Geochemical characteristics of mafic lavas from the Neotethyan ophiolites in western Turkey: implications for heterogeneous source contribution during variable stages of ocean crust generation

Abstract

The Late Triassic to Late Cretaceous age mafic lavas from the Neotethyan suture zone ophiolites in western Turkey exhibit a wide diversity of geochemical signatures, indicating derivation from extremely heterogeneous mantle sources. The rocks as a whole can be divided into three broad subdivisions based on their bulk-rock geochemical characteristics: (1) mid-ocean ridge basalts (MORB) that range in composition from light rare earth element (LREE)-depleted varieties (N-MORB; (La/Sm) N < 1) through transitional MORB to LREE enriched types (E-MORB; (La/Sm) N > 1); (2) the ocean island basalt (OIB)-type alkaline volcanic rocks with significant enrichment in LILE, HFSE and L-MREE, and a slight depletion in HREE, relative to normal mid-ocean ridge basalts (N-MORB); and (3) the supra-subduction zone (SSZ)-type tholeiites originated from arc mantle sources that are characterized by selective enrichments in fluid-soluble large ion lithophile elements (LILE) and LREE relative to the high field strength elements (HFSE). The formation of MORB tholeiites with variable enrichments and depletions in incompatible trace elements is probably related to the processes of crust generation along an oceanic spreading system, and the observed MORB-OIB associations can be modelled by heterogeneous source contribution and mixing of melts from chemically discrete sources from sub-lithospheric reservoirs. Evaluation of trace element systematics shows that the inferred heterogeneities within the mantle source regions are likely to have originated from continuous processes of formation and destruction of enriched mantle domains by long-term plate recycling, convective mixing and melt extraction. The origin of SSZ-type tholeiites with back-arc basin affinities, on the other hand, can be attributed to the later intra-oceanic subduction and plate convergence which led to the generation of supra-subduction-type oceanic crust as a consequence of imparting a certain extent of subduction component into the mantle melting region. Mixing of melts from a multiply depleted mantle source, which subsequently received variable re-enrichment with a subduction component, is suggested to explain the generation of supra-subduction-type oceanic crust. The geodynamic setting in which much of the SSZ-type ophiolitic extrusive rocks from western Turkey were generated can be described as an arc-basin system that is characterized by an oceanic lithosphere generation most probably associated with melting of mantle material along a supra-subduction-type spreading centre.

Petrogenesis of pillow basalts in West Junggar, NW China: Constraints from geochronology, geochemistry, and Sr–Nd–Pb isotopes

“…Plots of (a) Ce/Y versus Zr/Nb (Göncüoglu, Sayit, & Tekin, ). Fields for the OIB‐, E‐MORB, N‐MORB, and SSZ‐type Tethyan basaltic rocks are taken from Maheo et al () and Aldanmaz, Yaliniz, Güctekin, and Göncüoglu (). (b) Nb/Yb versus TiO 2 /Yb (Pearce, ).…”

Geochronology, geochemistry, and Hf isotopes of mafic rocks from Dalabute ophiolitic mélange in West Junggar, Xinjiang (NW China): Implications for the magmatic source and tectonic setting

“…(a) Zr/Nb‐Ce/Y diagram (Goncüoglu, Sayit, & Tekin, ). OIB, E‐MORB, N‐MORB, and SSZ fields cited from Mahéo et al, ; Saccani & Photiades, ; Aldanmaz, Yaliniz, Güctekin, & Cemal Göncüoglu, . (b) Nb/Yb‐TiO 2 /Yb diagram (Pearce, ), N‐MORB, E‐MORB, and OIB fields cited from Sun and McDonough, 1989.…”

“…(a) La/Yb‐Zr/Nb diagram (Zhao & Zhou, ). (b) La/Yb‐Zr/Nb diagram (Aldanmaz et al, ), N‐MORB, E‐MORB, and OIB data cited from Sun and McDonough, 1989. Geochemical data of mafic rocks from the Dalabute ophiolitic mélange are same as Figure [Color figure can be viewed at wileyonlinelibrary.com]…”

Diverse tectonic settings of formation of the metaigneous rocks in the Jurassic metamorphic accretionary complexes (Refahiye, NE Turkey) and their geodynamic implications

“…An appraisal of the geochemical data from the non-metamorphic and metamorphic accretionary complexes of different ages in Turkey (e.g. Aldanmaz et al, 2008;Eyüboğlu et al, 2007;Genç, 2004;Göncüoğlu et al, 2006;Göncüoğlu et al, 2010;Polat, Casey, & Kerrich, 1996;Sayit et al, 2010;Tankut, Dilek, & Önen, 1998) Windley, Alexeiev, Xiao, Kröner, & Badarch, 2007) reveals that the incorporation of the basic rocks with island arc affinity into the accretionary complexes is a common phenomena. Several possible processes can be considered: (i) forearc magmatic material (e.g.…”

“…Notwithstanding numerous studies dealing with petrogenetic modeling on the metabasic rocks from the accretionary complexes (e.g. Aldanmaz, Yalınız, Güçtekin, & Göncüoğlu, 2008;Dupuis et al, 2005;Göncüoğlu et al, 2010;Saccani, Beccaluva, Photiades, & Zeda, 2011;Yang et al, 2012) we evade such modeling because genetically unrelated rocks are mostly found next to each other in accretionary complexes, and even co-magmatic relationship within the same geochemical group cannot be proven.…”