resulted in the continuous northward wedging of the Qinghai-Tibet Plateau.At the same time,the lithospheric mantle of the Alxa Block located under the Qilian Mountain wedged southward(passive subduction)under the northeast of the Qinghai-Tibet Plateau,forming a two-way compression hedging model,resulted in a rapid uplifting and cooling of the Jinchuan intrusion during this period.

关 键 词：低温热年代学 金川铜镍硫化物矿床 矿床保存 抬升冷却 磷灰石裂变径迹 

分 类 号：P542[天文地球—构造地质学] P612[天文地球—地质学]