Trace metals in saline waters and brines from China: Implications for tectonic and climatic controls on basin-related mineralization

Research into mineralization using a deposit-centric approach has identified three principal factors (evolution of the hydrosphere–atmosphere, secular decrease in global heat production, and long-term global tectonic trends) that have influenced the global pattern of metallogenesis. However, these factors do not explain the peak occurrences of basin-related mineralization during particular periods of Earth's evolution. Here we shift the research perspective from an ore-deposit-centric approach to one focusing on the formation processes of ore-forming fluids by using mass spectrometry to analyze the concentrations of metallic elements (U, Cr, Fe, Mn, Co, Ni, Cu, Mo, Cd, Sn, Pb, Zn, and V) of naturally occurring saline water bodies (brines) in currently developing basins in China. Our aim is to determine the presence of metal-bearing fluids and establish the formation processes of ore-forming fluids that can subsequently generate mineral deposits. The concentrations of trace metals in evaporated seawater and surficial saline waters (brines) in continental basins can reach up to mg/L level, with the increase in salinity resulting from the significant evaporation that occurs in semi-arid to arid environments. The high salinities increase the density of metal-bearing brines, which in turn causes these brines to circulate and mix with groundwater, resulting in enriched metal element concentrations in the groundwater. Groundwater containing dissolved evaporites also shows relatively high concentrations of metal elements (up to mg/L level) that compare with fresh groundwater. These metal-bearing brines can be regarded as the initial ore-forming fluids of basin-related mineral deposits, such as unconformity-type U deposits, red-bed Cu deposits, and some stratiform Pb–Zn deposits. The metal-bearing brines are the result of substantial evaporation under arid to semi-arid climates. Therefore, we conclude that climate is an important control on the formation of basin-related mineralization and that the tectonoclimatic setting plays an essential role in the formation of metal-bearing brines in closed inland basins. The major climatic events, such as the snowball and greenhouse event can affect the basin-related mineralization globally. The super mantle plume event could affect the global basin-related mineralization by changing the global climate significantly.