44-2 Environmental and Mineralogical Controls on Preservation Potential: Lessons from the Lassen Hydrothermal System

Session: Advancing Mineral Science and Exploring Planetary Surfaces: In Honor of MSA Dana Medalist, Elizabeth B. Rampe, Part II

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Hydrothermal systems on Earth provide valuable analogs for ancient Mars, where mineral precipitation could entomb and preserve biosignatures against degradation. However, preservation potential varies with environmental gradients and mineralogy, and few studies have systematically compared these factors within a single, compositionally diverse hydrothermal field. Lassen Volcanic National Park (LVNP) hosts acidic, near neutral, and neutral hydrothermal systems depositing silica, carbonates, sulfates, and clays, which are minerals known to vary in their capacity to retain morphological and chemical biosignatures.

We investigated five hydrothermal sites: Devil’s Kitchen, Drakesbad, Upper Sulphur Works, Lower Sulphur Works, and Little Hot Springs Valley, spanning wide ranges in pH (~2–7), temperature (~9–91°C), redox potential (–488 to +450 mV), and salinity (<0.1–5 ppt). Field measurements with a Hydrolab Sonde were paired with water chemistry (AA, IC), mineralogy (XRD), bulk geochemistry (XRF), and morphological analyses (SEM–EDS). Results show strong site-specific controls on mineral deposition and preservation potential. Silica sinters at Drakesbad exhibit high preservation capacity, with porous amorphous matrices encapsulating diatoms and microbial filaments. Near-neutral travertines at Little Hot Springs Valley and Lower Sulphur Works preserve some microbial textures but are variably overprinted by recrystallization. Clays (montmorillonite) occur in both acidic and neutral systems, offering high potential for long-term organic adsorption. Sulfate deposits form rapidly in acidic to transitional zones, but their high solubility reduces long-term stability. Acid-sulfate muds at Devil’s Kitchen show chemical leaching, suggesting low preservation potential despite abundant secondary minerals.

Comparative analysis indicates that rapid precipitation (silica, active carbonates) and fine grained adsorption media (clays) yield the highest preservation potential, while highly soluble or recrystallized phases diminish biosignature detectability. These trends parallel key mineralogical targets on Mars, including silica at Columbia Hills, carbonates at the Comanche outcrop, clays at Nili Fossae, and acid sulfates at Columbia Hills. This multi-proxy framework links environmental gradients to preservation potential and detection likelihood, highlighting where biosignatures may persist or remain undetectable (“false negatives”). Our results inform Mars sample targeting strategies by identifying mineralogical–geochemical combinations most conducive to preservation potential and biosignature retention in ancient hydrothermal terrains.

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

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