Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.764010
Title: Provenance-related studies of Triassic-Miocene Tethyan sedimentary and igneous rocks from Cyprus
Author: Chen, Guohui
ISNI:       0000 0004 7654 4899
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2018
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Abstract:
Cyprus comprises three tectono-stratigraphic terranes: first, the Troodos Massif made up of Late Cretaceous oceanic lithosphere and its sedimentary cover in the centre of the island; secondly, the Mamonia Complex (and Moni Melange) a passive margin lithological assemblage in the west (and south) and thirdly, the Kyrenia Range, an active margin lithological assemblage in the north. This study focuses on the sedimentary cover of the Troodos Ophiolite in W Cyprus, the Triassic-Cretaceous sedimentary rocks of the Mamonia Complex and Late Cretaceous-Miocene igneous and sedimentary rocks in the Kyrenia Range, mainly based on combined sedimentology, geochemistry and geochronological dating. The Late Triassic-Early Cretaceous Mamonia Complex, SW Cyprus (and the Moni Melange, S Cyprus) represent parts of the emplaced passive continental margin of the S Neotethys. Late Triassic sandstones are characterised by a predominantly felsic source, with a subordinate mafic contribution. Jurassic-Early Cretaceous sandstones have a polycyclic felsic origin. Geochemical analyses are suggestive of progressive weathering and sediment recycling/sorting. The dominance of Ediacaran-Cryogenian and Tonian-Stenian-aged detrital zircon populations is suggestive of an ultimate north Gondwana source, probably recycled from Palaeozoic siliciclastic sedimentary rocks within Anatolia to the north. Similar detrital zircon populations characterise Early Cretaceous deltaic sandstone of the Moni Melange, S Cyprus. Sporadic Late Cretaceous subduction-related magmatism, represented by a Campanian volcaniclastic sequence (80.44±1.0 Ma) inWCyprus and a Late Campanian felsic volcanogenic sequence (72.9±1.0 Ma) in N Cyprus, represents early and more advanced stages of northward subduction during closure of the S Neotethys. Specifically, the Kannaviou Formation in W Cyprus (up to 750 m thick) is made up of deep-marine volcaniclastic sandstones that were mostly deposited by gravity flows and as air-fall tuff, interbedded with clay and radiolarian mudstones. Petrographic and geochemical analyses are indicative of a volcanic arc source, with deposition in a fore-arc basin. Petrographic evidence of terrigenous input (e.g. muscovite, muscovite schist, polycrystalline quartz) points to a subordinate continental source. Mineral chemistry is consistent with a volcanic arc origin. Elevated trace-element ratios in undevitrified volcanic glass (e.g. Th/Nb, Th/La) are indicative of involvement of continental crust or subducted terrigenous sediments in source-arc melting. Felsic volcanogenic rocks (Fourkovouno (Selvilitepe) Formation) in the Kyrenia Range, N Cyprus, occur as an up to 400 m-thick sequence of felsic tuffs, felsic debris-flowdeposits and rhyolitic lava flows. Geochemical analyses are indicative of evolved high-K and shoshonitic compositions, similar to those of the Andean active continental margin. Subduction continued to affect the northern continental margin of the S Neotethys in the Kyrenia Range during the Maastrichtian. This lead to the accumulation of Late Cretaceous sandstone turbidites and related basaltic volcanics, possibly in a back-arc setting. The volcanism took place in two phases (Late Cretaceous and Palaeogene-Early Eocene) during pelagic carbonate accumulation. These lavas have within-plate affinities, but with a variable subduction influence in some areas (e.g. western Kyrenia Range), which may be contemporaneous or inherited from previous subduction. The sedimentary sequences in the Kyrenia Range, N Cyprus, document diachronous closure of the S Neotethys. Late Cretaceous and Eocene sandstone turbidites, and the lower part of the overlying Oligocene-Miocene succession exhibit enrichment in ultramafic components that was probably sourced from ophiolite-related rocks in the Taurides to the north. In contrast, Miocene sandstone turbidites higher in the sequence show an increasing input of continent-derived siliciclastic material (and sorting effects). The terrigenous-influenced sediments are likely to represent erosion of thrust sheets that were emplaced from the S Neotethys onto the Arabian foreland in SE Turkey related to continental collision. Ediacaran-Cryogenian and Tonian-Stenian-aged zircons dominate the Late Cretaceous and Eocene sandstone turbidites, consistent with derivation from the Tauride micro-continent to the north and/or NE. Overlying Miocene sandstones include minor populations of Neoproterozoic-aged zircons, suggestive of reworking from source rocks of ultimately Gondwanan origin (e.g. NE Africa/Arabian-Nubian Shield). In summary, the thesis results exemplify the interaction of tectonic processes associated with the evolution of the S Neotethys Ocean. This began in the area studied with passive margin development (Triassic-Cretaceous), and was followed by multi-stage subduction-related volcanism and sedimentation (Late Cretaceous-Miocene). Final closure of the S Neotethys in this area took place during the Late Miocene-Recent.
Supervisor: Robertson, Alastair ; Ustaömer, Timur Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.764010  DOI: Not available
Keywords: Cypru ; sedimentology ; geochemistry ; geochronology ; Eastern Mediterranean ; Troodos ophiolite ; passive margin development ; subduction-related volcanism ; sedimentation
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