Numerical simulation of ore formation within skarn-type Pb-Zn deposits: Implications for mineral exploration and the duration of ore-forming processes

Abstract

Skarn-type deposits are typical hydrothermal mineral deposits distributed throughout the world with multiple metal resources and huge economic value. However, their extremely complex forming processes hinder us from further understanding their forming mechanism and exploring their economic potential. This study builds an integrated and simplified model of skarn-type Pb-Zn deposits and applies numerical simulation approach to quantitatively describe the formation of mineralization, analyzing the continuous dynamic changes of the concentrations of generated garnet, diopside and galena/sphalerite within the system. This numerical model includes chemical reactions, heat conduction, fluid-flow, materials migration and diffusion and their complex coupled relationships. The results show that the alterations at the contact of wall rocks and intrusions have clear zoning of garnet and diopside, and the amount of diopside exceeds that of garnet at the distal end of the generated alteration zone; the generation processes of garnet, diopside and galena/sphalerite follows a strict chronological order, controlling the variation of rock porosity; the cooling process of P3 (Fig. 4b) from 700 °C to 170 °C costs 55,000 years, within which the formation of galena/sphalerite merely lasts 30,000 years, meaning that the effective lifespan of Pb/Zn mineralization takes up only 54.54 % of the whole 55,000 years. All these results provide useful information for metallogenic research of skarn-type Pb-Zn deposits as well as magmatic-hydrothermal system. However, the method applied in this research still has limitations, such as the restriction from the single-period magmatic activity, the law of mass action, and the simplified chemical equations. Future development into both mathematical geosciences and geological analytical tests will definitely provide more appropriate calculation models and testing data with higher precision, improving the accuracy and practical significance of numerical simulation of ore formation, and providing more detailed quantitative answers for remaining hot issues related to economic geology research.