Türkiye Jeoloji Bülteni

Abstract: The fracture systems of Eocene age seem to be revealed volcanic materials and hydrothermal fluids byreactivating possibly in Upper Miocene. Thus hydrothermal neoformation minerals, the products of interactionof thermal water and volcanogenic compounds, are occurred in the west of Sivas. Kaolinite and I-S are dominantly developed in the white-yellow altered volcanic rocks in the Şeyhhalil, Canabdal, Kiremitli and Kavakareas. Besides jarosite, alunite, goyazite, gypsum, barite, hematite, goethite, pyrite, marcasite, gibbsite, sideriteand tridymite minerals are determined in these rocks. Alunite and goyazite from Canabdal area are derived fromK-feldspar. Jarosite appears in the areas observed no alunite and accompanies usually goethite. The alterationsofbiotite and/or opaque minerals are necessary for formation of this mineral. A formation type similar to tonsteins can be proposed for kaolinite and I-S. Here first stage is the hydrolysis of volcanic glass by acidichydrothermal solutions and then the synthesis ofkaolinite or I-S from an intermediate product such a hydratedAl-silicate gel is possibly postulated.

Abstract: This study comprises of modal and petrographical results of Elmedin hill reef and Kızılkaya hill reefcomplex that are situated approximately 4-5 km northeast of Mut town (Mersin). In the Mut basin, Mut formation, that contains reef limestone (Middle Miocene) has a lateral and vertical gradational contact with Köşelediformation which includes claystone-marl-clayey limestone alternation and deposited in among the reefs and relatively deeper region in the basin. The Mut formation unconformably overlies the Late Cretaceous limestone andBurdigalian aged Derinçay formation that contains fluvial and limnic deposits and Aqutanian-BurdigalianFakırca formation which contain limnic deposits.As a result of petrographical studies, three fades are distinguished in Kızılkaya hill reef complex andElmedin hill reef and surrounding sediments. According to modal analysis results, micrit: 60.4 %; sparit: 4.1 %;frame forming organisms: 18.7 %; intraclast: 5.3 %; other constituents: 11.5 % in average volume are found inthe base fades (wackestone-packstone). In reef core fades; in bindstone-framestone subfacies micrit: 26,4 %;sparit: 18.4 %; frame forming organisms: 43.5 %; intraclast: 3.5 %: other constituents: 8.1 %; in wackestonepackstone subfacies micrit: 48.8 %; sparit: 12.2 %; frame forming organism: 5.7 %; intraclast: 12.3 %; otherconstituents: 21.1 % are found. In sealing fades (wackestone-packstone) micrit: 54.8 %; sparit: 7.5 %; frameforming organism: 16.8 %; intraclast: 7.3 %; other constituents: 13.7 % are determined.Ratio of frame forming organisms (coral+red alga+bryozoa) were constant during the stable sea leveland suitable environmental condition. When high stand sea level; ratio of frame forming organism was relatively decreased, binding materials was increasing. Other constituents and depend on an effect of sea wave intraclastwere reach to significant ratio.

Abstract: 1 he northwest of Konya is covered by Neogene volcanic breccias, agglomerates, tuffites, tuffs and lavasof andesite, dacite and basaltic andesite. The basaltic andesites contain about 7-10% of olivine, 3-5 % clinopyroxene, 5-10 % orthopyroxene, 60-70 % plagioclase and 5-10 % opaque minerals while the andesitic lavasinclude 50-60 % plagioclase, 10-15 % hornblende, 5% biotite, 2 %, clinopyroxene, 1 % sanidine, 1 % quartz and3 % opaque minerals. Main constituents in the dacitic rocks are plagioclase (35-40%), quartz (10-15 %), hornblende (15-20 %), biotite (10-12 %), opaque minerals (2-3%) and sanidine (3 %). The plagioclase in dacites andandesitic rocks have oscillatory zoning and sieve texture .The volcanic rocks range in composition from basaltic andesites to dacites with calc-alkaline character.Co-variation of major and trace element contents suggest fractional crystallization of hornblende, plagioclase,pyroxene and titaniferous magnetite. The plagioclase fractionation is confirmed by a slight development of negative Eu anomaly. High LREE/HREE and L1LE/ HFSE ratios show that the samples were possibly formed froma subduction-related magma at active continental margin. The strong fractionated and riched REE patterns of therocks indicate that the formation of these rocks may have involved continental crust.

Abstract: Yeniköy Melange constituting the basement in southwest Thrace, is formed by various rock blocks metamorphised in blueschist and greenschist fades conditions. The main constitues of metamorphic rocks are glaucophane-lawsoniteschist, tremolite/actinolitefels, epidote-chloriteschist and serpentinites. Morover there existmetabasite, metachert, weakly recrystallized limestone and various volcanic rock blocks. This units is in the formsof tectonic melange and its age is Upper Cretaceous. The melange has limited amount of matrix material and ismainly build up of rock blocks. Yeniköy Melange is derived from basic origin magmatic rocks, under burial metamorphism conditions, resulted from subduction ofTntra-Pontide Ocean crust under the continental crust, whichis situated between Rodop-Pontide and Sakarya continents. During the Alpine orogeny two different metamorphic phase were effected the Yeniköy Melange. Firstly, the rock undergone high pressure/low temperature(HP/LT) metamorphism with blueschist fades (Ml) conditions. At the first metamorphic stage, the glaucophaneand lawsonite minerals were derived from metabasites. However in the M2 phase, the rocks types have experienced typical greenschist fades conditions. The minerals of this metamorphic stage are, chlorite, epidote, actinolite and albite. As a result of greenschist fades metamorphism, blueschist minerals, such as glaucophane rimmed by actinolite and lawsonite were partly replaced by epidote. For the HP/LT metamorphism (Ml),we can estimate a 6 to 10 kbars pressure and 250-400 oC temperature values. Nevertheles, in M2 phase wecould estimate 4-6 kbars pressure and 350-450 oC temperatures. In this way the mineral assemblageobserved rocks and their textural features of the Yeniköy Melange may indicate a polymetamorphic evolution in the PTt path. Likewise, the greenschist fades metamorphism partly overprints the blueschist metamorphism.