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Lunar Crustal History from Isotopic Studies of Lunar Anorthosites
| Content Provider | Semantic Scholar |
|---|---|
| Author | Nyquist, Laurence E. Shih, C.-Y. Bogard, Donald D. Yamaguchi, Akira |
| Copyright Year | 2010 |
| Abstract | Anorthosites occur ubiquitously within the lunar cr ust at depths of ~3-30 km in apparent confirmation of the Lunar Magma Ocean (LMO) hypothesis. We present recent chronological studies of anorthosites that are rel evant both to the LMO hypothesis and to the lunar cataclysm hypothesis. Old (~4.4 Ga) ages have been determined f or some Apollo 16 anorthosites, and primitive initial 87 Sr/ 86 Sr ratios have been measured for several, but well -defined Rb-Sr ages concordant with the Sm-Nd ages have not been determined until now. Lunar ferroan anorthosite (FAN) 67075, a Feldspathic Fragmental Breccia (FFB) collected ne ar the rim of North Ray Crater, has concordant Sm-Nd and RbSr ages of 4.47±0.07 Ga. Initial 143 Nd/ 144 Nd determined from the Sm-Nd isochron corresponds to eNd ,CHUR = 0.3±0.5 compared to a Chondritic Uniform Reservoir, or eNd ,HEDPB = -0.6±0.5 compared to the initial 143 Nd/ 144 Nd of the HED Parent Body. Lunar anorthosites often have eNd ,CHUR > 0 when compared to CHUR, apparently inconsistent with derivation from a single lunar magma ocean. If lunar initial 143 Nd/ 144 Nd is taken equal to that in the HED parent body, eNd ,HEDPB < 0 for most anorthosites, but enough variability remains among the anorthosite data alone to suggest that lunar anorthosites do not derive from a single sour ce, i.e., they are not all products of the LMO. An anorthosi tic clast from desert meteorite Dhofar 908 has an 39 Ar |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://www.lpi.usra.edu/exploration/publications/NyquistEtAl_GLUC2010.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
