caa a22 4500 465791816 CHVBK 20180323112027.0 cr unu---uuuuu 170327e19900301xx s 000 0 eng 10.1007/BF00678987 doi (NATIONALLICENCE)springer-10.1007/BF00678987 Petrogenesis and paleotectonic history of the Wild Bight Group, an Ordovician rifted island arc in central Newfoundland [Elektronische Daten] [H. Swinden, G. Jenner, B. Fryer, J. Hertogen, J. Roddick] The Wild Bight Group (WBG) is a sequence of early and middle Ordovician volcanic, subvolcanic and epiclastic rocks, part of the Dunnage Tectonostratigraphic Zone of the Newfoundland Appalachians. A detailed geochemical and Nd-isotopic study of the volcanic and subvolcanic rocks has been carried out to determine the geochemical characteristics of the rocks, interpret their palcotectonic environments and constrain their petrogenetic history. The lower and central stratigraphic levels of the WBG contain mafic volcanic rocks with island-arc geochemical signatures, including LREE-enriched are tholeiites with ε Nd(t) =-0.1 to +2.2 (type A-I), LREE-depleted arc tholeiites with ε Nd(t) =+5.6 to +7.1 (type A-II) and an unusual suite of strongly incompatible-element depleted tholeiites in which ε Nd(t) ranges from-0.9 to +4.6 and is negatively correlated with147Sm/144Nd (type A-III). High-silica, low-K rhyolites occur locally in the central part of the stratigraphy, associated with mafic rocks of arc affinity, and have ε Nd(t) =+4.7 to +5.4. The upper stratigraphic levels of the WBG dominantly contain rocks with non-arc geochemical signatures, including alkalic basalts with ε Nd(t) =+4.6 to +5.5 (type N-I), strongly LREE- and incompatible element-enriched tholeiites that are transitional between alkalic and non-alkalic rocks with ε Nd(t) =+4.4 to +7.0 (type N-II) and rocks with flat to slightly LREE-enriched patterns and ε Nd(t) =+5.1 to +7.4 (type N-III). Rocks with non-arc and arc signatures are locally interbedded near the stratigraphic type of the WBG. Nd-isotopic data in the type A-I and A-II rocks are generally compatible with mixing/partial melting models involving depleted mantle, variably contaminated by a subducted crustally-derived sediment. The petrogenesis of type A-III rocks must involve source mixing and multi-stage partial melting, but the details are not clear. The geochemistry and Nd isotope data for types N-I, N-II and N-III rocks are compatible with petrogenetic models involving variable partial melting of a source similar to that postulated for modern oceanic island basalts. Comparison of the WBG with modern analogues suggests a 3-stage developmental model: stage 1) island-arc volcanism (eruption of type mafic volcancs); stage 2) arc-rifting (continued eruption of type A-I, A-I, eruption of types A-II and A-III mafic volcanics and high-silica, low-K rhyolites); and stage 3) back-arc basin volcanism (continued minor eruption of type A-I basalts, eruption of types N-I, N-II, N-III basalts). Stages 1 and 2 volcanism involved partial melting of subduction contaminated mantle, while stage 3 volcanism utilized depleted-mantle sources not affected by the subducting slab. This model provides a basis for interpreting coeval sequences in central Newfoundland and a comparative framework for some early Paleozoic oceanic volcanic sequences elsewhere in the Appalachian orogen. Springer-Verlag, 1990 Swinden H. Newfoundland Department of Mines and Energy, Geological Survey Branch, P.O. Box 8700, A1B 4T6, St. John's, Newfoundland, Canada aut Jenner G. Department of Earth Science, Memorial University of Newfoundland, A1B 3X5, St. John's, Newfoundland, Canada aut Fryer B. Department of Earth Science, Memorial University of Newfoundland, A1B 3X5, St. John's, Newfoundland, Canada aut Hertogen J. Fysico-Chemische Geologie, Universitet Leuven, B-3030, Leuven, Belgium aut Roddick J. Continental Geosciences Division, Geological Survey of Canada, 601 Booth Street, K1A 0E8, Ottawa, Ontario, Canada aut Contributions to Mineralogy and Petrology Springer-Verlag 105/2(1990-03-01), 219-241 0010-7999 105:2<219 1990 105 410 https://doi.org/10.1007/BF00678987 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00678987 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Swinden H. Newfoundland Department of Mines and Energy, Geological Survey Branch, P.O. Box 8700, A1B 4T6, St. John's, Newfoundland, Canada aut NATIONALLICENCE 700 1- Jenner G. Department of Earth Science, Memorial University of Newfoundland, A1B 3X5, St. John's, Newfoundland, Canada aut NATIONALLICENCE 700 1- Fryer B. Department of Earth Science, Memorial University of Newfoundland, A1B 3X5, St. John's, Newfoundland, Canada aut NATIONALLICENCE 700 1- Hertogen J. Fysico-Chemische Geologie, Universitet Leuven, B-3030, Leuven, Belgium aut NATIONALLICENCE 700 1- Roddick J. Continental Geosciences Division, Geological Survey of Canada, 601 Booth Street, K1A 0E8, Ottawa, Ontario, Canada aut NATIONALLICENCE 773 0- Contributions to Mineralogy and Petrology Springer-Verlag 105/2(1990-03-01), 219-241 0010-7999 105:2<219 1990 105 410 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer