Mineralogical and ptrological characteristics of Martian meteorite NWA 13763 and magma evolution
NWA 13763 meteorite is a newly recovered Martian meteorite and classified as a gabbroic sherggottite with gabbro to sub-ophitic textures.The main mineral assemblages are pyroxene(45.1%,including augite 36.1%and pigeonite 9.0%)and plagioclase(42.3%,almostly change into maskelynite),while the secondary minerals are silica-rich phase(5.1%),olivine(2.7%),phosphate(2.4%)and ilmenite(2.2%),and very small amounts of titanomagnetite and baddeleyite.The symplektite of"Fe-rich olivine+silicon rich phase"and"Fe-rich olivine+hedenbergite+silicon rich phase"assemblages are extensive development in this meteorite.The core of main pyroxene is Fe-rich and Mg-poor(Fs24.7-55.3),and its rim is Fe-poor and Mg-rich(Fs61.5-86.1).The composition of maskelynite is uniform(An44.4-54.6 Ab43.7-53.7).Fe-rich olivines(Fa84.5-97.7)are distributed in the symplektite as a fine granular.The oxygen fugacity(FMQ)fO2 of NWA 13763 is-0.045,and the crystalli-zation temperature of ilmenite is about 975℃.When using the MELTS program simulation it shows that the liq-uidus-solid temperature of the parent magma of NWA 13763 meteorite is from 1 190℃to 830℃.The sequence of mineral crystallization from early to late may be bytownite→labradorite→olivine+clinopyroxene→andesine→phosphate mineral→ilmenite→silica-rich residual phase.
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