Fluid inclusion and isotopic constraints on the origin of ore‐forming fluid of the Jinman–Liancheng vein Cu deposit in the Lanping Basin, western Yunnan, China

Abstract

Extensive quartz-carbonate-Cu sulfide veins occur in clastic rocks and are spatially related to Paleocene granites in the western border of the Lanping Basin, western Yunnan, China. Abundant aqueous-carbonic fluid inclusions occur in these veins but their origin is debated. In the Jinman-Liancheng deposit, individual primary inclusion groups contain either exclusively liquid-rich inclusions (Gl), or coexisting liquid-rich and vapor-rich inclusions (Glv). Microthermometry and estimate of CO 2 content indicate that type Gl inclusions either have homogenization temperatures (Th) 238-263°C and contain c. 3.9-5.5 mole % CO 2 , or have Th 178-222°C and contain c. 1.6-3.2 mole % CO 2 . Type Glv inclusions are thought to represent samples of fluid unmixing that occurred at 183-218°C. At that time, the liquid phase in the unmixing fluid may contain c. 2.0-3.3 mole % CO 2 . As such, the correlation of CO 2 content with Th for type Gl inclusions is thought to be caused by fluid unmixing with decreasing temperature and subsequent CO 2 escape. indicate that the carbon and sulfur can be derived from (degassed) magma and/or nonmagmatic sources. The CO 2 -rich and magmatic-water-derived fluid at Jinman-Liancheng differs from the CO 2 -poor and basinally derived fluid in sediment-hosted stratiform Cu (SSC) deposits, which suggests that there are no genetic linkages between the vein Cu and SSC deposits in the Lanping Basin.

Genesis of Gypsum/Anhydrite in the World-Class Jinding Zn-Pb Deposit, SW China: Constraints from Field Mapping, Petrography, and S-O-Sr Isotope Geochemistry

“…The world-class Jinding Zn-Pb-Sr deposit and over 100 Pb-Zn-Ag-Cu deposits are located in the Lanping Basin. The latter includes carbonate-Pb-Zn sulfide veins in Jurassic to Cretaceous clastic rocks in the northern segment of the Lanping Basin, MVT Zn-Pb deposits in carbonate [18,19], and vein-type Cu sulfide mainly along the western basinal margin [20,21] (Figure 2). The world-class Jinding Zn-Pb-Sr deposit and over 100 Pb-Zn-Ag-Cu deposits a located in the Lanping Basin.…”

“…Figure 2. Simplified geological map showing the distribution of Jinding Zn-Pb-Sr deposit and Cu-Zn-Pb-Sr deposits in Lanping Basin (modified after[16,21]). …”

Application of the Mineralogy and Mineral Chemistry of Carbonates as a Genetic Tool in the Hydrothermal Environment

“…Carbonates are commonly present as part of the gangue in hydrothermal deposits associated with quartz, phyllosilicates, and barite. Carbonates are a focus of interest to researchers investigating ore-forming systems; fluid inclusion and isotopic data (C, O, Sr, Pb) can give important information on the provenance of hydrothermal fluids (e.g., [1][2][3][4][5][6][7][8][9][10][11][12][13]). However, only limited works on the composition of carbonates in ore-forming hydrothermal environments are available (e.g., [6,[14][15][16][17]).…”