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

Abstract

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 MiddleLate Triassic time, which was then incorporated into subduction-accretion prism forming the final picture, that is, ''the Karakaya Complex''.

Geochemical constraints on the origin of some intrusive igneous rocks from the Lower Benue rift, Southeastern Nigeria

“…The rocks are all basic in composition as can be seen from their SiO 2 (39.71-49.97%), MgO (4.2-11.21%). The rocks can be subdivided into two using high contents of LOI as an indication of some degree of alteration and the presence of secondary volatile and carbonate phases (Sayit and Goncouglu, 2009). The first group contains low LOI (2.84-3.94%) while the second group contains high LOI (7.39-10.95%).…”

“…Cs, Rb, Ba and Sr) and the transition metals Mn, Zn and Cu are easily mobilized by late and/or post-magmatic processes involving fluids and also during metamorphism (Pearce and Cann, 1973;Sayit and Goncouglu, 2009). Conversely, the HFSE (Y, Zr, Hf, Ti, Nb, Ta), the REE, the transition elements (V, Cr, Ni, Sc, Co), the LILE (Th) and the Nd isotopic composition are generally unchanged under a wide range of metamorphic conditions (up to the medium grade/lower amphibolite facies), including seafloor alteration (Edwards, 1978;Rollinson, 1993;Bienvenu et al, 1990as cited in Viruete et al, 2009).…”

The potential of cement stabilized shale quarry dust for possible use as road foundation material

“…The results of chemical composition of the studied SQD as presented in Table 1 [25], LOI gives a good indicator of deleterious substances most especially carbonates which considering the high LOI values recorded, strongly suggest the presence of secondary volatile and carbonate phase. The SQD consists mainly of high proportions of SiO 2 , Al 2 O 3 , CaO and LOI.…”

Whole-rock geochemistry of basic and intermediate intrusive rocks in the Ishiagu area: further evidence of anorogenic setting of the Lower Benue rift, southeastern Nigeria

“…The enrichment in LREEs relative to HREEs in the intrusives, which is reflected in the low (Tb/Yb) n ratios (2.12-2.48 in gabbro, 2.27-2.49 in dolerites, and 1.89-3.36 in diorites), indicates a garnet-bearing source. The Dy/Yb ratios, which range from 2.40 to 2.77 in gabbro, 2.5 to 2.68 in dolerites, and 2.15 to 2.48 in diorites, also suggest a garnet-bearing lherzolite source (Sayıt and Göncüoglu, 2009). According to Kearey and Vine (1990), the upper mantle has the composition of peridotite, containing abundant olivine and less than 15% garnet.…”

“…The presence of garnet as a residual phase in the melt source region is inferred from the (Tb/Yb) n ratio (Sayıt and Göncüoglu, 2009). The enrichment in LREEs relative to HREEs in the intrusives, which is reflected in the low (Tb/Yb) n ratios (2.12-2.48 in gabbro, 2.27-2.49 in dolerites, and 1.89-3.36 in diorites), indicates a garnet-bearing source.…”