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The source of ore-forming fluid and genesis of the Dadongchang Zn-Pb deposit in the Western Yunnan, China (Vol. 43, No. 5, 2023) TEXT SIZE: A A A

YANG Jia-fei1, LI Wen-chang1, DENG Ming-guo1*, SHA Jian-ze2, JIA Zhen1,CHEN Yu-hong3, ZHAO Xiao-yu1, YANG Zheng-liang1

(1. Faculty of Land Resource Engineering, Kunming University of Science and Technology, Kunming 650221, China; 

2. Yunnan Geological Survey Institute, Kunming 650216, China; 

3. Yunnan Nuclear Industry 209 Geological Brigade, Kunming 650034, China)

Abstract: The Datongchang Pb-Zn deposit is one of the representative skarn-type deposits within the Tengchong block in the central and southern section of the "Sanjiang" metallogenic belt in Southwest china. In this paper, we have carried out researches of fluid inclusions and C, O, S isotopes of the deposit, in order to identify the source of the ore-forming materials/fluid in the Dadongchang deposit, and to discuss the properties and evolution process of the ore-forming fluid, and then to reveal the genesis of the deposit. The mineralization process of the Dadongchang deposit can be divided into the skarn stage, quartz-sulfide stage and carbonate stage. The ore-forming fluid is the H2O-NaCl system, containing a small amount of N2, CO2 and CH4. Microthermometrric results show that homogenization temperatures and salinities are 340-464 °C and 2.90%-15.76% NaCl eqv for fluid inclusions in minerals of the skarn stage, 304-381 °C and 3.87%-9.98% for those of the quartz-sulfide stage, and 196-265 °C and 1.40%-8.81% for those of the carbonate stage, respectively. and the homogenization temperatures and salinities of fluid inclusions are gradually decreased with the evolution of ore-forming fluids. The C-O isotopic results show that the ore-forming fluids were mainly sourced from magmatic hydrothermal fluids which then could have been affected by the water/rock intereaction in the fluid migration process and meteoric water. The δ34SV-CDT values of sulfides vary from 2‰ to 5‰. Compared with the results of S isotopes of typical lead-zinc deposits in the Tengchong block and the adjacent Baoshan block, it is believed that the S in this deposit was mainly sourced from the deep magma. Combined with characteristics of deposit geology, fluid inclusions, and C, O, and S isotopes, it is inferred that the change of its metallogenic environment and the mixing of fluids could be the main factors leading to the large-scale precipitation of metallogenic materials in the Dadongchang lead-zinc deposit. Based on the regional metallogenic background, it is considered that the deposit is a skarn-type lead-zinc deposit related to the deeply concealed Yanshanian intrusions formed in the continental-continental collisional orogenic setting. 

Keywords: Dadongchang Pb-Zn deposit; fluid inclusions; C-O-S isotopes; genetic mechanism; Tengchong block

ACTA MINERALOGICA SINICA Vol. 43, No. 5, 2023, Page 693

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