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Titel Slab melting, adakite differentiation and emplacement in a fossile subduction channel: the late Paleocene Sabzevar magmatism (NE Iran)
VerfasserIn Federico Rossetti, Mohsen Nasrabady, Axel Gerdes, Patrick Monié, Thomas Theye, Federico Lucci, Gianluca Vignaroli
Konferenz EGU General Assembly 2014
Medientyp Artikel
Sprache Englisch
Digitales Dokument PDF
Erschienen In: GRA - Volume 16 (2014)
Datensatznummer 250088577
Publikation (Nr.) Volltext-Dokument vorhandenEGU/EGU2014-2697.pdf
 
Zusammenfassung
This study describes the structural setting, petrogenesis, and geochronology of a suite of acidic magmatic rocks that are intruded in the metamorphic core of the Tertiary ophiolitic suture zone of the Sabzevar Range, NE central Iran. This ophiolitic complex consists of a ductile-to-brittle, S/SE-verging orogenic domain, where a frontal nonmetamorphic and an inner metamorphic sector can be identified in the field. The metamorphic domain consists of a major ophiolitic tectonic mélange, where variably sized, foliated metabasic rocks (blueschists, greenschists, and amphibolites) occur dispersed as centimetre- to kilometre-size blocks into a highly sheared serpentinite matrix. The granitoids occur as leucocratic tabular bodies, with variably developed contact metamorphic zones that are typically gradational in the field and concordant with the regional country rock foliation. The field relations with the host rocks and the internal (magmatic to solid state) fabrics in the Sabzevar granitoids document a syntectonic magma emplacement scenario, based on: (1) concordance of pluton shapes and internal structures with regional structures (S-L fabrics); (2) the existence of a continuum of magmatic through solid-state noncoaxial flow consistent with the regional sense of shear (top-to-the-SSE); and (3) occurrence of foliated wall-rock xenoliths, incorporated by flowing magma into the marginal sectors of the intrusive bodies. These points, together with the evidence that magma preferentially migrated along flats, attest that the Sabzevar granitoids intruded into rocks that were actively deforming during compressional shearing. In the TAS diagram, the granitoid compositions define a medium-K calc-alkaline suite, spanning from basaltic andesite to the dacite and rhyolite fields. They show characteristic low MgO (0.15–0.60 wt%) and Ni (