Chemostratigraphic correlation, structure and sedimentary environments in the Dalradian' of the NW Co. Mayo inlier, NW Ireland

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.

Laurentian crustal recycling in the Ordovician Grampian Orogeny: Nd isotopic evidence from western Ireland

“…Winchester, Max & Long, 1987;Winchester & Max, 1996). The North Mayo Dalradian sequence includes the late Proterozoic Grampian, Appin and Argyll groups, which consist of, respectively, schists and psammites, quartzites derived from mature sands overlain by interbedded shales and carbonates, and quartzites interspersed with metabasic volcanic rocks (Winchester & Max, 1996).…”

“…Winchester, Max & Long, 1987;Winchester & Max, 1996). The North Mayo Dalradian sequence includes the late Proterozoic Grampian, Appin and Argyll groups, which consist of, respectively, schists and psammites, quartzites derived from mature sands overlain by interbedded shales and carbonates, and quartzites interspersed with metabasic volcanic rocks (Winchester & Max, 1996). SE-verging nappes within these Dalradian units in North Mayo, the Sperrin Mountains and the Ox Mountains inlier, have been shown to have originated during Grampian deformation, as the Dalradian sequence was overthrust over volcanic units and/or basement probably associated with the colliding Lough Nafooey Arc (Alsop & Hutton, 1993;Flowerdew et al 2000;Chew, 2003).…”

Geochemical evolution of Dalradian metavolcanic rocks: implications for the break-up of the Rodinia supercontinent

“…Tanner et al (2006) noted that a link can be made between the Vuirich Suite and a swarm of diverse A-type intrusions and associated extrusive rocks which, in a Neoproterozoic showed enriched characteristics. Second, the first major phase of volcanism is geographically extensive along the Dalradian outcrop (both within the current study area and, with correlatives in the west of Ireland (Winchester & Max 1996), comprising an along-strike distance of c. 700 km), whereas the second major phase, although voluminous, is geographically constrained to SW and NE Scotland. The Dalradian lithostratigraphy, as discussed above, indicates increasing instability with marked basin subsidence during Easdale Subgroup times.…”

“…Volcanic rocks crop out throughout the strike length of the Argyll Group succession, from the west coast of Ireland (Winchester et al 1987;Harris et al 1994;Winchester & Max 1996) to Shetland (Flinn 2007;Flinn et al, in press), a distance of at least 700 km and possibly up to 1000 km (on present configuration) (Fig. 2b).…”

The Erzgebirge, Germany, a subducted part of northern Gondwana: geochemical evidence for repetition of early Palaeozoic metasedimentary sequences in metamorphic thrust units

“…In addition to conventional structural and petrological studies, the geochemistry of metamorphic rocks has great potential for reconstructing their geological history. Geochemical correlation may be a valid stratigraphical tool if a metamorphic suite of uncertain affinity can be compared with a suite of known stratigraphic position (Winchester & Max, 1996).…”