Petrologic, stratigraphic and tectonic significance of Mesozoic volcanic rocks in the Río Wampú area, Eastern Honduras

Abstract

A thick sequence of dark-red lava flows and clastic rocks with abundant volcanic debris crops out along the Río Wampú of eastern Honduras. Lithologic characteristics of these rocks, field interpretations of the Río Wampú stratigraphy, and limited KAr age determinations on volcanic samples indicate that these redbeds and associated volcanic units are correlative with the Upper Cretaceous Valle de Angeles Group of central Honduras. These strata uncomformably overlie dark clastic units which are tentatively correlated with the Jurassic Agua Fría Formation of the Honduras Group. The lava samples are predominantly microporphyritic andesites and basaltic andesites with abundant fine-grained phenocrysts of plagioclase, clinopyroxene and FeTi oxides. Immobile-element whole-rock and mineral concentrations indicate a high-K tholeiitic composition. Elevated TiO 2 whole-rock and clinopyroxene concentrations found in the basaltic andesites apparently reflect a primary magmatic characteristic. Based on geochemical and modal data, it appears that these rocks were erupted from partial mantle melts which were modified by substantial fractionation of modal phases. The presence of widespread Mesozoic redbeds and associated volcanics in Honduras was previously cited as evidence of regional extensional tectonics. However, structural, geochemical and stratigraphic data collected during this study indicate that the Río Wampú volcanic suite was formed during a compressional (subduction-related) event. Similar high-TiO 2 basaltic andesites and andesites are reported along several active continental margins.