Bulletin of the Mineral Research and Exploration (BMRE)
Not a member yet
1932 research outputs found
Sort by
EMPLACEMENT CHARACTERISTICS OF THE GNEISSIC GRANITES IN THE MENDERES MASSIF (WESTERN ANATOLIA) AND THEIR IMPLICATIONS ON THE TECTONIC EVOLUTION OF THE MASSIF: NEW FIELD OBSERVATIONS AND RADIOGENIC AGE DETERMINATIONS
No full textUnderstanding the ages and emplacement mechanism of the gneissic granites cropping out in large areas of the Menderes Massif has a critical importance in its tectonic evolution. Based on some radiogenic age data, the gneissic granites and the surrounding high-grade micaschists have been advocated to be the Precambrian Core Succession that was undergone high-grade metamorphism during the Pan-African Orogenesis. The micascists and marbles of Palaezoic-Mesozoic age have been defined as the Cover Succession unconformably overlying the core assemblages. It has also been indicated that during the Alpine Orogenesis and by the Main Menderes Metamorphism the core and cover successions were metamorphosed together in relatively lower grade conditions. Although the Menderes succession underlies a large region in the western Anatolia and display uncovered outcrops, in nowhere structural evidences of the unconformity between Pan-African core and the Palaeozoic-Mesozoic cover series has been reported. It is very difficult to expect the Alpine Orogeny to erase the older Pan-African structures to a point of undefinable state. In this study, we have new mapped and examined the boundary relations between the so-called Pre-Cambrian core and PalaeozoicMesozoic country succession around Dibek Mountain, Çine-Yataðan and Ýncirliova Dam site. In Dibek Mountain gneissic granites were emplaced, as migmatitic fronts, into the marble lenses-bearing micaschists paralel to their foliation planes. Along the Çine-Yataðan road, migmatitic syn-tectonic granitic fronts injected into and engulfed the Palaeozoic black marble, black chert and micaschist alternation. In this region, the Palaeozoic units pass upward into the Triassic metadetritals with mafic volcanic intervals and they in turn grade into the Mesozoic platform-type marble succession. In this location the granites intrude into the Palaezoic and Mesozoic series which were paleontologically dated in some other areas of the masif. Similarly around the Ýncirliova Dam site the augen gneisse-migmatitic granite complex intruded into a complete stratigraphic section from Palaeozoic to Triassic and the Mesosozic marble succession. New field data indicate that the high-temperature-type Barrowien Main Menderes Metamorphism caused a rejuvenation in the crust and granites with large migmatitic fronts emplaced syntectonically into the entire section of the masif from thick metadetrital units below and the PalaeozoicMesozoic cower series above. Precambrian and Alpine zircon ages determined from the gneissic granites could be explained by the rejuvenation and migmatism during the Main Menderes Metamorphism
TAVŞANLI ZONE: THE NORTHERN SUBDUCTED MARGIN OF THE ANATOLIDETAURIDE BLOCK
No full textThe Tavşanlı Zone constitutes the northern margin of the Anatolide-Tauride Block that has undergone high pressure-low temperature metamorphism during the Cretaceous. It is bounded in the north by the İzmir-Ankara suture and in the south by the rocks of the Afyon Zone. The Tavşanlı Zone is subdivided into four tectonic units. At the base there is the Orhaneli Group, which shows a regular stratigraphic succession that has underdone metamorphism at ~24 kbar pressure and 430-500 °C temperature during the Late Cretaceous (~80 Ma). From the base upward the Orhaneli Group consists of micaschist, marble and metabasite-metachertphyllite, and is tectonically overlain by ophiolitic mélange or directly by ophiolite. The ophiolitic mélange consists of basalt, chert, pelagic shale and limestone, and has undergone an incipient blueschist facies metamorphism. The ophiolite constitutes the topmost member of the tectonic stack. It consists mainly of peridotite (\u3e%90) with minor gabbro and pyroxenite, and is cut by isolated diabase dykes. In the western part of the Tavþanlý Zone all these tectonic units are intruded by Lower to Middle Eocene granodiorites, and in the eastern part of the Tavþanlý Zone the blueschists and ophiolite are overlain by Lower Eocene marine limestones. The northern margin of the Anatolide-Tauride Block was buried in an intra-oceanic subduction zone during the Campanian and Paleocene underwent HP/LT metamorphism. The blueschists were exhumed during ongoing subduction and prior to continental collision through a thrust fault at the base and a normal fault at the top. In terms of tectonic setting and the timing of the geological events, the Tavşanlı Zone exhibits close similarities to the Semail ophiolite and the underlying blueschists
THE TECTONOSTRATIGRAPHIC FEATURES OF THE BELEMEDİK TECTONIC WINDOW AND ITS SURROUNDINGS
No full textThe study area includes Belemedik and its vicinity located in the eastern part of Ecemiþ Fault Zone which constitutes the boundary between Central and Eastern Taurides.The area generally presents Belemedik Sequence belonging to Aladað Unit, Ophiolithic Melange and ophiolithic rocks belonging to Bozkýr Unit and Tertiary sediments overlying all these units. Within Belemedik Sequence, Late Devonian aged Küçükali, Carboniferous aged Belemedik, Early Permian aged Sarýoluk, Late Permian aged Kýzýlgeriþ and Yellice, EarlyMiddle Triassic aged Katarasý, Middle-Late Triassic aged Sarýyarma, Jurassic-Cretaceous aged Çamlýk and Yavça Formations were differentiated. In the previous studies on the vicinity of Belemedik, it was suggested that an incomplete Mesozoic series overlaying the Palaeozoic core and as a result of the erosion of this cover, a tectonic window was exposed. However, in this study, it was demonstrated that a complete Mesozoic series of Early Triassic-Late Cretaceous age overlaying the Palaeozoic rocks in the vicinity of Belemedik are presented and hence a tectonic window does not exist in the vicinity of Belemedik. In addition, it was determined that Belemedik Sequence displayed similar features with the rock associations of Aladað Unit in terms of lithological properties and the ages of the units it comprises. In the region, at the bottom of the Bozkýr Unit, which tectonically overlies the Belemedik Sequence, Late Senonian aged Kýzýlcadað Ophiolithic Melange and olistostrome are present. And, at the top of the Bozkýr Unit, Late Cretaceous aged Pozantý-Karsantý Ophiolithic Nappe is located. While the Pozantý-Ecemiþ Corridor formed by Ecemiþ Fault Zone is represented by Oligocene-Miocene aged units, the Adana Basin is represented by Paleocene-Late Miocene units.
THE USE OF TILT ANGLE IN GRAVITY AND MAGNETIC METHODS
No full textTilt angle method, which has been recently used in investigating the boundaries of structures, reveals useful information on deep and shallow structures. Tilt angle is expressed as the arctan value of the ratio of the vertical derivative of the potential field to its horizontal derivative. The method was applied to Kýrþehir-Ý31 Sheet. As a result, the presence of volcanites buried under terrestrial sediments was demonstrated.
MINERALOGICAL, PETROGRAPHICAL AND GEOCHEMICAL CHARACTERISTICS OF ELDIVAN OPHIOLITE (ÇANKIRI) HARZBURGITIC TECTONITES
No full textThe Eldivan Ophiolite is located at the central part of the Ýzmir-Ankara-Erzincan Ophiolitic Belt and between Þabanözü, Eldivan and Korgun towns. Ophiolite consists of volcanic-sedimentary series, metamorphic series, tectonites, cumulates and sheeted dikes from bottom to top. Tectonites, which are the main subject of the study, are generally represented by harzburgites and occassionally include dunite, pyroxenolite and chromitite levels. Harzburgites display of traces of plastic deformation (foliation, lineasyon, fold) A clear orientation in minerals can be observed as a result of in the tectonic sequence and grinding mechanisms. The degree of deformation decreases upwards. Harzburgites are generally composed of olivine (60-90%) and orthopyroxene (10-35%). Clinopyroxene is rarely observed in the lower levels. A decrease in the amount of orthopyroxene and an increase in chromite ratio is observed in the upper levels. The composition of olivines is usually forsterite and orthopyroxene is enstatite. A slight decrease in Mg content noticed towards top direction. Furthermore, a decrease in chromium and an increase in aluminum content in chromites is observed towards top in the upwards direction. This situation can be explained by difference in the primary composition of the upper mantle and degree of partial melting processes
THE GEOLOGY AND GEOCHRONOLOGY OF THE PAN-AFRICAN AND TRIASSIC METAGRANITOIDS IN THE MENDERES MASSIF, WESTERN ANATOLIA, TURKEY
No full textThe Menders Massif is a metamorphic complex cropping out on a large region in the Alpine orogenic belt in Western Anatolia. The massif mainly, is made up of a Precambrian basement and the overlying Palaeozoic-Early Tertiary cover series. The basement comprises Late Proterozoic metaclastics composed of paragneiss and high grade micaschists, syn to post tectonical Pan African orthogneisses that have intruded into them, and metagabbros which have partly turned into eclogitic form. Cover series unconformably overlying the basement are divided into two units, in Palaeozoic and Mesozoic-Early Tertiary ages. The basement and cover series were influenced by an effective Alpine contractional deformation and a regional metamorphism in Tertiary time. Geological and geochronological data in the Menderes Massif, indicate the presence of three acidic magmatic activities of i) Pan African, ii) Triassic and iii) Miocene in ages. The acidic magmatics forming the protoliths of Pan African orthogneisses can be divided into three main types according to their textural and mineralogical compositions as; 1) Biotite orthogneiss, 2) Tourmaline leucocratic orhogneiss and 3) Amphibole orthogneiss. The relations of primary granites of these orthogneisses present a clear intrusive contact relationship among them and with the metaclastics of late Proterozoic age. The contact relationships show that these orthogneiss types can be ordered as biotite orthogneisses, tourmaline leucocratic orthogneisses and amphibole orthogneisses ranging from old to young, with respect to relative aging. Although there has been some problems originating from the definition of samples dated in previous studies, it is noted that radiometric data mainly show a consistency with this relative relationship (biotite orthogneiss: 550-570 Ma; tourmaline leucocratic orthogneiss: 541-547 Ma and amphibole orthogneiss: 531 Ma). These radiometric data indicate that different orthogneiss types in the Massif are differentiated products of the same Late Proterozoic - Early Cambrian acidic magmatic activity. When the paleogeographical position of the Massif in Early Cambrian and the close temporal relation of the metamorphic stage of cover series and the acidic magmatism are assessed with the geochemical character of orthogneisses, this widespread magmatic activity with an average age of about 550 Ma which is related to the Pan-African orogenesis can be attributed to proccesses of closure of the Mozambique Ocean, collision of East and West Gondwanaland, crustal thickening and partial melting of the lower crust. Triassic leucocratic orthogneisses constitutes the second effective acidic magmatic activity in the Menderes Masif with dimensions of 6-7 km. These plutonic leucocratic oithogneisses in 6-7 km dimensions are exposed in Ödemiþ-Kiraz and Demirci-Gördes submassifs. They show well-preserved intrusive contact relationships with Late Proterozoic metaclastics of the Pan-African basement and with metasediments of Late Palaeozoic cover series. Geochemical data show that protoliths of leucocratic orthogneisses are in calc alkaline and S type in character. Based on single zircon Pb/Pb evaporation method, these were radiometrically dated as ranging from 227 to 246 Ma. These ages are interpreted as the age of emplacement of protoliths of orthogneisses in Middle Triassic. The existence of Early-Middle Triassic magmatic activity is widely known not only in the Massif but also at tectonical zones belonging to Anatolides, at Karaburun peninsula, in Cyclades and at inner Hellenides. When the regional character of Triassic magmatic activities is considered, it is suggested that there is a close genetical relationship between these leucocratic orthogneisses and Triassic magmatics. It is also considered that it can be attributed to the opening of Neothethys Ocean
APATITE-BEARING MAGNETITE DEPOSIT OF PINARBAŞI (ADIYAMAN); GEOLOGICAL, GEOCHEMICAL PROPERTIES AND ECONOMICAL POTENTIAL
No full textIn the near vicinity of the apatitebearing magnetite deposit of Pýnarbaşı Permianaged Malatya Metamorphites consisting of, from bottom to top, chlorite schists, cericite schists, calcschists and recrystallized limestones cover large areas. These folded and faulted metamorphic rocks, which thrust over the Eoceneaged Maden Complex, underwent one regional metamorphism and one subsequent retrograde metamorphism in the greenschist facies. Mineralizations associated with chloritesericite schists are in the form of magnetitebearing apatite lenses. The ore horizons, which reach a thickness of 15 m and have a northsouth strike, dip approximately 30 degrees to the west. In the field, massive, banded and disseminated ore types are distinguished. The most important ore mineral is magnetite. It is followed by hematite, siderite, goethite and specularite. The proportion of the fluorapatite, the most valuable gangue mineral, reaches up to 30% in some places. Quartz, calcite, chlorite and sericite are other common gangue minerals. Rarely, rutile, zircon, monazite and xenotime are also observed. There is a significant positive correlation between Fe, P2O5 and depth. The variograms reveal holeeffects which reflect orerock alternations. Frequency distributions of the elements are logarithmic. Magnetite reserves with an iron content of over 20% Fe are approximately 78 Mt. The average P2O5 concentration of these reserves having an average Fe tenor of 35% is 1.57%. The F concentration of 3.46% in apatite is significant. However, rare earth element (REE) concentration of apatite (900 ppm) and V concentration of magnetite (800 ppm) are low. This deposit defined as classic Kirunatype sedimentary apatitebearing magnetite deposit, is not considered to be economically mined
ACTUAL BLOEDITE MINERAL PRECIPITATION IN A SEASONAL LAKE IN ÇANKIRI-ÇORUM BASIN
No full textBloedite (Na2Mg(SO4)2.4H2O) which is an economically important sodium sulfate mineral currently precipitates through evaporation in Lake İshaklı, a small seasonal lake (playa lake) situated to the north of İshaklı Village (Bayat - Çorum) in Çankırı-Çorum Basin. Lake İshaklı, in which actual bloedite precipitation has been determined for the first time by this work in Turkey, extends in East-West direction and covers an area of approximately 220 000 m2 . During winter and spring months it becomes a lake with a depth of more than 2 m. However, during hot periods when evaporation becomes effective, the lake dries up and is covered with a white mineral crust. Mineralogical determinations, chemical analyses and SEM examinations were carried out on the representative samples taken from conspicuous zonings in the lake. According to the results of the analysis, it has been determined that the predominant mineral in the area is bloedite; however, thenardite (Na2SO4), very little halite (NaCI) and gypsum (CaSO4.2H2O) accompany this precipitation. The sodium sulfate crustification (bloedite + thenardite), which reaches an average thicknes of 3 cm over an evaporation area of approximately 187 500 m2 in Lake Ýshaklý, has economical potential with its proven reserve of about 12 500 tons
THE GEOARCHEOLOGY OF THE YENİKAPI EXCAVATION SITE IN THE LAST 8000 YEARS AND GEOLOGICAL TRACES OF NATURAL DISASTERS (İSTANBUL - TURKEY)
No full textDuring the excavations of the Istanbul Archaeological Museum for the Marmaray Project, which will connect two sides of the Bosphorus by rail tube tunnel, an ancient Byzantine Port (Port of Theodosius) was explored around Yenikapı, district of Istanbul. The aim of the study is to understand the stratigraphical sequence observed in the excavation site, to recognize the traces of natural events observed within the sequence and to reach the geoarcheological data that will provide contribution to the archeological studies by geological findings. The sequence studied in the Yenikapý Excavation site was divided into 9 different units. The sequence is transgressive from 1st to 7th unit and regressive from 7th unit, to upper part of the 8th unit. These investigated sequences have been deposited during the last 8000 years. 32 ancient shipwrecks were detected in three different geological layers of nine units which were dated to the 6th century, 7th, 8th, 9th centuries and 10th, 11th centuries respectively. The 4th unit was formed under the effect of an earthquake and following tsunami waves occurred in A.D. 557. It is considered that some of the districts of Istanbul which are very close to shore have submerged by the effect of tsunami waves during the earthquakes in A.D. 553 and 557. It was also considened that the reason of the sinlang of the was 25 Byzantine vessels a very strong storm that affected the coasts of Istanbul city. The traces of this storm are detected in 5th and 6th units
SEDIMENT CORE STUDIES ON THE NORTH ANATOLIAN FAULT ZONE IN THE EASTERN SEA OF MARMARA: EVIDENCE OF SEA LEVEL CHANGES AND FAULT ACTIVITY
No full textSediment cores BUC-10A and ÝZ-30 located on the North Anatolian Fault Zone (NAFZ), 12 km south of Büyükçekmece and Ýzmit Gulf in the eastern part of the Sea of Marmara, respectively, were studied to investigate tectonics and paleo-oceanographic processes, using sedimentological and geochemical methods. Total inorganic carbon (TIC as total calcium carbonate) and total organic carbon (TOC) contents in core BUC-10A range between 12.1-34.3 and 0.5-4.1 dry wt. %, respectively. The organic matter-rich sapropel unit was identified between 1.60 and 2.43 m below sea floor (bsf) in this core. The concentration ranges of the metals in core BUC-10A were: Cr: 55-96, Cu: 21-37, Ni: 63 39-74, Mn: 345-693, Pb: 19-34, Zn: 79-143 ppm and Fe: 2.30-3.15 dry wt. %. The concentration ranges of TOC, TIC, Cr, Cu, Fe, Ni, Mn, Pb and Zn in core İZ-30 were 0.40-1.70 %, 0.25-31 %, 39-87 ppm, 13-32 ppm, % 2.10-4.80, 18-41 ppm, 315-528 ppm, 7-21 ppm and 78-185 ppm, respectively. Chalcophile element (Fe, Mn, Cu, Pb, and Zn) concentrations in cores İZ-30 and BUC-10A give no evidence of hydrothermal activity. A debris flow characterized in core İZ-30 and dated 3276±48 a (calendar) before present (BP) was most likely triggered by tectonic activity in the Ýzmit Gulf. Sediments of 49.5 mbsf palaeoshoreline dated 9364±64 a BP was also identified in the same core from the İzmit Gulf