A Study On Caledonian And Indosinian Mineralization Of Dushiling Tungsten Deposit In The Yuechengling Area, Northern Guangxi, China

The Miao’erShan-Yuechengling batholith is the largest multi-aged composite granite pluton in western Nanling, mainly composed of Caledonian and Indosinian granites. Many W-Sn deposits occurred in the interior periphery of the complex pluton. Therefore, it has become the ideal place to do research on pre yanshanian magmatism and mineralization. Based on previous studies, we selected Dushiling W deposit as our research target. Based on systematic study of magmatism and mineralization in the w deposit, we discussed the Indosinian granite magmatism and mineralization in MiaoerShan area.The Dushiling W deposit is a large, altered, skarn-type deposit, located in the northeastern part of the Miao’ershan-Yuechengling pluton, China. Two types of granite have been identified in the deposit:a medium-grained porphyritic biotite granite, and a medium-to fine-grained biotite granite. Both are spatially and temporally related to ore bodies, suggesting they may be the source of mineralization in the deposit. A medium-to fine-grained porphyritic biotite granite is exposed at the surface in the region of mineralization. U-Pb dating of zircons yielded magmatic ages of 423 Ma for the medium-grained porphyritic biotite granite and 421 Ma for the medium-to fine-grained porphyritic biotite granite, while a younger age (217 Ma) obtained for surface samples indicates later diagenesis. Thus, magmatism occurred during the Caledonian and Indosinian, respectively.The petrological and geochemical characteristics of the two Caledonian granites show that both are calc-alkaline and peraluminous. They are moderately enriched in Cs, Rb, U, and REE, and strongly depleted in Sr, Ba, P, and Ti; they show similar REE behavior, including negative Eu anomalies. These geochemical similarities suggest that the two granites were derived from the same source, although they were emplaced during different stages of the evolution of the magma. Furthermore, the granites are associated with mineralization, suggesting they were the source of mineralization in the Dushiling W deposit. Sm-Nd ages of scheelite from the Dushiling W deposit indicate that metallogenesis occurred at 417 ± 35 Ma, while the two types of titanite, intergrown with scheelite, yield U-Pb ages of 423-425 Ma (in altered granite sample) and 218 Ma (in skarn sample). These ages place the main mineralization event in the late Caledonian, and later W mineralization also happened in the Indosinian. According to the rare element in scheelite of Dushiling deposit in Caledonian and Indosinian, the fluid during the W mineralization of two periods were characteristic of F enrichment and in reducing environment. And the Indosinian W mineralization was divided into several stages, with decreasing oxygen fugacity over time. The ages obtained for the Dushiling deposit in the western Nanling Range, northern Yuechengling, together with the occurrence and ages of the Niutangjie W deposit in southern Yuechengling, provide insight into the process of ore concentration during the Caledonian and Indosinian.