Hydrothermal carbonate chimney event from yin’ e basin: Mineralogy, geochemistry, and mode of evolution

Abstract

Hydrothermal chimney, one of Earth's most mysterious geological events, is crucial for understanding Earth's systems and the history of life. Fine-scale studies of these events help us better understand geological processes, though their transient and complex nature presents significant challenges. Through TIMA, LA-ICP-MS in-situ elemental testing, and Sr and S isotope testing, a relatively complete picture of a carbonate chimney event in the upper section of the Bayingebi Formation in the Yin'e Basin was revealed with high precision. This event was divided into four distinct stages: the prehydrothermal eruption stage, the initial hydrothermal eruption stage, the strong hydrothermal eruption stage and the sustained hydrothermal overflow stage. The pre-hydrothermal eruption stage (Area I) indicates dominant terrigenous sedimentation in a low-energy hydrodynamic environment, with coarse-crystalline calcite enriched in Mn and depleted in K, Na, and Sr and featuring high ⁸⁷Sr/⁸⁶Sr values. Subsequently, a transient hydrothermal eruption initiated the deposits in Area II, marked by the appearance of thin-plate calcite and dolomite. During the strong hydrothermal eruption stage (Area III), radial pyrite intersected with calcite, and extensive dolomite precipitation occurred. The ⁸⁷Sr/⁸⁶Sr ratio and the δ³⁴S_V-CDT value observed may have been a result of the activities of sulfate-reducing bacteria (SRB). In the sustained hydrothermal overflow stage, the eruption intensity decreased, leading to the formation of abundant microcrystalline carbonates in Area IV. Results show regular changes in hydrothermal mineral combinations, eruption modes, material composition, depositional environments, etc., in each stage of the carbonate chimney event, which can provide important information for global lacustrine hydrothermal activity research.