Ultramafic and mafic inclusions and megacrysts in Pliocene basalt, Black Range, New Mexico

摘要: Inclusions in Pliocene alkalic basalt of the Black Range, southwestern New Mexico (and on western margin Rio Grande rift), are spinel Iherzolite, a differentiated suite clinopyroxenite and gabbroic (metagabbroic) rock types (olivine-spinel gabbro; gabbro), olivine andesine megacrysts. All gabbros have reaction zones mainly alkali feldspar surrounding orthopyroxene. Pyroxene oxide geothermometry indicates equilibrium temperatures for Iherzolite inclusions ∼1000 to 1050 °C. Mineral compositions indicate that nodules Cr-diopside group, representing mantle material equilibrated at ∼33- 45-km depth, whereas remaining megacrysts belong Al-augite group had high-pressure cumulate origin. The pyroxene modal mineralogy (no garnet) an origin 10- 20-kb range. absence + plagioclase one gabbro, however, restricts its maximum pressure about 11 14 kb. Differentiation among is displayed by progressive Fe enrichment pyroxenes attended decreasing Al oxides. gabbro developed from contact between orthopyroxene host-basalt magma. A bulk composition zone shows contribution was probably made basalt, account, particular, formation zones.