caa a22 4500 386401586 CHVBK 20180307112200.0 cr unu---uuuuu 161130e198911 xx s 000 0 eng 10.1017/S0016756800006968 doi S0016756800006968 pii (NATIONALLICENCE)cambridge-10.1017/S0016756800006968 Evans J. A. NERC Isotope Geology Centre, 64 Gray's Inn Road, London WCIX 8NG, U.K. Resetting of the Rb-Sr whole-rock isotope system of an Ordovician microgranite during Devonian low-grade metamorphism [Elektronische Daten] [J. A. Evans] The Bwlch y Cywion microgranite intrudes an Ordovician sedimentary sequence in northeast Snowdonia, North Wales. Its age is recorded by hornfelses within its metamorphic aureole which give an Ordovician age of 454 ± 20 Ma. The whole-rock Rb-Sr isotope systems of the intrusion, however, and of an associated ash-flow tuff and a rhyolite of the Llewelyn Volcanic Group (Caradoc), were reset during low-grade metamorphism and give Devonian ages of 392±11 Ma, 392±5 Ma, and 405 ± 6 Ma, respectively. Copyright © Cambridge University Press 1989 Geological Magazine Cambridge University Press 126/6(1989-11), 675-679 0016-7568 126:6<675 1989 126 GEO https://doi.org/10.1017/S0016756800006968 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1017/S0016756800006968 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Evans J. A. NERC Isotope Geology Centre, 64 Gray's Inn Road, London WCIX 8NG, U.K NATIONALLICENCE 773 0- Geological Magazine Cambridge University Press 126/6(1989-11), 675-679 0016-7568 126:6<675 1989 126 GEO CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge