Isotope geochemistry (O, H and Sr) of Late Cretaceous volcanic rocks, Haţeg Basin, South Carpathians, Romania
Published:January 01, 2013
Ana-Voica Bojar, Justin Dodd, Ioan Seghedi, 2013. "Isotope geochemistry (O, H and Sr) of Late Cretaceous volcanic rocks, Haţeg Basin, South Carpathians, Romania", Isotopic Studies in Cretaceous Research, A.-V. Bojar, M. C. Melinte-Dobrinescu, J. Smit
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Oxygen and strontium isotopic ratios belonging to Late Cretaceous volcaniclastic deposits of the Haţeg Basin, South Carpathians, are documented here for the first time. The analyses performed on mineral concentrates suggest that associated magmas account for an assimilation–fractional crystallization trend with 87Sr/86Sr ratios of between 0.705 and 0.706, and a large range of δ18O up to 16‰, and a trend with higher 87Sr/86Sr ratios (0.707–0.708) but lower δ18O (8.2–7.9‰) values for leucrocratic minerals, such as plagioclase and sanidine. The Sr–O modelling of the main trend, using mafic minerals (pyroxene and amphibole), indicate 1–3% source contamination associated with up to 20% crustal assimilation. Hydrogen isotopic composition of amphiboles, biotite and groundmass do not confirm any significant involvement of an external fluid, either hydrothermal or diagenetic.
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Isotopic Studies in Cretaceous Research
The Cretaceous was a period characterized by very warm climate, oceanic anoxic and oxic events and enhanced volcanic activity. The end of the Cretaceous is punctuated by a well-documented asteroid impact and the extinction of, among other groups, the dinosaurs. This volume elucidates various aspects of Cretaceous marine and continental environmental conditions. The articles in this book present a broad range of interdisciplinary contributions, which are grouped into sections on marine environments(including anoxic and oxic events, volcanism and the Cretaceous–Palaeocene boundary); mixed marine–freshwater environments and continental records. The isotopic data are combined with further geochemical, palaeontological, lithological and mineralogical proxies. The interdisciplinary approach offered here gives a solid investigation base for this fascinating period. There are examples from Europe, Asia, South and North America, and from the Early Cretaceous to the Cretaceous–Paleogene boundary.