Geological features and marble production qualities of Western Turkey

Purpose. Isparta Angle occurs along the Mesozoic carbonate axis. Carbonated rocks forming the Taurus belt are continuous with allochthonous and autochthonous features. The rocks in the region are abnormally contacted with each other and can be found as allochthons on each other. The contacts between the tectono-stratigraphic units are commonly tectonic with the carbonate platforms forming the autochthonous basement to the west and east. For this reason, the initial relations between the rock masses and their initial geographical locations are not known. Methods. Some of the carbonated rocks show similar characteristics to each other in terms of sedimentation environment, stratigraphic relations and some other characteristics; but they are separated from each other by different characteristics throughout the belt. Findings. In this study, relationships between mass and material properties of marbles, which are produced in the allochthonous and autochthonous parts of the carbonated rocks in the western part of the Taurus belt, were investigated. Originality. As a result of this study, it has been determined that the mass and material characteristics of autochthonous limestones are better in quality than those of allochthonous limestones. Practical implications. Marble production qualities and block efficiency of allochthonous and autochthonous rocks have been evaluated.Мета. Виявлення геологічних особливостей залягання і властивостей автохтонних та алохтонних карбонатних порід Західної Туреччини для можливості їх промислового освоєння. Методика. Аналіз геологічної й тектонічної карт Південно-Західної Туреччини для вивчення стратиграфічних і структурних особливостей автохтонних та алохтонних карбонатних порід. Досліджено фізико-механічні властивості карбонатних порід Таврського поясу. Міцність зразків на розтяг були виконані відповідно до процедур, рекомендованих ISRM. Програма лабораторних випробувань включала визначення природної маси одиниці, водонасиченості, пористості, міцності на одноосьове стиснення, втрати на стирання. Результати. Відзначено, що у Таврському поясі карстифікація і багатошарові надвиги, що впливають на автохтонні вапняки й пов’язані з ними системи розломів і тріщин зсуву, є провідними факторами, які безпосередньо впливають на виробництво мармуру та вихід блоків у регіоні. Надана кількісна оцінка фізико-механічним властивостями алохтонних та автохтонних карбонатних порід. Акцентується увага щодо необхідності вимірювання на поверхнях порід системи тріщинуватості й за допомогою комп’ютерної обробки визначення ідеальних розмірів блоків у процесі видобутку. Встановлено, що для збільшення виходу блоків під час роботи їх необхідно різати перпендикулярно домінуючим тріщинам і поверхням руйнування. Рекомендується всі необхідні стратиграфічні вимірювання проводити у польових умовах і в разі, якщо у досліджуваній зоні є карстифіковані й заповнені зони, вони повинні бути враховані у стратиграфічних картах і розрізах. Наукова новизна. Для умов Таврського поясу встановлено, що масові та матеріальні характеристики автохтонних вапняків перевершують за якістю характеристики алохтонних вапняків, і вони можуть розглядатися як першочергові родовища для видобутку блочного каменю відкритим способом. Практична значимість. Проведення інженерно-геологічних робіт до процесу видобутку мармурового блочного каменю дозволить уточнити запаси й підвищити привабливість родовища до освоєння, а також знизити майбутні виробничі витрати шляхом визначення необхідної структури виробництва відповідно до даних досліджень.Цель. Выявление геологических особенностей залегания и свойств автохтонных и аллохтонных карбонатных пород Западной Турции для возможности их промышленного освоения. Методика. Анализ геологической и тектонической карт Юго-Западной Турции для изучения стратиграфических и структурных особенностей автохтонных и аллохтонных карбонатных пород. Исследованы физико-механические свойства карбонатных пород Таврского пояса. Прочность образцов на растяжение были выполнены в соответствии с процедурами, рекомендованными ISRM. Программа лабораторных испытаний включала определение естественной массы единицы, водонасыщенности, пористости, прочности на одноосное сжатие, потери на истирание. Результаты. Отмечено, что в Таврском поясе карстификация и многослойные надвиги, воздействующие на автохтонные известняки и связанные с ними системы разломов и трещин сдвига, являются ведущими факторами, непосредственно влияющими на производство мрамора и выход блоков в регионе. Дана количественная оценка физико-механическим свойствам аллохтонных и автохтонных карбонатных пород. Акцентируется внимание о необходимости измерения на поверхностях пород системы трещиноватости и при помощи компьютерной обработки определения идеальных размеров блоков в процессе добычи. Установлено, что для увеличения выхода блоков во время работы их необходимо резать перпендикулярно доминирующим трещинам и поверхностям разрушения. Рекомендуется все необходимые стратиграфические измерения производить в полевых условиях и в случае, если в исследуемой зоне имеются карстифицированные и заполненные зоны, они должны быть учтены в стратиграфических картах и разрезах. Научная новизна. Для условий Таврского пояса установлено, что массовые и материальные характеристики автохтонных известняков превосходят по качеству характеристики аллохтонных известняков, и они могут рассматриваться как первоочередные месторождения для добычи блочного камня открытым способом. Практическая значимость. Проведение инженерно-геологических работ до процесса добычи мраморного блочного камня позволит уточнить запасы и повысить привлекательность месторождения к освоению, а также снизить будущие производственные потери путем определения подходящей структуры производства в соответствии с данными исследованиями.The authors would like to thank the anonymous reviewers for their valuable comments and suggestions to improve the quality of the paper. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors

Rifting and arc-related early Paleozoic volcanism along the North Gondwana margin: geochemical and geological evidence from Sardinia (Italy)

Three series of volcanic rocks accumulated during the Cambrian to Silurian in the metasediment-dominated Variscan basement of Sardinia. They provide a record of the changing geodynamic setting of the North Gondwana margin between Upper Cambrian and earliest Silurian. A continuous Upper Cambrian–Lower Ordovician succession of felsic submarine and subaerial rocks, dominantly transitional alkaline in character (ca. 492–480 Ma), is present throughout the Variscan nappes. Trace element data, together with Nd isotope data that point to a depleted mantle source, indicate an ensialic environment. A Middle Ordovician (ca. 465 Ma) calc-alkaline bimodal suite, restricted to the external Variscan nappes, overlies the Sardic Unconformity. Negative ϵNdi values (−3.03 to −5.75) indicate that the suite is a product of arc volcanism from a variably enriched mantle. A Late Ordovician–Early Silurian (ca. 440 Ma) volcano-sedimentary cycle consists of an alkalic mafic suite in a post-Caradocian transgressive sequence. Feeder dykes cut the pre-Sardic sequence. The alkali basalts are enriched in Nb-Ta and have Zr/Nb ratios in the range 4.20–30.90 (typical of a rift environment) and positive ϵNdi values that indicate a depleted mantle source. Trachyandesite lavas have trace element contents characteristic of within-plate basalt differentiates, with evidence of minor crustal contamination

U-Pn geochronology of deformed metagranites in central Sutherland, Scotland: evidence for widespread late Silurian metamorphism and ductile deformation of the Moine Supergroup during the Caledonian orogeny

Within the Caledonides of central Sutherland, Scotland, the Neoproterozoic metasedimentary rocks of the Moine Supergroup record NW-directed D2 ductile thrusting and nappe assembly, accompanied by widespread tight-to-isoclinal folding and amphibolite-facies metamorphism. A series of metagranite sheets which were emplaced and penetratively deformed during D2 have been dated using SHRIMP UâPb geochronology. Zircon ages of 424 8 Ma (Vagastie Bridge granite), 420 6 Ma (Klibreck granite) and 429 11 Ma (Strathnaver granite) are interpreted to date emplacement, and hence regional D2 deformation, during mid- to late Silurian time. Titanite ages of 413 3 Ma (Vagastie Bridge granite) and 416 3 Ma (Klibreck granite) are thought to date post-metamorphic cooling through a blocking temperature of c. 550â 500 8C. A mid- to late Silurian age for D2 deformation supports published models that have viewed the internal ductile thrusts of this part of the orogen as part of the same kinematically linked system of forelandpropagating thrusts as the marginal Moine Thrust Zone. The new data contrast with previous interpretations that have viewed the dominant structures and metamorphic assemblages within the Moine Supergroup as having formed during the early to mid-Ordovician Grampian arcâcontinent orogeny. The mid-to late Silurian D2 nappe stacking event in Sutherland is probably a result of the collision of Baltica with the Scottish segment of Laurentia

Thermal structure and exhumation history of the Lesser Himalaya in central Nepal

The Lesser Himalaya (LH) consists of metasedimentary rocks that have been scrapped off from the underthrusting Indian crust and accreted to the mountain range over the last ~20 Myr. It now forms a significant fraction of the Himalayan collisional orogen. We document the kinematics and thermal metamorphism associated with the deformation and exhumation of the LH, combining thermometric and thermochronological methods with structural geology. Peak metamorphic temperatures estimated from Raman spectroscopy of carbonaceous material decrease gradually from 520°–550°C below the Main Central Thrust zone down to less than 330°C. These temperatures describe structurally a 20°–50°C/km inverted apparent gradient. The Ar muscovite ages from LH samples and from the overlying crystalline thrust sheets all indicate the same regular trend; i.e., an increase from about 3–4 Ma near the front of the high range to about 20 Ma near the leading edge of the thrust sheets, about 80 km to the south. This suggests that the LH has been exhumed jointly with the overlying nappes as a result of overthrusting by about 5 mm/yr. For a convergence rate of about 20 mm/yr, this implies underthrusting of the Indian basement below the Himalaya by about 15 mm/yr. The structure, metamorphic grade and exhumation history of the LH supports the view that, since the mid-Miocene, the Himalayan orogen has essentially grown by underplating, rather than by frontal accretion. This process has resulted from duplexing at a depth close to the brittle-ductile transition zone, by southward migration of a midcrustal ramp along the Main Himalayan Thrust fault, and is estimated to have resulted in a net flux of up to 150 m^2/yr of LH rocks into the Himalayan orogenic wedge. The steep inverse thermal gradient across the LH is interpreted to have resulted from a combination of underplating and post metamorphic shearing of the underplated units

Exhumation history of eastern Ladakh revealed by Ar-40/Ar-39 and fission-track ages: the Indus River-Tso Morari transect, NW Himalaya

Fission-track and Ar-40/Ar-39 ages place time constraints on the exhumation of the North Himalayan nappe stack, the Indus Suture Zone and Molasse, and the Transhimalayan Batholith in eastern Ladakh (NW India). Results from this and previous studies on a north-south transect passing near Tso Morari Lake suggest that the SW-directed North Himalayan nappe stack (comprising the Mata, Tetraogal and Tso Morari nappes) was emplaced and metamorphosed by c. 50-45 Ma, and exhumed to moderately shallow depths (c. 10 km) by c. 45-40 Ma. From the mid-Eocene to the present, exhumation continued at a steady and slow rate except for the root zone of the Tso Morari nappe, which cooled faster than the rest of the nappe stack. Rapid cooling occurred at c. 20 Ma and is linked to brittle deformation along the normal Ribil-Zildat Fault concomitant with extrusion of the Crystalline nappe in the south. Data from the Indus Molasse suggest that sediments were still being deposited during the Miocene

Crustal structure beneath the Trondelag Platform and adjacent areas of the Mid-Norwegian margin, as derived from wide-angle seismic and potential field data

The outer mid-Norwegian margin is characterized by strong breakup magmatism and has been extensively surveyed. The crustal structure of the inner continental shelf, however, is less studied, and its relation to the onshore geology, Caledonian structuring, and breakup magmatism remains unclear. Two Ocean Bottom Seismometer profiles were acquired across the Trøndelag Platform in 2003, as part of the Euromargins program. Additional-land stations recorded the marine shots. The P-wave data were modeled by ray-tracing, supported by gravity modeling. Older multi-channel seismic data allowed for interpretation of stratigraphy down to the top of the Triassic. Crystalline basement velocity is ~6 km s-1 onshore. Top basement is difficult to identify offshore, as velocities (5.3-5.7 km s-1) intermediate between typical crystalline crust and Mesozoic sedimentary strata appear 50-80 km from the coast. This layer thickens towards the Klakk-Ytreholmen Fault Complex and predates Permian and later structur-ing. The velocities indicate sedimentary rocks, most likely Devonian. Onshore late- to post-Caledonian detachments have been proposed to extend offshore, based on the magnetic anomaly pattern. We do not find the expected correlation between upper basement velocity structure and detachments. However, there is a distinct, dome-shaped lower-crustal body with a velocity of 6.6-7.0 km s-1. This is thickest under the Froan Basin, and the broad magnetic anomaly used to delineate the detachments correlates with this. The proposed offshore continuation of the detachments thus appears- unreliable. While we find indications of high density and velocity (~7.2 km s-1) lower crust under the Rås Basin, similar to the proposed igneous underplating of the outer margin, this is poorly constrained near the end of our profiles. The gravity field indicates that this body may be continuous from the pre-breakup basement structures of the Utgard High to the Frøya High, suggesting that it could be an island arc or oceanic terrane-accreted during the Caledonian orogeny. Thus, we find no clear evidence of early Cenozoic igneous underplating of the inner part of the shelf

Polyphase thrust tectonic in the Barberton greenstone belt

In the circa 3.5 by-old Barberton greenstone belt, the supracrustal rocks form a thick and strongly deformed thrust complex. Structural studies in the southern part of the belt have shown that 2 separate phases of over-thrusting (D sub 1 and D sub 2) successively dismembered the original stratigraphy. Thrust nappes were subsequently refolded during later deformations (D sub 3 and D sub 4). This report deals with the second thrusting event which, in the study region appears to be dominant, and (unlike the earlier thrusting), affects the entire supracrustal pile. The supracrustal rocks form a predominantly NE/SW oriented, SE dipping tectonic fan (the D sub 2 fan) in which tectonic slices of ophiolitic-like rocks are interleaved with younger sedimentary sequences of the Diepgezet and malalotcha groups. Structural and sedimentological data indicate that the D sub 2 tectonic fan was formed during a prolonged, multi-stage regional horizontal shortening event during which several types of internal deformation mechanisms were successively and/or simultaneously active. Movement appears to have been predominantly to the NW and to the N. During D sub 2, periods of quiescence and sedimentation followed periods of thrust propagation. Although the exact kinematics which led to the formation of this fan is not yet known, paleoenvironmental interpretations together with structural data suggest that D sub 2 was probably related to (an) Archean collision(s)