Wojtulek PM, Schulz B, Klemd R, Gil G, Dajek M, Delura K (2021)
Publication Type: Journal article
Publication year: 2021
The Variscan Central-Sudetic Ophiolites (CSO) are located in the Sudetes, the NE segment of the Bohemian Massif. The Devonian CSO display highly depleted, harzburgite mantle sections containing gabbroic dykes and local occurrences of mostly isotropic, large gabbroic bodies as well as volcanic rocks. The ultramafic rocks locally show melt percolation-derived clinopyroxene-olivine aggregates and chromitites. The low REE composition and depletion in LREE relative to HREE of the clinopyroxene as well as the chromite Cr# and Mg# values are typical for phases formed from refractory melts occurring in the supra-subduction zone environment. The gabbroic bodies consist of differently evolved, mostly cumulate rocks, while the volcanic rocks form a relatively monotonous basalt sequence. The trace element compositions of both the plutonic and volcanic rocks display depleted N-MORB affinities, their derivation from a refractory mantle source is further reflected by previously published depleted mantle-like Sr-Nd isotopic compositions. The ultramafic and mafic members of the CSO show greenschist- to lower amphibolite-facies metamorphic overprints. The occurrence of depleted harzburgites and isotropic gabbros forming the mantle and the crustal sections of the CSO, respectively, indicate intermediate- to slow-spreading conditions and a heterogeneous structure of the oceanic lithosphere, untypical for layered ophiolites. The geochemical characteristics of the melt-percolation phases of the ultramafic rocks, the bulk-rock compositions of the mafic rocks and the homogeneous volcanic sequences suggest a formation of the CSO in a mature back-arc basin setting, lacking subduction-derived contamination. Spreading rate conditions and geochemical affinities of the CSO are similar to those of other Devonian ophiolites localized along the Variscan Belt, for instance the Upper Ophiolitic Units in the NW Iberian Massif (Spain), thereby confirming the general absence of N-MORB type lithosphere in the European Variscan Orogen.
Wojtulek, P.M., Schulz, B., Klemd, R., Gil, G., Dajek, M., & Delura, K. (2021). The Central-Sudetic ophiolites – Remnants of the SSZ-type Devonian oceanic lithosphere in the European part of the Variscan Orogen. Gondwana Research. https://dx.doi.org/10.1016/j.gr.2021.09.015
Wojtulek, Piotr Marian, et al. "The Central-Sudetic ophiolites – Remnants of the SSZ-type Devonian oceanic lithosphere in the European part of the Variscan Orogen." Gondwana Research (2021).