John, Timm, Scherer, E. E., Schenk, Volker, Herms, Petra, Halama, Ralf and Garbe-Schönberg, C.-Dieter (2010) Subducted seamounts in an eclogite-facies ophiolite sequence: the Andean Raspas Complex, SW Ecuador. Contributions to Mineralogy and Petrology, 159 . pp. 265-284. DOI 10.1007/s00410-009-0427-0.

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Abstract

The metamorphic Raspas Complex of southwest Ecuador consists of high-pressure mafic, ultramafic, and sedimentary rocks. The Lu–Hf ages of a blueschist, a
metapelite, and an eclogite overlap at around 130 Ma and
date high-pressure garnet growth. Peak metamorphic conditions in the eclogites reached 1.8 GPa at 600"C, corresponding to a maximum burial depth of *60 km. The
geochemical signatures of the eclogites suggest that their
protoliths were typical mid-ocean ridge basalts (MORB),
whereas the blueschists exhibit seamount-like characteristics, and the eclogite-facies peridotites seem to represent depleted, MORB-source mantle. That these rocks were subjected to similar peak PT conditions contemporaneously suggests that they were subducted together as an essentially complete section within the slab. We suggest that this section became dismembered from the slab during burial at great depth—perhaps as a consequence of scraping off the seamounts. The spatially close association of MORB-type eclogite, seamount-type blueschist, serpentinized peridotite, and metasediments points to an exhumed high-pressure ophiolite sequence.

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