Unraveling the Origin of the Lunar Highlands Crust

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Unraveling the Origin of the Lunar
Highlands Crust
• The chemical evolution of the lunar magma ocean was complex and set
the stage for later magmatic activity on the Moon, including the formation of
magnesium-rich anorthositic granulites.
• Clasts of magnesian anorthositic granulites in two lunar meteorites,
ALHA81005 (the first lunar meteorite ever recognized) and Dhofar 309 are
helping to unravel details of the origin of the lunar highlands crust.
http://www.psrd.hawaii.edu/Sept10/highlands-granulites.html
Unraveling the Origin of the Lunar
Highlands Crust
•REE patterns of analyzed clasts are distinct from Apollo magnesian granulites.
• Mg# in the magnesian anorthositic granulites are too high for a close relationship
to the FAN Suite or to have formed as floatation cumulates in the magma ocean.
http://www.psrd.hawaii.edu/Sept10/highlands-granulites.html
Unraveling the Origin of the Lunar
Highlands Crust
•Magnesian anorthositic granulites
are geochemically distinct yet
widespread across the lunar
highlands.
•Their bulk compositions are
comparable to those inferred for
parts of the FHT: about 4.5 wt% FeO,
about 28 wt% Al2O3, and <1 ppm Th.
The magnesian anorthositic granulite clasts may plausibly be samples of postmagma-ocean plutons that helped build the highlands crust.
These clasts suggests KREEP was not necessary for their formation and that postmagma-ocean plutons may or may not contain KREEP, depending on whether or
not they passed through the nearside or farside.
http://www.psrd.hawaii.edu/Sept10/highlands-granulites.html
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