191-6 Coupled Sedimentary, Hydrothermal and Biogenic Processes in Lacustrine Carbonate Systems: A Case Study of the Early Cretaceous Bayingebi Formation, Yin’e Basin

Session: Aspects of Carbonates (Posters)

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Given the increasing significance of unconventional energy reservoirs such as oil shale within lacustrine hydrocarbon systems worldwide, a profound understanding of organic and inorganic processes in lacustrine systems is essential—particularly in settings shaped by specialized conditions (e.g., biological activity, hydrothermal circulation, gravity flows), where the interactions among these processes provide a uniquely distinctive perspective on the mechanisms of organic matter enrichment in lakes. To deepen the understanding of such processes, this study focuses on the diagenesis of different types of carbonates from the upper section of the Bayingebi Formation in the Yin’e Basin, revealing the connection between lacustrine sedimentation and hydrothermal activity. Through mineralogical and geochemical testing, three carbonate types were identified: hydrothermal, hydrothermal-biogenic, and sedimentary carbonates. Hydrothermal carbonates are dominated by crystalline dolomite, with associated hydrothermal minerals rich in Fe, Ba, and Mg and ⁸⁷Sr/⁸⁶Sr values close to mantle source values, indicating substantial mantle hydrothermal fluid contributions. Hydrothermal-biogenic carbonates are dominated by mud-crystalline and spherical dolomite enriched in Mg, Na, and P. The ⁸⁷Sr/⁸⁶Sr values are between mantle source and palaeolake water values, suggesting synergistic interactions between hydrothermal and biological processes. Sedimentary carbonates are predominantly crystalline calcite, with ⁸⁷Sr/⁸⁶Sr values close to crustal source values, indicating the influence of terrestrial inputs. Moreover, there is a significant relationship between different types of diagenetic carbonates and organic matter. Intense hydrothermal activity suppresses primary productivity and hinders the preservation of organic matter. In contrast, sections with mild hydrothermal activity have higher TOC contents, and the nutrient contents and water temperatures are more conducive to organic matter enrichment. This study clearly reveals the dynamic interactions between carbonate diagenesis and organic matter enrichment in lacustrine environments, providing new perspectives on the interactions among minerals, microorganisms, and hydrothermal activity. Ultimately, integrating mineral-microbe-hydrothermal interactions into basin-scale frameworks not only enhances exploration strategies for unconventional energy plays but also sheds new light on the co-evolution of Earth’s lithosphere, hydrosphere, and biosphere.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-4773

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