Geochemical constraints on the Cenozoic, OIB-type alkaline volcanic rocks of NW Turkey: Implications for mantle sources and melting processes

Kaymakcı, Nuretdin
Gourgaud, Alan
The volcanic province of North-West Turkey contains a number of intra-continental alkaline volcanic eruption sequences formed along the localized extensional basins developed in relation with the Late Cenozoic extensional processes. The volcanic suite comprises the extracted melt products of adiabatic decompression melting of the mantle that are represented by small-volume intra-continental plate volcanic rocks of alkaline olivine basalts and basanites with compositions representative of mantle-derived, primary (or near-primary) melts. The volcanic rocks have near-uniform Sr-87/Sr-86 (0.70316-70353) and Nd-143/Nd-144 (0.51291-0.51297; epsilon(Nd) 5.08-6.32) ratios and are characterized by Ocean Island Basalt (OIB)-type trace element patterns with significant enrichment in LILE, HFSE and L-MREE, and a slight depletion in HREE, relative to NMORB. Trace element variations of individual basaltic eruption sequences indicate that each lava sequence shows remarkably similar temporal-compositional trends that are characterized by an increase in incompatible elements and MgO, with decreasing SiO2, as melt production proceeds. Systematic change in incompatible trace element concentrations (and ratios) of the lavas is not reflected by the isotopic ratios, leading to the suggestion that the temporal-compositional trends are not caused by source variations. The variations in melt chemistry with time does not reflect fractional crystallization nor can it be explained by variable proportions of mixing between melts produced by different degrees of partial melting of two (or more) compositionally distinct sources in the mantle. Instead, the observed trends are consistent with a progressive decrease in degree of melting from early-formed alkali olivine basalts to later basanites and systematic mixing between increments of melt derived from the same source but probably at different depths. Quantitative trace element modeling of fractionation-corrected data indicates that the mafic alkaline magmas originated from mixing of melts produced by variable degrees (similar to 2% to 8%) of incremental partial melting of a compositionally uniform, volatile-bearing mantle domain that is enriched in all incompatible elements (e.g. LILE, HFSE and L-MREE) relative to hypothetical Depleted MORB Mantle (DMM) and/or Primitive Mantle (PM) compositions.


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The Nemrut stratovolcano, with its well defined summit caldera, is the most recent volcanic eruption center (1441 A.D.) in the East Anatolian High Plateau, one of the best examples of an active colllision zone. Widespread volcanism has been active in this region for the last similar to 10 Ma, producing large volumes of lavas and pyroelastics covering a broad belt, across the Bitlis Suture Zone, from the Anatolian plate in the north to the Arabian plate in the south.
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Six box-cores, one boomerang core and one hundred sixty-six surface sediment samples recovered in the Sea of Marmara were analyzed in an attempt to establish the main controls on distribution and origin of trace metals within the oxic to suboxic basin of this sea.
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The mineralogy, texture and composition of rocks associated with the kaolin deposits in the Ahirozu-Hamidiye-Ucbasli area, SE of Mihaliccik, Eskisehir, Turkey, were investigated. In the study area, Triassic, blue-green schists and serpentinized ultramafic rocks are exposed. Kaolinization occurs at the contact between a Triassic granitic intrusion and metamorphic rocks. Textural and mineralogical characteristics were identified by X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive X-r...
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The Suphan stratovolcano is one of the major Quaternary eruption centers of post-collisional volcanism in eastern Anatolia, located in the zone of convergence between the Arabian and the Anatolian plates. We document the geological and geochemical evolution of Suphan in terms of volcanostratigraphy, geochronology (Ar-40-Ar-39), isotope composition (Sr, Nd, Pb) and bulk-rock geochemistry. Our new Ar-40-Ar-39 data, along with previously published K/Ar ages, indicate an age of 0 center dot 76-0 center dot 06 M...
Citation Formats
E. ALDANMAZ, N. KÖPRÜBAŞI, Ö. F. GÜRER, N. Kaymakcı, and A. Gourgaud, “Geochemical constraints on the Cenozoic, OIB-type alkaline volcanic rocks of NW Turkey: Implications for mantle sources and melting processes,” LITHOS, pp. 50–76, 2006, Accessed: 00, 2020. [Online]. Available: