Genesis of the Maka Pb-Zn-W deposit in southeastern Yunnan" Constraints from sphalerite Rb-Sr dating, cassiterite U-Pb dating and in -situ S, Pb isotopes of sulfide

The Maka Pb-Zn-W deposit is located at the northern margin of the Late Yanshanian Laojunshan granite pluton, the junction of Nanwenhe in Maguan County and Malipo County, Yunnan Province. Three different types of mineralization were identified in the Maka deposit, including skarn-type Pb-Zn mineralization, quartz vein -type Pb-Zn mineralization and fluorite -quartz vein -type scheelite mineralization. However, up to now, the mineralization mechanisms and relationships of different types of mineralization are still unclear. This paper reports the Rb-Sr dating and in -situ S, Pb isotopic compositions of sphalerite in different types Pb-Zn orebodies, as well as the in -situ U-Pb dating of cassiterite in quartz vein -type Pb-Zn orebody. The results show that Rb-Sr isochron ages of sphalerite samples from skarn type and quartz vein -type Pb-Zn ores are 88.9 +/- 1. 9Ma ( MSWD = 4. 5) and 85.18 +/- 0.72Ma ( MSWD = 1. 2), respectively. The LA-ICP-MS U-Pb age of cassiterite from the vein -type Pb-Zn ore is 84.3 +/- 4.7Ma ( MSWD = 0. 66). These ages indicate that the Pb-Zn ( -Sn) mineralization of the Maka deposit were formed in Late Cretaceous, which is highly consistent with the age of widely exposed Laojunshan granite ( similar to 90Ma) and granite porphyry (80 similar to 86Ma). The delta S-34 values of sulfides from the Pb-Zn ores range from 2. 53 parts per thousand to 9. 65 parts per thousand, with a mean value of 4. 7 parts per thousand, which is similar to the Laojunshan granite porphyry (4.07 parts per thousand), and lower than the host -strata ( 17. 5 parts per thousand similar to 25. 8 parts per thousand). The S-Pb isotope data indicate that the ore -forming materials were mainly derived from the Laojunshan granite, with a small amount from the ore -bearing strata. These results suggest that the formation of the Maka deposit is mainly related to the Late Yanshan Laojunshan granitic complex, and the metallogenetic geological conditions in this area are similar to those in the Dulong mining area. The skarn-type Pb-Zn mineralization in the Maka deposit is mainly related to granite, and the quartz vein -type Pb-Zn mineralization is formed by hydrothermal filling and replacement related to granite porphyry.