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    An approach to geochemical characterization of productive versus barren granitoids in terms of iron in Central Turkey
    (PERGAMON-ELSEVIER SCIENCE LTD, 2004) Kuscu, I; Gencalioglu-Kuscu, G; Sarac, C; Meinert, LD
    The granitoids associated with and without skarn type mineralizations in central Anatolia are. termed as productive and barren respectively. The Study of the relationships between plutonic rocks in the Central Anatolian Crystalline Complex in central Turkey suggests,:is a direct genetic connection between the composition of plutons, and their associated ore deposits. In order to discriminate between productive and barren granitoids, two Fe-skarn granitoids (Celebi and Karamadazi). and a series of barren plutons within central Anatolia were examined. The Karamadazi and Celebi granitoids are geochemically different from other barren plutons in Central Anatolia. The parameters governing the productivity of these granitoids were determined by principal component analysis (factor analysis) method. Based on this method, the factors controlling the geochemical characteristics of the Celebi granitoids are (Al2O3 divided by MgO divided by Fe2O3 divided by P2O5 divided by TiO2 divided by CaO)/(SiO2), (K2O + Rb)/(Na2O) and Rb/Sr ratios, and for the Karamadazi granitoid the (Fe2O3 divided by MnO divided by MgO divided by P2O5 divided byY)/(SiO2 divided by Rb) (FMMY/S) and (Na2O)/(K2O) ratios. These two granitoids are clearly distinguished front the barren Central Anatolian Granitoids (CAG) on Harker diagrams based oil these controlling factors (parameters). Barren CAG plutons are different front the productive Celebi granitoids in their higher silica content and generally higher total alkali values. This study suggests that iron-producing granitoids are less differentiated and receive little contribution from continental crust compared to the barren granitoids. Higher apatite and zircon abundance in the Celebi granitoids suggest that the Celebi granitoids have more I-type characteristics compared to barren plutons of CAG. The Karamadazi granitoid is the most striking example for the granitoids in CAG, having a higher contribution front the continental crust ass evidenced by higher Rb. Ba. Th, the highest mean Sc, V, and mean Zr, Y, Ni contents. Based on the factor analysis, it is proposed that the Karamadazi granitoid displays geochemical characteristics similar to the Terlermez and Agacoren granitoids of CAG. The factor analyses indicated that the first two factors are about the same for both the Fe-producing Celebi and Karamadazi granitoids. Therefore. this similarity has let to a conclusion that the productivity or non-productivity of the granitoids in Central Anatolia can be tested by examining and comparing the distribution of granitoids in diagrams designed according to the factors defined in this study. (C) 2004 Elsevier Ltd. All rights reserved.
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    Geochemical correlations between effusive and explosive silicic volcanics in the Saraykent region (Yozgat), central Anatolia, Turkey
    (WILEY, 2002) Gencalioglu-Kuscu, G; Floyd, PA
    Two main volcanic events are distinguished between Saraykent and Akqaki la in the Yozgat province of central Anatolia: (1) early Late Cretaceous-Palaeocene effusive activity, that produced a sequence of intermediate to felsic 'basal lavas'; and (2) marginally later Palaeocene explosive activity that formed a series of covering ignimbrite flows. Due to their close temporal and spatial relation, geochemical comparisons were made between the silicic members of the lavas and ignimbrites, to identify chemical groups and their relative petrogenesis. The basal lavas range from calc-alkaline basaltic andesites to dominant rhyolites. Based on trace element correlations three main geochemical groups were identified: the Akqakisla rhyolites (present as domes); Akcakisla rhyodacites-dacites (lava flows); and Ozan-Saraykent rhyolites (lava flows). Large-ion lithophile elements have been mobile in all the groups, but mainly in the Akqaki la rhyolites. Rare earth element (REE) patterns show marked similarity between the Ozan and Saraykent basal lavas. The Akqaki la dome rhyolites are more fractionated with lower La-N/Yb-N ratios (c. 10), whereas the Akqakisla basal lavas have much higher LaN/YbN ratios (c.30). The chemical coherence and petrographic similarities between the Saraykent and Ozan lavas suggest a single suite related via fractionation. Three geochemical groups were also established for the ignimbrites: Saraykent ignimbrite; Baglica ignimbrite-TokluKizildag crystal tuffs; and Keklikpinar ignimbrite. The ignimbrites, like the basal lavas, display a pronounced depletion in Ba on ORG-normalized plots. Relative to the basal lavas, chondrite-normalized patterns for the ignimbrites are different in displaying negative Eu anomalies that indicate feldspar fractionation. The lack of geochemical overlap or coherence between any of the lava and ignimbrite groups suggests that they represent distinct eruptive events and are not related in ally simple volcanic development and cogenetic sense. Two geochemical features are common to all the volcanic rock groups: (1) the presence of a Nb-Ta anomaly, which is generally accepted as a crustal signature; and (2) the relatively low Y abundances which appear characteristic for the region as a whole. These fundamental features of the local silicic volcanism largely reflect source composition and effects. Copyright (C) 2002 John Wiley Sons, Ltd.
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    Geochemical signatures of granitoids associated with skarns in central Anatolia
    (TAYLOR & FRANCIS INC, 2001) Kuscu, I; Gencalioglu-Kuscu, G; Erler, A
    Many studies have shown systematic correlations between the composition of plutons worldwide and the metal contents of associated skarns. This is the first report of similar correlations between plutons and the skarns of the Akdagmadeni, Akcakisla, and Keskin districts in Central Anatolia. Herein, die genetic associations of skarn occurrences are investigated using the geochemical compositions of the intrusives. In terms of major- and trace-element data, the granitoids associated with skarns show important differences. Three general groups of plutons, are distinguished, and the distinction among them is based largely on major-element data. In general, the granitoids associated with Pb-Zn skarns in all three districts are classified as subalkaline/calc-alkaline, based on TAS and AFM diagrams, respectively. The Akdagmadeni and Keskin granitoids display S-type characteristics, and those of Akcakisla display I-type characteristics. As a whole, the granitoids in all districts display major-element geochemical characteristics (Harker diagrams) that typify plutons associated with worldwide Zn, W, Mo, and Sn skarns. These data probably indicate that some other elements, like W in the Akdagmadeni district, and Mo + Sn in the Keskin district, could be associated with these skarns. Similarly, the granitoids of Akdagmadeni and Akcakisla have trace-element geochemical signatures (Zr versus Ba and Zr versus Rb/Sr diagrams) that typify plutons associated worldwide with Zn, Cu, Mo, and W skarns. This also helps to underline the possible association of W and Mo skarns in the Akdagmadeni district, and Cu skarns in the Akcakisla district. The average K2O/Na2O ratios of the plutons also serve to differentiate the granitoids associated with different types of skarns. The average K2O/Na2O ratio of the Keskin pluton it; 1.23, close to that of plutons associated with major Mo and Sn skarns. On the other hand, the average K2O/Na2O ratio of Akcakisla granite is very close to 1.0, close to that of plutons associated with major Cu (and W?) as well as Pb and Zn. Therefore, these skarns should be investigated in terms of the potential for those elements. This suggests new exploration possibilities for the Akcakisla, Akdagmadeni, and Keskin districts.