Mark, Darren F.; Parnell, John; Kelley, Simon P. and Sherlock, Sarah C.
Resolution of regional fluid flow related to successive orogenic events on the Laurentian margin.
Seven localities distributed along a 180-km-long outcrop within the UK sector of the Laurentian margin were sampled, and all showed two phases of authigenic K-feldspar. The first phase was precipitated from a cool fluid of moderate salinity, and the second phase was precipitated from a hotter, more saline fluid. Ar-Ar ages for the two episodes of authigenesis are ca. 470 Ma and ca. 432 Ma. The data can be interpreted to represent two phases of regional-scale fluid migration related to Ordovician arc accretion and Silurian continent-continent convergence, corresponding to the Grampian and Scandian episodes of the Caledonian orogeny, respectively.
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