| 赣南富城岩体黑云母及其蚀变产物绿泥石的矿物化学研究——对铀成矿的指示意义 |
| Received:April 20, 2015 Revised:July 21, 2015 点此下载全文 |
| 引用本文：ZHAO YouDong,WU JunQi,LING HongFei,WANG HongZuo.2016.Mineral chemistry of biotite and chlorite in western part of Fucheng granite, southern Jiangxi Province: Implications for uranium mineralization[J].Mineral Deposits,35(1):153~168 |
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| Author Name | Affiliation | E-mail | | ZHAO YouDong | State Key Laboratory for Mineral Deposits Research, School of Earth Sciences an d Engineering, Nanjing University, Nanjing 210023, Jiangsu, China | zhaoyoudongnju@163.com | | WU JunQi | State Key Laboratory for Mineral Deposits Research, School of Earth Sciences an d Engineering, Nanjing University, Nanjing 210023, Jiangsu, China | | | LING HongFei | State Key Laboratory for Mineral Deposits Research, School of Earth Sciences an d Engineering, Nanjing University, Nanjing 210023, Jiangsu, China | hfling@nju.edu.cn | | WANG HongZuo | State Key Laboratory for Mineral Deposits Research, School of Earth Sciences an d Engineering, Nanjing University, Nanjing 210023, Jiangsu, China | |
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| 基金项目:本文得到国家重点基础研究发展计划“973”项目(编号:2012CB416703)和中国核工业地矿事业部十二五高校基础科研项目的联合资助 |
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| 中文摘要:富城花岗岩体位于赣南会昌盆地东侧,该岩体西部与橄榄玄粗岩系列 火山岩接触, 河草坑铀矿田就产于该花岗岩体的内外接触带中。在矿区外围花岗岩中发育大面积的蚀变带 ,其中的黑云母普遍蚀变为绿泥石。为了深入探讨蚀变与铀矿化的关系,文章运用电子 探 针技术对该蚀变带的黑云母及其蚀变产物绿泥石进行了矿物化学研究。结果表明,黑云母大 部分属铁叶云母,估算出富城花岗岩岩浆的氧逸度lg(fO2)值约为-150～-143, 氧 逸度较低,源岩为还原性较强的岩石,有利于铀预富集于源区中；富城产铀花岗岩中黑云母 的w(F)高达141% ～ 201%,表明花岗质岩浆富F,而富F岩浆中U溶解度高,可能是 富城岩体富铀的 重要原因之一。黑云母被绿泥石交代后呈黑云母假象,绿泥石矿物化学分析结果表明,绿泥 石以鲕绿泥石和蠕绿泥石为主,属于富铁的绿泥石,主要形成于还原环境；绿泥石的形成温 度介于246 ～ 307℃之间,平均276℃。全岩U、Th含量分析结果表明,上部“红化”蚀变层 中的w(U)(35×10-6 ～ 94×10-6,平均66×10-6)明显低 于下部“绿色”蚀变层(77 ×10-6 ～ 231×10-6,平均139×10-6),而“红化”蚀变层与“ 绿色”蚀变层的Th含量 相似,w(Th)平均值分别为357×10-6和365×10-6。矿前期的带 状面型“绿色”蚀变 层活化了矿物晶格中的结构铀,后期高氧逸度的流体萃取“绿色”蚀变层中已经活化了的铀 而形成含铀热液,经迁移在还原带附近沉淀成矿。Th的价态(正四价)难以随这种氧化还原 条件的改变而改变,因此未参与流体成矿过程。 |
| 中文关键词:地质学 矿物化学 黑云母与绿泥石 铀成矿 富城岩体 赣南 |
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| Mineral chemistry of biotite and chlorite in western part of Fucheng granite, southern Jiangxi Province: Implications for uranium mineralization |
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| Abstract:The Fucheng granite is located to the east of Huichang basin, southern Jiang xi Province. There are several uranium deposits in the western part of the Fuche ng granite which is in contact with shoshonite series volcanic rocks, with the C aotaobei uranium deposit being one of them. Chloritization of biotite in the gra nite is very common in the western Fucheng granite. Based on electron microprobe analysis data and theoretic calculation results of biotites and chlorites from the western part of the Fucheng granite, the authors studied the mineral chemist ry of biotites and chlorites so as to discuss the relationship between chloritiz ation of biotites and uranium mineralization. The results show that most of the biotites belong to siderophyllite. The oxygen fugacity (lg(fO2)) of magma of the Fucheng granite is estimated to be relatively low (-150 ～-143), which mea ns that the magma was relatively strongly reduced. Its source rock was strongly red uced, which was beneficial to preliminary enrichment of uranium. The F content i n biotite is 141% ～ 201%, showing that granitic magma was rich in F. As U a re easy to form complex with F in magma, and this is probably one of the rea sons that the Fucheng granite is rich in uranium. Chlorite was mainly derived fr om biotite by alteration, so it exhibits the shape of biotite. Chemical analysis of chlorite shows that the biotite mostly belongs to chamosite and prochlorite, both of which are rich in Fe element, and were mainly formed in a reductive env ironment. The formation temperatures of chlorite are between 246 ～ 307℃ (with a n average of 276℃). The U values of the samples from the upper reddish alterati on zone vary from 35×10-6 to 94×10-6 (with an average of 66 ×10-6) , signif icantly lower than U values of the samples from the lower greenish alteration zo ne (77×10-6 ～ 231×10-6, 139×10-6 on average) . The T h values of the sample s from the reddish alteration and the greenish alteration zone are basically sim ilar, with the average value being 357×10-6 and 365×10-6, resp ectively. The large-volume greenish alteration of the granite at the early stage mainly promot ed the U activation, and at the late stage, the upper part of the greenish alter ation zone underwent hematitization during which U was leached out by oxidized f luids and mineralization when such U-rich fluids came across strongly reduced en vironment. Because the redox characteristics of Th are totally different from th ose of U, it is held that Th was not involved in this ore-forming process. |
| keywords:geology, mineral chemistry, biotite and chlorite, uranium mi neralization, Fucheng granite, southern Jiangxi Province |
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