The Mamonia Complex (SW Cyprus) revisited; remnant of Late Triassic intra-oceanic volcanism along the Tethyan southwestern passive margin

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doi: 10.1017/S0016756806002937
Authors:Lapierre, H.; Bosch, D.; Narros, A.; Mascle, Georges H.; Tardy, M.; Demant, A.
Author Affiliations:Primary:
Université J. Fourier, Laboratoire Géodynamique des Chaînes Alpines, Grenoble, France
Université de Montpellier II, France
Université de Savoie, France
Université Paul Cézanne, France
Volume Title:Geological Magazine
Source:Geological Magazine, 144(1), p.1-19. Publisher: Cambridge University Press, London, United Kingdom. ISSN: 0016-7568
Publication Date:2007
Note:In English. 71 refs.; illus., incl. 2 tables, geol. sketch map
Summary:Upper Triassic volcanic and sedimentary rocks of the Mamonia Complex in southwestern Cyprus are exposed in erosional windows through the post-Cretaceous cover, where the Mamonia Complex is tectonically imbricated with the Troodos and Akamas ophiolitic suites. Most of these Upper Triassic volcanic rocks have been considered to represent remnants of Triassic oceanic crust and its associated seamounts. New Nd and Pb isotopic data show that the whole Mamonia volcanic suite exhibits features of oceanic island basalts (OIB). Four rock types have been distinguished on the basis of the petrology and chemistry of the rocks. Volcanism began with the eruption of depleted olivine tholeiites (Type 1) and oceanic island tholeiites (Type 2) associated with deep basin siliceous and/or calcareous sediments. The tholeiites were followed by highly phyric alkali basalts (Type 3) interbedded with pelagic Halobia-bearing limestones or white reefal limestones. Strongly LREE-enriched trachytes (Type 4) were emplaced during the final stage of volcanic activity. Nd and Pb isotopic ratios suggest that tholeiites and mildly alkali basalts derived from partial melting of heterogeneous enriched mantle sources. Fractional crystallization alone cannot account for the derivation of trachytes from alkaline basalts. The trachytes could have been derived from the partial melting at depth of mafic material which shares with the alkali basalts similar trace element and isotopic compositions. This is corroborated by the rather similar isotopic compositions of the alkali basalts and trachytes. The correlations observed between incompatible elements (Nb, Th) and εNd and Pb isotopic initial ratios suggest that the Mamonia suite was derived from the mixing of a depleted mantle (DMM) and an enriched component of High µ (µ = 238U/204Pb, HIMU) type. Models using both Nd and Pb isotopic initial ratios suggest that the depleted tholeiites (Type 1) derived from a DMM source contaminated by an Enriched Mantle Type 2 component (EM2), and that the oceanic tholeiites (Type 2), alkali basalts (Type 3) and trachytes (Type 4) were derived from the mixing of the enriched mantle source of the depleted tholeiites with a HIMU component. None of the Mamonia volcanic rocks show evidence of crustal contamination. The Upper Triassic within-plate volcanism likely erupted in a small southerly Neotethyan basin, located north of the Eratosthenes seamount and likely floored by oceanic crust.
Sections:Geochemistry; Petrology
Subsections:Igneous petrology
Subjects:Alkaline earth metals; Basalts; Chemical composition; Crust; Enrichment; Geochemistry; ICP mass spectra; Igneous rocks; Isotope ratios; Isotopes; Lead; Magma contamination; Magmas; Magmatism; Major elements; Mantle; Mass spectra; Mesozoic; Metals; Mid-ocean ridge basalts; Models; Nd-144/Nd-143; Neodymium; Ocean floors; Ocean-island basalts; Oceanic crust; Ophiolite; Ophiolite complexes; Paleoenvironment; Pb-206/Pb-204; Petrography; Plate tectonics; Provenance; Radioactive isotopes; Rare earths; Rifting; Seamounts; Sedimentary rocks; Spectra; Sr-87/Sr-86; Stable isotopes; Strontium; Tethys; Tholeiitic composition; Trace elements; Trachytes; Triassic; Troodos Ophiolite; Upper Triassic; Volcanic rocks; Volcanism; Asia; Cyprus; Middle East; Akamas Suite; Halobia Limestones; Kannaviou Formation; Mamonia Complex; Perapedhi Formation; Varavara Formation
Coordinates:N343000 N354000 E0343000 E0323000
Abstract Numbers:07M/917
Record ID:2007023078
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Abstract, Copyright, Cambridge University Press, Reference includes data from GeoScienceWorld, Alexandria, VA, United States
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