Coyote Peak

The Coyote Peak diatreme measuring 500x260 m is emplaced in Franciscan melange. Numerous inclusions up to 10 cm in diameter of Franciscan greywacke and mudstone are metasomatized. Two rock types are distinguished, though not mappable because of lack of exposure (Morgan et al., 1985): a pristine, uncontaminated rock, and a variety of higher silica content considered to have been generated by assimilation of greywacke. The uncontaminated rock contains phenocrysts of olivine (Fo82-80) and titanomagnetite in a groundmass of phlogopite, melilite, nepheline, magnetite, perovskite, apatite, sodalite, and titanian garnet with up to 16% TiO2. Another assemblage of this rock type lacks melilite and is characterized by coronas of pyroxene and phlogopite around olivine. Coarse grained clots within these rocks comprise phlogopite, titanian garnet and minor sodalite, pectolite, pyrrhotine and a range of sulphide minerals. Complex textural features include abundant spherical autoliths of 3-25 mm diameter and rewelded autobreccias in which differing mineral assemblages are juxtaposed. The contaminated rocks contain pectolite and natrolite and a feathery, less titanian (1-8% TiO2) and more aluminous garnet. These rocks also contain fenitized greywacke inclusions of microcline, Ti-rich aegirine, alkali amphiboles, zoned from fluor-richterite cores to titanian-arfvedsonite rims, and natrolite (Czamanske and Atkin, 1985). Chemical analyses of rocks, including trace elements, REE and isotopic data will be found in Morgan et al. (1985). A number of new and rare minerals have been described including bartonite, rasvumite, djerfisherite, taeniolite, orichite and coyoteite (for References: see Erd and Czamanske, 1983).