Moon Canyon, Smith-Morehouse Canyon And Whites Creek

Within Moon Canyon dykes, plugs and flows of lamproitic rocks are associated with andesitic pyroclastics and Palaeozoic shales and quartzites. The flows are interstratified with andesitic tuffs and breccias and vary from a scoriaceous layer 1.6-3 m thick to a flow nearly 10 m thick with a vesicular top and bottom and a coarser, massive interior. Minor intrusions also have vesicular borders. Phlogopite phenocrysts are abundant and may be orientated, imparting a schistosity to the rock. The finer grained rocks contain phenocrysts of phlogopite and microphenocrysts of diopside and serpentinized olivine in a groundmass of tiny blebs of analcime, needles of diopside and a little phlogopite in a brown glass. Coarser varieties contain subradiating to randomly orientated sanidine with local marginal analcime, phlogopite with dark borders and interstitial sodic amphibole (?magnophorite). The finer grained rocks are referred to as analcime wyomingite by Best et al. (1968). Chemically similar rocks have been found at Whites Creek about 19 km north of Moon Canyon (Best et al., 1968, Fig. 1) consisting of phlogopite, and sometimes olivine, phenocrysts, sanidine and diopside, with minor apatite and rare brown amphibole. At the head of Smith-Morehouse Canyon, some 16 km northeast of Moon Canyon, loose pieces of mica peridotite have been found (Bestet al., 1968, p. 1042) containing phlogopite aggregates up to 1 cm in diamter, 20% olivine phenocrysts and 2% melilite in a fine matrix of pale orange, poikilitic phlogopite, granules of clinopyroxene and a little sanidine and opaques. Chemical analyses of all these rocks are given by Best et al. (1968, Table 1).