Ultramafic inclusions in basaltic rocks from Hawaii

Mantle Sulfides and their Role in Re–Os and Pb Isotope Geochronology

“…They have been observed as intergranular grains and as inclusions in silicate minerals in spinel lherzolite and spinel harzburgite xenoliths (Fig. 2;White 1966;Vakhrutshev and Prokoptsev 1972;MacRae 1979;Pasteris 1981;Amundsen 1987), garnet peridotite (e.g., Bishop et al 1975;Meyer and Tsai 1979) and pyroxenite xenoliths (e.g., O'Reilly and Griffin 1987;Wilshire et al 1988). Similar BMS grains are also found in abyssal peridotites ( Fig.…”

Ultramafic inclusions and megacrysts in olivine nephelinite, Aitutaki Island, Cook Islands

“…The lherzolite inclusions in the Aitutaki Island olivine nephelinite have mineral and whole-rock compositions similar to those of spinel lherzolite nodules occurring in undersaturated ba~alt on a worldwide basis (e.g., White 1966;Frey & Green 1974;Wilshire & Shervais 1975;Frey & Prinz 1978). It is generally agreed that these lherzolite inclusions have no direct genetic relationship with their host magmas, are accidental, and probably represent upper mantle material from which basaltic magma was derived (e.g., Frey & Green 1974;Hamlyn & Bonatti 1980).…”

“…Olivine in the lherzolites is Mg rich (F090-91) ( Table 2) and is compositionally similar to olivine in this rock type at worldwide occurrences (e.g., White 1966;Frey & Green 1974;Frey & Prinz 1978). In contrast, olivine in the clinopyroxenite G is substantially lower in MgO (richer in FeO), having Fo s2 , and is compositionally similar to the larger olivine grains in the host rock, which also average F0 82 (Table 2).…”

“…%) unequivocally classify the rock into the nephelinic suite of Macdonald & Katsura (1964) and as a nephelinite member of that suite (Macdonald 1968). Although basaltic rocks of such low SiO z content are not common, even in the nephelinic basalt suite, they have been reported from other oceanic provinces, such as Oahu, Hawaii (White 1966;Macdonald 1968;Jackson & Wright 1970), where they are called nephelinites and contain lherzolite inclusions. The analysis presented here is similar to 6 analyses of olivine nephelinite from Aitutaki Island published by Wood (1978).…”

Investigation of Mantle Dynamics from Platinum Group Elements and Rhenium-Osmium Isotope Systematics of Mantle Xenoliths from Oahu

“…There is a significant body of published information on petrography, mineral chemistry, trace element and isotope geochemistry of the SLC pyroxenite xenoliths (e.g., White 1966;Green 1966;Jackson and Wright 1970;Frey, 1980;Sen, 1988;Keshav and Sen, 2001;Bizimis et al, 2005;Sen et al, 2005;Keshav et al, 2007). On the basis of the available literature I summarize the possible origin of these rocks: (1) Based on mineral thermobarometry and the Sr-Nd-Hf isotope composition of the xenoliths, G. Sen and his co-workers proposed that the pyroxenites are high pressure (> 20 Kb) cumulates from a melt similar to the HV lava series (e.g., Sen et al 1983 Lassiter et al (2000) to propose that they represent 80-100 Myr old cumulates formed at a mid oceanic ridge setting.…”