Along- and Across-Arc Geochemical Variations in the Central American Volcanic Arc

Hoernle, Kaj, Heydolph, Ken, van den Bogaard, Paul and Hauff, Folkmar (2010) Along- and Across-Arc Geochemical Variations in the Central American Volcanic Arc [Talk] In: SFB 574 Subduction Workshop, 04.-07.11.2010, Pucon, Chile.

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Based on a comprehensive new geochemical data set (i.e. major and trace elements and Sr-Nd-Pb-Hf isotope ratios) of mafic volcanic front (VF), behind the volcanic front (BVF) and back-arc (BA) lava and tephra samples from the NW Central American Volcanic Arc (CAVA), we present a new model for the origin of volcanism from Nicaragua to Guatemala. Three endmembers are necessary to explain the variations in trace element and isotopic composition along and across the NW Central America arc: (1) NW Nicaraguan volcanic front (VF) endmember with very high Ba/(La, Th) and U/Th, low La/Yb, relatively radiogenic Sr, Nd and Hf but unradiogenic Pb, (2) enriched NW Guatemalan VF and BVF endmember with low Ba/(La, Th) and U/Th, high La/Yb, radiogenic Sr and Pb but unradiogenic Nd and Hf, and (3) depleted Honduran and Nicaraguan behind the volcanic front (BVF) endmember with low Ba/(La, Th) and U/Th, high La/Yb, unradiogenic Sr but radiogenic Nd, Hf and Pb. We interpret the NW Nicaragua VF endmember to be dominated by a largely serpentinite-derived fluid flux from the subducting slab, possibly with small amounts (<1 wt. %) of sediment melts, to a depleted N-MORB type of mantle wedge, resulting in large degrees of melting of primarily peridotitic material. The isotopically enriched Guatemala VF and BVF endmember could be derived from parental magmas for plutonic rocks in NW Central America, which crystallized pyroxenitic cumulates in the lithospheric mantle (and possibly lower crust) that were melted and contributed to Quaternary
subduction-related volcanism. The isotopically depleted Honduras and Caribbean BA endmember could be derived from melting of young, recycled, oceanic crust in the asthenosphere upwelling in the back-arc, based on the
OIB-like major and trace element but relatively depleted isotopic compositions of these samples. Mixing between these three endmember types of magmas can explain the observed systematic geochemical variations along and across
the NW Central American Arc.

Document Type: Conference or Workshop Item (Talk)
Keywords: Geodynamics; Volcanology; subduction; volcanic Arc
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS Magmatic and Hydrothermal Systems
OceanRep > SFB 574 > C2
OceanRep > SFB 574
Date Deposited: 13 Dec 2010 10:12
Last Modified: 23 Feb 2012 06:36

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