Mathematics – Logic
Scientific paper
Jan 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996jsc..rept.....z&link_type=abstract
Technical Report, NASA Johnson Space Center; Tennessee Univ. Houston, TX United States; Knoxville, TN United States Earth Scienc
Mathematics
Logic
Carbonaceous Chondrites, Meteoritic Composition, Silicates, Mineralogy, Volumetric Analysis, Argon Isotopes, Abundance
Scientific paper
Three parameters are proposed to determine the relative extent of alteration in CM chondrites. The mineralogic alteration index monitors the relative progress of coupled substitutions in the progressive alteration of cronstedtite to Mg-serpentine, and increases with increasing alteration. To calculate values of this index, an algorithm has been developed to estimate the average matrix phyllosilicate composition in individual CM chondrites. The second parameter is the volume percent of isolated matrix silicates, which decreases with progressive alteration due to mineral hydration. Finally, the volume percent of chondrule alteration monitors the extent of chondrule phyllosilicate production, and increases as alteration proceeds. These parameters define the first CM alteration scale that-relies on multiple indicators of progressive alteration. The following relative order of increasing alteration is established by this model: Murchison less than or equal to Bells less than Pollen less than or equal to Murray less than Mighei less than Nogoya less than Cold Bokkeveld. Bulk delta18O values generally increase with progressive alteration, providing additional support for this sequence. The relative degree of aqueous processing Cochabamba and Boriskino experienced is less precisely constrained, although both fall near the middle of this sequence. A comparison between the mineralogic alteration index and literature values of the whole-rock chemistry of CM chondrites reveals several correlations. For example, a positive, nearly linear correlation between bulk H content and progressive CM alteration suggests an approximately constant production rate of new phyllosilicates relative to the mineralogical transition from cronstedtite to Mg-serpentine. Furthermore, the abundance of trapped planetary Ar-36 decreases systematically in progressively altered CM chondrites, suggesting the wholesale destruction of primary noble gas carrier phase(s) by aqueous reactions. Multiple correlations between diverse alteration parameters indicate that different CM chondrites probably experienced the same kinds of processes and conditions during in situ parent body alteration.
Browning Lauren B.
McSween Harry Y. Jr.
Zolensky Michael E.
No associations
LandOfFree
Correlated Alteration Effects in CM Carbonaceous Chondrites does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Correlated Alteration Effects in CM Carbonaceous Chondrites, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Correlated Alteration Effects in CM Carbonaceous Chondrites will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-972095