T191 Mineralogical Evidence for the Co-Evolution of the Geosphere and Biosphere: In Honor of Robert M. Hazen, 2016 Roebling Medalist

Tuesday, 27 September 2016
8:00 AM - 12:00 PM
Room 207

UNUSUAL CARBONATE CRYSTAL FABRICS AS INDICATORS OF OCEAN CHEMICAL EVOLUTION

Paper number: T191-3
Program: Technical Sessions
Time: 8:30 AM – 8:50 AM

Authors

  • Linda C. Kah Presenting Author
    University of Tennessee, Knoxville, TN

Abstract

Crystal fabrics in precipitated carbonate provide fundamental information regarding he relative rates of crystal nucleation and crystal growth. Such information is critical to inferring potential mineralogy of ancient carbonate rocks (e.g. calcite vs high-Mg calcite vs aragonite), interpreting chemical environments of growth (e.g. marine vs meteoritc waters), and deciphering pathways of early diagenetic recrystallization.

There are, however, some carbonate crystal fabrics that remain relatively poorly understood. Herringbone carbonate, first described from Archean rocks (cf. Sumner and Grotzinger, 1996), consists of elongate lathes that show an unusual rotation of the c-axis from parallel, to perpendicular, to the growth axis of the crystal. Such rotation of the c-axis suggests that herringbone carbonate represents the neomorphic recrystallization of spherulitic, or curved, crystal growth. Curvature of crystals during growth commonly results from: (1) the presence of impurities (including organic macromolecules) that inhibit crystal growth along specific faces, (2) the presence of ions that favors secondary nucleation along the primary crystal growth front, or (3) conditions that favor rapid crystal growth and associated lattice defects.

Since its original description, documentation of the geologic distribution of herringbone carbonate has been ongoing. Original findings in such varied environments as Archean marine rocks and Eocene travertine place our primary constraints on the origin of herringbone carbonate. Here I describe occurrences from Mesoproterozoic, Early Paleozoic, and Late Paleozoic rocks, and suggest that marine environments containing herringbone carbonate broadly track the position of a marine chemocline, thereby providing a potential link between carbonate crystal morphology and ocean redox.

Geological Society of America Abstracts with Programs. Vol. 48, No. 7

doi: 10.1130/abs/2016AM-283209

© Copyright 2016 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.