Combined investigation of H isotopic compositions and U-Pb chronology of young Martian meteorite Larkman Nunatak 06319

We measured the hydrogen isotopic composition (D/H ratios) and U-Pb chronology of phosphate minerals in a young Martian meteorite: LAR 06319. D/H ratios of melt-inclusions in the meteorite were also investigated to evaluate the presence of water reservoirs on Mars in recent times. The total Pb/U dating of multiple grains of apatite and merrillite yield a concordant date of 167 +/- 57 Ma, interpreted as the crystallization age, suggesting that both apatite and merrillite in this meteorite have preserved their igneous histories. The D/H ratios of an apatite grain show good reproducibility yielding a delta D value of 4250 +/- 120%, whereas those of merrillite show larger D/H variations with the maximum delta D value of 5260 +/- 790%. However, mafic glass in melt-inclusions shows extremely large variation in delta D, ranging from ca. 1070% to 6830 +/- 460%. The different D/H signatures recorded in these phases reflect the contributions of different hydrous components with distinct D/H ratios, possibly incorporated at different times. It is inferred that several isotopically distinct water reservoirs exist in the present Martian surface/sub-surface system.