Subalkaline Volcanism in the Black Rock Desert and Markagunt Plateau Volcanic Fields of South-Central Utah

摘要: Abstract Recent volcanism in the Black Rock Desert and Markagunt Plateau volcanic fields south-central Utah is mainly subalkaline, which uncommon elsewhere Basin Range Province. The field (BRD) composed of five subfields spans about 170 km along eastern margin Province Utah. are: (1) Cove Fort, (2) Twin Peaks, (3) Beaver Ridge, (4) Ice Springs, (5) Fumarole Butte. Although BRD began late Miocene, 6 Ma, most activity has occurred past 2.5 million years. a tholeiitic suite ranging composition from basalt to dacite, calc-alkaline andesite, rhyolite. During year life field, alkali basalts erupted only rarely comprise no more than three flows. (MP) located east Cedar City at south end High Plateaus physiographic province (a structural stratigraphic transition zone between west Colorado east) been active since earliest Pliocene, with recent eruptions occurring latest Pleistocene or possibly Holocene time. It contains over 25 cinder cones associated Flows vary basalt, basaltic olivine tholeiite basalt. One puzzling attributes MP BRD, western general, presence abundant subalkaline units. In other an intraplate tectonic setting, particular Province, dominant eruptive product little, if any, intermediate silicic rocks. chemical characteristics both MP, while unlike typical intra-plate volcanism, are similar those continental rift zones like Rio Grande Rift on side Plateau. We suggest that may be signaling initiation Plateau, Rift. Alternatively, these signatures could simply characteristic at, near, margins