The aim of this study is to define mineralogical and geochemical characteristics of phlogopite-pargasite enriched ultramafic-mafic cumulate rocks from Kuranç / ali (Kirsehir) and their implications for petrology and regional geological setting. The Kuranç / ali rocks, found within an allochthonous sliver, are representative for the isolated members of the Central Anatolian Ophiolites, derived from closure of Izmir-Ankara-Erzincan branch of Alpine Neotethys. The rocks overthrust the Metamorphic Ophiolitic Mé / lange (the uppermost part of the Central Anatolian Metamorphics) and cut by felsic dykes of the Late Cretaceous Central Anatolian Granitoids. The Kuranç / ali rocks are unusually enriched in phlogopite and pargasite with varying crystal sizes. They are also composed of diopsidic augite, plagioclase, rutile, ilmenite, sphene, apatite and pyrite. The rocks are divided into six types / clinopyroxenite, clinopyroxenite-with-hydrous minerals-plagioclase, phlogopitite, hornblendite, layered gabbro and diorite. Evaluation of detailed EMP data from constituent minerals of different rock types showed that phlogopite with high Fe2+-Fe3+-Al[6]-Ti, diopsidic-augite with high Ca-Al(t)-Ti, Si-undersaturated pargasite with high Al[4]-K-Na-Ti-contents and intercumulus plagioclase with a wide range of composition (an%=40.61-98.58) display unusual compositions. Substitution mechanisms and elemental variations of the minerals suggest crystallization from hydrous metasomatized mantle, high water pressure and oxygen fugacities during formation of the Kuranç / ali rocks. Major oxide, trace and rare earth element abundances of the rock units were used to evaluate petrological characteristics. Chemical and tectonic discrimination diagrams, and parallel multi-element and REE patterns with highly enriched in LILE and LREE relative to HREE and HFSE show strong calc-alkaline affinity with slight alkaline features. Troughs at Nb-Ta and Ti characterize the rocks but these elements are slightly enriched than N-MORB. The rocks show high LREE/HREE ratios. Both unusual mineralogical and geochemical features of the rocks show that the rocks were generated in an arc environment. Moreover, they require a mantle wedge source strongly influenced by metasomatic components (fluid/melt) derived from subducting slab and/or OIB-like alkaline melt. Comparison of the rocks with tectonically well-defined rocks displays that they are generated in an intra-oceanic arc environment, but owe a comparison with fore-arc back-arc Central Anatolian Ophiolites within supra-subduction zone environment revealed that Kuranç / ali rocks are different and generated in an arc basement.
Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/4/655178/index.pdf |
Date | 01 January 2003 |
Creators | Koksal(toksoy), Fatma |
Contributors | Goncuoglu, M. Cemal |
Publisher | METU |
Source Sets | Middle East Technical Univ. |
Language | English |
Detected Language | English |
Type | Ph.D. Thesis |
Format | text/pdf |
Rights | To liberate the content for public access |
Page generated in 0.0016 seconds