Ophiolitic Melange Research Articles

Paleostress inversion of fault-slip in the Ayhan Basin, Kırşehir Block (Turkey) since the Late Cretaceous: Insights into the Neotethys closure

Kırşehir Block, a large triangular continental domain exposed in Central Anatolia, is surrounded by ophiolitic melanges that mark former subduction zones associated with the closure of the northern and southern branches of the Neotethys Ocean. Notably, the Ayhan Basin, located in the inner part of the block, is one of the few locations containing a geological record from the Upper Cretaceous to the Pliocene. It provides a unique opportunity to examine the crustal deformation and the temporal and spatial stress distribution over the Central Anatolian orogen. This study encompasses a comprehensive analysis of the Ayhan Basin’s stratigraphy and structure, combined with the paleostress inversion solutions derived from over 400 fault-slip data. The findings reveal that the Ayhan Basin underwent three distinct tectonic phases: (1) ∼ NE-SW extensional phase from Late Cretaceous to Lutetian, which refers to the main basin-forming stress configuration. Importantly, this extensional phase is crucial to delineate the spatial extent of the concurrent collision in the north. (2) ∼ N-S compressional phase during the Lutetian, mainly governed by the shortening of the Kırşehir Block. This compressional phase caused the inversion of the inherited normal faults in the basin; and (3) ∼ NE-SW extensional phase active since the Late Miocene was accompanied by volcanism and uplift in the region. The Cyprus Slab’s southward retreat might be this extension’s triggering mechanism. Consequently, the temporal and spatial extent of the tectonic phases and their resultant deformations are crucial for understanding the underlying geodynamic processes and establishing their timing.

Determination of model maps for the potential distribution of Anatolian black pine (Pinus nigra Arnold.) in natural forest areas in the Central Black Sea region

Özdemir ŞENTÜRK 1*, Serkan GÜLSOY 2, Mehmet Güvenç NEGİZ 3, Fatih KARAKAYA 2 ORCID: https://orcid.org/0000-0003-2513-6070; https://orcid.org/0000-0003-2011-8324; https://orcid.org/0000-0002-6338-3307; https://orcid.org/0000-0002-6534-6382 1 Gölhisar Vocational School, Departmant of Forestry, Burdur Mehmet Akif Ersoy University, Gölhisar, Burdur, Turkey 2 Faculty of Forestry, Department of Forest Engineering, Isparta University of Applied Sciences, Isparta, Turkey 3 Sütçüler Prof. Dr. Hasan GÜRBÜZ Vocational School, Department of Forest Engineering, Isparta University of Applied Sciences, Sütçüler, Isparta, Turkey *Corresponding author: e-mail: osenturk@mehmetakif.edu.tr Abstract The purpose of this study was to determine potential distribution modeling and mapping of Anatolian black pine in the Vezirköprü district. Presence / absence data of the species was collected from 586 sample areas. Environmental variables (elevation, slope, bedrock, radiation index etc.) were obtained from the digital maps. In addition, climatic variables were downloaded from WorldClim database. Generalized Additive Model and Classification and Regression Tree were used for potential distribution modeling of the species. The validation value of Generalized Additive Model was 0.84 while the cross-validation test value was found to be 0.82. Also, the ROC values of the tree model were found to be 0.804 for the training data set and 0.750 for the testing data set. According to the Classification and Regression Tree method, the locations above 650 m and without meta-sandstone are suitable for the potential distribution of the species. Under the condition that there is meta-sandstone, the areas where the temperature is between 7.6-11.0 °C and the slope degree is more than 23% coincide with the potential distribution of the species. Also, Generalized Additive Model showed that places where gabbro, ophiolitic melange, serpentine, and mixed material were seen as main bedrock type, sloping sites where average elevation was from 600 to 1150 m and temperature is between approximately 8.5-11.3 °C were the most suitable conditions for the potential distribution of the species in the district. In both models, it was determined that especially rock formations, climatic variable, and altitude are effective in the potential distribution of the species. On the other hand, although there are some differences in the variables in the models, the potential distribution maps formed by these variables overlapped quite. As a result, the information obtained in the study is important for the forestry practices such as afforestation, regeneration and the monitoring the species under future climate change conditions. Keywords: generalized additive model; classification and regression tree; species distribution model; Vezirköprü

Fate of an oceanic plate in the Neo-Tethys intra-oceanic subduction system: Evidence from elemental and Rb/Sr – Sm/Nd isotopic systematics

We report the coexistence of normal mid-ocean ridge basalt (NMORB)-type and alkaline ocean island basalt (OIB)-type mafic volcanics from the Zildat Ophiolitic Mélange (ZOM), Indus Suture Zone (ISZ), eastern Ladakh Himalaya. Trace element modeling portrays chemically heterogeneous mantle sources, wherein blueschists and sub-alkaline mafic volcanics depict almost flat REE-patterns [(La/Sm)N = 1.04–2.9] and respectively <20 % and >20 % degrees of partial melting from a depleted spinel-lherzolite mantle source. In contrast, alkaline mafic volcanics depict enriched LREE-patterns [(La/Yb)N = 35–48] with <5 % degrees of partial melting from a transitional garnet-spinel lherzolite enriched mantle source. Since the prevalent hypothesis considers seamounts and island arc rocks of the subducting oceanic plate within the Neo-Tethys Ocean to be the protolith for the contemporaneous Shergol Ophiolitic Melange (SOM) blueschists. In contrast, ZOM blueschists depict different protolith signatures. The εNd(t = 140 Ma) values for ZOM blueschists (+3.7 to +7.4) and sub-alkaline mafic volcanics (+9.2 to +9.3) are analogous to present-day Indian Ocean NMORB, while for OIB-type mafic volcanics (+3.7 to +4.3) are comparatively lower and analogous to Hawaii and Kerguelen OIB. Therefore, the observed protolith decoupling in the contemporaneous blueschists suggest the involvement of different protolith contenders, which were partially off-scraped from of the subducting plate during prolonged deep subduction followed by exhumation along the ISZ.

Field and Petrographic Characteristics of Photang Thrust Sheet of Zanskar Tethys Himalaya, Ladakh, India

The Photang thrust sheet is a distinct complex of rocks that lies under the Spongtang ophiolite, showing almost complete ophiolite sequences. The pre-collision tectonic setting, emplacement age, mechanism of association of diverse litho-units within Spongtang klippe, and their regional correlation is still debatable and partially known. The controversy exists as to whether the ophiolite was obducted onto the northern passive margin of the Indian plate during the Eocene or the late Cretaceous. Moreover, the fundamental question emerges whether the Photang thrust sheet is a part of the independent Spong arc, has been tectonically derived from the Ophiolitic Melange Zone in the Dras island arc, or is a representative of the accreted seamounts of the Indus suture zone. This paper presents the application of fundamentals of field geology and petrography to understand the pre-collision tectonic setting of the Photang thrust sheet, Spongtang ophiolite, and associated rock sequences in the Photoksar region of the Zanskar Himalaya. Keywords: Photang thrust sheet, Spongtang ophiolite, Tectonic setting, Obduction, Ophiolitic Melange Zone, Indus suture zone, Himalaya

Hallaçlar Volkanitleri’nde (Bayramiç, Çanakkale) Stratejik Element Zenginleşmeleri

In this study, Hallaçlar Volcanites located in Bayramiç-Çanakkale region were evaluated in terms of strategic element contents. Mineralogical-petrographical and geochemical investigations were carried out on the samples which were taken from the outcrops with intense hydrothermal alteration. The stratigraphy of the study area consists of the Sütüven Formation (Kazdağı Metamorfites), Çetmi Ophiolitic Melange, Evciler Pluton and Hallaçlar Volcanites. The intensity of hydrothermal alterations gradually increases in Hallaçlar Volcanites towards to the ophiolitic rocks and the Evciler Pluton. As a result of the geochemical analyzes carried out, it was observed that the yttrium (Y), zirconium (Zr), thorium (Th), tin (Sn) and antimony (Sb) elements were enriched in the Hallaçlar volcanites. It can be concluded that these elements were enriched in the volcanites with the hydrothermal solutions leaching from the elder metamorphic rocks.

The Early Paleozoic Tectonic Framework and Evolution of Northern West Qinling Orogen: By Zircon U-Pb Dating and Geochemistry of Rocks from Tianshui and Sunjiaxia

The Tianshui-Sunjiaxia area is located in the connection zone of West Qinling Orogen and North Qilian Orogen, which could provide great insights into the amalgamation processes between the northern and southern blocks of China. Three subduction- and rift-related rocks gneissic granite from North Qilian arc-interarc belt (NQAI) granite and metabasalt from North Qinling back-arc basin (NQBA) are distinguished across the connection zone. The gneissic granite was generated by melts from older crustal materials of Longshan Group with the addition of a relatively juvenile basaltic source from the lower crust during the collision process. The Liwanxincun metabasalt reflects the mixing of the partial melting of the shallow asthenospheric mantle and the metasomatized mantle in a back-arc extension setting. The LA-ICP-MS zircon U-Pb dating of gneissic granite (068, 069) yields crystallization ages of 457.0 ± 1.6 Ma and 445.9 ± 2.1 Ma. The study area is divided into six tectonic units in Early Paleozoic time involving NQAI (Yanjiadian-Xinjie) continental arc, interarc rift basin (Maojiamo-Xiwali), continental arc (Chenjiahe-Wangjiacha); NQBA back-arc rift basin (Huluhe-Hongtubao), island arc and ophiolitic melange belt (North Qinling-Shangdan). A tectonic model is proposed in which the NQAI continental arc (Yanjiadian-Xinjie) might represent the early period of subduction of North Qilian Ocean (NQO) and the interarc rift is the product of the extension triggered by southward subduction of NQO. The ongoing subduction of NQO then leads to the formation of Chenjiahe-Wangjiacha continental arc, as well as the Hongtubao back-arc spreading ridge in NQBA back-arc basin (Huluhe). The tectonic evolution of the connection zone is closely associated with the closure of the North Qilian Ocean and North Qinling-Shangdan Ocean in the context of the convergence process of micro-continental blocks, including North China block, Longshan group and North Qinling Terrane.

Natural Radionuclide Levels and Radiological Hazards of Khour Abalea Mineralized Pegmatites, Southeastern Desert, Egypt

Arranged from oldest to youngest, the main granitic rock units exposed in Khour Abalea are metagabbros, cataclastic rocks, ophiolitic melange, granitic rocks, pegmatite and lamprophyre dykes. The presence of radioactivity associated with the heavy bearing minerals in construction materials—like granite—increased interest in the extraction process. As it turns out, granitic rocks play an important economic part in the examination of an area’s surroundings. The radionuclide content is measured by using an NaI (Tl)-detector. In the mineralized pegmatites, U (326 to 2667 ppm), Th (562 to 4010 ppm), RaeU (495 to 1544 ppm) and K (1.38 to 9.12%) ranged considerably with an average of 1700 ppm, 2881.86 ppm, 1171.82 ppm and 5.04%, respectively. Relationships among radioelements clarify that radioactive mineralization in the studied pegmatites is magmatic and hydrothermal. A positive equilibrium condition confirms uranium addition to the studied rocks. This study determined 226Ra, 232Th and 40K activity concentrations in pegmatites samples and assessed the radiological risks associated with these rocks. The activity concentrations of 226Ra (13,176 ± 4394 Bq kg−1), 232Th (11,883 ± 5644 Bq kg−1) and 40K (1573 ± 607 Bq kg−1) in pegmatites samples (P) are greater than the global average. The high activity of the mineralized pegmatite is mainly attributed to the presence of uranium mineral (autunite), uranophane, kasolite and carnotite, thorium minerals (thorite, thorianite and uranothorite) as well as accessories minerals—such as zircon and monazite. To assess the dangerous effects of pegmatites in the studied area, various radiological hazard factors (external, internal hazard indices, radium equivalent activity and annual effective dose) are estimated. The investigated samples almost surpassed the recommended allowable thresholds for all of the environmental factors.

Radar İnterferometri Teknikleri Kullanarak Derin Kompleks Heyelanların İzlenmesi: Karaoğlan Havzası (Mersin-Türkiye)

Landslide inventory mapping studies around Mersin and Erdemli regions of southern Turkey revealed that numerous old large-scale and recent small-scale landslides were presumably aroused in different time intervals. While the recent active landslides have been mostly triggered by excessive rainfall, old landslides are considered to be occurred by geomorphologic valley incision processes besides the other preparatory environmental conditions. The evaluation of the spatial distribution of old landslides present retrogressive, deep-seated with complex and rotational slides in the ophiolites and ophiolitic melange units comprising also overlying reefal limestones. In this study, surface deformations caused by landslides were evaluated using radar interferometry techniques for a specified period in Karaoglan catchment. Landslide related deformations were detected over radar images of L-band ALOS-PALSAR sensor for the years between 2007 and 2011. Landslides which are active are investigated in detail cross-sections. The mean displacement from differential interferogram cross-sections was measured 3.5 cm in LOS direction. Differential SAR interferometry for studied period depicts that the average rate of movement for the entire area is extremely slow with a rate of 10 mm/yr.

Strain geometry and structural analysis of the Oshnavieh ophiolite: A new segment of the Neo-Tethys puzzle

The closure of the Neo-Tethys ocean associated with the ophiolite obduction and the Oshnavieh ophiolite is the unknown part of the Neo-Tethys suture zone. Three well-known band ratio combinations applied to ASTER satellite image the result shows the ((2+4) /3, (5+7) /6, (7+9) /8) band ratio is the proper combination for the reorganization of rock units in the ophiolite regions. Principal component analysis of the (PC2, PC4 and PC 5) is well discriminated against to the rock unit contacts. The general trend of thrust faults is the NW-SE and dip direction is toward the NE. The rake of slickenline on the fault plane is 80°-90° and the mechanism of movement is the pure thrust. The shear sense indicator such as Z-type parasitic folds or mica-fish and S-C fabrics confirm right-lateral shearing sense in the shear zone. Strain geometry on the obducted slab evaluated by the shape of the mineral grains. In the shear zone strain ellipsoid shape is the prolate type and formed under constrictional regime, the Flinn K-value of these samples changes between 2.71 to 11.67 and lode ratio between -0.42 to -0.63. Most of the samples taken from the thrust fault zone located in the flattening zone and strain ellipsoid are pancake-shaped and formed under contractional regime the k-value varied between 0.44 to 0.80 and Lode ratio range is 0.32 to 0.5. The displacement in the thrust zone and shearing by the shear zone disrupted the ophiolite sequence and created an ophiolite melange.

Arsenic fate in upper Indus river basin (UIRB) aquifers: Controls of hydrochemical processes, provenances and water-aquifer matrix interaction

Major river basins of the Himalayas contain a significant amount of arsenic (As) in the geological matrix, which tends to contaminate the groundwater at a local and regional scale. Although As enrichment in Quaternary deposits has been linked to primary provenances (Himalayan orogeny), limited studies have reported As enrichment in bedrock aquifers. In the present study, the hard rock and groundwater samples were collected across the upper Indus river basin (UIRB), Ladakh to assess the hydrogeochemical processes and environments responsible for As mobilization and release. The higher As concentrations were found in Khardung volcanics followed by Ophiolitic melange, Dras volcanics, Nindam sandstone, and Nindam Shale. The variability in As concentration among different rock samples is largely governed by the presence of felsic minerals and the type of magmatic setting. The groundwater is less mineralized, with moderate electrical conductivity (EC), and weakly acidic to alkaline in nature. The results indicated that mineral weathering, dissolution, and active cation exchange reactions have a strong influence on the major ion chemistry of the groundwater. Redox-sensitive processes are influencing the As mobilization and release under reducing environmental conditions. As in groundwater poses a serious threat to human health hence awareness is urgent towards achieving sustainable As mitigation globally. The study provided a significant dataset to better understand the processes and environmental conditions responsible for hydrogeochemical evolution, sources of solutes, and As mobilization and release in groundwater which will help in sustainable water resource management policies and ecosystem restoration across the Himalayas.

Geochemistry and tectonic setting of Middle Ordovician MORB-like basalts in the Kunlun Orogen: implications for a back-arc environment

The Central Kunlun ophiolitic melange zone, northern Tibetan Plateau, represents a remnant of the Early Paleozoic oceanic lithosphere. The Middle Ordovician Longshigeng basalts (LBs) are located in south of this melange zone and have important significance for reconstructing the opening and subduction processes of the Proto-Tethys Ocean. This study presents petrological, whole-rock geochemical, and zircon U-Pb data for these basalts. LA-ICP-MS U-Pb zircon data indicate that these basalts formed ca. 463 Ma. Geochemically, the basalts are characterized by low SiO2 (47.00–50.63 wt%) and K2O (0.22–1.05 wt%), intermediate Mg# (47–57) and high TiO2 (1.51–2.72 wt%), and are identified as tholeiitic basalts. Their chondrite-normalized REE patterns feature slight enrichments in LREEs (LREE/HREE = 2.11–3.08) with mild Eu anomalies (δEu = 0.89–1.06), and their patterns are similar to the reference line of enriched mid-ocean ridge basalt (EMORB). The primitive mantle-normalized trace element diagrams also show similarities with EMORB and are characterized by overall enrichments in large ion lithophile and high field strength elements, without notable Nb, Ta, and Ti depletions. Combining these data with the tectonic discrimination diagrams, we infer that these rocks formed in a back-arc environment in response to the northward subduction of the Proto-Tethys Ocean (South Kunlun Ocean) in the East Kunlun region, northern Tibetan Plateau.

Investigation Of Petrological Characteristics Of The Upper Mantle In Hadji-Abad Ophiolitic Complex (South Of Iran): Based On Mineral Chemistry

The mantle peridotites of the Hadji-Abad ultramafic complex in Hormozgan province, show some petrological evolutions of the upper mantle of southern Iran. The complex includes harzburgite, lherzolite, dunite and chromitite. Evidences such as different generations of minerals, lobate boundaries between grains, elongation of cr-spinels and pyroxenes, incongruent melting related textures and exsolution lamellae of clinopyroxene in orthopyroxene show that the rocks in this complex first underwent high temperature-pressure in the upper mantle, and then emplaced in the crust. The chemical composition of chromites in the Hadji Abad dunites and chromitites is similar to that of boninite melts, while, the mineral chemistry of the harzburgitic and lherzolitic show that the host peridotites belong to the upper mantle and have been depleted from incompatible elements due to 15 to 20 percent partial melting. Geo-thermometric calculations reveal that the studied peridotites equilibriated in upper mantle and spinel-peridotite stability field. Using tectonomagmatic discrimination diagrams shows that the Hadji-Abad ultramafic complex is part of an oceanic lithosphere above suprasubduction zone which has undegone partial melting, high temperature deformations and mantle metasomatism processes associated with this environment. These evidences along with the geological and tectonic setting of the Hadji Abad complex adjacent to the Zagros thrust indicate that the complex probably was created in the mantle section under a back-arc basin and then tectonically emplaced as part of Esfandagheh-Hadji-Abad melange in the current situation during the upper Cretaceous. These informations confirm the dependence of the Esfandagheh-Hadji-Abad ophiolite melange on the Neotethyan oceanic lithosphere in southern Iran.

Historiography and FTIR spectral signatures of beryl crystals from some ancient Roman sites in the Eastern Desert of Egypt

Beryl (mostly emerald) was mined in Egypt since Antiquity, particularly the so-called “Cleopatra’s Mines” in the Eastern Desert were a major source of emerald in the world during the Roman era in northeast Africa. Emerald from the Nugrus belt is located at Sikait, Um Sleimat, Um Addebbaa and Um Kabu areas where the ancient mines are confined structurally and genetically to “schist-type” deposits as a part of the Neoproterozoic ophiolitic melange. At Homret Mikpid and Homr Akarem occurrences, non-gem beryl occurs in greisinized granites, pegmatites and quartz veins. Fourier transform infrared (FTIR) spectroscopy is able to distinguish Egyptian emeralds from non-gem beryls. Different types of H2O molecules and OH-groups can be identified in all especially at ~ 3435–3480 cm−1 as an indication of X-site occupancy of Na and vacancy (□) and to the Y-site M2+ and M3+ cation distribution. High wavenumber bands > 3600 cm−1, e.g. at ~ 3865–3988 cm−1 are characteristics of non-gem beryl only. Structural CO2 molecules are seen in both emerald and beryl at ~ 2360 cm−1. About 97–99% (at a wavelength range of 335–611 nm.) infrared reflectance of non-gem beryl is much higher (97–99%) whereas it never exceeds ~ 88% (at ~ 360 nm) in emerald.

Early Paleozoic suprasubduction complexes of the North Balkhash ophiolite zone (Central Kazakhstan): Geochronology, geochemistry and implications for tectonic evolution of the Junggar-Balkhash Ocean

The Junggar-Balkhash region in the west of the Central Asian orogenic belt (САОВ) comprises Paleozoic flysch, dismembered ophiolites, cherts, basalts, and olistostromes within its accretionary wedges. The North Balkhash ophiolite zone hosts serpentinite mélange with slivers of early Paleozoic chert, basalt, tuffaceous chert and volcaniclastic rocks. For the first time in the North Balkhash ophiolite zone, we recognized the Cambrian to Early and Middle Ordovician supra-subduction complexes in the plutonic fragments along with the previously known Middle to Late Ordovician OIB, N-MORB, chert and Late Ordovician island arc volcanic slivers.The documented records of North Balkhash supra-subduction complexes therefore span 100 m.y.-long evolution of the early Paleozoic intraoceanic accretionary wedge that went through several reorganizations due to incorporation of oceanic island and oceanic floor units in its front.The Early Cambrian is represented by Tesiktas ultramafic-gabbro-plagiogranite (c. 530 Ma) and Eastern Arkharsu gabbro-dolerite-plagiogranite (520 ± 2 Ma) with boninitic signature, interpreted to have formed in fore-arc setting. The Late Cambrian (498 ± 8 Ma) and Early Ordovician (476 ± 3 Ma) rocks are represented by island arc plagiogranite and diorite blocks in serpentinite melange along with slivers of Middle Ordovician dacite and andesite with lenses of chert rocks, as well as tuff and tuffaceous sandstone.Correlation of the North-Balkhash zone with its possible equivalents in Kazakhstan and NW China revealed the same duration, stages and tectonic settings. Particularly, we propose that the North Balkhash and West Junggar ophiolite melanges can be considered as fragments of the formerly single subduction-accretionary wedge, dextrally displaced for 250 km along the Junggar strike-slip fault during the late Paleozoic to the early Mesozoic.

Berit Dağları’nda (Kahramanmaraş) Litolojik ve Jeomorfolojik Faktörlerin Bitki Örtüsünün Dağılışına Etkisi

Bu çalışmanın amacı, Berit Dağları’nda litolojik ve jeomorfolojik faktörlerin bitki örtüsünün dağılışına etkisini açıklamaktır. Bu amaçla litolojik ve jeomorfolojik faktörlere ait alt kriterler ile bitki örtüsü katman haritaları oluşturulmuştur. Oluşturulan katman haritaları, Coğrafi Bilgi Sistemleri (CBS) teknikleriyle, ArcGIS 10.7 yazılımı kullanılarak çakıştırılmıştır. Çakıştırma işlemi sonunda her bir jeomorfolojik faktörün alt kriterinde bulunan bitki türü ve alanı tespit edilmiştir. Buna göre, Berit Dağları’nda 1600,01-1800 m yükseltileri arasındaki yüksek plato ve yamaçlarda şist anakayası üzerinde 45,01º> eğimli alanlarda kuzeydoğu, doğu ve güneydoğu yönlerde bitki çeşitliliği ve yoğunluğu fazladır. Buna karşılık 2400 m’den yüksek alanlardaki zirve düzlükleri üzerinde, ofiyolitik melanj ve 0-15ºeğimli güney ve güneybatı yönlü alanlarda bitki tür çeşitliliği ve yoğunluğu azdır. Çalışma sonucunda, Berit Dağları’nda litoloji, yerşekilleri, yükselti, eğim ve bakı gibi jeomorfolojik faktörlerin bitki örtüsü çeşitliliğini ve dağılışını etkileyen önemli unsurlar olduğu anlaşılmıştır.

Application of remote-sensing techniques in geological and structural mapping of Atalla Shear Zone and Environs, Central Eastern Desert, Egypt

The Atalla Shear Zone (ASZ) is one of the crucial megashears which are geometrically and kinematically akin to the Najd-Shear Corridor in the central Eastern Desert of Egypt. The Landsat-8 and ASTER-based mapping techniques integrated with extensive petrographic and structural-field investigations enhanced the geological and structural maps of the study area. The Neoproterozoic basement complex in the study area discriminated into ditinctive rock suites: Meatiq Group, ophiolitic melange, arc assemblage, syn- to late-tectonic granitoids, Dokhan Volcanics, Hammamat Sediments, post-Hammamat Felsites and post-tectonic granitoids. The true color composites (TCC) (4 3 2 for Landsat-8; 3 2 1 for ASTER), false color composites (FCC) (1 6 4, 1 6 7 and 7 5 1 for Landsat-8; 5 4 3 and 9 6 4 for ASTER), principal component analysis (PCA) (1 2 3, 3 2 1 and 6 4 2 for Landsat-8; 1 2 3 and 5 4 2 for ASTER), minimum noise fraction (MNF) (1 2 3 and 3 5 1 for Landsat-8; 1 2 4 and 3 2 1 for ASTER) and band ratios (BR) (6/2, 6/7, 6/5*4/3 and 7/6, 7/5, 5/3 for Landsat-8; 2/6, 7/5, 7/6 and 4/7, 3/4, 2/1 for ASTER besides the new created ratio 2/6, 7/5, 7/6) are the best combinations that demonstrate efficiency in discrimination of lithologic contacts and structural elements, using the spectral signature of different rock units. Moreover, the BR b7/b5, b5/b7 and b6/b4 of grey scale for Landsat-8 are used as a tool for mineral detection along with the spectral indices created to detect muscovite (b7/b6), ferrous silicates b5/b4 (biotite, chlorite and amphiboles) and ferrous iron b5/b3 (mafic minerals). The automatic lineament extraction utilizing the SRTM data advocated the role of NE- to NNE-trending lineaments in the tectonic framework of the study area. The structural fabric of the study area is evaluated in three main structural domains: Meatiq (MD), Atalla Shear Zone (ASZD) and Wadi Hammamat (WHD). The pronounced structural implication is the transposition of NE-oriented fabric in MD into NW-oriented penetrative shear-related fabric, fully in the ASZD and partly in WHD. The combination of transcurrent shearing with ENE-directed shortening along the ASZ that was resulted in noteworthy transpressive structures resemble in many respects those observed in the Ajjaj Shear Belt in Western Arabia. Among these structures are shear zone-related folds, imbricated thrust sheets, antiformal stacks and thrust duplexes. The deformation history of the investigated area proposed four phases of deformation (D1–D4). It depicts a long lasted deformational event covering the main accretion-collision phases concurrent with the E-W assembly of Gondwana, and the subsequent post-collision Najd-related transpressional phase which resulted in several major left-lateral transcurrent shear zones along with the exhumation of gneissic core complexes in the Arabian-Nubian Shield.

Akkise-Yalıhüyük (Konya) Arasının Stratigrafisi

In the vicinity of Akkise-Yalıhüyük (south of Konya) region, the Mesozoic sequence of the autochthonous Geyikdağı and the allochthonous Bozkır units is overlain by Neogene-Quaternary Neo- autochthonous cover units with an angular unconformity. Geyikdağı Unit is represented by Late Cretaceous Saytepe formation cosisting of abundant rudist neritic carbonates at the bottom and Campanian-Maastrihtian Alan formation made up of cherty, clayey pelagic limestone and marls at the top. These autochthonous units are overlain by Maastrihtian Hatip ophiolitic melange forming the lower tectonic zone of the allochthonous Bozkır unit. The second allochthonous tectonic unit in the region is represented by Boyalıtepe formation including Late Cretaceous pelagic deposits such as cherty limestone, clayey limestone-marl and radiolarite. The upper allochthonous package of the study area is also represented by the Middle Triassic-Jurassic Gencek formation consisting of medium-thick bedded, abundantly jointed neritic carbonate. The boundaries of autochthonous and allochthonous and Neo-autochthonous rocks in the region are generally faulted. Therefore, the semi-peneplene-peneplene areas of the region are in the form of a depression area. As a result of lacustrine transgression in the Miocene-Early Pliocene period, lacustrine deposition environments were formed in these depression areas. Therefore, today, some lacustrine sediments such as gravelly-sandy-muddy detritics (Sille formation), muddy-clayey carbonates (Ulumuhsine formation) and volcano-sedimentary units (Küçükmuhsine formation) and also dacitic-andesitic volcanics (Erenlerdağı volcanics) are seen in these depression areas. The newest deposits of the study area are the foothill-alluvial fan deposits (Topraklı formation) which were deposited in Late Pliocene-Pleistocene and alluvials in Holocene age.

Discovery of eclogites in Jinsha River suture zone, Gonjo County, eastern Tibet and its restriction on Paleo-Tethyan evolution

ABSTRACT As the important component of the eastern Tethys tectonic region, the Jinsha River-Ailao Mountain suture zone is often considered to be an ophiolitic melange belt. However, the P-T-t path and chronological framework of the metamorphic evolution in the collisional orogenetic process of this zone are still poorly understood owing to the lack of metamorphism research of symbolic high-pressure rocks. During a regional geological survey on a scale of 1 : 50000 in Gonjo County, Tibet Autonomous Region involved in this paper, (retrograde) eclogites lenses of different scales were found in Jinsha River suture zone, eastern Tibet for the first time. The (retrograde) eclogites can be divided into garnet-albite-chlorite-actinolite schists and eclogites according to retrograde degrees. The mainly mineral components of eclogites include garnet (45%–50%), clinopyroxene (about 25%), and hornblende (5%–10%) primarily, and biotite, quartz, rutile, and muscovite secondarily. According to the data of electron probe micro analysis (EPMA), clinopyroxenes feature high content of Na2O (5.6%–6%) and corresponding jadeite (Jd) molecules of 37%–44%, and they fall within the omphacite region in Quad-Jd-Ae diagram. The temperature and pressure of the metamorphism at peak are P≈2.2–2.34 GPa and T≈622–688 °C respectively as measured with geobarometry Grt-Omp-Phe and geothermometer Grt-Omp. This will provide a new reference for the understanding of Paleo-Tethyan evolution. In this paper, two samples of eclogites were chosen for LA-ICP-MS zircon U-Pb dating and their 206Pb/238U ages obtained are 240 ± 3 Ma and 244 ± 1 Ma respectively. Furthermore, the zircons feature extremely low Th/U ratio (

Formation analysis of Maglajci-Moštanica ophiolytic zones in the North of Kozara for the use of rocks in construction

Based on the field work and laboratory research, the basic geological characteristics of the ophiolitic melange of northern Kozara are presented, with an emphasis on the Maglajci ophiolitic block. Criteria for separations of formations were established and then applied in the analysis, especially those geologically directly recognizable in the field and outcrops, so one ore formation with two ore subformations was separated in the Maglajci block. In the central zone of block, the basalt outflows and diabase are dominant, while in the south of the block it is an outflow basaltic sequence of the ocean floor with the acidic differences of rhyolites and keratophyres. The second subformation also includes the Moštanica and Vojkova Bloc as a whole. The ore bearing formation is evaluated as a medium to low perspective formation, while parts of the Maglajci block with a massive to brecciated outflow are highly perspective terrain. There are rocks of good physical-mechanical characteristics and they meet the most requesting standards for road building. The results of formation analysis have denied a prior prognosis of ore bearing characteristics of this area, because it was thought that the ophiolitic blocks was built almost exclusively of diabase, and that the fields with those blocks are equally and good perspective for researching the deposits of construction stone.

Origin and geochemical evolution of groundwaters at the northeastern extend of the active Fethiye-Burdur fault zone within the ophiolitic Teke nappes, SW Turkey

Thermal and nonthermal, mineral and non-mineral spring waters in different physical and chemical characters occur along the active Fethiye-Burdur fault zone (FBFZ) in the southwestern Turkey and discharge mainly within the supra-subduction-type ophiolitic units of the Teke nappes. This research aims to determine the physical and hydrogeochemical characteristics, origin, and geochemical evolution of the groundwaters discharging from the same lithology and tectonic zone within the northeastern extend of the active Fethiye-Burdur fault zone. A total of representative nine groundwater samples were collected from the study area. Of which, one of the samples is thermal, and others are nonthermal groundwaters. One of the nonthermal groundwaters is mineral water type, and the other one is hyperalkaline (pH > 10). Based on the analytical results, the waters in the study area are divided into six different groundwater facies: (i) Mg-Ca-HCO3-SO4, (ii) Mg-HCO3-CO3, (iii) Ca-HCO3, (iv) Ca-Mg-HCO3, (v) Mg-HCO3, and (vi) Ca-Na-Cl-CO3 facies. The chemical characteristics of the groundwaters are mainly related to mineralogic and hence chemical composition of sub-surface rocks, residence time of the groundwater, and water-rock intereactions, whether or not the conditions closed to CO2. Neutral to moderate alkaline (pH 10) Ca-Na-Cl-CO3-type waters within deeper ultramafic rock aquifers under the conditions closed to CO2. Mainly altered mafic-ultramafic silicates and carbonate rocks are the major sources of mineralization in the study area. On the other hand, H2S (most probably magmatic origin) reacted with carbonate rocks underlying the ophiolitic melange units produced CO2(g). Dissolution of CO2 within groundwaters is thought to cause arising of acidic conditions, higher degree dissolution of mafic-ultramafic silicates, and mineral water formation.