An ANGSA Study: Crystal Size Distributions of Ilmenite in Basalts From Apollo 17 Drive Tube 73002

Double drive tubes 73002 (upper) and 73001 (lower) were collected during Apollo 17 from a landslide deposit at the base of the South Massif in the Taurus-Littrow valley. The drive tubes were opened for the first time as part of the Apollo Next Generation Sample Analysis (ANGSA) project, representing “new” samples from the Moon. Many lithic fragments (>1 mm in size) were extracted from the core during core dissection and preliminary examination (PE), including high-Ti mare basalt clasts. Those >4 mm fragments were three-dimensionally imaged using X-ray computed tomography (XCT). The crystal size distributions of ilmenite were measured in 10 high-Ti mare basalts and within the matrix of an impact melt breccia from drive tube 73002 using thin section “slices” from the 3D XCT scans. Residence times (of the crystals in the melt from which they grew) were estimated using experimental growth rates for each sample with all but 73002,2015 being relatively short (<1 year). Linear (constant) cooling rates were determined, expanding upon data already obtained from other Apollo 17 high-Ti basalts showing that these ANGSA basalt clasts had similar cooling histories to those previously studied. Comparison with ilmenite cooling rate experiments estimated cooling rates of <10°C/h for each clast.