University of Texas at Austin, Austin, TX, United States

Volcaniclastic sand/sandstone facies associated with hotspot island chains and submarine plateaus vary from those associated with magmatic arcs primarily as a function of magma composition. Differences in magma composition are reflected not only in the phenocryst assemblages, but also the composition and texture of associated glassy volcanic-lithic fragments or pyroclasts. Hotspot/plateau sand lacks quartz and potassium feldspar and is enriched in dense minerals such as pyroxene and olivine with respect to sand derived from magmatic arcs. Other felsic components such as colorless glass and felsitic volcanic-lithic fragments are generally absent from hotspot/plateau suites. The volcanic lithic proportions of hotspot/plateau sand can be enriched in fragments exhibiting lathwork textures and black, tachylitic groundmass. This sand-provenance model is based on a large petrographic data base assembled from point-count analyses of (1) modern beach sand from Hawaii, and (2) sand and sandstone samples from Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) sites situated near magmatic arcs and on intraplate seamounts and volcanic plateaus. These DSDP and ODP samples are primarily Cenozoic in age and the sampled sites are located within and around the Pacific Ocean. The Kronotsky Peninsula is a spur of the Kamchatka Peninsula that lies on trend with the subducting Emperor Seamount chain. We applied the above sand-provenance model to Paleogene(?)-Neogene volcaniclastic units interbedded with and covering the mafic basement rocks of Kronotsky Peninsula in order to test the hypothesis that the mafic basement represents an accreted segment of the Emperor seamount chain. Our preliminary results, in combination with other geologic lines of evidence, do not support a seamount origin for this sequence.