Impact melt differentiation in the South Pole-Aitken basin_ Some observations and speculations
نویسندگان
چکیده
The stratigraphy of the South-Pole Aitken basin (SPA) interior is consistent with that of a massive impact melt sheet that differentiated to form cumulates. Spectroscopic and geophysical constraints on the stratigraphy of SPA suggest a 12.5 km thick layer of norite above ultramafic pyroxenite and dunite layers. A similar stratigraphy is produced from differentiation by crystal settling of a 50 km thick impact melt sheet (lunar impact melt sheets 410 km thick likely undergo differentiation by crystal settling) formed by an oblique impact (and thus containing 20 vol. % crustal material). We propose that impact melt differentiation can account for geophysical (nonzero crustal thickness) and geochemical ( 2 ppm Th) anomalies in SPA. & 2013 Elsevier Ltd. All rights reserved.
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