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Coesite in suevites from the Chesapeake Bay impact structure

May 1, 2016

The occurrence of coesite in suevites from the Chesapeake Bay impact structure is confirmed within a variety of textural domains in situ by Raman spectroscopy for the first time and in mechanically separated grains by X-ray diffraction. Microtextures of coesite identified in situ investigated under transmitted light and by scanning electron microscope reveal coesite as micrometer-sized grains (1–3 μm) within amorphous silica of impact-melt clasts and as submicrometer-sized grains and polycrystalline aggregates within shocked quartz grains. Coesite-bearing quartz grains are present both idiomorphically with original grain margins intact and as highly strained grains that underwent shock-produced plastic deformation. Coesite commonly occurs in plastically deformed quartz grains within domains that appear brown (toasted) in transmitted light and rarely within quartz of spheroidal texture. The coesite likely developed by a mechanism of solid-state transformation from precursor quartz. Raman spectroscopy also showed a series of unidentified peaks associated with shocked quartz grains that likely represent unidentified silica phases, possibly including a moganite-like phase that has not previously been associated with coesite.

Publication Year 2016
Title Coesite in suevites from the Chesapeake Bay impact structure
DOI 10.1111/maps.12638
Authors John C. Jackson, J. Wright Horton, I-Ming Chou, Harvey E. Belkin
Publication Type Article
Publication Subtype Journal Article
Series Title Meteoritics and Planetary Science
Index ID 70191257
Record Source USGS Publications Warehouse
USGS Organization Eastern Mineral and Environmental Resources Science Center