Geochemical and isotopic data of meta-gabbroic dikes in Alaşehir area in the Menderes Massif, Western Turkey: Evidence for the Early Cambrian back-arc rifting?

Gürsu, Semih
Köksal, Serhat
Möller, Andreas
Stratigraphic feature of undated garnet-bearing meta-gabbroic dikes cross-cutting basement rocks of meta-pelitic successions in the Alaşehir areas (Central Menderes Massif - CMM) are still in debate and are distinct from the eclogitic meta-gabbroic dikes, garnet amphibolites and biotite rich meta-gabbroic dikes cross-cutting Neoproterozoic basement rocks (meta-tonalites/meta-granodiorites and meta-granites) that crop out in the Birgi, Tire and Çine areas of the CMM. The garnet-bearing meta-gabbro dikes in the Alaşehir areas have low Nb (0.6 to 4.9 ppm), low Th (0.2 to 0.5 ppm), low Zr (10.1 to 54.6 ppm), low to moderate Y (8.4 to 15.1 ppm), Ti (2518 t 6175 ppm), Zr/Yb (13.33 to 41.31 ), Ti/Zr (57.05 to 346.86), Y/Zr (0.23 to 0.98) ratios. They are highly depleted in LREE and display flat patterns in MREE and HREE compared to the eclogitic meta-gabbroic dikes, garnet amphibolites, biotite rich meta-gabbroic dikes of the Late Neoproterozoic basement rocks. Nb, Zr, Ti contents with Nd/Sm and La/Yb ratios compared to La/Yb and Eu/Eu* indicate distinct enrichment of the garnet-bearing meta-gabbroic dikes (Alaşehir areas) relative to the eclogitic meta-gabbroic dikes, garnet amphibolites and biotite rich gabbroic dikes (Birgi, Tire and Çine areas). The low Nb, low Th, low Zr contents, and high Ti/Zr and low Zr/Yb ratios in the garnet-bearing meta-gabbroic dikes (Akşehir areas) compared to the eclogitic meta-gabbroic dikes, biotite rich meta-gabbroic dikes indicates that they may have been derived from melting of mafic lower crustal sources. Variable ɛ Nd(540) (-2.9 to +1.9) and 147Sm/144Nd ratios (0.1320 to 0.2277) of the garnet-bearing meta-gabbroic dikes in Alaşehir areas indicate extensive mixing of a mafic lower crustal source with depleted mantle during their formation. Apparent crustal residence Nd model ages (TDM) determined using the two-stage model of Liew and Hofmann (1988) range from 1.08 - 1.47 Ga, also indicating mixing of older sources with depleted mantle. We suggest that Andean-type subduction was followed by lithospheric thinning of the continental crust, resulting in an initial stage of back-arc basin formation in the peri-Gondwanan crust during the Late Neoproterozoic. The biotite-rich meta-gabbroic dikes may have been generated during the initial stage of this rifting, whereas garnet-bearing meta-gabbroic dikes (Alaşehir areas) may have been generated later during the mature stage of continental rifting in the Early Cambrian. Similar tectonic scenarios have been suggested for other peri-Gondwanan terranes in Europe, the Middle East, and eastern Asia.
GEOBONN 2018, (2 - 06 Eylül 2018)


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In the Sandikli (Afyon) region, western Taurides, the Late Proterozoic rocks of the Sandikli basement complex are composed of low-grade meta-sedimentary rocks (Guvercinoluk Formation) intruded by felsic rocks (Kestel Cayi Porphyroid Suite, KCPS). The KCPS is a deformed and highly sheared, dome-shaped rhyolitic body with a granitic core. Quartz porphyry dikes intrude both the slightly metamorphic igneous and the sedimentary rocks of the basement complex. Both the quartz porphyries and rhyolites were converte...
Citation Formats
S. Gürsu, S. Köksal, and A. Möller, “Geochemical and isotopic data of meta-gabbroic dikes in Alaşehir area in the Menderes Massif, Western Turkey: Evidence for the Early Cambrian back-arc rifting?,” presented at the GEOBONN 2018, (2 - 06 Eylül 2018), Bonn, Almanya, 2018, Accessed: 00, 2021. [Online]. Available: