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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.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,
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
kusw.kuauthorWalker, J. Douglas
kusw.oanotesPer SHERPA/RoMEO, 3/19/15: Author's Pre-print: green tick author can archive pre-print (ie pre-refereeing) Author's Post-print: green tick author can archive post-print (ie final draft post-refereeing) Publisher's Version/PDF: green tick author can archive publisher's version/PDF General Conditions:

Author's pre-print on author's own website only Author's pre-print must be accompanied by a statement indicating article is under review Author's pre-print must be removed upon publication of final version and replaced with either Author'' post-print, Publisher's Version/ PDF or citation with link to published abstract Authors' post-print and Publisher's version/PDF on author's personal website, employer's website or institutional repository Publisher copyright and source must be acknowledged with citation Must link to publisher version with DOI Publisher's version/PDF may be used On a non-profit server Must be accompanied by a statement indicating reuse is subject to SEG terms of use and conditions
kusw.oaversionScholarly/refereed, publisher version
kusw.oapolicyThis item does not meet KU Open Access policy criteria.

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