scholarly journals Late Palaeozoic extensional volcanism along the northern margin of Gondwana in southern Turkey: implications for Palaeotethyan development

2021 ◽  
Author(s):  
Alastair H. F. Robertson ◽  
Osman Parlak ◽  
Timur Ustaömer
Keyword(s):  
Continental Margin ◽  
Carbonate Platform ◽  
Late Carboniferous ◽  
Geochemical Data ◽  
Low Grade ◽  
Thrust Sheet ◽  
The North ◽  
Late Palaeozoic ◽  
Granitic Magmatism ◽  
North Gondwana

AbstractThe Late Palaeozoic–Early Mesozoic Tethyan development of the Eastern Mediterranean region remains debatable, especially in Turkey, where alternative northward and southward subduction hypotheses are proposed. Relevant to this debate, new whole-rock geochemical data are provided here for early Carboniferous (Late Tournaisian-Late Visean; c. 340–350 Ma) tuffaceous sedimentary rocks within the Çataloturan thrust sheet (Aladağ nappe), eastern Taurides. The tuffs accumulated from evolved alkaline volcanism, variably mixed with terrigenous and radiolarian-rich sediments. In addition, Late Palaeozoic meta-volcanic rocks, c. 150 km farther NE, within the Binboğa (= Malatya) metamorphics (a low-grade high-pressure unit), are indicative of a within-plate setting. An impersistent geochemical subduction signature in these volcanics may represent an inherited, rather than contemporaneous, subduction influence, mainly because of the absence of a continental margin arc or of arc-derived tuff. Both the Binboğa metamorphics and the Çataloturan thrust sheet (Aladağ nappe) restore generally to the north of the relatively autochthonous Tauride carbonate platform (Geyik Dağ), within the carbonate platform bordering north-Gondwana. The Çataloturan thrust sheet is interpreted, specifically, as a c. E–W, deep-water, volcanically active rift that progressively infilled. Regional geological evidence suggests that melange units (Konya Complex, Afyon zone), Teke Dere unit, Lycian nappes), and Chios–Karaburun melange, E Aegean) accreted to the north-Gondwana continental margin during the late Carboniferous; this was coupled with localised calc-alkaline granitic magmatism (Afyon zone of Anatolide crustal block). We propose an interpretation in which Late Devonian–Carboniferous alkaline intra-plate volcanism relates to extension/rifting along the north-Gondwana margin. In contrast, the melange accretion and granitic magmatism could relate to short-lived late Carboniferous southward subduction that accompanied the diachronous closure of Palaeotethys.

scholarly journals Middle Paleozoic-Mesozoic boundary of the North Asian craton and the Okhotsk terrane: new geochemical and geochronological data and their geodynamic interpretation

2009 ◽  
Vol 4 ◽  
pp. 71-84 ◽  
Author(s):  
A. V. Prokopiev ◽  
J. Toro ◽  
J. K. Hourigan ◽  
A. G. Bakharev ◽  
E. L. Miller
Keyword(s):  
Continental Margin ◽  
Sedimentary Cover ◽  
Late Devonian ◽  
Low Grade ◽  
The South ◽  
Metamorphic Belt ◽  
North Asian Craton ◽  
The North ◽  
North Asia ◽  
Middle Paleozoic

Abstract. The Okhotsk terrane, located east of the South Verkhoyansk sector of the Verkhoyansk fold-and-thrust belt, has Archean crystalline basement and Riphean to Early Paleozoic sedimentary cover similar to that of the adjacent the North Asian craton. However, 2.6 Ga biotite orthogneisses of the Upper Maya uplift of the Okhotsk terrane yielded Early Devonian 40Ar/39Ar cooling ages, evidence of a Mid-Paleozoic metamorphic event not previously known. These gneisses are also intruded by 375±2 Ma (Late Devonian) calc-alkaline granodiorite plutons that we interpret as part of a continental margin volcanic arc. Therefore, Late Devonian rifting, which affected the entire eastern margin of North Asia separating the Okhotsk terrane from the North Asian craton, was probably a back-arc event. Our limited 40Ar/39Ar data from the South Verkhoyansk metamorphic belt suggests that low grade metamorphism and deformation started in the Late Jurassic due to accretion of the Okhotsk terrane to the North Asia margin along the Bilyakchan fault. Shortening and ductile strain continued in the core of the South Verkhoyansk metamorphic belt until about 120 Ma due to paleo-Pacific subduction along the Uda-Murgal continental margin arc.

scholarly journals Evidence from the Kyrenia Range, Cyprus, of the northerly active margin of the Southern Neotethys during Late Cretaceous–Early Cenozoic time

2011 ◽  
Vol 149 (2) ◽  
pp. 264-290 ◽  
Author(s):  
ALASTAIR H. F. ROBERTSON ◽  
KEMAL TASLI ◽  
NURDAN İNAN
Keyword(s):  
Continental Margin ◽  
Carbonate Platform ◽  
Middle Eocene ◽  
Active Continental Margin ◽  
Volcanic Rocks ◽  
Basaltic Rocks ◽  
Tectonic Model ◽  
The North ◽  
Basic Volcanic ◽  
Upper Maastrichtian

AbstractSedimentary geology and planktonic foraminiferal biostratigraphy have shed light on the geological development of the northern, active continental margin of the Southern Neotethys in the Kyrenia Range. Following regional Triassic rifting, a carbonate platform developed during Jurassic–Cretaceous time, followed by its regional burial, deformation and greenschist-facies metamorphism. The platform was exhumed by Late Maastrichtian time and unconformably overlain by locally derived carbonate breccias, passing upwards into Upper Maastrichtian pelagic carbonates. In places, the pelagic carbonates are interbedded with sandstone turbidites derived from mixed continental, basic volcanic, neritic carbonate and pelagic lithologies. In addition, two contrasting volcanogenic sequences are exposed in the western-central Kyrenia Range, separated by a low-angle tectonic contact. The first is a thickening-upward sequence of Campanian–Lower Maastrichtian(?) pelagic carbonates, silicic tuffs, silicic lava debris flows and thick-bedded to massive rhyolitic lava flows. The second sequence comprises two intervals of basaltic extrusive rocks interbedded with pelagic carbonates. The basaltic rocks unconformably overlie the metamorphosed carbonate platform whereas no base to the silicic volcanic rocks is exposed. Additional basaltic lavas are exposed throughout the Kyrenia Range where they are dated as Late Maastrichtian and Late Paleocene–Middle Eocene in age. In our proposed tectonic model, related to northward subduction of the Southern Neotethys, the Kyrenia platform was thrust beneath a larger Tauride microcontinental unit to the north and then was rapidly exhumed prior to Late Maastrichtian time. Pelagic carbonates and sandstone turbidites of mixed, largely continental provenance then accumulated along a deeply submerged continental borderland during Late Maastrichtian time. The silicic and basaltic volcanogenic rocks erupted in adjacent areas and were later tectonically juxtaposed. The Campanian–Early Maastrichtian(?) silicic volcanism reflects continental margin-type arc magmatism. In contrast, the Upper Maastrichtian and Paleocene–Middle Eocene basaltic volcanic rocks erupted in an extensional (or transtensional) setting likely to relate to the anticlockwise rotation of the Troodos microplate.

scholarly journals Geohistorical analysis of the northern part of the Pai-Khoi carbonate parautochthone in Late Devonian–Carboniferous

LITOSFERA ◽  
2020 ◽  
Vol 20 (5) ◽  
pp. 668-681
Author(s):  
D. A. Gruzdev ◽  
A. I. Gerasimova ◽  
A. V. Zhuravlev ◽  
Ya. A. Vevel
Keyword(s):  
Open Porosity ◽  
Carbonate Platform ◽  
Water Environment ◽  
Geological Structure ◽  
Late Carboniferous ◽  
Tectonic Activity ◽  
Late Devonian ◽  
Thermal Maturity ◽  
The North ◽  
Middle Paleozoic

Research subject. This article focuses on the geological structure of the northern part of the Pai-Khoi carbonate parautochthone.Materials and methods. The study was based on the data obtained on the key sections of the North-Western Pai-Khoi. Research methods included lithological and facies analysis, subsidence curves, reconstruction of the thermal maturity of deposits based on conodont alteration indexes, X-ray microtomography for determining porosity values.Results. The Upper Devonian–Carboniferous succession (ca. 900 m thick) is composed of the terrigenous and carbonate Pyrkov Fm. (Frasnian), carbonate Lymbadyakha Fm. (Famennian-Tournaisian), Bolvanskii Fm. (Visean-Bashkirian), and Hoiponganase Fm. and Reef Chaika (Moskovian-Kasimovian). The early Frasnian part of the succession was deposited in a shallow-water environment. In the Middle–Late Frasnian, the Korotaikha paleodepression and an isolated carbonate platform was formed on the shelf edge. Filling of the paleodepression was completed at the end of the Early Visean. In the Late Visean–Late Carboniferous, a carbonate platform (ramp) formed. A Middle Paleozoic paleogeothermal gradient reconstructed on the basis of conodont alteration indexes is much higher in the Pai-Khoi carbonate parautochthone than in the most of Pechora Plate regions. This is likely to have been caused by the tectonic activity of the plate border in the Late Carboniferous–Mesozoic. A downward decrease in open porosity (from 6% to 0.1%) is likely to have been associated with increased compaction and recrystallization of the carbonates.Conclusions. Famennian-Tournaisian carbonate formations of the Pai-Khoi carbonate parautochthone were deposited under the conditions of isolated platform environment; however, the Visean–Late Carboniferous deposits were formed in the outer ramp environment. The Late Devonian–Middle Carboniferous carbonate deposits of the Pai-Khoi parautochthone demonstrate an extremely low open porosity and a high thermal maturity. These properties, along with the pronounced faulting and folding of the rocks, significantly decrease petroleum-bearing prospects of these deposits.

Alpine tectonic evolution of the Northern Serbo-Macedonian sub-unit: inferences from kinematic and petrological investigations

2021 ◽  
Author(s):  
Bojan Kostić ◽  
Uroš Stojadinović ◽  
Nemanja Krstekanić ◽  
Marija Ružić ◽  
Aleksa Luković
Keyword(s):  
Continental Margin ◽  
Late Cretaceous ◽  
Pannonian Basin ◽  
Oceanic Lithosphere ◽  
Normal Faults ◽  
Low Grade ◽  
The South ◽  
The North ◽  
Neogene Sediments ◽  
Subduction System

<p>The Serbo-Macedonian Massif represents a belt of medium to lower amphibolite facies metamorphics situated along the European continental margin between the Pannonian Basin in the north and the Aegean Sea in the south. Structurally, it comprises the innermost segments of the Dacia mega-unit of the European affinity and is juxtaposed against the Adria-derived units of the Dinarides across the Adria-Europe zone of collision. The peak metamorphic event in the Serbo-Macedonian Massif is Variscan in age, while its magmatism had a complex pre-Alpine evolution, with the youngest stage being related to the crustal extension during the Triassic opening of the northern branch of Neotethys Ocean (or the Vardar Ocean). The subsequent Late Jurassic–Paleogene closure of the Vardar Ocean led to the E-ward subduction of the Neotethys oceanic lithosphere beneath the upper European plate (i.e., the Sava subduction system). The retreating and steepening of subducting lithosphere during the Late Cretaceous triggered syn-subductional extension in the upper plate of the Sava subduction system. The Late Cretaceous extension exhumed and structurally juxtaposed<strong> </strong>the high-grade Serbo-Macedonian metamorphics against the low-grade metamorphics of the Carpathians Supragetic Unit. The contact is marked by the E-dipping shear zone that can be traced along the eastern margin of Serbo-Macedonian Massif, from the Vršac Mts in the north, across the Jastrebac Mts and further towards the south in the Central Serbo-Macedonian sub-unit of south-eastern Serbia. The Late Cretaceous extension exhumed the Serbo-Macedonian metamorphic core, concurrently creating subsidence in a forearc basin along the frontal part of the European continental margin.</p><p>Due to its unique position in the interference zone of the two retreating Carpathian and Dinaridic slabs, the Northern Serbo-Macedonian sub-unit between the Vršac Mts in the north and the Jastrebac Mts in the south was strongly influenced by processes associated with the Oligocene–Miocene Pannonian extension. Hence, large segments of the Northern Serbo-Macedonian sub-unit including its contact with the Supragetic Unit were buried beneath the Neogene sediments of the Morava Valley Corridor, as the southern prolongation of the Pannonian Basin. In order to segregate and quantify the effects of the Oligocene–Miocene extension we have conducted a coupled kinematic, petrological and thermochronological study in the segments of Northern Serbo-Macedonian sub-unit adjacent to the Dinarides and Carpathians. The recent tectonic uplift of the Vršac Mts occurred in the Middle to Late Miocene along the WSW-dipping normal faults that control deposition in the adjacent Zagajica depression. The ENE-WSW oriented extension, which was triggered by the retreat of Carpathian slab, exhumed the core of the mountains and exposed the Late Cretaceous Serbo-Macedonian\Supragetic extensional contact. South from the Vršac Mts such exhumation was hampered by the presence of rigid Moesian indenter. Tectonic exhumation of the Jastrebac Mts, together with a cluster of Serbo-Macedonian gneiss domes that emerge from the surrounding Neogene sediments in the western-central part of the Morava Valley Corridor, was induced by corrugated detachment faults during the Oligocene–Miocene E-W oriented Dinaridic extension.</p>

scholarly journals Eoalpine (Cretaceous) evolution of the Oman Tethyan continental margin: insights from a structural field study in Jabal Akhdar (Oman Mountains)

GeoArabia ◽  
2004 ◽  
Vol 9 (2) ◽  
pp. 41-58 ◽  
Author(s):  
Jean-Paul Breton ◽  
François Béchennec ◽  
Joël Le Métour ◽  
Laure Moen-Maurel ◽  
Philippe Razin
Keyword(s):  
Subduction Zone ◽  
Continental Margin ◽  
Carbonate Platform ◽  
Outer Part ◽  
Crustal Thickening ◽  
Continental Subduction ◽  
The North ◽  
Oman Mountains ◽  
Ductile Shear ◽  
Arabian Platform

ABSTRACT A structural study in Jabal Akhdar (an autochthonous window in the Oman Mountains) shows that the thrusts and imbrications, mapped in the Permian-Cretaceous formations of the Arabian Platform, have a vergence top to the north-northeast and are associated with a regional cleavage resulting from a ductile shear deformation of the same vergence. This deformation affects the entire autochthonous unit, from the southwestern edge of Jabal Akhdar to the northeastern edge of Saih Hatat, with an increasing strain intensity towards the northeast. The same domain is also affected by a HP/LT metamorphism with a northeastward increase from chlorite facies to blueschist and eclogite facies, i.e. characteristic of a northeast-dipping subduction. However, the retrograde character of the metamorphic parageneses associated with the ductile shear, as well as its north-northeast vergence, indicate that this deformation is linked to the exhumation of the autochthon during the Campanian. These observations have been synthesised in a new lithospheric-scale interpretation of the geodynamic development of the North Oman continental margins during the middle to late Cretaceous. The sequential evolution along a transect passing from southwest of Jabal Akhdar to northeast of Muscat can be summarised as follows: An intra-continental subduction zone affected the autochthon of the Arabian Platform with a basal rupture lying in the proximal part of the continental margin, to the south of the northern edge of the carbonate platform. A North Muscat microplate was created between the intra-continental subduction zone and the intra-oceanic subduction that gave rise to the Samail Ophiolite; this microplate includes the outer part of the Arabian Platform, the continental slope and the entire Hawasina Basin. From Early Turonian to Late Santonian the obduction and the intra-continental subduction were coeval and parallel. The northeast edge of the North Muscat microplate plunged below the Samail Nappe whilst the emergent southwest part overthrust the innermost parts of the Arabian Platform. The leading edge of the Samail and Hawasina Nappes advanced across the southwestern border of the North Muscat microplate just before obduction and intra-continental subduction ceased at the Santonian–Campanian boundary. Towards the end of the intra-continental subduction, the lower part of the crust of the subducted autochthon delaminated the upper part, marking the first stage of the metamorphic rocks exhumation. From Early Campanian to Early Maastrichtian, the North Muscat microplate moved to the northeast, its northeastern edge sinking by gravity into the asthenosphere. The subducted autochthon rose up, and came into contact with the base of the obducted units. The resulting uplift of the ophiolite nappes produced its emergence and partial erosion. Local crustal thickening, related to the lithospheric delamination, caused doming at Saih Hatat and subsequent erosion that locally extended to the pre-Permian sedimentary basement during the Early Maastrichtian. The present day domal shape of Jabal Akhdar is however related to Tertiary tectonic events.

Trace-element geochemistry of metabasaltic rocks from the Yukon-Tanana Upland and implications for the origin of tectonic assemblages in east-central Alaska

1999 ◽  
Vol 36 (10) ◽  
pp. 1671-1695 ◽  
Author(s):  
Cynthia Dusel-Bacon ◽  
Kari M Cooper
Keyword(s):  
Trace Element ◽  
Continental Margin ◽  
Ocean Floor ◽  
Late Triassic ◽  
Geochemical Data ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
East Central ◽  
The North ◽  
Augen Gneiss

We present major- and trace- element geochemical data for 27 amphibolites and six greenstones from three structural packages in the Yukon-Tanana Upland of east-central Alaska: the Lake George assemblage (LG) of Devono-Mississippian augen gneiss, quartz-mica schist, quartzite, and amphibolite; the Taylor Mountain assemblage (TM) of mafic schist and gneiss, marble, quartzite, and metachert; and the Seventymile terrane of greenstone, serpentinized peridotite, and Mississippian to Late Triassic metasedimentary rocks. Most LG amphibolites have relatively high Nb, TiO2, Zr, and light rare earth element contents, indicative of an alkalic to tholeiitic, within-plate basalt origin. The within-plate affinities of the LG amphibolites suggest that their basaltic parent magmas developed in an extensional setting and support a correlation of these metamorphosed continental-margin rocks with less metamorphosed counterparts across the Tintina fault in the Selwyn Basin of the Canadian Cordillera. TM amphibolites have a tholeiitic or calc-alkalic composition, low normalized abundances of Nb and Ta relative to Th and La, and Ti/V values of <20, all indicative of a volcanic-arc origin. Limited results from Seventymile greenstones indicate a tholeiitic or calc-alkalic composition and intermediate to high Ti/V values (27-48), consistent with either a within-plate or an ocean-floor basalt origin. Y-La-Nb proportions in both TM and Seventymile metabasalts indicate the proximity of the arc and marginal basin to continental crust. The arc geochemistry of TM amphibolites is consistent with a model in which the TM assemblage includes arc rocks generated above a west-dipping subduction zone outboard of the North American continental margin in mid-Paleozoic through Triassic time. The ocean-floor or within-plate basalt geochemistry of the Seventymile greenstones supports the correlation of the Seventymile terrane with the Slide Mountain terrane in Canada and the hypothesis that these oceanic rocks originated in a basin between the continental margin and an arc to the west.

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