Late Jurassic Magmatism and Stratigraphy in the Eastern Sakarya Zone, Turkey: Evidence for the Slab Breakoff of Paleotethyan Oceanic Lithosphere

2017 ◽  
Vol 125 (1) ◽  
pp. 1-31 ◽  
Author(s):  
Abdurrahman Dokuz ◽  
Emre Aydınçakır ◽  
Raif Kandemir ◽  
Orhan Karslı ◽  
Wolfgang Siebel ◽  
...  
Keyword(s):  
Late Jurassic ◽  
Oceanic Lithosphere ◽  
Slab Breakoff ◽  
Sakarya Zone

scholarly journals The evolution of the Triassic-Jurassic Maliac oceanic lithosphere: insights from the supra-ophiolitic series of Othris (continental Greece)

2015 ◽  
Vol 186 (6) ◽  
pp. 399-411 ◽  
Author(s):  
Jacky Ferrière ◽  
Frank Chanier ◽  
Peter O. Baumgartner ◽  
Paulian Dumitrica ◽  
Martial Caridroit ◽  
...  
Keyword(s):  
Continental Crust ◽  
Late Jurassic ◽  
Structural Data ◽  
Oceanic Lithosphere ◽  
Late Triassic ◽  
Major Result ◽  
Data Set ◽  
Thrust Sheets ◽  
Sedimentary Succession ◽  
Major Reference

AbstractMajor ophiolitic thrust sheets are widespread within the internal Hellenides, particularly in the Pelagonian domain (Greece and Albania). The ophiolitic sheets are notably well exposed in western Othris mountains of continental Greece. In that area, the structural stacking of oceanic nappes obducted in the Jurassic is particularly well constrained. New sedimentological and structural data from recently studied outcrops, together with new micro-paleontological data, allow to reconsider the architecture of the ophiolitic nappes and their evolution in the Othris mountains. Our new data set includes notably the description of a Mid-Late Jurassic sedimentary succession, from basal litharenites and radiolarites to syn-obduction mélange, on top of the uppermost Mega Isoma ophiolitic Unit. These results are crucial in the perspective of constraining the Jurassic contractional evolution of the Maliac Ocean from the beginning of the subduction and intra-oceanic obduction to the final obduction on the Pelagonian continental crust. Another major result concerns the dating of primary conformable series of Middle and Late Triassic age on top of the pillow-lavas of the Fourka unit. Since this lava unit, with MORB affinities, is one of the syn-obduction Jurassic nappes, we propose that this very large Fourka nappe represents the major reference unit of the initial (Triassic) Maliac oceanic crust.

Latest Cretaceous “A2-type” granites in the Sakarya Zone, NE Turkey: Partial melting of mafic lower crust in response to roll-back of Neo-Tethyan oceanic lithosphere

Lithos ◽  
2018 ◽  
Vol 302-303 ◽  
pp. 312-328 ◽  
Author(s):  
Orhan Karsli ◽  
Faruk Aydin ◽  
Ibrahim Uysal ◽  
Abdurrahman Dokuz ◽  
Mustafa Kumral ◽  
...  
Keyword(s):  
Partial Melting ◽  
Lower Crust ◽  
Oceanic Lithosphere ◽  
Sakarya Zone ◽  
Roll Back ◽  
Mafic Lower Crust

Eocene post-collisional magmatism in Himalaya orogenic belt: evidence from petrography, zircon U-Pb age and Sr-Nd-Hf isotope of the Mayum alkaline complex, southern Lhasa subterrane

2020 ◽  
Author(s):  
Xiaoshuang Chen ◽  
Haijin Xu
Keyword(s):  
Oceanic Lithosphere ◽  
Hf Isotope ◽  
Alkaline Magmatism ◽  
Early Eocene ◽  
Alkaline Complex ◽  
Southern Tibet ◽  
Quartz Syenite ◽  
Alkaline Rocks ◽  
Slab Breakoff ◽  
T Values

<p>Alkaline magmatism is commonly generated in extensional settings, playing an important role in constraining the timing of slab breakoff. Eocene post-collisional magmatism is widely distributed along the Gangdese belt of southern Tibet. However, few Eocene post-collisional alkaline magmatism has been identified. Here, we present a comprehensive study of whole-rock geochemistry, zircon U-Pb ages and Sr-Nd-Hf isotopes of the Mayum alkaline complex from the Southern Lhasa Subterrane, providing an insight into the timing of breakoff of the Neo-Tethyan slab. The alkaline complex is composed of amphibolite syenite, quartz syenite and alkaline granite. The mafic microgranular enclaves are ubiquitous in the syenites. Zircon U-Pb analyses indicates that the alkaline rocks were generated in Early Eocene (ca. 53-50 Ma). These ages suggest that the alkaline rocks emplaced shortly (10-15Ma) after the continental collision between the Indian and Eurasian plates. The alkaline rocks have high SiO<sub>2 </sub>(64.32-77.36 wt.%), Na<sub>2</sub>O + K<sub>2</sub>O (6.63-9.03 wt.%) contents, low MgO (0.14-2.52 wt.%) contents. These rocks show obvious arc-like geochemical features in trace elements, i.e., enrichment in LILEs (e.g., Rb, K), LREEs, Th and U, and depletion in HFSEs (e.g., Nb, Ta, Ti), HREEs with strongly to moderately negative Eu anomalies (δEu=0.28–0.72). These features together with high FeO<sup>T</sup>/MgO, Ga/Al, Ce/Nb and Y/Nb values, and low Ba, Sr contents, suggesting that the Mayum alkaline rocks belong to an A2-type granitoids. Besides, the alkaline rocks have homogeneous initial <sup>87</sup>Sr/<sup>86</sup>Sr ratios (0.7052-0.7059) and negative ε<sub>Nd</sub>(t) values (-2.1 to -0.9) for whole-rock, and positive zircon ε<sub>Hf</sub>(t) values (+0.73 to +11.16). Nd-Hf isotope decoupling suggests that the alkaline was likely produced by mixing of mantle- and crust-derived magmas under a post-collisional extensional setting. Combined with previous published results, we propose that the slab breakoff of the subducting Neo-Tethyan oceanic lithosphere at least prior to Early Eocene (ca. 53Ma). The Eocene Mayum alkaline complex might be related to asthenosphere upwelling trigged by the slab breakoff.</p>

Origin and emplacement of an inferred late Jurassic subduction-accretion complex, Euboea, eastern Greece

1991 ◽  
Vol 128 (1) ◽  
pp. 27-41 ◽  
Author(s):  
A. H. F. Robertson
Keyword(s):  
Shallow Water ◽  
Subduction Zone ◽  
Late Jurassic ◽  
Carbonate Platform ◽  
Accretionary Prism ◽  
Oceanic Lithosphere ◽  
Passive Margin ◽  
Late Triassic ◽  
Accretionary Complex ◽  
Alkali Basalts

AbstractIn northern Euboea, central eastern Greece, an up to 3 km-thick polygenetic melange (Pagondas complex) is structurally interleaved between a Triassic–Jurassic carbonate platform (Pelagonian Zone) and an overriding harzburgitic ophiolite. The melange mainly comprises late Triassic shallow-water limestone and calciturbidites, radiolarites, Triassic–Jurassic tholeiites, alkaline basalts and minor andesites. The units concerned range from kilometre-sized thrust sheets, and detached blocks, to broken formation and structureless, or bedded matrix-supported conglomerates (diamictite). The melange includes remnants of Neotethyan oceanic lithosphere, overlain by radiolarites, hemipelagic carbonates and distal calciturbidites derived from a Mesozoic carbonate platform. Tholeiites were erupted at a Triassic–Jurassic spreading axis, whilst within-plate-type alkali basalts are interpreted mainly as seamounts. Kilometre-scale detached blocks of shallow-water coralline limestone are identified as collapsed atolls, formed within an ocean and/or along the rifted continental margin. Volcaniclastic sediments are locally interbedded with radiolarite, and reflect post-volcanic erosion of the ocean floor. Intra-oceanic convergence began, apparently in late early Jurassic time, giving rise to the Euboea ophiolite above an inferred westwards-dipping subduction zone. The Pagondas Complex then developed as an accretionary prism. The subduction trench later collided with the Pelagonian passive margin, driving the hot Euobea ophiolite over the accretionary complex, to produce amphibolites and greenschists of the metamorphic sole. Trench–margin collision then drove the entire supra-subduction zone complex, apparently eastwards, downflexing the Pelagonian carbonate platform to form a foredeep in which late Jurassic (Kimmeridgian–Tithonian) radiolarian sediments accumulated. During emplacement, the accretionary complex was disrupted and partly resedimented as debris flows, turbiditic volcaniclastic sandstone and shale in a foredeep, or foreland basin setting.

scholarly journals Magmatic record of India-Asia collision

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Di-Cheng Zhu ◽  
Qing Wang ◽  
Zhi-Dan Zhao ◽  
Sun-Lin Chung ◽  
Peter A. Cawood ◽  
...  
Keyword(s):  
Mafic Rock ◽  
Oceanic Lithosphere ◽  
Indian Plate ◽  
Geochemical Data ◽  
Southern Tibet ◽  
Collision Zone ◽  
Slab Rollback ◽  
Continental Arc ◽  
Slab Breakoff ◽  
Sudden Decrease

Abstract New geochronological and geochemical data on magmatic activity from the India-Asia collision zone enables recognition of a distinct magmatic flare-up event that we ascribe to slab breakoff. This tie-point in the collisional record can be used to back-date to the time of initial impingement of the Indian continent with the Asian margin. Continental arc magmatism in southern Tibet during 80–40 Ma migrated from south to north and then back to south with significant mantle input at 70–43 Ma. A pronounced flare up in magmatic intensity (including ignimbrite and mafic rock) at ca. 52–51 Ma corresponds to a sudden decrease in the India-Asia convergence rate. Geological and geochemical data are consistent with mantle input controlled by slab rollback from ca. 70 Ma and slab breakoff at ca. 53 Ma. We propose that the slowdown of the Indian plate at ca. 51 Ma is largely the consequence of slab breakoff of the subducting Neo-Tethyan oceanic lithosphere, rather than the onset of the India-Asia collision as traditionally interpreted, implying that the initial India-Asia collision commenced earlier, likely at ca. 55 Ma.

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