Provenance and tectonic setting of Carboniferous–Triassic sandstones from the Karaburun Peninsula, western Turkey: A multi-method approach with implications for the Palaeotethys evolution

Abstract

Carboniferous-Triassic siliciclastic sediments of the Karaburun Peninsula in western Turkey were studied to unravel their provenance and the tectonic setting of depositional basins within the Palaeotethyan realm. A set of complementary techniques including petrography, bulk-rock geochemistry and single-grain analysis of rutile, garnet and chrome spinel were applied to provide a diverse dataset for testing existing palaeotectonic models using both, established and recently published diagrams. We show that tectonic discrimination diagrams of siliciclastic sediments based on major and trace element whole-rock geochemical data do yield ambiguous results and are only partly in accordance with regional geological events. Chondrite-normalised REE patterns of Upper Palaeozoic samples are characterised by enrichment of LREE and a flat trend towards HREE. The degree of fractionation allows for discrimination between sandstones of Karaburun (La N /Yb N = 8.00-14.79) and adjacent Greek islands of Chios (5.82-9.23) and Inousses (7.40-9.95). Petrographic observations and compositional data from single-grain analysis indicate significant supply from low-to medium-grade metamorphic rocks of generally felsic character and minor input of (ultra)mafic detritus. Detrital chrome spinels in the Lower Triassic Gerence Formation are different in composition and shape compared to chrome spinels in Carboniferous-Permian sandstones. They were derived from a very proximal source and exhibit variable, but generally high Crand Mg-numbers, consistent with chrome spinels from podiform chromitites that have been formed in an intra-oceanic back-arc setting above a supra-subduction zone. We conclude that most of the Carboniferous-Triassic successions were deposited along the southern active margin of Eurasia in a continental-arc environment during the time period when Palaeotethys diminished in size and finally vanished. Large volumes of detritus were probably derived from rock units located in the present-day Balkan region and the Sakarya Zone, or equivalent successions that are not present anymore.

Evolution of the Palaeotethys in the Eastern Mediterranean: a multi-method approach to unravel the age, provenance and tectonic setting of the Upper Palaeozoic Konya Complex and its Mesozoic cover sequence (south-central Turkey)

“…Nevertheless, a considerable amount (up to 25%) of high-temperature rutiles in the Dikendağı Formation implies the existence of high-grade (granulite-facies) rocks in the source area. In terms of source rock composition, detrital rutiles from the Upper Palaeozoic rocks of Karaburun were (with few exceptions) dominantly derived from felsic lithologies, which is also recorded by grains from the Permian-Carboniferous and Permian-Triassic units of Chios (Meinhold et al 2008a;Löwen et al 2018). Despite the many similarities, detrital garnet and Cr-spinel do only occur in the Chios-Karaburun units, while they are virtually absent in studied rocks from the Konya Complex.…”

“…Previously, the tectono-stratigraphic similarities of the Chios, Karaburun and Konya units were used as strong arguments to correlate these units and interpret them as different parts of the same active continental margin (Robertson and Ustaömer 2009b). Essential provenance data to test if this correlation is viable were scarce but were provided over the last years for both, Chios and Karaburun (Meinhold et al 2007(Meinhold et al , 2008aLöwen et al 2017Löwen et al , 2018. These studies have identified lowgrade metamorphosed sedimentary rocks as major sources but locally also recognized high proportions of (sub)angular grains derived from a felsic volcanic source that was interpreted as an indication for the presence of a relatively proximal continental-arc.…”

“…Even though these areas have been the subject of several studies their role within the Palaeotethyan realm is controversial. Provenance data have been published for the islands of Chios and Inousses (Meinhold et al 2007(Meinhold et al , 2008aMeinhold and Frei 2008) and recently for the Karaburun Peninsula (Löwen et al 2017(Löwen et al , 2018. This kind of data is crucial for the understanding of the evolution of the Palaeotethys but is not yet available for the Konya Complex.…”

Melting by numbers: Assessing the effective melt fertility of crustal rocks

“…10). Continental eolian sediments (CB) are from the Older and Lower Red Sandstones from England (Hillier et al, 2006) and from the Tarim Basin, China (Rittner et al, 2016) and Turkey (Löwen et al, 2018). They are characterised by a relative abundance of quartz, with few micas, but K-feldspars.…”

Petrography, geochemistry, and provenance of Jurassic sandstones from the Sakarya Zone, NW Turkey

“…The large-ion lithophile elements (LILEs) (Rb, Ba, Sr, Th, U) are compared to the UCC, in which Sr (61.4-375 ppm) and Rb (22.3-108.5 ppm) are depleted with minor enrichment of Th (2.12-12.65 ppm) in sandstone samples (Figure 7a). Incompatible and easily mobilized LILE concentrations are usually controlled by the existence/ lack of feldspar, and LILEs show enrichment in the UCC compared with the mantle (Löwen et al, 2018). The incompatible high field-strength elements (HFSEs) are considered to be relatively immobile elements and thus could give additional information for the provenance of the sedimentary rocks (Taylor and McLennan, 1985).…”