Biology
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufm.p53d..01h&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #P53D-01
Biology
0414 Biogeochemical Cycles, Processes, And Modeling (0412, 0793, 1615, 4805, 4912), 0419 Biomineralization, 0424 Biosignatures And Proxies, 0448 Geomicrobiology, 3665 Mineral Occurrences And Deposits
Scientific paper
Earth's near-surface mineralogy has diversified over geologic time as a consequence of three primary mechanisms: (1) the progressive separation and concentration of the elements from their original relatively uniform distribution in the pre-solar nebula; (2) an increase in range of intensive variables such as pressure, temperature, and the activities of H2O, CO2, and O2; and (3) the generation of far-from- equilibrium conditions by living systems. Following planetary accretion and differentiation, the initial mineral evolution of Earth's crust depended on a sequence of geochemical and petrologic processes, including volcanism and degassing, fractional crystallization, crystal settling, assimilation reactions, regional and contact metamorphism, plate tectonics, and associated large-scale fluid-rock interactions. These processes produced the first continents with their associated granitoids and pegmatites, hydrothermal ore deposits, metamorphic terrains, evaporites, and zones of surface weathering, and resulted in an estimated 1500 different mineral species. Biological processes began to affect Earth's surface mineralogy by the Eoarchean Era (3.85 to 3.6 Ga), when large-scale surface mineral deposits, including banded iron formations, were precipitated under the influences of changing atmospheric and ocean chemistry. The Paleoproterozoic "Great Oxidation Event" (2.2 to 2.0 Ga), when atmospheric oxygen may have risen to greater than one percent of modern levels, and the Neoproterozoic increase in atmospheric oxygen, which followed several major glaciation events, ultimately gave rise to multicellular life and skeletal biomineralization and irreversibly transformed Earth's surface mineralogy. Biochemical processes may thus be responsible, directly or indirectly, for most of Earth's 4300 known mineral species. 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, and to teaching, the mineral sciences.
Bleeker W.
Downs Robert T.
Ferry John M.
Hazen Robert M.
McCoy Timothy James
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