Detrital heavymineral and bulk rock geochemistry and a review of sandstone petrographic data have been usedto investigate the post-collisional effusive magmatismthat followed the closure of the Vardar Ocean and the generationof volcanic sediments in a complex and compositionally variable volcanic region. Available petrographicdata gives evidence of contributions fromthree key source areas corresponding to the three main tectonic units:the structurally lower Gneiss–Migmatite Complex (Byala Reka-Kechros and Kesebir-Kardamos domes) and theupper Variegated (Kimi) Complex, both fringed by the low-to-medium-grade Mesozoic rocks of the Circum-Rhodope Belt. Besides the deposition of siliciclastic material, volcanic contributions from both, intermediateand acid products represent an important source of sediment in the area. Despite dominant intermediate toacid volcanic products, volcanic lithic fragments in sandstones (microlithic, lathwork and brown vitric textures)indicate main inputs fromintermediate and basic-intermediate products generating questions on the interpretationof volcanic detritus in reconstruction of provenance. Detrital amphibole and pyroxene chemistry is used tocharacterise the supply of volcanicmaterial as well as the dispersal mechanisms and understand the role playedby each of the volcanic centers present in the area in the infill of the north-western Thrace basin. Amphibolechemistry reveals high compositional heterogeneity according to both compositional variability of the numerousvolcanic centres active at the time of deposition and presence ofmetamorphic amphibole. 4Al and AlT apfu valuesindicate that most of the amphiboles fromthe NERZ are not of volcanic origin and their presence can only be attributedto the numerous amphibolite facies metamorphic rocks abundantly documented in the area. Detritalamphibole compositions from the ZKVS indicate major contributions from the Iran Tepe and Zvedzel volcanoes.Analysed detrital clinopyroxenes from the NERZ are mostly diopside–augite, with no hedenbergite or Fe–augitedetected. The 4Al/6Al ratio is comparable with compositions of volcanic pyroxenes from the Momchilgrad–Arda(ZKVS) region and products from the pre-caldera phase of the Borovitza.
Provenance of Tertiary volcanoclastic sediment in NWThrace (Bulgaria): Evidence from detrital amphibole and pyroxene geochemistry
CRITELLI, Salvatore
Membro del Collaboration Group
;
2016-01-01
Abstract
Detrital heavymineral and bulk rock geochemistry and a review of sandstone petrographic data have been usedto investigate the post-collisional effusive magmatismthat followed the closure of the Vardar Ocean and the generationof volcanic sediments in a complex and compositionally variable volcanic region. Available petrographicdata gives evidence of contributions fromthree key source areas corresponding to the three main tectonic units:the structurally lower Gneiss–Migmatite Complex (Byala Reka-Kechros and Kesebir-Kardamos domes) and theupper Variegated (Kimi) Complex, both fringed by the low-to-medium-grade Mesozoic rocks of the Circum-Rhodope Belt. Besides the deposition of siliciclastic material, volcanic contributions from both, intermediateand acid products represent an important source of sediment in the area. Despite dominant intermediate toacid volcanic products, volcanic lithic fragments in sandstones (microlithic, lathwork and brown vitric textures)indicate main inputs fromintermediate and basic-intermediate products generating questions on the interpretationof volcanic detritus in reconstruction of provenance. Detrital amphibole and pyroxene chemistry is used tocharacterise the supply of volcanicmaterial as well as the dispersal mechanisms and understand the role playedby each of the volcanic centers present in the area in the infill of the north-western Thrace basin. Amphibolechemistry reveals high compositional heterogeneity according to both compositional variability of the numerousvolcanic centres active at the time of deposition and presence ofmetamorphic amphibole. 4Al and AlT apfu valuesindicate that most of the amphiboles fromthe NERZ are not of volcanic origin and their presence can only be attributedto the numerous amphibolite facies metamorphic rocks abundantly documented in the area. Detritalamphibole compositions from the ZKVS indicate major contributions from the Iran Tepe and Zvedzel volcanoes.Analysed detrital clinopyroxenes from the NERZ are mostly diopside–augite, with no hedenbergite or Fe–augitedetected. The 4Al/6Al ratio is comparable with compositions of volcanic pyroxenes from the Momchilgrad–Arda(ZKVS) region and products from the pre-caldera phase of the Borovitza.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
