Field evidence and K, Rb, Sr data bearing on the origin of the Mt. Taylor volcanic field, New Mexico, U.S.A.

摘要: The Mt. Taylor volcanic field straddless the southern margin of San Juan Basin in southeast corner Colorado Plateau. Central activity resulted extrusion rhyolite, dacite alkali andesite, and basaltic andesite flows, from a limited now deeply eroded area. Coeval with central basalt magma erupted more remote centres, local has apparently continued until few thousand years ago or less. Major element Rb, Sr, K2O abundances allow following rock types to be recognized: early basanite flows pipes; mildly undersaturated basalts; ‘big-feldspar’ basaltic-andesites; andesites; dacites; rhyolites. There is marked composition gap between basalts andesites. K/Rb, Rb/Sr and87Sr/86Sr data suggest that both olivine hypersthene normative are mantle derived whereas andesites, dacites, rhyolites not. It suggested have arisen by partial melting granite basement.