Abstract: We present an updated synthesis of the widely accepted ‘single-arc Pacific-origin ’ and ‘Yucatán-rotation ’ models for Caribbean and Gulf of Mexico evolution, respectively. Fourteen palaeogeographic maps through time integrate new concepts and alterations to earlier models. Pre-Aptian maps are presented in a North American reference frame. Aptian and younger maps are presented in an Indo-Atlantic hot spot reference frame which demonstrates the surprising sim-plicity of Caribbean–American interaction. We use the Müller et al. (Geology 21: 275–278, 1993) reference frame because the motions of the Americas are smoothest in this reference frame, and because it does not differ significantly, at least since c. 90 Ma, from more recent ‘moving hot spot ’ reference frames. The Caribbean oceanic lithosphere has moved little relative to the hot spots in the Cenozoic, but moved north at c. 50 km/Ma during the Cretaceous, while the American plates have drifted west much further and faster and thus are responsible for most Caribbean– American relative motion history. New or revised features of this model, generally driven by new data sets, include: (1) refined reconstruction of western Pangaea; (2) refined rotational motions of the Yucatán Block during the evolution of the Gulf of Mexico; (3) an origin for the Caribbean Arc that invokes Aptian conversion to a SW-dipping subduction zone of a trans-American

quent growth of the 41km3 Santiaguito dacite dome complex, Santa Mar| ¤ a volcano grew into an 8 km3 composite cone over 75 kyr in four phases (at 103^72, 72, 60^46, and 35^25 ka). The 1902 eruption occurred after an 25 kyr period of repose in growth of the composite cone.To provide context for processes that ultimately led to the 1902 eruption, we present geochemical and isotopic (Sr, Nd, Pb, U-series) data from lavas of the composite cone for which ages are constrained by 40Ar/39Ar dating. The four cone-building phases comprise basaltic to basaltic-andesite lava (51·4^56·1% SiO2) whose major- and trace-element compositions suggest that crystallization was important in differentiation. Relative to other Central American arc volcanoes, these lavas also have large 238U excesses and high 207Pb/204Pb ratios that imply melting of a mantle wedge modified to an unusual extent by fluid from subducted crust and sediment of the Cocos plate. Major- and trace-element and iso-

Abstract: The Plinian eruption in October 1902 of 8.5 km3of dacitic pumice and minor basaltic andesite scoria and ash at Volcán de Santa Marı́a, Guatemala violently interrupted a 25 kyr period of repose that had followed75 kyr of cone-growth via extrusion of 8 km3 of basaltic ande-site lava. Two-oxide and pyroxene thermometry reveal an oxidized (Ni-NiO+ 2 log units) and thermally-zoned magma body in which basaltic andesite with 54 wt % SiO2 at 1020 8C and dacite with 65 wt % SiO2 at 870 8C coexisted. Plagioclase in dacite pumice and basaltic andesite scoria shows remarkably similar zoning characterized by repeated excursions toward high anorthite and increases in Mg, Fe, and Sr associated with resorption surfaces along which dacitic to rhyolitic melt inclusions are trapped. The melt inclusions increase slightly in K2O as SiO2 increases from 69 to 77 wt%, whereas H2O contents between 5.2 and 1.4 wt % drop with increasing K2O. These observations suggest that crystallization of the plagioclase, and evolution of a high-silica rhyolitic residual melt, occurred mainly in the conduit as the compositionally-zoned magma body decompressed and degassed from.180 MPa, or.5 km depth, toward the surface. The similarity of plagioclase composition, zoning, and melt inclusion compositions in pumice and scoria suggests that crystals which grew initially in the cooler dacite, were exchanged

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www.solid-earth.net/5/1243/2014/ doi:10.5194/se-5-1243-2014 © Author(s) 2014. CC Attribution 3.0 License. Future accreted terranes: a compilation of island arcs, oceanic plateaus, submarine ridges, seamounts, and continental fragments

A. gArCíA-CASCO J.A. prOENZA M.A. itUrrAldE-ViNENt departamento de Mineralogía y petrología, Universidad de granada

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subduction