NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Mineralogical Studies of Experimentally Shocked Dolomite: Implications for the Outgassing of CarbonatesCommon rock-forming rhombohedral carbonates - calcite and dolomite - constitute a considerable fraction of terrestrial sediments that may be shocked during hypervelocity impacts, such as during the Cretaceous-Tertiary (K/T) event or at the Haughton structure. The relatively modest temperatures needed to decompose carbonates and to release their CO2 are easily attained during such impacts. However, detailed and quantitative understanding of the CO2 release of carbonates as a function of shock stress is still the subject of controversy, as are a number of other reactions and phase transitions that were suggested for carbonates. The first devolatilization studies of carbonates in the early 1980s suggested that incipient devolatilization of calcite and/or dolomite commences at modest pressures, in the range < 10-18 GPa (amounting to 0.03-0.3% CO2 loss), with massive decarbonation (30-40% CO2 loss) occurring at shock pressure of 20 GPa and above. However, most later studies revealed that both calcite and dolomite are unexpectedly stable under shock conditions and no significant outgassing has been observed at pressures as high as 40 GPa for calcite and 60 GPa for dolomite. Despite these uncertainties, the calculations of O'Keefe and Ahrens (and others) serve to illustrate that the K/T bolide liberated sufficient CO2 that a substantial temperature increase of the global atmosphere is possible due to CO2-triggered greenhouse effects. The quantitative understanding of the devolatilization of carbonates as a function of shock stress is obviously critical to refine such calculations. Additional information is contained in the original extended abstract.
Document ID
20010007168
Document Type
Conference Paper
Authors
Skala, R.
(Geological Survey of Czech Republic Prague, Czech Republic)
Hoerz, F.
(NASA Johnson Space Center Houston, TX United States)
Date Acquired
August 20, 2013
Publication Date
January 1, 2000
Publication Information
Publication: Catastrophic Events and Mass Extinctions: Impacts and Beyond
Subject Category
Geophysics
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

Related Records

IDRelationTitle20010007049Analytic PrimaryCatastrophic Events and Mass Extinctions: Impacts and Beyond
Document Inquiry
No Preview Available