Mineralization Process of MVT Zn-Pb Deposit Promoted by the Adsorbed Hydrocarbon: A Case Study from Mayuan Deposit on the North Margin of Sichuan Basin

Abstract

The Mayuan Zn-Pb deposit on the northern margin of the Sichuan Basin is rich in Zn-Pb deposit resources. Additionally, a large amount of bitumen is observed in outcrops, and these deposits represent a key template for exploring the migration of hydrocarbon fluids and metal elements within an ancient oil reservoir. In this study, a chemical experimental method was used to extract the adsorbed hydrocarbon from the chosen five groups of samples, and mathematical statistical methods were also used. The varied metal concentrations before and after the extraction experiments have been noticed, due to the direct carrying action of the adsorbed hydrocarbon. In addition, a strong correlation was observed between the Mayuan Zn-Pb deposit and their source rocks, as well as the same distribution trend from the rare earth element distribution curve. A moderate correlation was observed between the two groups of black shales and Mayuan Zn-Pb ores, and the rare earth partition curve showed consistent trends. The results show that organic matter exists in two forms, among which hydrocarbon organic matter is extracted due to the carrying effect of extraction experiment, and the remaining non-hydrocarbon organic matter is combined with metal elements to form a metal complex. Hydrocarbons are involved in mineralization, asphaltenes are derived from bitumen, and one of the potential sources of Pb/Zn in the Mississippi Valley type (MVT) Zn-Pb deposit is black shale rich in organic matter.