Late Precambrian Balkan-Carpathian ophiolite — a slice of the Pan-African ocean crust?: geochemical and tectonic insights from the Tcherni Vrah and Deli Jovan massifs, Bulgaria and Serbia

• Published in: Journal of volcanology and geothermal research Vol. 110; no. 3-4; pp. 299 - 318
• Main Authors: Savov, Ivan, Ryan, Jeff, Haydoutov, Ivan, Schijf, Johan
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Lausanne Elsevier B.V 01.10.2001; Amsterdam Elsevier; New York, NY
• Subjects: Balkan-Carpathian region; Crystalline rocks; Earth sciences; Earth, ocean, space; Exact sciences and technology; Geochemistry; Igneous and metamorphic rocks petrology, volcanic processes, magmas; MORB; ophiolite; Pan-African-Cadomian connection; Precambrian; Soil and rock geochemistry; Southern Europe; Carpathians; Bulgaria; Serbia; ophiolite; Pan-African-Cadomian connection; Precambrian; MORB; Balkan-Carpathian region; microgabbro; olivine gabbro; textures; dikes; gabbros; stratigraphy; rare earths; mineral assemblages; hyaloclastites; lava; basalts; troctolite; Proterozoic; lava flows; pillow lava; petrography; cumulates; oceanic crust; upper Proterozoic; petrology; Europe; volcanic rocks; serpentinization; igneous rocks; ultrabasic rocks; diabase; chemical analysis; pyroclastics; hypabyssal rocks; wehrlite; dunite; anorthosite; plutonic rocks; ultramafics; peridotites
• ISSN: 0377-0273; 1872-6097
• DOI: 10.1016/S0377-0273(01)00216-5

The Balkan-Carpathian ophiolite (BCO), which outcrops in Bulgaria, Serbia and Romania, is a Late Precambrian (563Ma) mafic/ultramafic complex unique in that it has not been strongly deformed or metamorphosed, as have most other basement sequences in Alpine Europe. Samples collected for study from the Tcherni Vrah and Deli Jovan segments of BCO include cumulate dunites, troctolites, wehrlites and plagioclase wehrlites; olivine and amphibole-bearing gabbros; anorthosites; diabases and microgabbros; and basalts representing massive flows, dikes, and pillow lavas, as well as hyaloclastites and umbers (preserved sedimentary cover). Relict Ol, Cpx and Hbl in cumulate peridotites indicate original orthocumulate textures. Plagioclase in troctolites and anorthosites range from An60 to An70. Cumulate gabbro textures range from ophitic to poikilitic, with an inferred crystallization order of Ol-(Plag+Cpx)-Hbl. The extrusive rocks exhibit poikilitic, ophitic and intersertal textures, with Cpx and/or Plag (Oligoclase-Andesine) phenocrysts. The major opaques are Ti-Magnetite and Ilmenite. The metamorphic paragenesis in the mafic samples is Chl-Trem-Ep, whereas the ultramafic rocks show variable degrees of serpentinization, with lizardite and antigorite as dominant phases. Our samples are compositionally and geochemically similar to modern oceanic crust. Major element, trace element and rare earth element (REE) signatures in BCO basalts are comparable to those of MORB. In terms of basalt and dike composition, the BCO is a ‘high-Ti’ or ‘oceanic’ ophiolite, based on the classification scheme of Serri [Earth Planet. Sci. Lett. 52 (1981) 203]. Our petrologic and geochemical results, combined with the tectonic position of the BCO massifs (overlain by and in contact with Late Cambrian island arc and back-arc sequences), suggest that the BCO may have formed in a mid-ocean ridge setting. If the BCO records the existence of a Precambrian ocean basin, then there may be a relationship between the BCO and the Pan-African ophiolites from the Arabian–Nubian Shield. We suggest that the BCO is the missing link between the Pan-African and the Avalonian–Cadomian peripheral orogens of Murphy and Nance [Geology 19 (1995) 469].