The source of Fengjia and Langxi barite–fluorite deposits in southeastern Sichuan, China: evidence from rare earth elements and S, Sr, and Sm–Nd isotopic data

The barite–fluorite metallogenic belt in southeastern Sichuan is one of the most important barite–fluorite ore‐concentrated areas in China. In order to find the ore‐forming source and the mineralization age of the Fengjia and Langxi barite–fluorite deposit, we systematically evaluated the rare earth element (REE) contents and isotopic characteristics of S, Sr, and Sm–Nd. The results show that the δ34S values of barites and pyrites are high and similar to S isotopic values of gypsum in the Cambrian Qingxudong Formation (∈1q), suggesting that the sulphur source was from Cambrian evaporite strata. The initial87Sr/86Sr ratios of fluorites and barites range from 0.708800 to 0.712999, and these values are similar to Cambrian carbonate rocks and Lower Ordovician limestone. Except for black shales of the Lower Cambrian Niutitang Formation, the Ba content of other strata was generally low. The REE characteristics of barite and fluorite have close relationships, in regard to the source of ore‐forming materials, to the Lower Cambrian Niutitang Formation black shales. Hence, we have concluded that the Cambrian carbonate rocks and Lower Ordovician limestone provide the source of calcium for mineralization and that the source of barium comes from the Lower Cambrian Niutitang Formation black shales. The fluorine contents of the Upper Sinian Doushantuo Formation and the Lower Cambrian Mingxinshi Formation are much higher than other strata, and these formations could provide the source for fluorine. The Sm–Nd isochron age of fluorites is 104 ± 11 Ma, which demonstrates that the mineralization mainly occurred during the late Yanshanian.