Geochemical and isotopic variability controlled by slab detachment in a subduction zone with varying dip: the Eastern Trans-Mexican Volcanic Belt

Orozco-Esquivel, M. T. and Petrone, C. M. and Tagami, T. and Ferrari, L. and Manetti, P. (2007) Geochemical and isotopic variability controlled by slab detachment in a subduction zone with varying dip: the Eastern Trans-Mexican Volcanic Belt. Lithos, 93 (1-2). pp. 149-174. DOI 10.1016/j.lithos.2006.06.006

[img] PDF
Petrone_Lithos.pdf
Restricted to Registered users only

Download (2MB)

Abstract

Strong compositional variations are observed in the late-Miocene to Quaternary volcanic rocks of the eastern Trans-Mexican Volcanic Belt. Geochemical and isotopic analyses of samples well constrained in age indicate an abrupt change in magma composition in the late-Miocene (not, vert, similar 7.5 Ma), when calc-alkaline, subduction-related magmatism was replaced by mafic, alkaline, OIB-like volcanism. Afterwards, volcanism migrated toward the trench and the erupted lavas showed increasing contributions of subduction components reflected in higher Th/Nb, La/Sm(n), Ba/Nb, and Ba/Th ratios. Lavas from volcanic fields located closer to the trench show clearer, although strongly variable, arc signatures as well as evidence of subducted sediment contributions. Farther from the trench, only lavas emplaced in late-Pliocene time appear to be slightly modified by subduction components, whereas the youngest Quaternary lavas can be regarded as intraplate lavas modified by crustal assimilation. The sudden change in magma composition in the late-Miocene is related to detachment of the subducting slab, which allowed the infiltration of enriched asthenospheric mantle into the mantle wedge. After detachment, the subducting plate started to increase its dip because of the loss of slab pull. This caused (1) the migration of the arc toward the trench, (2) convection of enriched asthenosphere into the mantle wedge, and (3) an increasing contribution of slab components to the melts, in a process that resulted in a highly heterogeneous source mantle. The variable contribution of subduction-related components to the magmas is controlled by the heterogeneous character of the source, the depth of the subducting plate, and the previous magmatic history of the areas.

Item Type: Article
Uncontrolled Keywords: NIL AREP 2007
Subjects: 05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Divisions: 05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Journal or Publication Title: Lithos
Volume: 93
Page Range: pp. 149-174
Identification Number: 10.1016/j.lithos.2006.06.006
Depositing User: Sarah Humbert
Date Deposited: 16 Feb 2009 13:03
Last Modified: 23 Jul 2013 10:08
URI: http://eprints.esc.cam.ac.uk/id/eprint/568

Actions (login required)

View Item View Item

About cookies