Palaeomagnetism of porphyritic stocks and rhyolite sills, Avalon Zone of eastern Newfoundland

Details Palaeomagnetism of porphyritic stocks and rhyolite sills, Avalon Zone of eastern Newfoundland Palaeomagnetism of porphyritic stocks and rhyolite sills, Avalon Zone of eastern Newfoundland

Jun 1986

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1986pepi...43..148s&link_type=abstract

Physics of the Earth and Planetary Interiors, Volume 43, Issue 2, p. 148-159.

Physics

1

Scientific paper

The eastern segment of the Appalachian orogen is largely underlain by late Precambrian (Hadrynian) rocks affected by the Avalonian, Acadian and possibly Alleghenian orogenies. The provenance of the Avalon Zone of Newfoundland is uncertain. The region investigated in this segment consists of porphyrite stocks and sills (laccoliths) intrusive into the sedimentary, tuffaceous and volcanic rocks of the Harbour Main Group and rhyolite sills intrusive into the porphyrites. Some 55 oriented samples (148 specimens) collected at 11 sites were thermally (20-650°C) and AF (0.05-100 mT) demagnetized. Three components of magnetization were isolated: C (311°, +48°, α95 = 11°, k = 21, 10 sites), A (13°, +37°, α95 = 14°, k = 22, 6 sites), and B (67°, +45°, α95 = 15°, k = 27,5 sites). Based on coercivity spectra, unblocking temperatures, frequency distribution and precision parameters of the respective components, it is suggested that component C is older than component A which is turn is older than component B. The palaeopoles of components C, A and B are: 211°E, 48°N (dp = 9.8°, dm = 14.7°) 101°E, 61°N (dp = 9.6°, dm = 16.4°) 33°E, 34°N (dp = 12°, dm = 19°), respectively. Component C is most probably primary. Component A is secondary and its pole is near that of Carboniferous and Early Permian North America poles, indicating that the porphyrites and the rhyolites were remagnetized in the late Palaeozoic. Component B remains unexplained; it is possible that it is an unresolved pseudo-component but it is more likely an overprint. There are few palaeomagnetic results for the late Precambrian period in Avalon terrane(s). The preliminary results of this study suggest the presence of a separate plate from North American at that time. These results will prove useful for the palaeoreconstruction of the continents (North Africa, northeast Europe) in the late Precambrian period.
Present address: The Department of Geology and Geophysics, University of Calgary, Calgary, Alberta, T2N 1N4, Canada.

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