Relationship between basin formation and mare emplacement: Examining mare basalt deposits in the lunar Orientale basin
Abstract
Several different lunar data sets, including Moon Mineralogy Mapper (M3) image and spectral reflectance data, are combined to analyze mare basalt units inside the Orientale multi-ring impact basin. A number of different models predicting the relationship between basin formation and mare basalt emplacement are assessed, including models of crustal and lithospheric asymmetry, pressure-release melting (and associated secondary convection), and global and regional stresses. The earliest post-basin mare basalt emplacement occurred in the center of the basin (Mare Orientale) and postdated the formation of the Orientale basin by approximately 60-100 Ma. Over the next several hundred million years basalt patches were emplaced first along the base of the Outer Rook ring (Lacus Veris) and then along the base of the Cordillera ring (Lacus Autumni), with some overlap in ages. The last basalt patches to be emplaced are comparable in age to some of the youngest basalt deposits on the lunar nearside. The previously documented increase in mare abundance in Orientale basin from the southwest toward the northeast remains prominent. We attribute this distribution to crustal and lithospheric trends that differ from the nearside to the farside, with correspondingly shallower density and thermal barriers to basaltic magma ascent and eruption toward the nearside. The wide range of model ages for Orientale mare deposits (3.70 -1.66 Ga) mirrors the range of nearside mare ages, indicating that the small amount of mare fill in Orientale is not due to early cessation of mare emplacement. Instead, the small amount of fill is the result of limited volumes of mare basalt material being emplaced on the surface over the entire period of nearside volcanic activity. This suggests that nearside and farside source regions may be similar, but that other factors, such as thermal and crustal thickness barriers to magma ascent and eruption, may be determining the abundance of surface deposits on the limbs and farside. The sequence and timing of mare basalt emplacement suggests that regional basin-related stresses exerted control on their distribution.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.P31E1734W
- Keywords:
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- 5480 PLANETARY SCIENCES: SOLID SURFACE PLANETS / Volcanism