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Carboniferous high-potassium I-type granitoid magmatism in the Eastern Pontides: The Gumushane pluton (NE Turkey)

Journal article
Authors G. Topuz
R. Altherr
W. Siebel
W. H. Schwarz
Thomas Zack
A. Hasozbek
M. Barth
M. Satir
C. Sen
Published in Lithos
Volume 116
Issue 1-2
Pages 92-110
ISSN 0024-4937
Publication year 2010
Published at Department of Earth Sciences
Pages 92-110
Language en
Keywords high-k granite, sr-nd isotopy, ar-ar dating, u-pb zircon dating, variscan progeny, eastern pontides, turkey, u-pb zircon, calc-alkaline, northern turkey, pulur complex, leukogranite associations, isotopic characteristics, european variscides, tectonic evolution, crustal components, natural zircon
Subject categories Earth and Related Environmental Sciences, Geochemistry, Geology, Solid earth geology and petrology

Abstract

The Gumushane pluton, a high-K calc-alkaline I-type granodionte/granite complex, forms an important component of the pre-Liassic basement of the Eastern Pontides (NE Turkey) In its eastern part, the pluton shows a compositional zonation ranging from biotite-hornblende granodiorite in the NW through biotite-hornblende granite to leucogranite/granophyre in the SE Numerous mafic microgranular enclaves (up to similar to 40 cm in diameter) suggest the former presence of globules of mafic melt during crystallization Emplacement of the pluton occurred during the latest Early Carboniferous, as shown by the 320 +/- 4 Ma (40)Ar-(39)Ar bionte/homblende and 324 +/- 6 Ma LA-ICP-MS U-Pb zircon ages. In Harker diagrams, samples of the different rock types exhibit well-defined data trends. With increasing SiO(2), the abundances of TiO(2), Al(2)O(3), Fe(2)O(3)(tot), MnO, MgO, CaO, P(2)O(5) and Sc decrease, but those of K(2)O and Rb increase However, the variations of Sr, Ba, (La/Yb)(cn) Sr/Y and Sigma REEs vs SiO(2) form distinctive groupings, which cannot be explained by a simple fractional crystallization Chondrite-normalized (cn) REE patterns of granodionte/granite samples show concave-upward shapes with (La/Yb)(cn) ranging from 5.2 to 124 and Eu/Eu* from 084 to 0.47, while there is almost no fractionation of the middle REE relative to the heavy REE In primitive mantle-normalized element concentration diagrams, all rocks display marked negative anomalies in Ba, Nb/Ta, Sr, P and Ti. but positive anomalies in K and Pb. These geochemical features imply a fractionating mineral assemblage of clinopyroxene, amphibole and plagioclase without significant involvement of garnet. The granophyres are, on the other hand, characterized by higher K(2)O/Na(2)O and Rb/Sr ratios, lower (La/Yb)(cn), ratios (1 3 to 4 8) and more pronounced negative anomalies in Ba, Nb/Ta, Sr, Eu, P and Ti Initial epsilon(Nd) values range from -3 78 to -5.30 and Nd model ages from 1 38 to 163 Ga The magmas of the granite/granodiorite portion were probably generated by partial melting of high-potassic amphibolitic rocks, and those of the granophyres by a relatively felsic micaceous crustal source. The Gumushane pluton was emplaced at the wake of the lowpressure-high-temperature metamorphism, and is regarded as a late phase of Hercynian orogeny in the Eastern Pontides (C) 2010 Elsevier B.V All rights reserved

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