Introduction: Aqueously formed hydrated or hydroxylated minerals (H2O/OH bearing) were first detected on Mars by the OMEGA instrument on Mars Express [1]. In particular, dense dune fields containing gypsum (CaSO4·2H2O) occupy the northern peri-polar Martian cap [2, 3] and more recently, the Opportunity rover identified gypsum veins on the rim of the Endeavour Crater [4]. Hence, research on terrestrial gypsum deposits are gaining relevance as potential analogues for the genesis of Martian gypsum. The δ 18O and δ 2H of gypsum hydration water (GHW) can be used to reconstruct the isotopic composition of the solution at the time of mineral precipitation, with potential paleoclimate/hydrological implications. This approach has been used to reconstruct the Earth´s past climate from gypsum deposits [6-8]. Yet, isotopic analyses of GHW in secondary gypsum deposits of lava tubes have not been reported. Here, we analyze the δ18O and δ 2H of GHW in speleothems collected in several lava tubes of the Volcán de la Corona area (northern Lanzarote Island) to investigate their formation mechanisms. This includes the Puerta Falsa (La Corona), Las Breñas, and Maguez lava tubes

Field work for this study was supported by the TUBOLAN project (PID2019-108672RJ-I00) from the Spanish Ministry of Science and Innovation, the MICROCENO project (PTDC/CTA-AMB/0608/2020) from the Portuguese FCT (Fundação para a Ciência e a Tecnologia) and the MICROLAVA research project (PROYEXCEL_00185) from the Regional Government of Andalusia. Dr. Fernando Gázquez acknowledges the Ramón y Cajal fellowship, RYC2020- 029811-I of the Spanish Ministry of Science and Innovation. The analyses were funded by the PALEOQUANT research project (P18-RT-871) of the Regional Government of Andalusia and the GYPCLIMATE research project (PID2021- 123980OA-I00) of the Spanish Ministry of Science and Innovation

Resumen de la comunicación oral presentada en 4th International Planetary Caves Conference, held 4-7 May, 2023 in Lanzarote, Spain. LPI Contribution No.2697

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