投稿时间：2021-01-15
修订日期：2021-07-03
网络发布日期：2021-08-30
中文摘要:幕阜山是中国重要的稀有金属矿集区，区域内多期次岩浆活动形成的复式花岗岩基与稀有金属成矿关系密切。目前，区域内黑云母花岗岩阶段和二云母花岗岩阶段的稀有金属成矿作用已有报道，而岩浆演化晚期白云母花岗岩阶段的相关成矿作用缺乏研究。文章选取了幕阜山东部麦埚铍矿床内由白云母花岗岩分异形成的含绿柱石伟晶岩作为研究对象，对其进行了LA-ICP-MS锆石U-Pb定年和Hf同位素组成测试。结果显示，伟晶岩中锆石U-Pb年龄为（124.9±0.34） Ma，表明麦埚地区以铍为主的稀有金属成矿作用发生在早白垩世，同时也代表了幕阜山地区与白云母花岗岩相关的稀有金属成矿作用。此外，麦埚含绿柱石伟晶岩的εHf（t）值为-7.6~-5.2，二阶段模式年龄为1668~1512 Ma，与复式岩体中各阶段花岗质侵入体的εHf（t）和二阶段模式年龄值大致吻合，显示出它们相似的源区特征。综合区域内已有的年代学数据，与稀有金属成矿相关的岩浆活动主要分布在早白垩世，大致可分为3个阶段：黑云母花岗岩阶段（145 Ma）以Be矿化为主，矿化强度较低；二云母花岗岩阶段（140~138 Ma）为区域稀有金属成矿的主阶段，矿化种类包括Be-Nb-Ta-Li-Cs，矿化强度高；白云母花岗岩（125~122 Ma）阶段以BeNb-Ta矿化为主，矿化强度不高。幕阜山岩体是典型的“体中体”模式复式岩基，白云母花岗岩作为晚期分异程度最高的侵入体，却未发生大规模成矿作用，其原因在于受到了岩浆活动规模、岩浆冷却速率和容矿空间等多重因素的制约。
Abstract:Mufushan is an important rare metal concentration area in China. The granite complex formed by multiple magmatic activities is closely related to the mineralization of rare metals. Now, the mineralization of biotite granite stage and two mica granite stage in Mufushan area has been reported, but the mineralization of muscovite granite stage in late magmatic evolution is lacking, so the beryl-bearing pegmatite which formed by differentiation of muscovite granite in Maiguo Be deposit of Eastern Mufushan was selected as the research object. In this research, the LA-ICP-MS was employed for U-Pb dating and Hf isotopic compositions of zircon grains from pegmatite in Maiguo. The results show that the zircon U-Pb age of the pegmatite is (124.9±0.34) Ma. This age indicates that the Be-dominated rare metal mineralization occurred at about 125Ma in the early Cretaceous, it also represents that the third stage of rare metal mineralization relates to muscovite granite in Mufushan. The εHf(t) value of the beryl-bearing pegmatite in Maiguo is -7.6~-5.2, and the Hf two-stage model age is 1668~1512 Ma. The εHf(t) and Hf two-stage model age of Maiguo pegmatite correspond roughly with those of various granites in Mufushan granite complex, which indicates the pegmatite and the granites share similar source characteristics. According to the chronological data available in Mufushan, the magmatic activity closely related to the mineralization of rare metals in the Mufushan were occurred in early Cretaceous and can be roughly divided into three stages. The biotite granite stage (145 Ma) is dominated by Be mineralization, with low mineralization intensity. The two-mica granite (140~138 Ma) stage is the main stage of rare metal mineralization. The mineralization types include Be-Nb-Ta-Li-Cs with high mineralization intensity. The Muscovite granite (125~122 Ma) stage is dominated by Be-Nb-Ta mineralization, with low mineralization intensity. Mufushan intrusive mass is a typical "body in body" model composite batholith, the muscovite granite is the intrusive body with the highest degree of late differentiation, has no large-scale mineralization, which is controlled by multiple factors such as the scale of magmatic activity, the cooling rate of magma and the ore-hosting space.
keywords:geochemistry zircon U-Pb geochronology Hf isotopic composition Maiguo Be deposit muscovite granite Mufushan granite complex
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基金项目:本文得到国家重点研发计划课题（编号：2019YFC06505203、2016YFC0600204、2019YFC06050202）、国家自然科学基金（编号：42002109、41872096）和中央级公益性科研院所基本科研业务费（编号：IMRKK1927）联合资助
引用文本：
姜鹏飞,李鹏,李建康,何雪梅,冷双梁.2021.幕阜山东部麦埚铍矿床伟晶岩锆石U-Pb年龄、Hf同位素组成及其地质意义[J].矿床地质,40(4):723~739JIANG PengFei,LI Peng,LI JianKang,HE XueMei,and LENG ShuangLiang.2021.Zircon U-Pb geochronology and Hf isotopic composition of Be-pegmatites in Maiguo deposit, eastern Mufushan, and their geological implications[J].Mineral Deposits40(4):723~739
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