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dc.contributor.authorFaulds, James E.
dc.contributor.authorFeuerbach, Daniel L.
dc.contributor.authorReagan, Mark K.
dc.contributor.authorMetcalf, Rodney V.
dc.contributor.authorGans, Phil
dc.contributor.authorWalker, J. Douglas
dc.date.accessioned2015-03-19T21:49:58Z
dc.date.available2015-03-19T21:49:58Z
dc.date.issued1995-08-10
dc.identifier.citationFaulds, J. E., D. L. Feuerbach, M. K. Reagan, R. V. Metcalf, P. Gans, and J. D. Walker (1995), The Mount Perkins block, northwestern Arizona: An exposed cross section of an evolving, preextensional to synextensional magmatic system, J. Geophys. Res., 100(B8), 15249–15266, http://dx.doi.org/10.1029/95JB01375.en_US
dc.identifier.urihttp://hdl.handle.net/1808/17143
dc.descriptionThis is the published version. Reuse is subject to Society of Exploration Geophysicists terms of use and conditions.en_US
dc.description.abstractThe steeply tilted Mount Perkins block, northwestern Arizona, exposes a cross section of a magmatic system that evolved through the onset of regional extension. New 40Ar/39Ar ages of variably tilted (0–90°) volcanic strata bracket extension between 15.7 and 11.3 Ma. Preextensional intrusive activity included emplacement of a composite Miocene laccolith and stock, trachydacite dome complex, and east striking rhyolite dikes. Related volcanic activity produced an ∼18–16 Ma stratovolcano, cored by trachydacite domes and flanked by trachydacite-trachyandesite flows, and ∼16 Ma rhyolite flows. Similar compositions indicate a genetic link between the stratovolcano and granodioritic phase of the laccolith. Magmatic activity synchronous with early regional extension (15.7–14.5 Ma) generated a thick, felsic volcanic sequence, a swarm of northerly striking subvertical rhyolite dikes, and rhyolite domes. Field relations and compositions indicate that the dike swarm and felsic volcanic sequence are cogenetic. Modes of magma emplacement changed during the onset of extension from subhorizontal sheets, east striking dikes, and stocks to northerly striking, subvertical dike swarms, as the regional stress field shifted from nearly isotropic to decidedly anisotropic with an east-west trending, horizontal least principal stress. Preextensional trachydacitic and preextensional to synextensional rhyolitic magmas were part of an evolving system, which involved the ponding of mantle-derived basaltic magmas and ensuing crustal melting and assimilation at progressively shallower levels. Major extension halted this system by generating abundant pathways to the surface (fractures), which flushed out preexisting crustal melts and hybrid magmas. Remaining silicic melts were quenched by rapid, upper crustal cooling induced by tectonic denudation. These processes facilitated eruption of mafic magmas. Accordingly, silicic magmatism at Mount Perkins ended abruptly during peak extension ∼14.5 Ma and gave way to mafic magmatism, which continued until extension ceased.en_US
dc.publisherAmerican Geophysical Unionen_US
dc.titleThe Mount Perkins block, northwestern Arizona: An exposed cross section of an evolving, preextensional to synextensional magmatic systemen_US
dc.typeArticle
kusw.kuauthorWalker, J. Douglas
kusw.kudepartmentGeologyen_US
dc.identifier.doi10.1029/95JB01375
kusw.oaversionScholarly/refereed, publisher version
kusw.oapolicyThis item does not meet KU Open Access policy criteria.
dc.rights.accessrightsopenAccess


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