Cooling history of lunar Mg-suite gabbronorite 76255, troctolite 76535 and Stillwater pyroxenite SC-936: The record in exsolution and ordering in pyroxenes

Chromite symplectites in Mg-suite troctolite 76535 as evidence for infiltration metasomatism of a lunar layered intrusion

“…Therefore, we believe that the age of $4.23 Ga for 76535 represents closure of the systems that give this age in the event that excavated the rock from the lower crust, and not a primary crystallization age. This interpretation has previously been suggested by Premo and Tatsumoto (1992) and McCallum et al (2006). By extension, if intimate interaction of FAN-Mg-suite crustal rocks with migrating melts was a widespread occurrence during the first few hundreds of millions of years after the solidification of the LMO, the process described above had the potential to reset isotopic ages of both lithologies.…”

“…high in REEs) characteristics, intruded the lunar crust between $4.46 to at least 4.1 Ga (e.g. Nyquist and Shih, 1992;Premo and Tatsumoto, 1992;Shih et al, 1993;McCallum and OBrien, 1996;Jolliff et al, 1999;Snyder et al, 2000;McCallum et al, 2006;Shearer et al, 2006;Edmunson et al, 2009), although, the question of whether Mg-suite magmatism was limited to the Procellarum KREEP Terrane (PKT) remains unanswered (Jolliff et al, 2000;Korotev, 2000;Wieczorek and Phillips, 2000;Namur et al, 2011).…”

“…Its size (155.5 g), antiquity (pre-Serenitatis, $4.23 Ga; Bogard et al, 1975;Hinthorne et al, 1975;Huneke and Wasserburg, 1975;Lugmair et al, 1976;Papanastassiou and Wasserburg, 1976;Premo and Tatsumoto, 1992;Dalrymple and Ryder, 1996;Nyquist et al, 2012), remarkable pristinity (Warren and Wasson, 1977) and provenance as an early crustal plutonic rock have made it one of the most heavily studied lunar samples (i.e. Gooley et al, 1974;Haskin et al, 1974;Rhodes et al, 1974;Bell et al, 1975;Dymek et al, 1975;Haggerty, 1975;Caffee et al, 1981;McCallum and Schwartz, 2001;McCallum et al, 2006;Garrick-Bethell et al, 2009;Day et al, 2010;Nyquist et al, 2012). The troctolite was originally a magmatic cumulate in the deep lunar crust (40-50 km;McCallum and Schwartz, 2001), but extensive annealing has erased most signs of original cumulate textures and chemical zoning (Gooley et al, 1974;Haskin et al, 1974;Dymek et al, 1975).…”

Water in evolved lunar rocks: Evidence for multiple reservoirs

“…Reaction relations in symplectitic intergrowths in troctolite 76535 indicate a depth of origin of $40 km (Gooley et al, 1974;McCallum et al, 2006), corresponding to a pressure of over 1.5 kb. On the other hand, gabbronorite sample 76255 may have formed as shallow as a few kilometers (McCallum et al, 2006), and quartz-monzodiorite 14161,7373 as shallow as 1 km (Jolliff et al, 1999), at a pressure of 50 b.…”

“…Reaction relations in symplectitic intergrowths in troctolite 76535 indicate a depth of origin of $40 km (Gooley et al, 1974;McCallum et al, 2006), corresponding to a pressure of over 1.5 kb. On the other hand, gabbronorite sample 76255 may have formed as shallow as a few kilometers (McCallum et al, 2006), and quartz-monzodiorite 14161,7373 as shallow as 1 km (Jolliff et al, 1999), at a pressure of 50 b. The liquidus temperatures and presence of quartz in highly fractionated lunar felsites (Hess et al, 1975(Hess et al, , 1978(Hess et al, , 1989Robinson and Taylor, 2011;Robinson et al, 2015) indicate crystallization at a pressure of at least $1 kb (Tuttle and Bowen, 1958), corresponding to a depth of over 20 km, assuming a crustal density of 2550 kg/m 3 (Wieczorek et al, 2013).…”