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    Geochemical characterisation and petrogenesis of the Polat Granitoid in Eastern Taurus Belt, Turkey
    (Geological Soc India, 2000) Önal, A; Bingöl, AF
    The Eastern Taurus Belt represents a collision zone between Cimmerian and the Arabian continents. Along this orogenic belt, metamorphics, ophiolitic rocks and are magmatics occur widely. The Polat Granitoid, whose size is approximately 80 so. km (length 24, width 3.5), is located to the west of Malatya in this belt. This granitoid comprises plutonic rocks such as diorite, quartzdiorite, monzodionite, tonalite, granodiorite and other intrusive rocks. There are many mafic enclaves (ME) seen within the granitoids. Based on field, petrographical and geochemical data, this granitoid is classified into two clusters viz; diorite and tonalite. The diorite shows SiO2, variation from 52.47 to 57.80 % and tonalite from 61.40 to 68.00 %. The differentiation index (D1) varies from 22.73 to 49.15 for diorite and from 59.40 to 68.12 for tonalite. All samples plot in the subalkalic field. Most of them are calc alkaline and all of them belong to middle-lower K Magma Series. CaO-Y trends indicate either a constant or a slight increase in Y value. TiO2,- Zr relationship does not show a clear fractionation trend. But, a regular TIO2, decrease and the low Ni and Cr abundance can be explained by minor biotite and hornblende fractionation. All samples fall within the VAG field. Low TiO2, concentrations of samples (generally <1%) are consistent with other are-derived rocks. ORG-normalised geochemical patterns are observed to be similar to Chilean type are granitoids. Polat Granitoid shows features similar to calc alkaline granitoids, which were emplaced in continental or island arcs above subduction zones. This granitoid was developed as a product of an island are which was near the Malatya-Keban platform in late Cretaceous. The magma is formed by the melting of the subducted slab. Presence of a skarn zone between the metamorphics and granitoids indicates that this are was not far from the continental platform.
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    K-Ar age determination, whole-rock and oxygen isotope geochemistry of the post-collisional Bizmisen and Calti plutons, SW Erzincan, eastern Central Anatolia, Turkey
    (Wiley, 2005) Önal, A; Boztug, D; Kürüm, S; Harlavan, Y; Arehart, GB; Arslan, M
    Post-collisional granitoid plutons intrude obducted Neo-Tethyan ophiolitic rocks in central and eastern Central Anatolia. The Bizmisen and Calti plutons and the ophiolitic rocks that they intrude are overlain by fossiliferous and flyschoidal sedimentary rocks of the early Miocene Kemah Formation. These sedimentary rocks were deposited in basins that developed at the same time as tectonic unroofing of the plutons along E-W and NW-SE trending faults in Oligo-Miocene time. Mineral separates from the Bizmisen and Calti plutons yield K-Ar ages ranging from 42 to 46 Ma, and from 40 to 49 Ma, respectively. Major, trace, and rare-earth element geochemistry as well as mineralogical and textural evidence reveals that the Bizmisen pluton crystallized first, followed at shallower depth by the Calti pluton from a medium-K calcalkaline, I-type hybrid magma which was generated by magma xing of coeval mafic and felsic magmas. Delta O-18 values of both plutons fall in the field of I-type granitoids, although those of the Calti pluton are consistently higher than those of the Bizmisen pluton. This is in agreement with field observations, petrographic and whole-rock geochemical data, which indicate that the Bizmisen pluton represents relatively uncontaminated mantle material, whereas the Calti pluton has a significant crustal component. Structural data indicating the middle Eocene emplacement age and intrusion into already obducted ophiolitic rocks, suggest a post-collisional extensional origin. However, the pure geochemical discrimination diagrams indicate an arc origin which can be inherited either from the source material or from an upper mantle material modified by an early subduction process during the evolution of the Neo-Tethyan ocean. Copyright (c) 2005 John Wiley & Sons, Ltd.
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    Origin and nature of the mineralizing fluids of thrust zone fluorites in Celikhan (Adiyaman, Eastern Turkey)
    (Geochemical Soc Japan, 2005) Sasmaz, A; Önal, A; Sagiroglu, A; Önal, M; Akgul, B
    The Celikhan fluorite mineralization is concentrated in the thrust zone between the Ptnarbast Formation, which forms the hanging wall, and the Kalecik Limestone foot wall. Fluorite occurs as fracture fills in the thrust zone and as replacement of the foot wall. The wall rock alteration consists of calcite, barite, quartz and kaolinite. The total REE contents of the country rocks, especially the mica- and calc-schists of the Pinarbasi formation at 519 ppm, are higher than those of fluorites. The chondrite normalized REE patterns of country rock and fluorites display generally identical trends. However, fluorite patterns show positive Eu and negative Cc anomaly indicative of low temperature and high fo(2) conditions. Cross plots of the Tb/Ca - Tb/La, (La/Yb)(n) - (Tb/Yb)(n) and (La/Yb)(n) (Eu/Eu*)(n) ratios of the fluorites indicate deposition by low temperature hydrothermal waters. The REE and F were probably leached from the Pinarbasi Formation by the mineralizing solutions. The mineralizing fluids are probably meteoric and formation waters heated at depth along the thrust zone by the natural thermal gradient and/or formation waters heated and mobilized by thrusting.