%0 Journal Article
%T Tectonothermal history of the Mesoproterozoic Novillo Gneiss of eastern Mexico: support for a coherent Oaxaquia microcontinent
%A Trainor
%A Robert J.
%A Nance
%A R. Damian
%A Keppie
%A J. Duncan
%J Revista mexicana de ciencias geol¨®gicas
%D 2011
%I Universidad Nacional Aut¨®noma de M¨¦xico
%X the novillo gneiss is one of several exposures of mesoproterozoic (ca. 1.0-1.2 ga) basement in eastern mexico interpreted to be outcrops of a single crustal block (oaxaquia) that has figured prominently in continental reconstructions for the late precambrian-paleozoic. exposed within the sierra madre oriental near ciudad victoria, the novillo gneiss comprises two major mesoproterozoic igneous suites that intrude rare metasedimentary rocks. the older suite, previously dated at 1235-1115 ma, principally comprises garnet k-feldspar augen gneiss and granite gneiss with arc/back-arc geochemical affinities. the younger suite (charnokitic gneiss, anorthositic metagabbro) has been dated at 1035-1010 ma and is interpreted to be part of an anorthosite-mangerite-charnockite-granite assemblage. both suites are intruded by two sets of amphibolite dikes, the earlier of which predates metamorphism under granulite facies conditions at ca. 990ˇŔ5 ma, whereas the later set is of low grade and was emplaced at ca. 546 ma. new structural data in both major igneous suites are dominated by the presence of a composite nw-trending, steeply dipping metamorphic banding/foliation (s1) axial planar to rare isoclinal folds, and a lineation defined by stretched, 12:2:1, k-feldspar augen and quartz ribbons developed under high-grade metamorphic conditions. the irregular contacts between leucosome and mesosome boundaries may be a remnant of earlier, pre-s1 migmatization. these are overprinted by tight-isoclinal f2 sheath folds associated with a moderately ese-plunging clinopyroxene mineral lineation that bisects the great circle distribution of s- and z-shaped asymmetrical f2 fold axes, indicating oblique sinistral, top-to-nw relative movement. the l1 lineations also have a great circle distribution suggesting that inhomogeneous stretching in the foliation rotated l1 towards l2. syntectonic fabrics are overprinted by a granoblastic granulite facies mineralogy followed by retrograde amphibolite and g
%K novillo gneiss
%K oaxaquia
%K mesoproterozoic
%K oaxacan complex
%K mexico.
%U http://www.scielo.org.mx/scielo.php?script=sci_abstract&pid=S1026-87742011000300018&lng=en&nrm=iso&tlng=en