Hydrothermal alteration episodes reflect multiple Proterozoic tectonic and magmatic events in the Kangdian region, western Yangtze Block

Abstract

Hydrothermal fluids are major agents for mass and heat transfer in the upper crust. Precise age dating and tracing of the origins of fluid fluxes can provide vital information on the geological past, yet detailed reconstructions of past hydrothermal fluid activity in Precambrian terranes are commonly hindered by multistage overprints and recrystallization events. In this contribution, we present integrated U-Pb and Re-Os isotopic analyses of texturally resolved hydrothermal minerals including allanite, monazite, apatite, rutile, and sulfides, in order to constrain the timing of hydrothermal activity in the 1710−1660 Ma Dahongshan Group, which hosts the largest Fe-Cu-Au deposit in the Kangdian region of the western Yangtze Block, South China. We identify six discrete periods of fluid activity at ca. 1650, 1140, 1040, 930, 870, and 830 Ma, as well as several other cryptic hydrothermal events in metasomatised rocks, all of which can be correlated with regional tectonic and magmatic events. Our reconstruction provides a framework for evaluating Proterozoic hydrothermal and metallogenic histories of the Kangdian region along the western margin of the Yangtze Block. Furthermore, our results highlight the sensitivity of minerals to the hydrothermal response of regional tectonomagmatic events. Demonstration of these relationships is further ascertained by contrasting hydrothermal histories among the Kangdian region and other Paleoproterozoic terranes that have similar polymetallic Fe-Cu mineralization worldwide. An additional implication is that hydrothermal archives hold potential to serve as unique fingerprints to aid recognition of geological events, complementary to conventional detrital and lithotectonic records.