Türkiye Jeoloji Bülteni

Abstract: In the study area, where Devonian, Permo-Carboniferous, Jurassic, Cretaceous and Tertiary rocks crop out, volcanics produced through polyphase volcanism are the most abundant lithological units. The Devonian includes Pulur metamorphics that havelocally been intruded by Gümüşhane granite, whilst the Permo-Carboniferous overlying the Pulur metamorphics with an angularunconformity comprises coalbearing sediments. In the light of field data and major element analyses, the volcanics represented bybasalt, andesite, trachyte, dacite and rhyolite of the Liassic (Jurassic), Upper Cretaceous, Eocene and Miocene age groups, havebeen the main subject of this paper. Studies have revealed that most of these samples are calc-alkaline and alkaline, whilst only afew of them were specified as tholeiitic in composition. Except for several Liassic ones comprising entirely simatic, all samples ofthese volcanics, as the derivatives of magmas subjected to fractional crystallization, are rich in sialic material. The studies have alsoshown that the great majority of the volcanics in the region are "orogenic region volcanics" in character, whilst the rest are the products of rifting occurred in different times. 

Abstract: İnler Yaylası Pb-zn deposits are situated in an area 20 km NW of Şebinkarahisar (Giresun). The deposits are confined to a large fault zone in Upper Cretaceous volcanics. The mineralized veins strike NE-SW and E-W. Three main mineralized zones are present distinguished. These are Azak-Yarar mine, Aşçı mine and Karadeniz mine. The dominant minerals of the veins are sulphide minerals in the lower levels and these grade upwards in oxide, carbonate and sulphate minerals. The main mineral assemblage of the İnler Yaylası mineralizations are; sphalerite, galena, pyrite, chalcopyrite, fahlore group minerals, enargite, linneite, pyrhotite, alcocitite-covellite, klaprotite, tetradymite-telluro-bismuthinite, Bi-fahlore groups minerals, altaite, gold, magnetite and hematite. The gangue minerals are quartz, calcite, clay minerals, chlorite, hematite andbaryite.The mineralizations are accompanited with intense alteration zones. Associations of carbonates silica minerals and epidote+chlorite+silica minerals are repeated several times towards depths. This alternation is probably due to the compositional changes and represents hidrothermal alteration of mafic mineral rich dacitic and andesitic volcanics and mafic mineral-poor pyroclastics.

Abstract: The metamorphic rock succession between Kula-Ala§ehir region, Demirci-Gördes submassif, can be given, in ascending order,as follows; micaschists compraising gneiss levels and leuococratic metagranile bodies; gneiss, migmatites associated with granitesand acidic metavolcanites of the core series and garnet micaschists of the cover series. Also, metagabbro stock, approximentally Ikm in wide, and a number of metagabbro sills occur in the acidic metavolcanites.It was determined that the metagabbro stock represent some textural and mineralogical changes toward the core which were resulted from the highgrade metamorphism affected both the country rocks and metagabbros. These metaigneous rocks can be petrographically subdivided in three rock types from the margin to the core; garnet amphibolite, amphibolitic metagabbro and metagabbro. The metagabbros were completely converted to the garnet amphibolites at the marginal zone in which they were stronglyaffected by the metamorphism. In these zones were the rocks were strongly foliated parallel to those of the country rocks, the garnetamphibolites have a purely metamorphic mineralogy and texture. In the amphibolitic metagabbro zone, the primary igneous textureand mineralogy were partly preserved. In the inner parts of the stock, the metagbbros are remarkably free of metamorphic effectsand consist of "Plagioclase + Ortho I Clinopyroxene + Hornblende + Clinozoisite ± Garnet ± Biotite ± Sphene ± Opaquoxide". Anumber of metagabbro sills, up to 100 m in lenght, which were partly completely converted to garnet amphibolite occur in thecountry rocks around the metagabbro stock.At the nortlwr part of Alaşehir, these basic igneous rocks gabbroic in composition occuring in the core series of the MenderesMassif were contemporaneously subjected to highgrade metamorphism with the country rocks. It is obviously understood that, interms of the geological setting, structural features, mineralogical composition and textural evidence, the metagabbros, probablyPrecambrianJCambrian in age, which are exposed in Ala§ehir-Kula region have great similarities with the gabbros all over theMenderes Massif which are previously regarded to be Middle Mioce in age and post-metamorphic in character (According to thesenew evidences, it can be postulated that the gabbros which are exposed all over the Menderes Massif are of PrecambrianiCambrianin age and were subjected to high - grade metamorphism effected the Menderes Massif during the Middle Eocene time.

Abstract: The Kaletaş disseminated gold occurrence, hosted by thin-bedded, silty to sandy limestones, consists of siliceous lenses developed along permeable zones such as fault, fiacture and bedding planes. These were initially major inflow zones for hydr other mal fluids. Silicification occurs as replacement bodies and tiny veinlets. Gold is enriched in silicified limestones, especcially along zones ofextensive carbonate removal. Carbonate dissolution and silicification are two separate processes, both of which are resulted fromdifferent hydrothermal solutions. Carbonate removal is intensified along highly permeable zones. Argillic alteration characterizedby dominance ofillite is formed subsequent to mineralization. Oxidation of ore minerals and altered rocks are resulted in the formation of alunite, natrojarosite, kaolinite, limonite and native sulfur which eventually fill the pores of dissolved limestones. Realgarand orpiment postdate gold mineralization and are related to late-stage quartz veining. The gold deposition in the area of interest ismainly a factor of adsorption of gold on organic matter in silicified zones. Temperature decrease or mixing of gold-bearing hydrothermal fluid with meteoric fluid may also be an effective mechanism in gold precipitation. The Kaletaş gold occurrence is similar toCarlin-type deposits in carbonate hostrocks, alteration, geochemical signature and ore mineralogy, but is different in tectonic setting, being located in an island arc environment rather than a continental setting in which the Carlin gold deposits occur. 

Abstract: An olistostrome is an impotant tectonosedimentary unit common in melanges. Its (internal) geology and contact relationshipsprovide valuable information about the geological evolution and engineering geological evaluation of the area. In this respect, anarea of 105 sq km, including the Yayla olistostrome (a geological units in the Ankara melange), is mapped and its relationships withsurrounding units are investigated.The Yayla olistostrome is a member of the Ortaköy formation which has two other members, namely the Lower and Upper matadetritics. The oldest member, Lower metadetritic, deposited in a relatively shallow environment and it does not have any biogenic level in the study area. It has well preserved diabase dykes which cut schistosity as well as bedding. It is well observable in Eymir Lake basin. The Yayla olistostrome was placed somewhat later within the Upper metadetritic as a tectonosedimentary deposit whiledetritics were being deposited in a basin which was tectonically active and consequently high sedimentary energy environment.The blocks (olistoliths) of diabase, spilite, deformed pillow lavas, and different types of chert and limestone, metadetritics, andtheir binding materials; volcanic mudstone, calcilutite-calcirudite, and siliceous in places metallifereous materials are the mainconstituents of the Yayla olistostrome.Homoclinal, isoclinal, and in places overturned fods, small scale faults, and joints constitute the main structural elements in theOrtaköy formation which indicate that all three members have been suffered intensively from the Early Alpine orogenic events.

Abstract: Fe, Mn, Co, Pb, Zn, Cu and Hg contents of the soils along the coast between Akçaabat and Yomra are measuredand interpreted in this study. The elements exept Hg were determined by flame AAS. Mercury was analyzed by cold vaporization technique. All the elements but Hg show local anomalous areas. The detection limit ofHgfor the analyticalmethod employed is 0,005 ppm. Any anomalous areas ofHg are not a::, led in the soils of `study areas. The analysedelements snow following concentrations as Fe 8%; Mn 1%; Cu 100 ppm; Pb 250 ppm, Co 150 ppm, Zn 170 ppm andHg <0.005 ppm.

Abstract: 9 celestite occurences which arefound in Tertiary sediments of Sivas-Ulaş basin, are examined in this study. These celestites are divided in 3 groups according to the relationship between bedding types and the host rock. These groups are: 1. Celestite foundin carbonaceous units (void Jilling-zebroide), 2. Celestite found in detritial units (nodular). 3. Celestite Johnd in evaporitic units(massive) These occurrences are also divided in 3 main petrographic types according to their crystallization and microtextoral characteristics. These types are; a elongated-prismatic, b.tabular and c. fibrous-radial crystals.All these celestite types take place in diffrent levels of the Tertiary evaporitic section. According to the fluid inclusion studiescarried on these occurrences, the homogenization temperatures of voidfilling-zebroide celestites (type I) in Middle-Upper Eocene, concentrate between 320-360 C. nodular celestites (type 2) in Oligocene, between 260-290 C and massive celestites (types 3) in Middle Miocene between 220-270 C. The salinities ofthese types do not differfrom one to another and are about 14-23 % NaCI equivalent. These high salinity and temperature values support the idea ofhydrothermal effects during the formation of Tertiary celestite mineralizations at Sivas basin.

Abstract: The Başören area is located about 670 km. southeast of capital Ankara, within northwest margin of the eastern Tauride belt. Inthe studied area the principal rock units are; Karapınar Limestone (Upper Cretaceous), Kızılkaya ophiolites (Upper Cretaceous),Ardıçh syenitoids (Upper Cretaceous-Lower Paleocene), Alibeyli carbonatites (Middle-Upper Paleocene), Başören formation(Middle-Upper Eocene), Kepez volcanites (Middle-Upper Miocene).Karapınar limestone is overthrusted by ophiolites during Upper Cretaceous. Hie limestones are also intruded by syenitoids. Thecontact between limestones and syenitoids are abrupt. No contact metamorphism has been observed. The syenitoids are intruded bycarbonatites. Two varieties of carbonatite have been distinguished.The aegirine-fluorite-apalile carbonatite (CI) and fluorite-apatitecarbonatite (C2). Fertilization in syenitoids are caused by carbonatite emplacement. Başören formation is represented by conglomerate, sandstone and limestone. Kepez volcanites are represented by andesitic lava and pyroclastics and olivine basaltic lava.Britholite (/?ZsZs,Ca,Na)5[(Si,P)04]3 (OH,F) veinlets are confined to carbonatites. The mineral is thorian member. Britholite occurs in the form of fine grain aggregates. It is dark brown, has greasy luster, and empirical d=4,5669 gr/cm3` The optical propertiesare £= 1.771, W= 1.774, uniaxial negative. Chemical analyses reveal that the britholite has % 57,13 REO and %2.68 ThO->. Microprobe analyses of britholites reveal an empirical formula of;(^0,869 Cg 1,392 ^r0,U8 ^0,324 ^m0,060 ^0,030 ^0,168 `^l0,084 ^a 1,826 ^a0,040 0,08^ (^2,804 ?0.154 l-J0,042^(^ 12^ (OH lM F0()3)Britholites are assocciated with late stage fluorite-apatite carbonatite (C2) dykes injected during last stage of carbonatite intrusion.