Regional implications of the Jurassic-Cretaceous volcanosedimentary Cuicateco Terrane, Oaxaca, Mexico

Abstract

The association of andesitic lavas and tuffs with sedimentary rocks is comparable to an island arc which includes small internal basins. The "roots' of the magmatic province are exposed in the western side of the terrane corresponding to granodioritic-monzonitic rocks showing ultramafic segregations. The crystalline rocks show a strong mylonitic solid-state ductile flow fabric decreasing toward inner zones. Where the intrusives are absent, the western side of the magmatic belt is occupied by meta-andesites showing the same metamorphic fabric. A large wedge of serpentinized ultramafics and leucodiorites are tectonically emplaced in the sequence of metatuffs. Chrysotile and lizardite structural water shows a D/H average ratio of -59 per mil, indicating its tectonically related formation. Structurally, the sedimentary sequence defines a thrust-faulted, folded and weakly metamorphosed belt verging eastward. -from English summary