粤北茶山岩体岩石成因与铀、钨成矿潜力探讨
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本文为国家自然科学基金青年基金项目(41703042),南京大学内生金属矿床成矿机制研究国家重点实验室开放基金项目(2017- LAMD- K06)和中国核工业地矿事业部十二五高校基础科研项目联合资助的成果。


Petrogenesis of the Chashan granite in the northern Guangdong Province and its implication for the metallogenic potential of tungsten and uranium mineralization
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    摘要:

    粤北诸广山地区是我国重要的花岗岩型铀矿床产地之一,该地区部分岩体亦与钨成矿关系密切。茶山岩体位于诸广山南部岩体的中北部,研究程度较低。茶山岩体锆石U- Pb年龄为148. 2±1. 9Ma,形成于燕山早期。岩相学上可见原生白云母。岩体富硅、略富碱,贫铁、镁、钙、磷,分异演化程度高(DI=92. 2~95. 6),弱过铝质(ACNK=1. 00~1. 08);稀土含量较低(∑REE=90. 5×10-6~163×10-6),Eu强烈亏损(δEu=0. 04~0. 08),富集Rb、U和Ta,亏损Ba、Sr、Ti和P。以上特征表明茶山岩体属于高分异的S型花岗岩。此外,岩体εNd(t)值低(-10. 6~-9. 4),两阶段Nd模式年龄为1. 70~1. 80Ga,结合其高的Rb/Sr比值(12. 6~77. 3)和低的CaO/Na2O比值(0. 10~0. 28),这些特征表明茶山岩体可能由古元古代从地幔分离出的地壳岩石演变而成的变质泥岩部分熔融而来,并经历后期高分异作用,成岩构造背景属于燕山早期板内伸展环境。对比研究显示,茶山岩体与华南印支期产铀花岗岩和燕山期产钨花岗岩在主要地球化学指标和源区特征上相似,但其W含量较低(1. 60×10-6~3. 94×10-6),钨成矿潜力较小;而U含量较高(平均19. 0×10-6),且主要以铀钍石等易淋滤的富铀矿物存在。该区断裂构造发育,岩体中见晚期岩脉侵入且热液蚀变强烈。岩体西北部有明显的铀矿化显示,钻孔ZK55- 4见有沥青铀矿。综上,茶山岩体具有较强的铀成矿潜力。

    Abstract:

    The southern Zhuguangshan complex pluton (SZCP) is one of the important uranium mineralization areas hosted in granitoid in China, and a few granites in SZCP show tungsten mineralization. The Chashan granite in the north central area of the SZCP has received less attention. The LA- ICP- MS zircon U- Pb dating yields an age of 142. 8±1. 9 Ma, suggesting that the Chashan granite was formed in the Early Yanshanian. Petrographically the Chashan granite commonly contains muscovite, and is characterized by enrichment of SiO2, mildly high alkalinity, and depletion of FeOT, MgO, CaO and P2O5. Geochemically it is also highly fractionated (DI=92. 2~95. 6) and peraluminous (ACNK=1. 00~1. 08). Most of samples display low total REE contents (∑REE=90. 5×10-6~163×10-6), negative Eu anomalies (δEu=0. 04~0. 08), enrichment of Rb, U and Ta, and depletion of Ba, Sr, Ti and P. Petrographical and geochemical features of these samples suggest a highly fractionated S- type granite. Isotopically, the Chashan granite has low and constant εNd(t) values (-10. 6~-9. 4) with two stage model age of 1. 70~1. 80 Ga. Integrated with the values of Rb/Sr (12. 6~77. 3) and CaO/Na2O (0. 10~0. 28), we suggest that the granitic magma of the Chashan granite, formed in the Early Yanshanian intraplate extensional environment, may have been derived from the partial melting of metapelite that originated from the ancient crust rocks separated from the mantle in the Paleoproterozoic. An intercomparison shows that the Chashan granite shows similar geochemical properties as the Indosinian uranium- bearing granites and the Yanshanian tungsten- bearing granites in South China, but has extremely low tungsten concentration (1.60×10-6~3.94×10-6), indicating a relatively low tungsten metallogenic potential. These samples exhibit high uranium content (averaging 19×10-6) and common presence of uranium in some U- rich accessory minerals (such as uranothorite) which are prone to be leached. In addition, the faults were well and extensively developed in this area, resulting in the granite being intruded by late stage granitic dykes and experiencing significant hydrothermal alteration. Uranium mineralization found in the northwest part of the Chashan granite and pitchblende was discovered by drilling zk55- 4. In conclusion, the Chashan granite shows a greater uranium than tungsten metallogenic potential.

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兰鸿锋,王洪作,凌洪飞,陈卫锋,王凯兴,王丹.2020.粤北茶山岩体岩石成因与铀、钨成矿潜力探讨[J].地质学报,94(4):1143-1165.
LAN Hongfeng, WANG Hongzuo, LING Hongfei, CHEN Weifeng, WANG Kaixing, WANG Dan.2020. Petrogenesis of the Chashan granite in the northern Guangdong Province and its implication for the metallogenic potential of tungsten and uranium mineralization[J]. Acta Geologica Sinica,94(4):1143-1165.

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  • 收稿日期:2019-02-18
  • 最后修改日期:2019-11-20
  • 录用日期:2019-11-28
  • 在线发布日期: 2019-11-28
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