Supercontinents, Orogenesis and Magmatism
CONTAINS OPEN ACCESS

A tribute to the career of J. Brendan Murphy, this volume covers topics that encompass the three main fields of his influence: (i) supercontinents and the supercontinent cycle; (ii) orogenesis and terranes; and (iii) magmatism and magmatic processes. Papers range from strongly field-based studies to conceptual analyses, and focus on clarifying some crucial geological processes.
Review and tectonic interpretation of Precambrian Avalonia Available to Purchase
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Published:April 22, 2024
Abstract
Avalonia, defined by its distinctive uppermost Ediacaran–Ordovician overstep sequence, extends from New England through Atlantic Canada to Wales. It unconformably overlies: (1) parts of one cratonic Neoproterozoic arc that which records several pulses at: 760–730 Ma, 680–600 Ma and 580–540 Ma; (2) an 800–760 Ma passive margin sequence; and (3) c. 976 Ma isolated plutons, possibly basement. Comparisons with modern arc dimensions suggest the dip of the Benioff Zone ranged from c. 22° W in Newfoundland to c. 52–67° elsewhere. A 600–580 Ma hiatus in arc magmatism in Cape Breton Island is attributed to overriding an oceanic plateau, leading to a 15° decrease in the dip of the Benioff Zone. The Collector magnetic anomaly along the Grand Banks and the Minas Fault is inferred to mark the Neoproterozoic southern margin of the Avalon Plate consisting of leaky transform faults and trench segments characterized by magnetite serpentinite mantle wedge beneath forearcs. The Minas Fault/Collector Anomaly connects similar arc units in Cape Breton Island and southern New Brunswick, suggesting that they were already offset by the Minas transform fault in the late Neoproterozoic. Similar tectonic, palaeomagnetic and isotopic data in the Timan Orogen of Baltica suggest that Avalonia may correlate with the Kipchak arc.