Carboniferous and Permian magmatism in Scotland

Upton, B. G. J.; Stephenson, David; Smedley, Pauline; Wallis, Susan M.; Fitton, J. Godfrey

doi:10.1144/gsl.sp.2004.223.01.09

Cited by 40 publications

(28 citation statements)

References 82 publications

(85 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Ebinger and Sleep (1998) (Read et al, 2002). Basalt erupted over this time interval is OIB-like in its incompatible-element abundances and Sr-Nd-Pb-isotope ratios (Smedley, 1986(Smedley, , 1988Upton et al, 2004), and also has generally positive ∆Nb (Figure 14). Unlike the African rifts, which formed on a plate that was stationary with respect to hotspots, the Scottish Midland Valley moved ~15º northwards across the Equator during the 70 Ma when it was volcanically active (Smith et al, 1981;Lawver et al, 2002; Figure 15).…”

Section: Rift Systemsmentioning

confidence: 95%

The OIB paradox

Fitton¹

2007

Special Paper 430: Plates, Plumes and Planetary Processes

View full text Add to dashboard Cite

Ocean-island basalt (OIB) and OIB-like basalt are widespread in oceanic and continental settings and, contrary to popular belief, most occur in situations where mantle plumes cannot provide a plausible explanation. They are readily distinguished from normal mid-ocean ridge basalt (N-MORB) through ∆Nb, a parameter that expresses the deviation from a reference line (∆Nb=0) separating parallel Icelandic and N-MORB arrays on a logarithmic plot of Nb/Y vs. Zr/Y (Fitton et al., Earth and Planetary Science Letters, v. 153, p. 197-208). Icelandic basalts provide a useful reference set because (1) they are by definition both enriched mid-ocean ridge basalt (E-MORB) and OIB, and (2) they represent a larger range of mantle melt fractions than do intraplate OIBs. Virtually all N-MORB has ∆Nb<0 while all Icelandic basalts have ∆Nb>0. E-MORB with ∆Nb>0 is abundant on other sections of ridge, notably in the South Atlantic and South Indian Oceans. E-MORB and N-MORB from this region form strongly bimodal populations in ∆Nb, separated at ∆Nb=0, suggesting that mixing between their respective mantle sources is very limited. Most OIBs and basalts from many small seamounts, especially those formed on old lithosphere, also have ∆Nb>0. HIMU OIB (OIB with high 206 Pb/ 204 Pb and therefore a high-(U/Pb) source) has higher ∆Nb on average than does EM (enriched mantle) OIB, consistent with the presence of recycled continental crust (which has ∆Nb<0) in the EM source. Although EM OIBs tend to have the lowest values, most still have ∆Nb>0 suggesting that a relatively Nb-rich component (probably subducted ocean crust) is present in all OIB sources. The OIB source components seem to be present on all scales, from small streaks or blobs of enriched material (with positive ∆Nb) carried in the upper mantle

show abstract

Section: Rift Systemsmentioning

confidence: 95%

The OIB paradox

Fitton¹

2007

Special Paper 430: Plates, Plumes and Planetary Processes

View full text Add to dashboard Cite

show abstract

“…Precision and accuracy (both better than 10% for concentrations at ppm level) were assessed by repeated measurements of SNR NIST 612 and BCR-2 standards. The data obtained have been processed with the GLITTER software package (Van Achterberg et al 2001). Calcium was used as an internal standard for quantifying clinopyroxenes, and magnesium for orthopyroxenes.…”

Section: Methodsmentioning

confidence: 99%

“…A review of this activity in Scotland has been given by Upton et al (2004). A wide assortment of mantle and lower crustal xenoliths, together with high-pressure phenocrysts and megacrysts, was entrained by some of the silica-poor mafic magmas (basanite to mela-nephelinite compositions).…”

mentioning

confidence: 99%

Palaeozoic subduction-related and kimberlite or carbonatite metasomatism in the Scottish lithospheric mantle

Bonadiman

Coltorti

Duggen

et al. 2007

Self Cite

View full text Add to dashboard Cite

Mantle xenoliths entrained in late Carboniferous to mid-Permian silica-poor basic magmas from northern Scotland were investigated using major and trace element compositions of minerals and isotopic compositions of whole-rocks and clinopyroxenes. The aim of the study was to gain more precise information on the nature of the lithospheric mantle beneath this terrane, including evidence for its metasomatic modification and evolution. This study concerns peridotites from two localities in the ENE and WSW of the Scottish Northern Highlands Terrane: Rinibar (South Ronaldsay, Orkney) and Streap Com'laidh (near Glenfinnan). Two groups of clinopyroxenes can be distinguished both at Streap Com'laidh (Type-S1 and Type-S2) and Rinibar (Type-R1 and Type-R2) based on different trace element contents and isotopic ratios. Type-S1 is characterized by an almost flat profile from middle rare earth elements (MREE) to heavy REE (HREE) accompanied by an overall light REE (LREE) enrichment. It shows the highest Th and U, coupled with low Sr, Zr and TiO 2 contents. Type-S2 exhibits humped LREE-enriched patterns and a steep decrease from Nd to Yb. It has the lowest Th and U, coupled with the highest Sr, TiO 2 and Zr contents. Both groups of clinopyroxenes present analogous isotopic features. They have measured 87 Sr/ 86 Sr values from 0.70652 to 0.70826, 144 Nd/ 143 Nd from 0.512093 to 0.512687 and 176 Hf/ 177 Hf from 0.282727 to 0.283088. These isotopic features could be explained by the addition in the mantle wedge of a slab component, made up of altered oceanic crust plus a moderate quantity of subducted sediments. The most recent subduction event in the geological history of Scotland is at about 400 Ma. It may have been during this convergent stage that the metasomatism affecting the sub-Streap lithospheric mantle occurred. Type-R1 is characterized by the lowest concentrations of Ba, Rb, Sr, LREE and U-Th, associated with remarkably high levels of Ti and Zr. These clinopyroxenes have measured 87 Sr/ 86 Sr ranging from 0.70330 to 0.70383, 144 Nd/ 143 Nd from 0.512643 to 0.512761 and 176 Hf/ 177 Hf from 0.282705 to 0.282899. In contrast, Type-R2 shows the highest concentrations of Ba, Rb, Sr, LREE and U-Th, and pronounced Ti and Zr negative anomalies. They have measured 87 Sr/ 86 Sr isotopic ratios similar to Type-R1, but lower 144 Nd/ 143 Nd (0.512431-0.512524) and higher 176 Hf/ 177 Hf (0.282921-0.283014). Calculated melt in equilibrium with Type-R1 is very similar to inferred primary kimberlitic magmas and the clinopyroxene trace element profiles may have resulted from an efficient chemical exchange between a percolating melt and the peridotite host rock. On the other hand the calculated Type-R2 melt overlaps the field of Proterozoic carbonatites. Significantly, at the age of 550 (+50) Ma, the two groups have almost identical Sr-Nd compositions, similar to average depleted mid-ocean ridge basalt mantle (DMM) at 550 Ma. This strongly suggests contemporaneous overprinting of DMM by kimberlitic and carbonatitic metasomatic agents at c. ...

show abstract

“…Magmatism was not seen again in Scotland after the intrusion of the Glen Gollaidh aillikite until intra-plate magmatism which was at its most active from 341 to 335 Ma but occurred considerably further south (Upton et al 2004). This magmatism, which included the Clyde Plateau basalts (Monaghan and Parrish 2006) is interpreted to be a consequence of hot-spot magmatism and continental collision further south between Gondwana and Laurasia (8°W).…”

Section: Mantle Lithosphere Compositionmentioning

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

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

show abstract

Carboniferous and Permian magmatism in Scotland

Cited by 40 publications

References 82 publications

The OIB paradox

The OIB paradox

Palaeozoic subduction-related and kimberlite or carbonatite metasomatism in the Scottish lithospheric mantle

The mantle of Scotland viewed through the Glen Gollaidh aillikite

Contact Info

Product

Resources

About