Geochemical and petrological aspects of dike intrusions in the Lycian ophiolites (SW Turkey): a case study for the dike emplacement along the Tauride Belt Ophiolites

摘要

Lycian ophiolites located in the Western Taurides, are cut at all structural levels by dolerite and gabbro dikes. The dolerite dikes from this area are both pristine and metamorphosed. The non-metamorphosed dikes are observed both in the peridotites and in the metamorphic sole rocks. Accordingly, the non-metamorphosed dikes cutting the metamorphic sole were generated after cooling of the metamorphic sole rocks. The metamorphosed dolerite dikes are only observed in the peridotites. The physical conditions and timing of the metamorphism for the metamorphosed dolerite dikes are similar to those of the metamorphic sole rocks of the Lycian ophiolites suggesting that the metamorphosed dolerite dikes were metamorphosed together with the meta-mprphic sole rocks. Therefore, the dike injections in the western part of the Tauride Belt OphioUtes occurred before and after the generation of the metamorphic sole rocks. All metamorphosed and non-metamorphosed dikes are considered to have the same origin and all of them are sub-duction-related as inferred from whole-rock geochemistry and lead isotopes. Lead isotope compositions of whole rocks of both dike groups cluster in a narrow field in conventional Pb isotope diagrams (~(206)Pb/~(204)Pb = 18.40-18.64; ~(207)Pb/~(204)Pb = 15.56-15.58; ~(208)Pb/~(204)Pb = 38.23-38.56) indicating a derivation from an isotopically homogeneous source. On the ~(207)Pb/~(204)Pb versus ~(206)Pb/~(204)Pb diagram, isotope compositions of the dikes plot slightly below the orogen curve suggesting contributions from mantle reservoir enriched by subducted oceanic lithosphere. Such a signature is typical of island arc magmatic rocks and supports the formation of the investigated rocks in a sub-duction-related environment.