Rare Potassium-Bearing Mica in Allan Hills 84001: Additional Constraints on Carbonate Formation

Details Rare Potassium-Bearing Mica in Allan Hills 84001: Additional Constraints on Carbonate Formation Rare Potassium-Bearing Mica in Allan Hills 84001: Additional Constraints on Carbonate Formation

Jan 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998mmws.work....6b&link_type=abstract

Workshop on the Issue Martian Meteorites: Where do we Stand and Where are we Going?, p. 6

Computer Science

Mars (Planet), Microorganisms, Petrography, Snc Meteorites, Chronology, Extraterrestrial Life, Silicates, Mica, Carbonates, Transmission Electron Microscopy, Feldspars, Potassium

Scientific paper

There have been presented several intriguing observations suggesting evidence of fossil life in martian orthopyroxenite ALH 84001. These exciting and controversial observations have stimulated extensive debate over the origin and history of ALH 84001, but many issues still remain unresolved. Among the most important is the question of the temperature at which the carbonates, which host the putative microfossils, formed. Oxygen- isotopic data, while showing that the carbonates are generally out of isotopic equilibria with the host rock, cannot constrain their temperature of formation. Both low- and high-temperature scenarios are plausible depending on whether carbonate growth occurred in an open or closed system. Petrographic arguments have generally been used to support a high-temperature origin but these appear to be suspect because they assume equilibrium between carbonate compositions that are not in contact. Some observations appear to be consistent with shock mobilization and growth from immiscible silicate-carbonate melts at high temperatures. Proponents of a low-temperature origin for the carbonates are hampered by the fact that there is currently no evidence of hydrous phases that would indicate low temperatures and the presence of a hydrous fluid during the formation of the carbonates. However, the absence of hydrous phases does not rule out carbonate formation at low temperatures, because the carbonate forming fluids may have been extremely CO2 rich, such that hydrous phases would not have been stabilized. In this study, I have carried out additional Transmission electron microscopy (TEM) studies of ALH-84001 and have found evidence of very rare phyllosilicates, which appear to be convincingly of pre-terrestrial origin. At present these observations are limited to one occurrence: further studies are in progress to determine if the phyllosilicates are more widespread.

Affiliated with

Also associated with

No associations

Rating

Rare Potassium-Bearing Mica in Allan Hills 84001: Additional Constraints on Carbonate Formation 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 Rare Potassium-Bearing Mica in Allan Hills 84001: Additional Constraints on Carbonate Formation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rare Potassium-Bearing Mica in Allan Hills 84001: Additional Constraints on Carbonate Formation will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1611902