Sphalerites Rb-Sr Dating and geological significance of the Shuitoushan Pb-Zn deposit in Yunnan Province,SW China

The Shuitoushan lead-zinc deposit is located in Luziyuan ore concentration area at the southern margin of the Baoshan block, Yunnan Province. The Luziyuan ore concentration area is characterized by the development of skarn type and hydrothermal vein type lead-zinc mineralization. The Rb and Sr isotopic composition of Sphalerite formed in the main mineralization stage of Shuitoushan hydrothermal vein lead-zinc deposit is determined to investigate the process of lead-zinc polymetallic mineralization in the area. The obtained Rb-Sr isochron age of sphalerite is 135.8 ±4.2Ma (MSWD = 1.70, n = 6), which is equivalont to the metallogenic ages of other deposits in the area, indicates that a large-scale lead-zinc polymetallic metallogenic event had occurred in Luziyuan ore concentration area in the Early Cretaceous. The initial Sr isotopic composition of sphalerite ((⁸⁷Sr/⁸⁶Sr) _i = 0.710258~0.710430) and the existing sulfur and lead isotopic characteristics of sulfides jointly reveal that the metallogenic materials of Shuitoushan lead-zinc deposit are mainly derived from the concealed intermediate-acid intrusive rocks in the deep part of the region, with a small contribution of surrounding rocks. Basing on the geological characteristics and metallogenic geological background of the deposit in the area, we put forward the point of view that the collision orogeny of Tengchong block and Baoshan block in the Early Cretaceous triggered crustal remelting, which produced a large number of granitic magma rich in Fe, Cu, Pb and Zn in Luziyuan ore concentration area. Intrusion of these magmas led to the emplacement of the regional concealed granite body, and formed Luziyuan skarn type iron-lead-zinc deposit at the contact zone between the granite and the marble of Shahechang Formation. After that, the hydrothermal fluids continued to move along the Northeast and near East-West faults in the area, and formed a series of hydrothermal vein lead-zinc polymetallic deposits such as Shuitoushan, Fangyangshan, Luojiazhai and Pipashui.