MINERAL MICROHABITATS: PROPERTIES, PROCESSES, AND PRODUCTS OF SMALL SCALE GEOLOGICAL SYSTEMS AND THEIR CAPABILITIES TO SUPPORT LIVING ORGANISMS

The relationships between minerals and microorganisms are a critical field of study to understand the most basic and the most complex environments in which organisms might originate, can evolve, and can ultimately live. From identifying the precursor ingredients for life, to locating the settings and conditions in which life can carry out its processes, to finding the products of organic decay, mineral rich geological settings are the primary environments to explore. The scale of mineral grains and the spaces enclosed between them, combined with the size of microbial organisms that can arise and live therein, are the main ingredients for the concept of mineral microhabitats. We aim to define mineral microhabitats from the standpoints of habitat composition and the influence of microorganisms.

Generally, biota enter a system from its surroundings, and by adapting to their new micro environment they evolve under its influence over time. The precursors to life may also originate from the interaction of specific mineral compositions and geochemical conditions. The concept of mineral microhabitats seeks to bring together the components provided by 1) mineralogy and geochemistry; 2) the physical structure defined by morphology and spatial dynamics; 3) the alterations incurred through mechanical and chemical weathering; and 4) the influence of and onto biological organisms and organic matter. This blueprint will be ultimately used to define the properties and quantify the processes occurring within the smallest habitats on Earth and beyond.

To illustrate this concept, we apply data obtained from the analysis of clay minerals sampled from a coastal temperate exposure on the north shore of Long Island, NY. Initial results allow us to supply data for our proposed classification criteria as follows. 1) Clay mineral species identified by XRD analysis show the coexistence of 1:1 layer and 2:1 layer clays, kaolinite and illite respectively. 2) SEM analysis reveals a variety of spaces and surfaces provided by stacked flakes of well crystallized kaolinite; aggregates of platelets; K-feldspar crystals and microquartz. 3) EDS mapping indicates Si to Al substitution as K-feldspar crystals are weathered into platy clay. 4) Previous biogeochemical analysis of these samples indicates that clays with higher Fe and C content have an increased capacity to support microbial biomass and activity.