Episodic Nb–Ta mineralisation in South China: Constraints from in situ LA–ICP–MS columbite-tantalite U–Pb dating

Abstract

South China hosts many Nb–Ta deposits that show evidence for episodic mineralization, which were generated during the emplacement of composite granites. To constrain the spatio-temporal distribution of Nb–Ta mineralisation in the region and to identify future targets for mineral exploration, we used in situ laser ablation-inductively coupled plasma-mass spectroscopy to date 23 columbite-tantalite group mineral (CGM) samples from 14 Nb–Ta deposits. Our CGM U–Pb data, supplemented by previous results, reveal five distinct Nb–Ta mineralisation events in South China as follows: (1) Late Silurian–Middle Devonian (ca. 424–391 Ma; e.g., the Xigang and Nanping deposits in eastern Jiangxi and western Fujian Provinces); (2) Triassic (ca. 248–204 Ma; e.g., the Houxi, Cunxin, Dongtounan, Shenkeng, Limu and Gaoling deposits in western Guangdong Province and northeastern Guangxi Zhuang Autonomous Region; (3) Late Jurassic (ca. 160–150 Ma; e.g., the Gedongping, Yichun, Laiziling, Jianfengling and Jinzhulong deposits in Guangxi, Jiangxi and Hunan Provinces); (4) Early Cretaceous (ca. 130 Ma; e.g., the Huangshan and Songshugang deposits in northeastern Jiangxi province); and (5) Late Cretaceous (ca. 90 Ma; e.g., the Jiepailing deposit, located along the boundary between Hunan and Jiangxi Provinces). We show that Nb–Ta mineralisation in South China was controlled by multiple tectono-magmatic events. Our CGM samples yielded Caledonian (ca. 424–391 Ma), early Indosinian (ca. 248 Ma) and late Yanshanian (ca. 130 Ma) ages, indicating that Nb–Ta mineralisation was abundant during these times and should form the focus for future studies of mineralisation in the region. Early Triassic granite in the Guangning Nb–Ta metallogenic district in western Guangdong Province, Indosinian and early Yanshannian granites in the Miao’ershan–Yuechengling batholith in northeastern Guangxi, and the Late Cretaceous Lingshan batholith in northern Jiangxi Province are identified as targets for future Nb–Ta exploration.