Towards a morphology diagram for terrestrial carbonates: Evaluating the impact of carbonate supersaturation and alginic acid in calcite precipitate morphology

Ancient and recent terrestrial carbonate-precipitating systems are characterised by a heterogeneous array of deposits volumetrically dominated calcite. In these environments, calcite precipitates display an extraordinary morphological diversity, from single crystal rhombohedral prisms, to blocky crystalline encrustations, or spherulitic dendritic aggregates. Despite many decades thorough descriptive interpretative work on fabrics, relating micro-morphology with sedimentary hydrogeochemical conditions remains challenge. Environmental interpretations have been hampered the fact that morphogenesis results complex interaction between different physico-chemical parameters which often act simultaneously (e.g., carbonate mineral supersaturation, Mg/Ca ratio parental fluid, organic inorganic additives). To try experimentally address sedimentological causes morphogenesis, experimental approach yielding first attempt at growth-form phase diagram is presented here. The initial aim was account for products nucleated in alkaline, saline lake settings. These result least two competing precipitation ‘driving forces’ affect morphogenesis: supersaturation level concentration microbial-derived molecules (alginic acid). A key finding this study common naturally-occurring such as floating rafts, prismatic forms, di-pyramid crystals, grains, vertically stacked spheroidal aggregates, can be related specific contexts, their physical transitions pinpointed diagram. By exploring binary ternary responses forcing phase-space, links growth forms (palaeo)environmental determined. This provides truly process-oriented means navigating questions around precipitate future.