Browsing by Author "Yaliniz K.M."

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    Terlemez quartz monzonite of Central Anatolia (Aksaray-Sarikaraman): Age, petrogenesis and geotectonic implications for ophiolite emplacement
    (John Wiley and Sons Ltd, 1999) Yaliniz K.M.; Aydin N.S.; Göncüoǧlu M.C.; Parlak O.
    The Terlemez quartz monzonite is one of the Central Anatolian Granitoids and is exposed to the east of one of the main granitoid belts trending in a NW-SE direction and situated at the western end of the Central Anatolian Crystalline Complex. The Terlemez quartz monzonite is medium- to coarse-grained with granoblastic texture. It is essentially composed of quartz, plagioclase, hornblende and K-feldspar and variable contents of biotite. It is mostly compact and massive, but close to the contact with the ophiolitic basic rocks it shows a chilled margin. It characteristically includes K-feldspar megacrysts up to 3 cm in width and 10 cm in length, and contains irregular, angular or sub-rounded micromafic granular enclaves as well as xenoliths and large 'roof-pendants' of gabbroic composition derived from the Sarikaraman Ophiolite, which is the most representative member of the supra-subduction zone type of Central Anatolian Ophiolites. The Terlemez quartz monzonite is a calc-alkaline, metaluminous intrusion. It typically displays moderately developed negative Ba and Nb trace element anomalies and enrichment in light rare earth elements relative to heavy rare earth elements without any significant Eu, Sr and Ti anomalies. On the basis of field, petrographic and geochemical data, the Terlemez quartz monzonite has been classified as H-type (hybrid type), which requires significant input from a mantle-derived mafic magma. The intrusion represents the advanced stage of the post-collisional magmatism of the Central Anatolian Crystalline Complex. Unlike the other Central Anatolian Granitoids, the Terlemez quartz monzonite has a clear intrusive contact with the well studied Middle Turonian-Lower Santonian Sarikaraman Ophiolite. The K-Ar hornblende age obtained from the quartz monzonite (81.5 ± 1.9 Ma) is interpreted as the intrusion age. These data suggest a post-Early Santonian to pre-Early Campanian emplacement age for the supra-subduction zone type of Central Anatolian Ophiolites. The data further suggest that the post-collisional magmatism in Central Anatolia post-dates the emplacement of fore arc-type ophiolites onto the passive margin of the Tauride-Anatolide platform. The very short time interval between the formation and emplacement ages of supra-subduction zone-type ophiolites seems to be a very typical feature of the fore arc-type Eastern Mediterranean Ophiolites.
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    Geochemistry of volcanic rocks from the Cicekdag Ophiolite, Central Anatolia, Turkey, and their inferred tectonic setting within the northern branch of the Neotethyan Ocean
    (2000) Yaliniz K.M.; Floyd P.A.; Göncüoǧlu M.C.
    The Central Anatolian Ophiolites (CAO) comprise a number of little studied Upper Cretaceous ophiolitic bodies that originally represented part of the northern branch of the Neotethyan ocean. The Cicekdag Ophiolite (CO) is an dismembered example of this ophiolite group that still retains a partially preserved magmatic pseudostratigraphy. The following units (bottom to top) can be recognized: (1) layered gabbro; (2) isotropic gabbro: (3) plagiogranite; (4) dolerite dyke complex; (5) basaltic volcanic sequence; and (6) a Turonian-Santonian epi-ophiolitic sedimentary cover. The magmatic rock units (gabbro, dolerite and basalt) form part of a dominant comagmatic series of differentiated tholeiites, together with a minor group of primitive unfractionated basalts. The basaltic volcanics mainly consist of pillow lavas with a subordinate amount of massive lavas and rare basaltic breccias. Petrographic data from the least altered pillow lavas indicate that they were originally olivine-poor, plagioclase-clinopyroxene phyric tholeiites. Immobile trace element data from the basalt lavas and dolerite dykes show a strong subduction-related chemical signature. Relative to N-mid-ocean ridge basalt the Cicekdag basaltic rocks (allowing for the effects of alteration) have typical suprasubduction zone features with similarities to the Izu-Bonin Arc, i.e. enriched in most large-ion lithophile elements, depleted in high field strength elements and exhibiting depleted light rare earth element patterns. The geochemical characteristics are similar to other eastern Mediterranean Neotethyan SSZ-type ophiolites and suggest that the CO oceanic crust was generated by partial melting of already depleted oceanic lithosphere within the northern branch of the Neotethyan ocean. The Cicekdag body, along with the other fragmented CAO, is thus representative of the Late Cretaceous development of new oceanic lithosphere within an older oceanic realm.