文献类型：期刊文献

英文题名：Origins of titanite in the Emeishan basalts: Implications for niobium enrichment in the upper Permian Xuanwei Formation, eastern Yunnan-western Guizhou region, Southwest China

作者：Du, Shengjiang Ling, Kunyue Luo, Chongguang Li, Yang Wen, Hanjie

第一作者：杜胜江

通信作者：Ling, KY[1];Wen, HJ[2]

机构：[1]Guizhou Inst Technol, Sch Min Engn, Guiyang 550003, Peoples R China;[2]Chinese Acad Sci, Inst Geochem, State Key Lab Ore Deposit Geochem, Guiyang 550081, Peoples R China;[3]Changan Univ, Sch Earth Sci & Resources, Xian 710054, Peoples R China;[4]Univ Chinese Acad Sci, Coll Earth & Planetary Sci, Beijing 100049, Peoples R China

第一机构：贵州理工学院矿业工程学院

通信机构：corresponding author), Chinese Acad Sci, Inst Geochem, State Key Lab Ore Deposit Geochem, Guiyang 550081, Peoples R China;corresponding author), Changan Univ, Sch Earth Sci & Resources, Xian 710054, Peoples R China.

年份：2024

卷号：476-477

外文期刊名：LITHOS

收录：;EI(收录号：20240033675);Scopus(收录号：2-s2.0-85190720293);WOS:【SCI-EXPANDED(收录号:WOS:001232690400001)】；

基金：The authors thank Dr. Wei Deng for assisting with EPMA analysis. This work was supported by the National Natural Science Foundation of China (grants 92162214, 41962005, 41903038) , the Start-up Fund for High-level Talents of Guizhou Institute of Technology (2023GCC048) , the Guizhou Science and technology innovation talent team project (CXTD [2023] 008) , and the Guizhou Provincial Science and Technology Project (ZK [2021] key program 046) .

语种：英文

外文关键词：Emeishan basalt; Titanite; Polymetallic Nb layer; Xuanwei Formation; Weathering process

摘要：The occurrence of the polymetallic Nb layer in the upper Permian Xuanwei Formation in southwest China has been documented extensively. The origin of Nb, as well as other metals like Zr and rare earth elements (REEs), has received much research attention; however, the source of these elements remains enigmatic. In recent studies, an uncommon Nb-rich titanite (CaTiSiO5) has been discovered in the Emeishan basalts beneath the Xuanwei Formation in the eastern Yunnan-western Guizhou region. However, its origins and genetic relationship to the polymetallic Nb layer remain unclear. In this study, we used in situ microanalytical and U-Pb dating techniques to investigate the titanite in these Emeishan basalts. Our objectives were to determine the origins of the titanite and its relationship to the polymetallic Nb layer in the lowermost Xuanwei Formation. The titanite U-Pb dating of basalt sample reveals a Tera-Wasserburg lower intercept age of ca. 259.6 +/- 4.3 Ma, which corresponds to the age of the eruption timing of Emeishan large igneous province (260.9-257.4 Ma). The LA-ICP-MS analysis reveals that the trace element composition of titanites in the Emeishan basalts exhibits similarities to weathering-type titanite, as evidenced by elevated La-N/Yb-N ratios and low concentrations of Y, Sigma REE, Th, and U, as well as reduced Lu/Hf and Th/U ratios. This implies that formation of the Nb-rich titanites can be attributed to weathering that occurred shortly after basalt formation under greenhouse climatic conditions. As weathering progressed, the Nb-rich titanite underwent a transformation into Nb-rich anatase and gradually became enriched in the regolith. This material was subsequently transported to nearby basins and deposited in terrestrial environments, resulting in formation of the polymetallic Nb layer in the lowermost Xuanwei Formation. Our findings provide insights into the origins and evolution of titanite in the Emeishan basalts, as well as formation of the polymetallic Nb layer in the lowermost Xuanwei Formation in the eastern Yunnan-western Guizhou region, southwest China.