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    Mineral compositional and textural evidence for magma mingling in the Saraykent volcanics
    (ELSEVIER SCIENCE BV, 2001) Kuscu, GG; Floyd, PA
    Upper Cretaceous-Paleocene calc-alkaline dacitic and rhyodacitic lava flows and domes are exposed in the Saraykent (Yozgat) region within Central Anatolian Crystalline Complex (CACC). Saraykent volcanics are generally plagioclase + hornblende + biotite + titanomagnetite +/- quartz +/- augite-phyric, Subrounded, vesicular magmatic enclaves, ranging from a few millimeters to a few centimeters in size, an present in the Saraykent dacites. The enclaves are mainly holocrystalline and have similar mineral assemblage to the host dacites. Almost all phases in Saraykent volcanics exhibit varying degrees of disequilibrium features indicative of magma mingling. Plagioclase phenocrysts display sieved and normal type populations, a wide range in rim compositions, and oscillatory zoning, Maximum core to rim compositional change in sieved rhyodacite plagioclases is up to 24 mol% increase in An. Some plagioclase core compositions are unusually Ca-rich. They range from An(27) to An(75) for the Saraykent dacites and from An(30) to An(66) for the Saraykent rhyodacites. Hornblende and biotite phenocrysts have reaction rims indicating disequilibrium crystallization with magma. Both hornblende and biotite crystals show reverse zoning in terms of decreasing Mg/Mg + Fe. Quartz phenocrysts are corroded and embayed. Presence of normally and reversely zoned augites in the same sample, and high-Ti high-Al augites more comparable with basaltic compositions, are other lines of evidence for disequilibrium. The enclave hornblendes are both edenitic and pargasitic, the latter being more typical of mafic compositions. The enclave biotite crystals have higher Mg/Mg + Fe2+ ratios than the host dacite biotite crystals and display normal, reverse and oscillatory zoning. Plagioclase core compositions vary between An(44) and An(55) in the enclaves. Although the development of sieve texture in plagioclase and reaction rims on mafic minerals may be attributed to decompression, this cannot explain the observed compositional change and normal type of plagioclase in the same sample. Similarly, a cognate (i.e. fractionation) origin for the enclaves can be suggested due to their mineralogical similarity to the host dacite, However, other criteria such as oscillatory zoning and unusually calcic cores of plagioclases; heterogeneity of plagioclase rims; resorbed and embayed phenocrysts and augite compositions indicating a more mafic magma are enough to support the suggestion that magma mingling was a viable process in the generation of the Saraykent volcanics. (C) 2001 Elsevier Science B.V. All rights reserved.
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    Post-collisional H-type granitoid magmatism in Central Anatolia and time-space relation with Fe-oxide mineralization
    (MILLPRESS SCIENCE PUBLISHERS, 2003) Kuscu, I; Kuscu, GG; Soylu, M; Eliopoulous, DG
    The distribution, in both space and time, of the mineral deposits of the Central Anatolia reveals some interesting and enigmatic features of mineralization in a collision related setting. Central Anatolia is a polymetallic metallogenic province hosting mineral deposits of various size and type. Present study concerns with the formation and distribution of the Fe-oxide mineralization in terms of granite metallogeny, and reveals the genetic coexistence of H-type post-collisional granitoid magmatisin and Fe-oxide mineralization.
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    Tectonic setting and petrogenesis of the Celebi granitoid, (Kirikkale-Turkey) and comparison with world skarn granitoids
    (ELSEVIER SCIENCE BV, 2002) Kuscu, I; Kuscu, GG; Meinert, LD; Floyd, PA
    Many studies have shown systematic correlations between the composition of plutons worldwide and the metal content of associated skarns. This is the first report of similar correlations between the composition of Celebi granitoid and skarns of the Celebi district in Central Anatolia, Turkey. The Celebi district is well known for its polymetallic Fe-Wand Cu vein ores. These are hosted by calcic skarn zones. Both exoskarns (pyroxene-gamet) and endoskarns (epidote-pyroxene) occur in the district formed mainly along the granitoid contacts and along the fractures within the marble. Based on mineralogy, petrology and geochemistry, two different igneous rocks were recognized in the Celebi granitoid, referred to as leucocratic (felsic) and mesocratic (intermediate) Celebi granitoid. The leucocratic Celebi occurs as dominant rock type, and is classified as granite. The mesocratic Celebi is not widespread and is classified as adamellite, tomalite, quartz monzonite and quartz monzodiorite. The mesocratic Celebi has I-type characteristics, and have subalkaline, calc-alkaline and metaluminous characteristics like most worldwide skarn granitoids. A post-collisional tectonic setting is proposed on the basis of field evidence, the relative timing of intrusions with respect to metamorphic and obducted ophiolitic rocks and trace element geochemistry. The high abundance of La and Ce and the enrichment of V in mafic components suggest that Celebi granitoids are formed by partial melting of mantle rocks, but have been contaminated by interaction with continental crust involving possible magma mixing processes (i.e. mixing of coexisting felsic and mafic magmas). In the district, the mesocratic type and mafic microgranular enclaves (MME) mainly within leucocratic type represent a mafic underplating magma that was mixed with and/or injected into felsic magma of the leucocratic type. The present study shows that Fe mineralization is associated with mesocratic Celebi type, whereas W mineralization is associated with leucocratic type. Mesocratic Celebi granitoid is significantly different from the worldwide average of plutons associated with Fe skarns. In particular, MgO vs. SiO2, FeOt+CaO+Na2O/K2O vs. SiO2, Fe2O3/Fe2O3+FeO vs. SiO2 and V vs. Ni vary from typical values (are lower than values typical for plutons associated with Fe skarns) for plutons associated with Fe skarns. Instead, it resembles the geochemical characteristics of plutons associated with worldwide Cu and possibly An skarns. This suggests new exploration possibilities for copper and gold in the Celebi district. (C) 2002 Elsevier Science B.V. All rights reserved.