|Title:||Ion microprobe measurements of 18O/16O ratios of phosphate minerals in the Martian meteorites ALH84001 and Los Angeles|
|Authors:||J.P. Greenwood, R.E. Blake, and C.D. Coath|
|Publication:||Geochim. Cosmochim. Acta, v. 67, p. 2289‐2298.|
|Publish Date:||Jun 2003|
Oxygen isotope ratios of merrillite and chlorapatite in the Martian meteorites ALH84001 and Los Angeles have been measured by ion microprobe in multicollector mode. δ18O values of phosphate minerals measured in situ range from ⁓3 to 6‰, and are similar to Martian meteorite whole−rock values, as well as the δ18O of igneous phosphate on Earth. These results suggest that the primary, abiotic, igneous phosphate reservoir on Mars is similar in oxygen isotopic composition to the basaltic phosphate reservoir on Earth. This is an important first step in the characterization of Martian phosphate reservoirs for the use of δ18O of phosphate minerals as a biomarker for life on Mars. Cumulative textural, major‐element, and isotopic evidence presented here suggest a primary, igneous origin for the phosphates in Los Angeles and ALH84001; textural and chemical evidence suggests that phosphates in ALH84001 were subsequently shock‐melted in a later event.