Compositional variation and provenance of Late Cenozoic distal tephra beds, Fairbanks area, Alaska

摘要: Abstract Thin, fine-grained, discontinuous tephra beds from interior Alaska can be divided into two compositional groups by their mineralogy and major- trace-element glass geochemistry. The source vents of these are unknown but believed to in the Aleutian arc, Alaskan Peninsula Wrangell Volcanic Field. Type I has evolved profiles, while II is primitive. contains abundant hydrous minerals that absent or rare I. Trace elements were used compare Fairbanks volcanic rocks potential areas. There very few published analyses regions. This necessitates comparing whole rock with analyses. For this reason, incompatible elements, particularly rare-earth most useful. Whole petrography lavas throughout Field similar tephra. Lavas intrusive occur at one volcano three volcanoes