Experimental studies of the interactions between biomolecules and minerals under conditions simulating harsh planetary environments provide key insights into possible prebiotic processes and the search for life. Despite protection from cosmic rays, UV, and oxidative degradation, buried biosignatures may undergo diagenetic processes that decrease the concentration of organic matter. Additionally, other degradation mechanisms occur as a result of elevated temperatures, pressures, mineral-organic interactions, and fluid/brine processes. In this study, we aim to provide a fuller understanding of preservation potential by considering several variables, including pressure, temperature, the mineral matrix environment, and fluid chemistry (salinity, pH, composition). This research expands previous anhydrous work to investigate the influence of lower pressure regimes, especially in a combined fluid/brine environment with various mineral matrices. To test the preservation potential of various biomolecules, we subjected samples to temperature, pressure, fluid, and mineral matrix conditions representative of different environmental stressors. The starting materials included: 1) isolated organic compounds added to various mineral standards, 2) An endolithic and microbe-rich natural calcite deposited from a CO2-rich hot spring, 3) cyanobacteria necromass. Experiments were conducted in three different devices 1) a piston-cylinder press reaching up to 15 kbar and 550 °C, 2) high-volume batch reaction vessels generating up to 15 MPa pressure and 80 °C, and 3) ambient pressure, high temperature furnaces. Samples were analyzed by GC-MS and LC-MS, while ICP-MS, XRD, and Raman were used for additional characterization. The influence of pressure can be clearly identified. Similarly, fluid transport, complex thermal degradation, and oxidation mechanisms are identified.