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GSA Annual Meeting in Indianapolis, Indiana, USA - 2018

Paper No. 10-6
Presentation Time: 9:35 AM

ECOLOGY AND EVOLUTION OF MANGANESE MINERALS: IMPLICATIONS FOR THE REDOX HISTORY OF EARTH AND LIFE


HUMMER, Daniel R.1, HAZEN, Robert M.2, ELEISH, Ahmed3, LIU, Chao4, MORRISON, Shaunna M.4, DOWNS, Robert T.5, GOLDEN, Joshua J.5, PIRES, Alexander J.5, HYSTAD, Grethe6 and MEYER, Michael7, (1)Department of Geology, Southern Illinois University, Carbondale, IL 62901, (2)Geophysical Laboratory, Carnegie Institution, 5251 Broad Branch Road NW, Washington, DC 20015, (3)Tetherless World Constellation, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, NY 12180, (4)Geophysical Laboratory, Carnegie Institution for Science, Washington, DC 20015, (5)Department of Geosciences, University of Arizona, Tucson, AZ 85721, (6)Department of Mathematics, Statistics, and Computer Science, Purdue University Northwest, Hammond, IN 46323, (7)Earth and Environmental Science, Harrisburg University of Science and Technology, 326 Market St., Harrisburg, PA 17101

Manganese is a widespread redox sensitive transition element with three naturally occurring oxidation states and 560 mineral species, making it a useful proxy for the redox state of Earth’s crust. Network analysis of Mn minerals using large mineral databases (mindat.org), which graphically displays the coexistence of mineral species, reveals three distinct clusters: (1) a central cluster composed of primary Mn2+ silicates, oxides, and carbonates formed in igneous intrusions, hydrothermal ores, and skarns, together with secondary Mn3+ and Mn4+ oxidative weathering products, (2) a side cluster of predominantly Mn2+ phosphates and oxides arising in granitic pegmatites, and (3) a side cluster of predominantly Mn2+ silicates arising in agpaitic intrusives. Clusters 2 and 3 display some co-occurrence with minerals in cluster 1, but not with each other.

Ages of first appearance reveal that common, primary igneous and metamorphic minerals of clusters 1 and 2 appear early in the geologic record, at or before 2.0 Ga. Oxidative weathering products in cluster 1 predominantly appear after photosystem-II initiated the Great Oxidation Event at ~ 2.3 Ga. Minerals of cluster 3 are geologically recent, appearing in the last 1.2 Ga as a result of further reworking and differentiation of the crust. The increasing prevalence of oxidized Mn minerals during the last 1 billion years raised the average oxidation state of crustal Mn in a pattern mirroring reconstructions of atmospheric oxygen, documenting the oxidation of Earth’s crust in response to photosynthetic oxygen.

Session No. 10

T115. Mineral Evolution and Ecology: Potential Directions for the Next 100 Years with the Mineralogical Society of America
Sunday, 4 November 2018: 8:00 AM-12:00 PM
Room 233 (Indiana Convention Center)
Geological Society of America Abstracts with Programs. Vol. 50, No. 6
doi: 10.1130/abs/2018AM-323624
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