川南上二叠统宣威组底部黏土岩型镓矿地球化学特征及镓元素的富集成因  

GEOCHEMICAL CHARACTERISTICS OF CLAYSTONE TYPE GALLIUM DEPOSITS AT THE BOTTOM OF THE UPPER PERMIAN XUANWEI FORMATION IN SOUTHERN SICHUAN AND ORIGIN OF GALLIUM ENRICHMENT

作　　者：刘治成 赵伟 文俊 陈敏 赵俊兴[4] 郑梦天[1] 竹合林 郭宇衡 赵凱莉[2] LIU Zhicheng;ZHAO Wei;WEN Junn;CHEN Min;ZHAO Junxing;ZHENG Mengtian;ZHU Helin;GUO Yuheng;ZHAO kaili(Sichuan Institute of Land Science and Technology,Chengdu,Sichuan 610045,China;The 7th Geologicai Brigade of Sichuan,Leshan,Sichuan 614000,China;Zhang Jinyuan Model Worker Innovation Studio of Sichuan Bureau of Geology&Mineral Resources,Leshan,Sichuan 614000,China;Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu,Sichuan 610059,China)

机构地区：[1]四川省国土科学技术研究院,四川成都610045 [2]四川省第七地质大队,四川乐山614000 [3]四川省地质矿产勘查开发局张金元劳模(专家)创新工作室,四川乐山614000 [4]成都理工大学沉积地质研究院,四川成都610059

出　　处：《矿物岩石》2024年第2期74-87,共14页Mineralogy and Petrology

基　　金：四川省自然科学基金项目(编号:2023NSFSC0270);2024年四川省政府性投资地质勘查项目(编号:DZ202402);四川省自然资源厅科技项目(编号:Kj-2022-6);四川省自然资源厅2020年省政府性投资地质勘查项目(编号:DZ202002)。

摘　　要：川滇黔地区上二叠统宣威组底部发育一套富镓黏土岩,但目前对镓富集的沉积环境和成因研究较少。本次在川南沐川地区开展了地质调查、岩石学和岩石地球化学研究,总结了镓元素含量垂向变化规律,探讨了沉积环境及镓元素的富集成因,以期为今后的选区研究和勘探开发提供参考。结果表明,含镓岩系主要由紫红色铁质黏土岩型镓矿、杂色铁铝质黏土岩型镓矿、浅灰绿色铝质黏土岩型镓矿、灰白色铝质黏土岩型镓矿、灰色黏土岩型镓矿、深灰色碳质黏土岩型镓矿组成,3个钻孔揭示镓矿层平均厚度12.14m,Ga平均品位70×10^(-6),Ga元素在灰白色铝质黏土岩中最为富集。含镓岩系的ΣREE为263.87×10^(-6)~12820.56×10^(-6),ΣLREE/ΣHREE为4.31~24.67,La_(N)/Yb_(N)为3.83~122.71,表明轻稀土的富集程度较高。镓矿层的物源与峨眉山大火成省的形成有关:下部紫红色铁质黏土岩型镓矿的物源与峨眉山玄武岩的风化剥蚀产物有关,上部灰白、浅灰绿、灰、深灰色黏土岩型镓矿的物源主要源自于碱性火山灰和少量玄武岩风化产物。含镓岩系形成于多次受到海水侵入的陆相湖泊环境中,严格受岩相古地理的制约。Ga元素的富集过程受风化淋滤作用和沉积作用的双重控制,成因类型属古风化壳一沉积型。上述研究成果对丰富和完善峨眉山地幔柱成矿系统具有重要意义,同时可为川滇黔地区镓矿的找矿工作提供重要线索。A suite of gallium-rich clay rocks developed at the base of the Upper Permian Xuanwei Forma-tion in Sichuan,Yunnan,and Guizhou regions,yet their sedimentary environment and genesis of gallium enrichment remain extremely limited understood.This paper investigates the Ga-rich clay rocks at the base of the Upper Permian Xuanwei Formation in the Muchuan area of southern Sichuan Province.The investi-gation employs field geological surveys,petrology,and petrogeochemistry,accompanied by summarizing the vertical variation of gallium content and discussing the sedimentary environment and origin of gallium enrichment.The results reveal that the gallium-bearing rock series primarily consists of purplish-red ferric claystone-type gallium,miscellaneous ferric aluminous claystone-type gallium,light grayish-green alumi-nous claystone-type gallium,grayish-white aluminous claystone-type gallium,grey claystone-type galli-um,and dark grey carbonaceous claystone-type gallium.Data from three boreholes indicates an average thickness of the gallum layer of 12.14 meters,with an average grade of Ga at 70×10^(-6),with Ga being most enriched in the gray-white aluminous clay rock.Geochemical analysis reveals that the ZREE of galli-um-bearing rocks ranges from 263.87×10^(-6) to 12820.56 ×10^(-6),ZLREE/ZHREE ranges from 4.31 to 24.67,and Lan/Ybn ranges from 3.83 to 122.71,indicating a high degree of enrichment of light rare earth elements.The source of gallium deposits is related to the formation of the Emei Mountain igneous prov-ince,with the lower purplish-red iron claystone-type gallium deposit sourced from weathering and denuda-tion products of Emeishan basalt.The upper gray,light gray-green,gray,and dark gray claystone-type gallium deposits are mainly derived from alkaline volcanic ash and a small amount of weathering products of basalt.The gallium-bearing rock series formed in a terrestrial lacustrine environment that has been sub-merged by seawater multiple times,and is restricted by lithofacies paleogeography.The enrichment process

关 键 词：上二叠统宣威组 峨眉山玄武岩 稀散元素 沐川 

分 类 号：P588.2[天文地球—岩石学] P611[天文地球—地质学]