Therma–Volvi–Gomati complex of the Serbo-Macedonian Massif, northern Greece: a Middle Triassic continental margin ophiolite of Neotethyan origin

Abstract

We present field, chemical and U–Pb age data for metamafic–ultramafic bodies of the Triassic rift-related Therma–Volvi–Gomati (TVG) complex of the Serbo-Macedonian Massif (SMM) in the northern Aegean region. The TVG rocks record igneous textures overprinted by Alpine metamorphism and deformation. The high-Ti Volvi body was transformed into amphibolites, which also rim the low-Ti Gomati and Nea Roda bodies. The compositions are compatible with normal (N-) and enriched (E-) mid-ocean ridge basalt (MORB) and weak ocean island basalt (OIB) signatures of the high-Ti rocks, whereas the low-Ti rocks are depleted with respect to MORB, suggesting melt extraction from a mantle source. U–Pb geochronology reveals Triassic crystallization of the Volvi body at 240 Ma. Ordovician to Carboniferous xenocrystic zircons were found in the Stratoni body of the TVG complex, which were sampled from the SMM basement. The Triassic Arnea rift-related metagranite intrudes the Volvi body. Comparison of the compositions of the Volvi body and the Arnea metagranite of the SMM with Triassic metagranite of the Rhodope Massif (RM) supports the presence of a regional bimodal rift suite. The location of the TVG complex at the SMM–RM margin of Eurasia confirms its origin as a Middle Triassic rift suite, and its nature as a continental margin ophiolite representing an ocean–continent transition of the propagating Neotethys. Supplementary material: Whole-rock chemical analyses and U–Pb geochronology analytical results data tables are available at https://doi.org/10.6084/m9.figshare.c.4087022 Thematic collection: This article is part of the ‘Tethyan ophiolites and Tethyan seaways collection' available at: https://www.lyellcollection.org/cc/tethyan-ophiolites-and-tethyan-seaways

Factors Controlling the Gallium Preference in High-Al Chromitites

“…All chromitite samples selected for the present study come from deposits and occurrences, which have been the subject of detailed geological, mineralogical and geochemical investigation [26][27][28][29][30][31][32][33][34][35][36] and references therein. The main ophiolite complexes of Greece (Vourinos, Othrys and Pindos) belong to the Upper Jurassic to Lower Cretaceous Tethyan ophiolite belt, and are characterized by heterogeneous deformation and rotation, during their original displacement and subsequent tectonic incorporation into continental margins [33].…”

“…The main ophiolite complexes of Greece (Vourinos, Othrys and Pindos) belong to the Upper Jurassic to Lower Cretaceous Tethyan ophiolite belt, and are characterized by heterogeneous deformation and rotation, during their original displacement and subsequent tectonic incorporation into continental margins [33]. The studied samples of chromitites are massive ( Figure 1) and exhibit variations in the chromitite tonnage, the composition of chromite (Tables 1 and 2), the degree of transformation of ores and the associated ophiolites [27][28][29][30][31][32][33][34][35][36][37].…”

“…They are completely serpentinized, locally sheared and metamorphosed to antigorite-tremolite and/or talc schists. Detailed description of the characteristic mineralogy and texture of those chromitites have been published in previous studies [17,18,31,32,36].…”

“…The structure of spinel is a cubic close-packed array of 32 oxygen ions, with 64 tetrahedral vacancies and 32 octahedral vacancies in one unit cell each, containing 8 formula units, with the general formula: A 2+ B 3+ 2 O 4 , where A = Fe 2+ , Mn 2+ , Mg 2+ , Co 2+ , Zn 2+ , Ni 2+ and B = Fe 3+ , Cr 3+ , Al 3+ , Ga 3+ , V 3+ [36]. Spinels are traditionally denoted as either "normal", where the A cation occupies T sites, the B cation occupies M sites, whereas in the "inverse" type cation B occupies the T site and the M site is occupied by both cations A and B [4,[8][9][10][11][12].…”

Detrital zircon age and Sr isotopic constraints for a Late Palaeozoic carbonate platform in the lower Rhodope thrust system, Pirin, SW Bulgaria

“…1b). Early-Middle Triassic metagranitoids and gabbroids (Christofides et al 2007;Himmerkus et al 2009b;Peytcheva et al 2009a;Drakoulis et al 2013;Bonev et al 2019c) in the Serbo-Macedonian and Rhodope massifs record Triassic rifting during opening of the Neotethys (Fig. 1b).…”