Lectures at the Smithsonian (19 MAR 2008) and NASA Goddard Spaceflight Center (20 MAR 2008)

Mineralogical Coevolution of the Geo- and Biospheres

The mineralogy of terrestrial planets evolves as a consequence of varied physical, chemical and biological processes. Initial evolutionary stages saw the transition from ~12 nano-scale mineral phasesin pre-stellar dense molecular clouds, to ~250 different minerals in altered chondrites, achondrites and differentiated asteroids. Earth's subsequent prebiotic mineral evolution depended on a sequence of geochemical and petrologic processes that resulted in perhaps 1500 different mineral species. Biological processes began to affect Earth's surface mineralogy by the Eoarchean, and culminated in the Paleoproterozoic "Great Oxidation Event," when increases in atmospheric O2 transformed Earth's mineralogy and were rsponsible, directly or indirectly, for most of earth's 4300 known mineral species. Mineral evolution arises from three primary mechanisms: (1) progressive separation and concentration of elements from their original relatively uniform distribution; (2) an increase in range of intensive variables such as pressure, temperature, and activities of H2O, CO2 and O2; and (3) generation of far-from-equilibrium conditions by living systems. The sequential evolution of Earth's mineralogy from chondritic simplicity to Phanerozoic complexity introduces the dimension of geologic time to mineralogy and thus provides a dynamic alternate approach to framing the mineral sciences.