摘要
大湖塘矿田是我国新发现的世界级钨多金属矿产资源基地,位于江南造山带中段,地处九岭山脉北部的武宁、修水、靖安三县交界区域,面积约500km^2,储藏着近二百万吨WO_3资源(伴生Cu和Mo)。该区以晋宁期花岗岩类的大面积出露为特色,而燕山期花岗岩为全隐伏,前者作为矿田最主要的细脉-浸染型白钨矿的赋存载体,后者则在成岩时代上与钨成矿时间基本一致。两期岩浆岩对区内大规模钨成矿作用的贡献问题,及其内在成因联系问题具有重要的研究意义。本文在矿田地质和岩石地球化学研究基础上,以锆石的矿物地球化学研究为切入点,对晋宁期和燕山期花岗岩类的年代学、Hf同位素、微量元素特征进行系统的对比研究。结果显示,大湖塘矿田石门寺花岗岩成岩时代为147.7Ma、靖安钨矿成矿时代为134.9Ma、赋矿花岗岩成岩时代为815.8Ma,两个时代的岩浆岩均为过铝质S型花岗岩系列;更有意义的是,燕山期花岗岩(石门寺)中发现多颗继承锆石,且继承锆石与晋宁期岩浆锆石具有相近的Hf同位素和微量元素组成,这指示燕山期花岗岩与晋宁期花岗岩具有亲缘关系,包括晋宁期花岗岩在内的中新元古代基底岩石可能参与了该区中生代花岗岩的源区重熔。锆石微量元素特征表明,这两期重熔的岩浆结晶温度都在700℃左右,经历了低氧逸度、水近饱和条件下的熔融。晋宁期花岗岩富含W、Ca等成矿所需元素,在中生代华南岩石圈地幔上涌导致的中上地壳大规模熔融的背景下,燕山期岩浆期后含矿热液与晋宁期花岗岩围岩发生交代,成为本区大型白钨矿为主的钨多金属矿床形成的必要条件。
The Dahutang ore-field is a newly discovered world-class W-polymetallic ore cluster in South China.It is located in the middle part of the Jiangnan orogenic belt,at the junction of Wuning,Xiushui and Jing’an counties of Jiangxi Province.Dahutang orefield covers an area of about 500 km2 and reserves nearly two million tons of WO3 resources(associated Cu and Mo).This area is characterized by a large area of exposure of Jinning Period granitoids,while the Yanshanian granitoids are completely concealed.The former one is the main vein-disseminated scheelite carrier,and the latter one is consistent with the W mineralization in time.It is of important significance whether there is a genetic connection between the two-period magmatism and how they contribute to the W mineralization.On the basis of studies of ore-field geology,petrology and geochemistry,this paper is a comparative research of geochronology,Hf isotoic and trace elemental geochemistry of the zircons from the Jinning Period and Yanshanian granotoids.The results show that Shimensi granite has zircon U-Pb ages of is 147.7 Ma,Jing’an W desposit has molybdenite Re-Os ages of is 134.9 Ma,and the age of ore-host Jinning Period granite is 815.8 Ma in Dahutang W ore-field.The granitoids of the two-period are all peraluminous and S-type series.Some inherited zircons are discovered in Shimensi Yanshanian granite,which have similar Hf isotopes and trace element compositions with the Jinning Period magmatic zircons,indicating the Jinning Period granitoids and Yanshannian granite may have an inheritance relationship.The Meso-Neoproterozoic basement,including the Jinning Period granitoids could take part in the original remelting source of the Mesozoic granite.The trace element of zircon indicates that the crystallization temperature of the two-period granitic magma were both around 700℃,then experienced low oxygen fugacity and water saturated molten during magma evolution.In Mesozoic,large-scale remelting of the middle and upper crust formed granitic magma under the background of lithospheric extension in South China.The W-bearing hydrothermal fluid accumulated following the Yanshanian granitic magma intrusion and metasomatized with the surrounding Jinning Period granitoids(rich in W and Ca),which became the necessary condition for the formation of large scale veinlet-disseminated type scheelite-dominated mineralization.
作者
李宏伟
赵正
陈振宇
郭娜欣
甘加伟
李小伟
尹政
LI HongWei;ZHAO Zheng;CHEN ZhenYu;GUO NaXin;GAN JiaWei;LI XiaoWei;YIN Zheng(Schoo of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China;MNR Key Laboratory of Metallogeny and Mineral Asessment,Instiute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China)
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2021年第5期1508-1530,共23页
Acta Petrologica Sinica
基金
国家重点研发计划项目(2016YFC0600208)
国家自然科学基金项目(41973046)
中国地质调查局项目(JYYWF20180502)联合资助。
关键词
燕山期
大湖塘矿田
锆石
成岩成矿时代
The Yanshanian
Dahutang ore-field
Zircon
Rock forming and ore forming ages
