The distribution, characteristics and fluid sources of lode gold deposits: An overview

Abstract

Lode gold deposits are among the most economically important types of gold deposits in the world. Globally, they formed mainly in three time intervals, 2.8 to 2.5 Ga, 2.1 to 1.8 Ga, and 700 Ma to the present. Sources of ore-forming fluids and other components are of critical importance in a better understanding of the genesis and the geodynamic controls of these deposits. Although ore-forming fluids were mostly derived from devolatization of sedimentary and/or volcanic sequences during greenschist to amphibolite facies metamorphism associated with orogenic deformation, magmatic hydrothermal fluids have been increasingly shown to be important in many gold deposits in various regions. In this review paper, we summarize the major features of lode gold deposits, possible sources of ore-forming fluids, and mechanisms of gold mineralization. While we acknowledge the critical role of metamorphically derived fluids in the genesis of such deposits worldwide, we emphasize that mantle-or basaltic magma-derived fluids may have been much more important than commonly thought. We use the Liaodong peninsula of the North China Craton as an example to demonstrate the significance of mantle-derived fluids. Integrating earlier studies and new data, we show that some of the late Mesozoic lode gold deposits in the North China Craton may have formed from magmatic hydrothermal fluids due to the extension and partial melting of the hydrated, metasomatized subcontinental lithosphere mantle, as best exemplified by the Wulong gold deposit.

Orogenic gold: is a genetic association with magmatism realistic?

“…The gold deposits are suggested to have been formed at relatively shallow levels where melts could theoretically exsolve large S-and Au-rich fluid volumes. Wang et al (2021) suggest SCLM-derived hydrous basalts erupted coevally with the gold event could represent causative magmas that formed the gold deposits. They also however show, significantly, that the xenoliths of the SCLM are depleted, not enriched in Au relative to primary mantle and argue it is only the volatile-rich nature of the basalts that enriched their hypothesized causative magmas with gold.…”