title: The age of the carbonates in martian meteorite ALH84001.
abstract: The age of secondary carbonate mineralization in the martian meteorite ALH84001 was determined to be 3.90 +/- 0.04 billion years by rubidium-strontium (Rb-Sr) dating and 4.04 +/- 0.10 billion years by lead-lead (Pb-Pb) dating. The Rb-Sr and Pb-Pb isochrons are defined by leachates of a mixture of high-graded carbonate (visually estimated as approximately 5 percent), whitlockite (trace), and orthopyroxene (approximately 95 percent). The carbonate formation age is contemporaneous with a period in martian history when the surface is thought to have had flowing water, but also was undergoing heavy bombardment by meteorites. Therefore, this age does not distinguish between aqueous and impact origins for the carbonates.
authors.affiliation: SN2/NASA Johnson Space Center Houston, TX 77058, USA. lborg@unm.edu
authors.forename: L E
authors.initials: LE
authors.lastname: Borg
authors.forename: J N
authors.initials: JN
authors.lastname: Connelly
authors.forename: L E
authors.initials: LE
authors.lastname: Nyquist
authors.forename: C Y
authors.initials: CY
authors.lastname: Shih
authors.forename: H
authors.initials: H
authors.lastname: Wiesmann
authors.forename: Y
authors.initials: Y
authors.lastname: Reese
mesh_terms: D002118:Calcium / Q000032:analysis; D002130:Calcium Phosphates; D002254:Carbonates / Q000032:analysis; D007501:Iron / Q000032:analysis; D007554:Isotopes / Q000032:analysis; D007854:Lead / Q000032:analysis; D008274:Magnesium / Q000032:analysis; D018535:Mars; D019110:Meteoroids; D008903:Minerals; D012414:Rubidium Radioisotopes / Q000032:analysis; D013325:Strontium Isotopes / Q000032:analysis
chemical_list: D002130:Calcium Phosphates; D002254:Carbonates; D007554:Isotopes; D008903:Minerals; D012414:Rubidium Radioisotopes; D013325:Strontium Isotopes; C092478:pyroxene; C021767:whitlockite; D007854:Lead; D007501:Iron; D008274:Magnesium; D002118:Calcium