首页|西藏拿若铜(金)矿床隐爆角砾岩对成矿时代的约束

西藏拿若铜(金)矿床隐爆角砾岩对成矿时代的约束

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[研究目的]拿若矿床是多龙矿集区 4个超大型矿床之一,由斑岩型和角砾岩型矿体组成.斑岩型矿体研究资料丰富,角砾岩矿体研究程度较浅,隐爆作用与成矿作用的时代关系还缺乏详细的研究.隐爆角砾岩整体呈筒状产出,角砾成分为长石石英砂岩和花岗闪长斑岩,胶结物成分主要为岩粉.[研究方法]本次研究旨在通过年代学证据探讨隐爆角砾岩形成与成矿的时代关系.[研究结果]锆石矿物学显示花岗闪长斑岩(NR1)锆石边部发生溶蚀边,震荡环带减弱,未彻底重结晶;胶结物(NR2)锆石结晶较好,震荡环带清晰.两种样品的锆石微量元素特征显示,两期岩浆源区均为陆壳环境;稀土配分曲线均较陡,富集重稀土,亏损轻稀土;具有显著的正Ce异常和负Eu异常.LA-ICP-MS锆石U-Pb定年结果显示,花岗闪长斑岩的锆石206Pb/238U年龄为 117.3～125.4 Ma,加权平均年龄为(120.8±1.4)Ma,成岩时间在 120.8 Ma左右;胶结物的锆石206Pb/238U年龄为 113.5～119.9 Ma,加权平均年龄为(116.4±1.2)Ma,隐爆时代在 116.4 Ma左右.[结论]拿若矿床共发生两期成岩作用,分别为～120 Ma和～117 Ma.拿若矿床成矿作用发生在 116～117 Ma,而非～120 Ma.根据年代学证据认为,成矿作用和隐爆作用受同期岩浆作用控制,隐爆作用在前而成矿作用在后,岩浆演化在时间和空间上存在差异.
Constraints on metallogenic age from cryptoexplosive breccia in Naruo Cu(Au)deposit,Xizang
This paper is the result of mineral exploration engineering.[Objective]The Naruo deposit is one of four super large deposits in Duolong ore district.It is composed of porphyry and breccia type orebodies.Previous researches have focused on porphyry orebody,while the research on cryptoexplosive breccia ore bodies is relatively weak.The temporal relationship between cryptic explosion processes and mineralization remains inadequately studied.The cryptoexplosive breccia is generally produced in a cylindrical shape,with the breccia composed of feldspar quartz sandstone and granodiorite porphyry,and the cement mainly composed of rock powder.[Methods]This study is to explore the age relationship between the formation and mineralization of cryptoexplosive breccia through chronological evidence.[Results]Zircon mineralogy shows that the zircon edge of the granite diorite porphyry(NR1)is characterized by dissolution,weak oscillation zone,and incomplete recrystallization.Zircons in cement(NR1)is characterized by fine crystalline form,clear oscillatory zone.The trace element characteristics of these two types of zircons show that the source of two stages of magma is continental crust.The rare earth distribution curves are relatively steep,with enrichment of heavy rare earth elements,loss of light rare earth elements,significant positive Ce and negative Eu anomalies.LA-ICP-MS zircon U-Pb dating results show that the zircon 206Pb/238U age of granite diorite porphyry is between 117.3 Ma and 125.4 Ma,with weighted average age of(120.8±1.4)Ma,indicating the diagenetic age of 120.8 Ma.The zircon 206Pb/238U age of cement is between 113.5 Ma and 119.9 Ma,with weighted average age of(116.4±1.2)Ma,indicating the cryptoexplosive age of 116.4 Ma.[Conclusions]The results in this study show two stages of diagenesis in Naruo deposit,～120 Ma and～117 Ma,respectively.Mineralization occurred between 116 Ma and 117 Ma,rather than～120 Ma.The chronological data shows that the mineralization and cryptoexplosion are controlled by contemporaneous magmatism,with cryptoexplosion occurring first and mineralization occurring later,and there are differences in the time and space of magma evolution.

zircon U-Pb datingcryptoexplosive timediagenesis and mineralizationcryptoexplosive brecciasNaruoXizangmineral exploration engineering

高轲、宋扬、刘治博、杨欢欢、林彬、李发桥

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中国地质调查局成都地质调查中心,四川 成都 610081

中国地质科学院矿产资源研究所,北京 100037

中国地质大学(北京),北京 100083

锆石U-Pb定年 隐爆时代 成岩成矿时代 隐爆角砾岩 拿若 西藏 矿产勘查工程

中国地调局项目中国地调局项目中国地调局项目中国地调局项目国家自然科学基金国家自然科学基金国家重点研发计划深地资源开采项目

DD20242518DD20230031DD20190167DD2019014741702080919552082018YFC0604103

2024

10.12029/gc20201104002

中国地质
中国地质调查局

中国地质

CSTPCD北大核心
影响因子：2.317
ISSN：1000-3657
年,卷(期)：2024.51(2)
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