The role of the subducting lithospheric slab in the genesis of mantle-derived (primitive) magmas is investigated through a study of volcanic rocks formed in the tectonically strike-slip–dominated western Aleutian arc. Two types of chemically and petrologically distinctive primitive andesites have been found among the Miocene– late Pleistocene–age volcanic rocks in the western Aleutians. These a...

introduction the generation and evolution of granitic magmas has been a hot debated subject among petrologists. the diversity of their origin has led different authors to propose that these rocks are not simple in their origin and might be generated in more ways than one. in the past several decades, many petrologists used a variety characteristics to subdivide the granitoid rocks. such proposa...

Abstract A comprehensive mineralogical, geochemical and isotopic review of six ultramafic-alkaline-carbonatite magmatic intrusions the Shillong Plateau (Sung Valley, Jasra, Swangkre-Rongjeng, Mawpyut) Mikir Hills (Samchampi-Samteran Barpung) is presented here, using published data. These emplaced ca. 115–102 Ma ago, thus are significantly younger than tholeiitic flood basalts erupted in Rajmaha...

Introduction: Throughout the history of Mars, aqueous solutions should have existed at some depths below the surface. On early Mars, high geothermal gradients and intensive volcanic activity would have favored near-surface existence of aqueous solutions and sapping of ground water (e.g., [1]). During later epochs, solutions could have been stable deep below the surface, usually below ice-bearin...

Two fundamentally different types of silicic volcanic rocks formed during the Cenozoic of the western Cordillera of the United States. Large volumes of dacite and rhyolite, mostly ignimbrites, erupted in the Oligocene in what is now the Great Basin and contrast with rhyolites erupted along the Snake River Plain during the Late Cenozoic. The Great Basin dacites and rhyolites are generally calc-a...