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Geology and petrology of the mid-Miocene Santa Rosa-Calico volcanic field, northern Nevada [CD-ROM]



 
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Title: Geology and petrology of the mid-Miocene Santa Rosa-Calico volcanic field, northern Nevada

Author: Matthew E. Brueseke and William K. Hart
Year: 2008
Series: Bulletin 113
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Format: CD-ROM
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This study provides a detailed examination of the physical evolution of a complex continental volcanic field, the Santa Rosa-Calico volcanic field (SC), and provides first-order information on the nature of the magmatic processes responsible for the physical, geochemical, and isotopic diversity documented by the products of this volcanic field. In the SC, numerous mafic through intermediate eruptive loci and shallow intrusive bodies crop out along north-south- and northwest-southeast-trending alignments, just west of the northward projection of the northern Nevada rift. Across the volcanic field, at least 16 physically and compositionally distinct units are present and represent the products of over 2-Ma of volcanism. Local mafic units physically and chemically resemble regional Steens Basalt and high alumina olivine tholeiite and erupted over the duration of SC volcanism. SC andesite to dacite lava flows are found throughout the volcanic field and represent the products of at least four temporally, geographically, and chemically distinct magmatic systems. Complex open system magma generation and evolution processes including both magma mixing and assimilation-fractional crystallization gave rise to these intermediate units.

Contemporaneous faulting likely stimulated these processes via further emplacing mafic magma into the upper crust and also by providing a mechanism that could drive magma mixing. SC silicic products vary physically, chemically, and isotopically according to geographic location and again, require the presence of numerous magmatic systems throughout the >2-Ma duration of the SC. The physical, chemical, and isotopic characteristics of SC silicic units are also consistent with their derivation via crustal anatexis of local Cretaceous granitoid upper crust, as well as the potential incorporation of Triassic metasedimentary rocks. Similar processes of mafic magma upper crustal intrusion and coeval silicic melt generation appear to have occurred in other regions across the Pacific Northwest during the mid-Miocene flood basalt event. Caldera-derived eruptive products are present in the SC; however, voluminous caldera-forming events did not typify SC activity. Rather, a paucity of caldera-forming silicic volcanism distinguishes the SC from coeval mid-Miocene Oregon Plateau volcanic fields (e.g., McDermitt, Lake Owyhee, northwest Nevada) as well as other silicic-dominated volcanic fields that are typically associated with the younger Snake River Plain--Yellowstone volcanic province.



Original Product Code: B113 dox