Geological Society of America

T10 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

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

Paper number: T10-7
Program: Technical Sessions
Time: 9:35 AM – 9:50 AM

Authors

Daniel Hummer Presenting Author
Southern Illinois University, Carbondale, IL
Michael Meyer
Harrisburg University of Science and Technology, Harrisburg, PA
Robert Hazen
Carnegie Institution for Science, Washington, DC
Ahmed Eleish
Rensselaer Polytechnic Institute, Troy, NY
Chao Liu
Carnegie Institution for Science, Washington, DC
Shaunna Morrison
Carnegie Institution for Science, Washington, DC
Robert T. Downs
University of Arizona, Tucson, AZ
Joshua J. Golden
University of Arizona, Tucson, AZ
Alexander J. Pires
University of Arizona, Tucson, AZ
Grethe Hystad
Purdue University Northwest, Hammond, IN

Abstract

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.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-323624

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