Provenance and magmatic-tectonic setting of Campanian-aged volcaniclastic sandstones of the Kannaviou Formation in western Cyprus: Evidence for a South-Neotethyan continental margin volcanic arc

Abstract

Regionally developed late Cretaceous subduction-related magmatism in the eastern Mediterranean records progressive closure of the Southern Neotethys. In western Cyprus, the late Cretaceous (c. 90 Ma) Troodos ophiolite is depositionally overlain by volcaniclastic sandstones (up to 750 m thick) that are dominated by redeposited pyroclastic fallout, interbedded with both non-calcareous and calcareous radiolarian-bearing mudstones. The sands were mainly deposited by channelised mass-flow processes and to a lesser extent by turbidity currents in a deep-water forearc basin. The succession was folded and locally thrust-deformed related to latest Cretaceous emplacement of adjacent Mesozoic continental margin and oceanic units (Mamonia Complex). SIMS U-Pb analysis of euhedral to subhedral magmatic zircon crystals yielded a weighted mean 206Pb/238U age of 80.1 ± 1.1 Ma (Campanian). Sandstone petrography including compositional framework (Q12F21L67) suggests sediment supply from a volcanic arc. Subordinate continentally-derived detritus suggests a continental margin arc setting for the mafic to felsic fallout ash. SIMS analysis of little-altered volcanic glass indicates high Th/Nb and Th/La ratios that suggest the involvement of continental crust and/or subducted terrigenous sediments in magma genesis. Whole-rock chondrite-normalised REE patterns have comparable trends to modern and ancient forearc basin volcaniclastic sands and sandstones (e.g., northwest Pacific region). Trace element chemistry, although scattered towards the continental island arc fields on some geochemical diagrams (e.g., Th-Sc-Zr), mainly suggests an oceanic island arc source for the Kannaviou Formation sandstones, with variable enrichments in V-Cr-Ni-Sc, depletion in Nb-Ta, and relatively low trace element ratios (e.g., La/Co, Th/Co, La/Sc, Th/Sc). An explanation for this apparent discrepancy is that the volcaniclastic sandstones were derived from a relatively primitive arc constructed on previously depleted, rifted (thinned) Neotethyan continental crust. The inferred continental margin arc developed during early-stage northward subduction of the Southern Neotethys beneath a Tauride microcontinent to the north. Large volumes of volcanic ash were derived from continental margin arc volcanism, probably in the vicinity of the Kyrenia Range in northern Cyprus.