Geochemistry of mafic rocks of the Karakaya complex, Turkey: evidence for plume-involvement in the Palaeotethyan extensional regime during the Middle and Late Triassic

2009-03-01
The Karakaya Complex within the Early Mesozoic Cimmerian Orogeny in northern Turkey represents the remnants of the Palaeotethys. It includes slivers and/or mega-blocks of slightly metamorphic basic volcanic rocks associated with fossiliferous sediments as well as hypabyssal and intrusive rocks with basaltic-andesitic to ultramafic compositions. They display two distinct compositional groups; namely alkaline and variably tholeiitic. The alkaline basalt samples are more akin to oceanic-island basalts (OIB) with relatively enriched trace element characteristics together with strong partitioning in HREE ([La/Yb](N) = 5.8-16.2), suggesting that garnet is present as a residual phase in the source of those basalts. The variably tholeiitic samples apart from diabases display E-MORB characteristics; being relatively depleted compared to the alkaline counterparts and less fractionated REE patterns ([La/Yb](N) = 2.1-3.6). The diabases, on the other hand, are distinctively different with a significant negative Nb anomaly (Zr/Nb = 28.9-43.4) and flat REE patterns ([La/Yb](N) = 0.8-1.4), suggesting their generation above a supra-subduction zone, probably a back-arc basin. These results may suggest that a mantle plume-related magmatism associated with extensional oceanic system should have been installed within Palaeotethys during Middle-Late Triassic time, which was then incorporated into subduction-accretion prism forming the final picture, that is, "the Karakaya Complex''.
Citation Formats
K. Sayıt and M. C. Göncüoğlu, “Geochemistry of mafic rocks of the Karakaya complex, Turkey: evidence for plume-involvement in the Palaeotethyan extensional regime during the Middle and Late Triassic,” pp. 367–385, 2009, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/32138.