江西宜丰同安花岗细晶岩年代学及其成因研究
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本文为江西省科技厅重点研发计划一般项目(编号20212BBG73045)、江西省科技厅重点研发计划“揭榜挂帅”项目(编号20223BBG71015)、江西省自然科学基金面上项目(编号20224BAB203037)、江西省“科技+地质”联合计划项目(编号2023KDG01003)、江西省地质局青年科学技术带头人培养计划项目(编号2022JXDZKJRC02,2023JXDZKJRC05)和鹰潭市科技计划项目(编号20233- 185656)联合资助的成果


Chronology and genesis of the Tongan granitic aplite in Yifeng, Jiangxi Province
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    摘要:

    燕山期甘坊复式岩体是宜丰锂铌钽稀有金属矿田重要的赋矿岩体,细晶岩作为甘坊岩体晚阶段岩浆演化的产物,与区内细晶岩型稀有金属成矿作用关系密切,但前人对该类岩石及其成矿作用特征研究较薄弱。本文以甘坊岩体南侧同安矿区内的花岗细晶岩为研究对象,对其展开系统的岩相学、锡石U- Pb年代学和全岩地球化学分析。锡石U- Pb定年结果表明,同安花岗细晶岩形成时代为138. 3 Ma。全岩地球化学分析结果显示,该类岩石具高磷铝、富碱钙、贫镁铁钛的特征,且A/CNK值(1. 71~1. 88)较高,σ值(1. 40~1. 72) 较低,属于典型的强过铝质、高钾钙碱性岩石。全岩微量及稀土元素成分显示,同安花岗细晶岩具有稀土元素强烈亏损,相对富集Rb、U、Nb、Ta、Pb、P、Hf和明显亏损Ba、Th、Sr、Ti等元素的特征。综上所述,同安花岗细晶岩属高分异的S型花岗岩,来源于地壳浅部变沉积岩物质的部分熔融。在演化过程中,经历过早期高度结晶分异过程和晚期的岩浆- 热液相互作用,其中早期的高度结晶分异过程对Li成矿起到了初始富集的作用,而演化晚期的岩浆- 热液相互作用才是Li元素高度富集并成矿的关键。

    Abstract:

    The Ganfang granite batholith formed in the Yanshan period is the most important ore- hosting rock in the Yifeng Li- Nb- Ta rare metals ore field. The aplite, being product of the late stage of magmatic evolution in the Ganfang granite, is closely related to the mineralization of aplite- vein type rare metals in the Yifeng area. However, little research has been done on these rocks. In this paper, petrographic, cassiterite U- Pb chronological and whole- rock geochemical analysis have been performed on the Tongan granitic aplite in the Tongan mining area, south of the Ganfang granite. Results of cassiterite LA- ICP- MS U- Pb dating show that the aplite formed at about 138.3 Ma. According to the results of geochemical analysis, aplite samples are characterized by high Al2O3, P2O5, CaO, and alkali (Na2O+K2O) contents and low Mg, Fe, and Ti contents. They have high A/CNK ratios (varying from 1.71 to 1.88) and low σ values (between 1.40 and 1.72), belonging to high potassium calc- alkaline rocks that are also highly peraluminous. In terms of trace and rare earth elements, the Tongan granitic aplite is enriched in Rb, U, Ta, Pb, P, and Hf elements and depleted in Ba, Th, Sr, and Ti elements, as well as highly depleted in rare earth elements. These characteristics indicate that the Tongan granitic aplite belongs to highly fractionated S- type granites. It was probably derived from the partial melting of metasedimentary rocks in the shallow crust, and experienced high degree of fractional crystallization in early stages, and magmatic- hydrothermal interaction in late stage. In addition, we believe that the early highly- fractional crystallization played an initial enrichment role in lithium mineralization, while the magmatic- hydrothermal interaction in the late evolution stage was the key to high enrichment of lithium and the eventual mineralization.

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曾闰灵,章敬若,贺玲,欧阳永棚,魏锦,孟德磊.2023.江西宜丰同安花岗细晶岩年代学及其成因研究[J].地质学报,97(11):3750-3765.
ZENG Runling, ZHANG Jingruo, HE Ling, OUYANG  Yongpeng, WEI Jin, MENG Delei.2023. Chronology and genesis of the Tongan granitic aplite in Yifeng, Jiangxi Province[J]. Acta Geologica Sinica,97(11):3750-3765.

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  • 收稿日期:2023-05-20
  • 最后修改日期:2023-06-17
  • 录用日期:2023-07-03
  • 在线发布日期: 2023-11-23
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