The tectonomagmatic evolution of Scotland

Macdonald, Ray; Fettes, D. J.

doi:10.1017/s0263593300001450

Cited by 32 publications

(27 citation statements)

References 264 publications

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“…In mainland Scotland, minor alkali intrusives and fenitised rocks were intruded along the Great Glen Fault at ca. 390 Ma (Macdonald and Fettes 2007). This age still pre-dates the age of the Glen Gollaidh aillikite by ca.…”

Section: Mantle Lithosphere Compositionmentioning

confidence: 86%

“…However, more typically, there is also a progression from dominant, deep-sourced Mg chromite (Clare Island; Upton et al 2001), to Mg-Al chromite (Loch Roag, Upton et al 2011; with minor Mg chromite, Glen Gollaidh), to Mg-Al chromite with Mg-Cr-Al spinel (Rinibar) to shallow-sourced Mg-Cr-Al spinel (off-craton at Streap Com'laidh and Fidra). While the variability in chemistry of the Glen Gollaidh mantle component has a partial explanation in a range of sampling depths, the majority of the variability is explained by a complex history of metasomatism and partial melting; a consequence of the upheavals associated with the closure of the Iapetus and accumulation of Laurussia (Macdonald and Fettes 2007). It is concluded that this same complex mantle chemistry created suitable conditions to allow melting of the mantle below Glen Gollaidh at this late stage in the deformations of the margins of the NAC.…”

Section: Glen Gollaidh's Place At the Nac Marginmentioning

confidence: 99%

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The mantle of Scotland viewed through the Glen Gollaidh aillikite

Hutchison¹,

Faithfull

Barfod

et al. 2018

Miner Petrol

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The Glen Gollaidh aillikite dyke (58.36741°N 4.69751°W), N.W. Scotland, occurs within the Neoproterozoic sedimentary rocks of the Moine Supergroup~4 km east of the Moine Thrust. Phlogopite 40 Ar/ 36 Ar measurements give a late Devonian maximum emplacement age of 360.3 ± 4.9 (2σ) Ma. This age occurs in a quiet period of Scottish magmatic history c. 30 Ma after the closure of the Iapetus and before the start of intra-plate alkali magmatism which affected southern Scotland for~60 My from c. 350 Ma. Abundant chromites and Cr-diopsides and a few unaltered olivines, reflecting a mantle provenance, were recovered from heavy mineral concentrates. The North Atlantic Craton, exposed in Lewisian gneisses west of the Moine thrust, is therefore inferred to extend east at depth under Glen Gollaidh, presenting an opportunity to investigate the thickness and composition of the cratonic margin in the Devonian. The aillikite was found to be barren of diamond and no picro-ilmenites or garnets were definitively identified. However, mineral chemistry suggests that a proportion of Glen Gollaidh xenocrysts crystallised in equilibrium with garnet. Most spinels are Mg, Al chromites, with some Mg chromite present. All fall within the garnet peridotite field based on Ti and Cr but with insufficient Cr 2 O 3 (up to 47.2 wt%) to be consistent with the diamond stability field. Amongst Cr-diopsides 30% of grains have Cr and Al contents consistent with derivation from garnet peridotite. The majority of clinopyroxenes also show a marked depletion in heavy compared to light rare-earth elements, again consistent with equilibration with garnet. The opx-cpx solvus thermometer demonstrates that average Cr-diopside compositions require at least 37 kbar to give a temperature (979°C) lying even on a relatively warm 40 mWm −2 geotherm (Hasterok and Chapman Earth Planet Sc Lett 307:59-70, 2011). Large variations in the chemistry of mantle minerals reflect a complex history of metasomatism akin to constituents of alkali igneous rocks elsewhere in the Hebridean and Northern Highlands Terranes. Fertilised mantle provided the conditions for generation of aillikite melts, probably triggered by break-off of the advancing Avalonia slab. The cratonic root underlying the Glen Gollaidh aillikite during the late Devonian was apparently too thin to lie within the diamond stability field, consistent with xenoliths from alkali basalts further south. Nonetheless, sufficient geophysical and mineral chemical evidence supports Glen Gollaidh aillikite sitting close to the edge of diamond-prospective mantle therefore suggesting diamond potential a short distance to the west within the Lewisian and what is now East Greenland. (2018) 112 (Suppl 1):S115-S132

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Section: Mantle Lithosphere Compositionmentioning

confidence: 86%

Section: Glen Gollaidh's Place At the Nac Marginmentioning

confidence: 99%

The mantle of Scotland viewed through the Glen Gollaidh aillikite

Hutchison¹,

Faithfull

Barfod

et al. 2018

Miner Petrol

View full text Add to dashboard Cite

show abstract

“…Accepting these reservations and given the above time-scales, our best estimates of the age of the volcanic episodes across the Dalradian belt may be summarised as follows. It is noteworthy, in this context, that an extensive suite of rift-related silicic intrusions, the Vuirich suite, is believed to have been emplaced at c. 600 Ma, suggesting a major episode of bimodal magmatism at that time (Tanner et al 2006;Macdonald & Fettes 2007).…”

Section: Age Of Volcanismmentioning

confidence: 88%

“…Indeed, the scale of the magmatism has perhaps been underappreciated. For example, the lavas and sills of the Tayvallich Volcanic Formation alone have a minimum volume of 3000 km 3 , to which can probably be added comparable amounts of underplated material (Halliday et al 1985;Macdonald & Fettes 2007). These volumes are substantial although significantly less than the plume-related large igneous provinces, where volumes are typically 10 ; Hofman et al 1997).…”

Section: Geological Settingmentioning

confidence: 99%

“…Svenningsen (2001) has suggested that the onset of seafloor spreading in the Iapetus Ocean along the margin between Laurentia and Baltica occurred at c. 608 Ma. In the Scottish Highlands the rifting is marked by bimodal magmatism, the beginning of which is poorly constrained (probably c. 650 Ma) and lasting until 590 Ma (Macdonald & Fettes, 2007). Overall it is probable that the phases of extensional tectonics were diachronous, from c. 700 Ma in east-central Laurentia to near the close of the Proterozoic (c. 545 Ma) in northeastern Laurentia (Li et al 2008;Prave et al 2009a).…”

Section: Introductionmentioning

confidence: 99%

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

Fettes

Macdonald

Fitton

et al. 2011

JGS

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Provenance of Triassic sandstones in the basins of Northern Ireland—Implications for NW European Triassic palaeodrainage

et al. 2020

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Palaeodrainage models for the mixed fluvial‐aeolian systems, which supplied detritus to Triassic basins on and offshore Britain and Ireland are well established. Basins such as those across Northern Ireland are not as well understood. Provenance studies of Triassic sandstones in the Slyne Basin offshore western Ireland and in basins west of Shetland have indicated that sediment supply was through a southward flowing fluvial system. Similar work on Triassic sandstones in the Wessex and East Irish Sea basins on and offshore Britain identified source rocks to the south supporting models, which evoke the northward flowing “Budleighensis” river system. The basins across Northern Ireland are potentially situated along the drainage divide between these two large‐scale drainage systems. K‐feldspar Pb‐isotopic analysis, apatite U–Pb geochronology and trace element geochemistry identify the Hebridean Platform, and the Scottish and Irish massifs to the north and west, respectively, and the remnant Variscan Uplands to the far south of the basins as source areas. The proportion of the northern‐ and southern‐derived detritus fluctuates several times over the sampled intervals, suggesting the dominance of drainage systems supplying sand to the basins “switched” intermittently over time. This may be due to abnormally heavy rains periodically powering the Budleighensis river system farther north or perhaps localised subsidence temporarily disconnecting Triassic basins on and offshore Britain and Ireland. The Triassic basins in Northern Ireland acted as either a major drainage divide between southern and northern river systems or as a regional sink for sediment preventing further expansion of either system.

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The tectonomagmatic evolution of Scotland

Cited by 32 publications

References 264 publications

The mantle of Scotland viewed through the Glen Gollaidh aillikite

The mantle of Scotland viewed through the Glen Gollaidh aillikite

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

Provenance of Triassic sandstones in the basins of Northern Ireland—Implications for NW European Triassic palaeodrainage

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