Lead isotopic systematics for native copper-chalcocite mineralization in basaltic lavas of the Emeishan large igneous province, SW China: Implications for the source of copper

Abstract

The Emeishan continental flood basalt, which is widespread in Yunnan, Guizhou and Sichuan provinces of Southwest China, is the volcanic product of a Permian mantle plume, and native copper-chalcocite mineralization associated with the basalt is very common in the border area of Yunnan and Guizhou provinces. The mineralization occurred in the tuff intercalation and terrestrial sedimentary rock intercalation which were formed during the main period of basalt eruption. The orebodies are controlled by the stratigraphic position and faults. Metal ore minerals in the ores are mainly native copper, chalcocite and tenorite, with small amounts of chalcopyrite, bomite, pyrite and malachite, and sometimes with large amounts of bitumen, carbon and plant debris. Several decades of ore deposits are distributed in the neighboring areas of the two provinces, while most of them are small-scale deposits or only ore occurrences. By comparing the lead isotopic composition of the ores with that of the wall-rocks, cover and basement rocks of various periods, the source of copper in this type of ore deposits was studied in this paper. The results showed that: (1) The Pb isotopic composition of the ores from ten deposits is absolutely different from that of siliceous-argillaceus rocks of the Upper Permian Xuanwei Formation, limestones of the Lower Permian Series and Carboniferous, Cambrian sandstone-shale and recta-sedimentary rock and dolomite from the upper part of the Meso-Proterozoic Kunyang Group. This indicates that ore lead was derived neither from the cover rock nor from the basement rocks; (2) Although the Neo-Proterozoic Siman dolomite and silicalite, and dolomite in the lower part of the Kunyang Group are similar in Pb isotopic composition to the ores, lead and copper contents in these rocks are very low and they have not made great contributions to copper mineralization; (3) The ores have the same Pb isotopic composition as the basalt, the latter being enriched in copper. These facts indicate that lead and copper were derived from the basalt. According to the regional geological data and the geological-geochemical characteristics of the ore deposits, it is suggested that ore-forming materials were leached out from the basalt. The thickness and buried depth of the basalt and regional tectonic dynamics can affect the formation of large-scale copper deposits. Therefore, exploration for this type of ore deposits should be conducted in the areas from western Yunnan to western Sichuan, where there are developed basalts of great thickness, with extensive tectonic movement and magmatic activity.

Risk Assessment and Source Identification of Toxic Metals in the Agricultural Soil around a Pb/Zn Mining and Smelting Area in Southwest China

“…The statistical results above were further justified by many studies [ 11 , 14 , 17 , 30 , 53 ]. The findings obtained by correlation analysis, PCA and CA were solid for the reasons that Zn, Pb, Cd, As and Cu in the lead/zinc ore and copper ore [ 24 , 25 ] would be released by emitting exhaust, discharging wastewater and acid mine drainage. Hg, Cd and As carried by the exhaust would return to soil through atmospheric deposition.…”

“…It is the central part of the Sichuan-Yunnan-Guizhou triangular area of poly-metallic Pb/Zn mineralization. The geological background of the study area has ‘double-layer’ structure which consists of a weathered Permian basalt as the overlying cover rocks and dense massive Permian basalt as the lower basement [ 24 , 25 ]. The average elevation of the territory is around 2120 m, and the main soil type is Alfisols.…”

“…Huize County, in Yunnan Province, is a famous area worldwide for its abundance of non-ferrous metal ores, especially lead-zinc ore [ 24 ] and copper ore [ 25 ]. Zhehai, a town under Huize’s jurisdiction, has a long history of lead-zinc mining and a smelting industry dating back to the 1960s.…”

Palynological constraints on the provenance and stratigraphic range of a Lopingian (Late Permian) inter-extinction floral lagerstätte from the Xuanwei Formation, Guizhou Province, China

“…The Xuanwei Formation is dominated by interbedded sandstones, conglomerates, mudstones and coals that formed primarily in terrestrial, fluvial, mire and proximal deltaic environments (Wang et al, 2011), and has occasional volcaniclastic tuffaceous horizons that contain anatomically preserved fossil plants (Zhou et al, 2000;Hilton et al, 2004;Wang et al, 2006;Zhang et al, 2009Zhang et al, , 2010Dai et al, 2010Dai et al, , 2014. Whereas the volcaniclastic horizons constitute konservat lagerstätten as they preserve fossil plants in exquisite cellular detail, some have also been designated as 'polymetallic ore beds' (Dai et al, 2010).…”