In Situ Trace Element and S-Pb Isotope Characteristics of Pyrite from the Shiganghe W-Sn and Tiechang Sn Deposits in Western Yunnan Province, China

The Shiganghe tungsten–tin deposit and the Tiechang tin deposit are located in the northern part of the Baoshan Block, approximately 25 km apart. They were formed in the Late Cretaceous and Early Oligocene, respectively, and exhibit distinct deposit characteristics. This study presents a comparative analysis of in situ trace elements and S-Pb isotopes of pyrite from the two deposits to trace the sources of ore-forming fluids and materials and to further constrain the evolution of the metallogenic setting in the Baoshan Block. The trace element compositions of pyrite from the Shiganghe tungsten–tin deposit differ significantly from those of the Tiechang tin deposit. The former is relatively enriched in Se, Al, and W, while the latter contains relatively high concentrations of Cu, As, Sb, Pb, Bi, and Ag. The sulfur isotopic compositions of pyrite from the Shiganghe deposit are lower than those from the Tiechang deposit, with δ34SCDT values ranging from 2.11‰ to 6.86‰ and 6.74‰ to 8.72‰, respectively. The two deposits share consistent lead isotopic ratios, characterized by a mixture of upper crustal and orogenic belt sources. Therefore, the mineralization of the Shiganghe tungsten–tin deposit may be related to deep seated, concealed Late Cretaceous magmatism. Relatively oxidized and W-rich magmatic fluids contributed to tungsten–tin mineralization that characterized by a zoning pattern of “tungsten above and tin below”. In contrast, the Tiechang tin deposit is likely associated with coeval leucogranites present in the shear tectonic zone near Caojian. The ore-forming fluids underwent long distant migration with extensive crustal contamination, resulting in a relatively reduced hydrothermal system. Combined with the regional geological setting, the mineralization of the Shiganghe tungsten–tin deposit and the Tiechang tin deposit records the geological event from Neo-Tethys Ocean subduction to the collisional orogeny between the Indian and Eurasian blocks. The ore-forming materials originated from a mixture of upper crustal materials and orogenic belt materials.