Petrology and geochemistry of the teloloapan subterrane: a lower cretaceous evolved intra-oceanic island-arc

Abstract

The Teloloapan subterrane is a tectonostratigraphic sequence in the composite Guerrero Terrane. It includes an Hauterivian to Aptian, essentially volcanic unit (Villa Ayala formation) composed predominantly of basalts overlain by upper Aptian volcaniclastic turbidites (Acapetlahuaya formation), Albian to lower Cenomanian limestones (Teloloapan and Amatepec formations) and post-lower Cenomanian sandstones and shales (Pachivia/Miahuatepec formations). Volcanics show typical petrographic, mineralogical, geochemical and isotopic characteristics of calc-alkaline suites: (i) presence of two-pyroxene and amphibole basalts and andesites; (ii) early crystallization of Fe-Ti oxides; (iii) clinopyroxene chemistry; (iv) Fe-depletion trend; (v) high concentrations of LILE and LREE; (vi) high (La/Yb)N ratios; and, (vii) low ENd· This is compatible with origin in art intra-oceanic island-arc. Compared to primitive intra-oceanic calc-alkaline suites, Teloloapan volcanics are enriched in HFS elements (Y, Nb, Zr and in lesser degree Ti02) and HREE and are similar to medium- to high-K calc-alkaline suites from evolved intra-oceanic island-arcs, e.g. from the Sunda or Lcsser Antilles ares. We suggest that Teloloapan lavas may reflect partía! melting of a slightly enriched mantle so urce modified by subducted pelagic sedirnents, and later differentiation by crystal fractionation and/or crystal accumulation.