Magmatism and crustal extension: Constraining activation of the ductile shearing along the Gediz detachment, Menderes Massif (western Turkey)

作者：Rossetti Federico; Asti Riccardo; Faccenna Claudio; Gerdes Axel; Lucci Federico; Theye Thomas

来源：Lithos, 2017, 282: 145-162.

DOI：10.1016/j.lithos.2017.03.003

• Extensional tectonics
• Magmatism
• Mylonite shearing
• Thermobarometry
• U-Pb geochronology
• Menderes Massif

The Menderes Massif of western Turkey is a key area to study feedback relationships between magma generation/emplacement and activation of extensional detachment tectonics. Here, we present new textural analysis and in situ U-(Th)-Pb titanite dating from selected samples collected in the transition from the undeformed to the mylonitized zones of the Salihli granodiorite at the footwall of the Neogene, ductile-to-brittle, top-to-the-NNE Gediz-Ala heir (GDF) detachment fault. Ductile shearing was accompanied by the fluid mediated sub-solidus transformation of the granodiorite to orthogneiss, which occurred at shallower crustal levels and temperatures compatible with the upper greenschist-to-amphibolite fades metamorphic conditions (530-580 degrees C and P < 2 GPa). The syn-tectonic metamorphic overgrowth of REE-poor titanite on pristine REE-rich igneous titanite offers the possibility to constrain the timing of magma crystallisation and solid-state shearing at the footwall of the Gediz detachment. The common Pb corrected Pb-206/U-238 (Pb-206U-238) ages and the REE re-distribution in titanite that spatially correlates with the Th/U zoning suggests that titanite predominantly preserve open-system ages during fluid-assisted syn-tectonic re-crystallisation in the transition from magma crystallization and emplacement (at similar to 16-17 Ma) to the syn-tectonic, solid-state shearing (at similar to 14-15 Ma). A minimum time lapse of ca. 1-2 Ma is then inferred between the crustal emplacement of the Salihli granodiorite and nucleation of the ductile extensional shearing along the Gediz detachment. The reconstruction of the cooling history of the Salihti granodiorite documents a punctuated evolution dominated by two episodes of rapid cooling, between similar to 14 Ma and similar to 12 Ma (similar to 100 degrees C/Ma) and between similar to 3 and similar to 2 Ma (similar to 105 degrees C/Ma). We relate the first episode to nucleation and development of post-emplacement of ductile shearing along the GDF and the second to brittle high-angle faulting, respectively. Our dataset suggests that in the Menderes Massif the activation of ductile extension was a consequence, rather than the cause, of magma emplacement in the extending crust.

• 出版日期2017-6