Dense inclusions in the Sullivan buttes latite, Chino Valley, Yavapai County, Arizona

Dense inclusions are abundant in potassic latite about 25 m.y. in age which occurs in the southwestern structural transition zone of the Colorado Plateau (Krieger, 1965; Krieger and others, 1971).The host rock (1, Table 1) consists of shallow intrusions, breccias, and flows in Precambrian and Paleozoic country rock.Phenocrysts of biotite (Mg/Mg+ Fe = 0.65), clinopyroxene (Ca44Mg4^Fej^Q), feldspar (An55Ab430r2) and apatite are present in the latite of Table 1; amphibole is prominent elsewhere.The inclusions are distributed on the order of 1 per 0.25 square meter on host rock surfaces and vary in size from 1 to 50 cm.Freshest samples are near country rock contacts.Estimates of rock type abundances are based on grid counts and indicate approximately 60% of the nodules at the chief locality are eclogites.These are composed of variable proportions of garnet (near Pyr37Alm2yGross25) and clinopyroxene (5-25 mol.% jadeite).Crystal sizes vary from O'.l to 10 mm although most eclogites contain equant grains ^2 mm.Amphibole is a common additional phase together with rutile, apatite, ilmenite and rare, altered clinozoisite.The eclogites are typically phase-layered and assemblages of strikingly different garnet/clinopyroxene proportions are in sharp contact.Compositional differences exist between different layers.Representative chemical analyses of eclogites of contrasted phase proportions together with microprobe analyses of individual phases are presented in Table 1.Inclusions with major pargasitic amphibole comprise about 30% of the population at the chief locality and are more abundant elsewhere.Assemblages grade from eclogites with trace amphibole to those with 90% amphibole and minor clinopyroxene and garnet.Phlogopite, apatite, and Fe-Ti oxides are usually associated with amphibole-rich inclusions.In some samples, rutile and garnet are phase-layered with amphibole, giving rise to layers with up to 20 modal % rutile.In these nodules, amphibole crystals are up to 15 mm in length.Websterites and orthopyroxenites form 2% of the inclusion population and typically contain deformed low-Ca pyroxene porphyroclasts with exsolved garnet in a groundmass of mosaic-textured garnet and pyroxene.The pyroxene porphy¬ roclasts also contain exsolution lamellae of clinopyroxene, and broad beam microprobe analysis suggests that the assemblage results from the reaction of original aluminous pyroxene to an opx-cpx-gnt assemblage (8-10, Table 1).The porphyroclasts are up to 30-50 mm in length and display an undulatory schistosity defined by the garnet and cpx-opx lamellae, with superimposed kink de¬ formation.In general, the inclusions have metamorphic fabrics ranging from granular mosaic through to lineated.Rare undeformed biotite-apatite-clinopyroxenite inclusions may be cumulate from the host magma, but the other inclusions cannot be direct high-pressure cumulates from the host.The occurrence of amphibole, phlogopite and biotite in association with eclogitic assemblages is of direct interest in relation to K20 and H20 budgets of the lower crust and upper mantle.Amphibole and phlogopite (Table 1) occur