赣南小坑超大型高岭土矿床原岩时代及源区:锆石及独居石U⁃Pb年代学及Hf同位素制约  

Geochronology and Sources of the Giant Xiaokeng Kaolin Deposit in Southern Jiangxi Province:Insight from U-Pb Ages of Zircon and Monazite,and Hf Isotopic Compositions

作　　者：吴俊华 龚敏 周雪桂 王川 杨紫文 罗青 李艳军[4] Wu Junhua;Gong Min;Zhou Xuegui;Wang Chuan;Yang Ziwen;Luo Qing;Li Yanjun(Jiangxi Bureau of Geology,Nanchang 330046,China;The First Geological Brigade,Jiangxi Bureau of Geology,Nanchang 330052,China;Jiangxi Mineral Resources Co.,Ltd.,Nanchang 330030,China;School of Earth Resources,China University of Geosciences,Wuhan 430074,China)

机构地区：[1]江西省地质局,江西南昌330046 [2]江西省地质局第一地质大队,江西南昌330052 [3]江西省地矿资源勘查开发有限公司,江西南昌330030 [4]中国地质大学资源学院,湖北武汉430074

出　　处：《地球科学》2023年第9期3245-3257,共13页Earth Science

基　　金：江西省地质局科研项目《赣南小坑高岭土矿床成因及找矿方向研究》.

摘　　要：华南是我国风化型高岭土矿床的重要分布区,但鲜有三叠纪岩浆岩形成的风化型高岭土矿床的报道.小坑高岭土矿床是赣南地区新近发现的超大型风化型高岭土矿床,远景资源量超30 Mt.本文以该矿床为研究对象,开展了高岭土矿LA-ICPMS锆石和独居石U-Pb定年及Hf同位素研究,精确限定其原岩形成时代和岩浆源区.锆石U-Pb法厘定该矿床成矿原岩年龄为231~230 Ma.独居石为岩浆成因,其U-Pb年龄为230±1 Ma.晚三叠世锆石ε_(Hf)(t)=‒19.9~‒1.2,二阶段Hf模式年龄T_(DM2)=2228~1198 Ma.Hf同位素及1018~987 Ma的继承锆石表明小坑矿床成矿原岩来源于中‒新元古代基底物质的熔融,且有部分幔源物质加入.小坑高岭土矿床的发现表明华南地区晚三叠世含电气石白云母(二云母)花岗岩可形成优质高岭土,拓展了高岭土矿找矿方向.Weathering-type kaolin deposits are widespread in South China,and they are associated with the intense intermediateacid magmatism of granitic rocks and dikes.Ore-related magmatism were dominantly formed during the Caledonian and Yanshanian.However,no Kaolin mineralization associated with Triassic magmatism has been reported in South China so far.The Xiaokeng kaolin deposit,which has been discovered and explored recently,is a giant deposit with mineral resources more than 30 Mt in southern Jiangxi Province.The kaolin ore-bodies distribute on the surface of a muscovite granite as stratoid or crescent in shapes.It is a weathering-type kaolin deposit associated with granite and is characterized by low contents of iron and titanium.In this paper,the U-Pb laser ablation inductively coupled plasma mass spectrometry(LA-ICPMS)dating of zircon and monazite,and Lu-Hf isotopes of zircon on kaolin ore are documented,in order to study the age and magmatic sources of ore-related granite.Mean ages of 231±2 to 230±2 Ma were obtained for two samples of zircon with intercept ages of 232±5 to 231±3 Ma.Based on micro-textures,and contents and ratios of trace and rare earth elements,a magmatic origin was proposed for monazite from kaolin ore at Xiaokeng.A yielded age of 230±1 Ma was obtained using UPb dating at monazite grains.These ages indicate that the ore-related granite was formed during the Late Triassic.Late Triassic zircon grains haveε_(Hf)(t)values ranging from-19.9 to-1.2 with two-stages Hf model ages(T_(DM2))of 2228-1198 Ma.These Hf isotopic values,together with the presence of two Meso-to Neoproterozoic inherited zircon grains(1018-987 Ma),indicate that the ore-related granite in the Xiaokeng deposit was originated from partial melting of Meso-to Neoproterozoic basement beneath South China,with minor contribution of mantle sources.This study on ages and sources of kaolin ore at Xiaokeng,not only suggests that Late Triassic tourmaline bearing muscovite or two-mica granites in South China can form high-quality weatheri

关 键 词：晚三叠世 岩浆源区 白云母花岗岩 风化型高岭土矿床 小坑 赣南 矿床地质 地球化学 

分 类 号：P619.23[天文地球—矿床学]