Shuitoushan magmatic hydrothermal lead-zinc deposit in western Yunnan: Evidence from REE and C-O isotopes

This paper is the result of mineral exploration engineering.

Objective The Shuitoushan deposit is located in the south part of Baoshan block in the "Sanjiang" metallogenic belt, SW China. It is another important newly discovered epithermal Pb-Zn deposit in Zhenkang ore concentration area. Since no igneous rock exposed in the mining area, the origin of the ore deposit is still controversial. This paper aims to determine the genetic type of the deposit by studying on the sources of ore-forming materials and fluids.

Methods Based on the detailed division of ore-forming stages of Shuitoushan deposit, the inductively coupled plasma mass spectrometer (ICP-MS) was used to systematically analyze rare eath elements of the rocks (ores) and sulfides in different stages. C and O isotopic compositions of the ore-hosted carbonate rocks, marbles and calcites of different stages were analyzed as well. Compared with the adjacent Luziyuan super-large Pb-Zn-Fe polymetallic deposit, we discuss the sources of ore-forming materials and the characteristics of ore-forming fluids in the Shuitoushan deposit, and reveal the ore-forming mechanism of the deposit.

Results The Shuitoushan deposit can be divided into mineralization stage and epigenetic stage. Among them, the mineralization stage can be further divided into stage Ⅰ (pyrite-chalcopyrite-calcite stage), stage Ⅱ (sphalerite-galena-calcite stage) and stage Ⅲ (chalcopyrite-calcite stage). The studies of rare earth elements and C-O isotopic compositions show that the Y/Ho values of minerals and ores from each stage of Shuitoushan deposit indicate the source of the ore-forming materials is related to deep magmatic activity. Comparing the REE distribution model of minerals and ores from Shuitoushan deposit with the Yanshanian Kejie and Zhibenshan granites in the Baoshan block shows that the REEs in the ore-forming fluid of this deposit was mainly originated from deep magmatic hydrothermal fluid. As shown in the δ¹³C_V-PDB-δ¹⁸O_V-SMOW diagram, the ore-forming fluids are also mainly from magmatic hydrothermal fluids. During the migration processes, the ore-forming hydrothermal fluids was contaminated by sedimentary rocks in early stage, and may be affected by low-temperature alteration and atmospheric precipitation in later stages.

Conclusions Both the sources of ore-forming materials and fluids of Shuitoushan deposit are closely related to the magmatic hydrothermal fluid in the deep part of the mining area. It has the same origin with the adjacent Luziyuan super-large Pb-Zn-Fe polymetallic deposit, and is an epithermal deposit related to acidic magmatic hydrothermal fluids.