Abstract

A thorough geochemical survey of the Dalradian rocks in the NW Mayo inlier has shown that each formation has a characteristic geochemical signature, within regional geochemical trends that vary systematically with stratigraphic age. This geochemical characterization enables correlation between geographically and tectonically isolated stratigraphic successions in the NW Mayo inlier. An almost complete succession of late Proterozoic Grampian. Appin and Argyll Group Dalradian rocks structurally overlies earlier basement Annagh Division gneisses in structural blocks bounded by Caledonian thrusts, extensional low-angle faults, and steeply dipping faults. Grampian–Appin Group relationships are better seen here than anywhere else in Scotland or Ireland. but no Tayvallich Subgroup or Southern Highland Group Dalradian rocks are present.

Comparison with chemostratigraphic data from Scottish Dalradian rocks reveals broadly similar chemical trends with time. suggesting that the geological evolution of the Dalradian took place in a related depositional environment, probably an unbroken continental margin, along the entire Dalradian outcrop seen in both Scotland and Ireland.

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