The Rhinns Complex: Proterozoic basement on Islay and Colonsay, Inner Hebrides, Scotland, and on Inishtrahull, NW Ireland

1994 ◽  
Vol 85 (1) ◽  
pp. 77-90 ◽  
Author(s):  
R. J. Muir ◽  
W. R. Fitches ◽  
A. J. Maltman
Keyword(s):  
Igneous Rocks ◽  
Mobile Belt ◽  
Precambrian Basement ◽  
Isotopic Data ◽  
Large Area ◽  
Isotopic Signatures ◽  
The North ◽  
North Side ◽  
Proterozoic Basement ◽  
Complex Forms

ABSTRACTThe Precambrian basement on the islands of Islay, Colonsay and Inishtrahull comprises a deformed igneous association of mainly syenite and gabbro, with minor mafic and felsic intrusions. This association is collectively referred to as the Rhinns Complex. Isotopic data indicate that the complex represents new addition of material to the crust at c. 1·8 Ga. The igneous protolith was juvenile mantle-derived material, not reworked Archaean crust. Overall, the complex has an alkalic composition, with major and trace element patterns similar to igneous rocks generated in a subduction-related setting: high LILE/HFSE and LREE/HREE ratios, together with negative Nb, P and Ti anomalies.The formation of the Rhinns Complex was contemporaneous with the Laxfordian tectonothermal cycle in the Lewisian Complex. These Proterozoic events are most likely associated with an extensive 1·9–1·7 Ga mobile belt around the southern margin of Laurentia-Baltica. As part of this belt, the Rhinns Complex forms a link between the Ketilidian province of South Greenland and the Svecofennian of Scandinavia.Inherited isotopic signatures in the Caledonian granites on the north side of the Highland Boundary Fault may reflect the presence of a large area of Proterozoic basement (?Rhinns Complex) beneath Scotland and NW Ireland. Alternatively, the Proterozoic signature could be derived from the incorporation of Moine or Dalradian sediment into the granitic magmas.

scholarly journals Silicic volcanism in the Scottish Lower Carboniferous; lavas, intrusions and ignimbrites of the Garleton Hills Volcanic Formation, SE Scotland

2020 ◽  
Vol 56 (1) ◽  
pp. 63-79
Author(s):  
Brian G. J. Upton ◽  
Linda A. Kirstein ◽  
Nicholas Odling ◽  
John R. Underhill ◽  
Robert M. Ellam ◽  
...  
Keyword(s):  
Extensional Tectonics ◽  
Isotopic Data ◽  
Central Type ◽  
Lower Carboniferous ◽  
The North ◽  
Basaltic Magmatism ◽  
North Side ◽  
Volcanic Formation ◽  
History Of ◽  
Magmatic History

Extensional tectonics and incipient rifting on the north side of the Iapetus suture were associated with eruption of (mainly) mildly alkaline olivine basalts. Initially in the Tournaisian (Southern Uplands Terrane), magmatic activity migrated northwards producing the Garleton Hills Volcanic Formation (GHVF) across an anomalous sector of the Southern Uplands. The latter was followed by resumption of volcanism in the Midland Valley Terrane, yielding the Arthur's Seat Volcanic Formation. Later larger-scale activity generated the Clyde Plateau Volcanic Formation (CPVF) and the Kintyre lavas on the Grampian Highlands Terrane. Comparable volcanic successions occur in Limerick, Ireland. This short-lived (c. 30 myr) phase was unique in the magmatic history of the Phanerozoic of the British Isles in which mildly alkaline basaltic magmatism locally led to trachytic differentiates. The Bangly Member of the GHVF represents the largest area occupied by such silicic rocks. The most widespread lavas and intrusions are silica-saturated/oversaturated trachytes for which new whole-rock and isotopic data are presented. Previously unrecognized ignimbrites are described. Sparse data from the fiamme suggest that the magma responsible for the repetitive ignimbrite eruptions was a highly fluid rhyolite. The Bangly Member probably represents the remains of a central-type volcano, the details of which are enigmatic.

Geological correlations between Cape Breton Island and Newfoundland, northern Appalachian orogen

1998 ◽  
Vol 35 (11) ◽  
pp. 1252-1270 ◽  
Author(s):  
S M Barr ◽  
R P Raeside ◽  
C E White
Keyword(s):  
Sensu Stricto ◽  
Mobile Belt ◽  
Cape Breton Island ◽  
Small Areas ◽  
Isotopic Signatures ◽  
The North ◽  
Rock Types ◽  
Cape Breton ◽  
Appalachian Orogen ◽  
Back Arc

Geological correlations between Cape Breton Island and Newfoundland are apparent both in surface geology and at deeper crustal levels, based on similarities in Sm-Nd isotopic signatures. The Mira terrane of southeastern Cape Breton Island is part of the Avalon terrane sensu stricto and is composed of Neoproterozoic volcanic-sedimentary-plutonic belts and overlying Cambrian rocks directly comparable to those in the western part of the Newfoundland Avalon terrane. The Bras d'Or terrane is also mainly of Neoproterozoic age, but shows lithological and isotopic contrasts with the Mira terrane. Small areas of similar Neoproterozoic rocks occur in southern Newfoundland and to the north as inliers in the Exploits terrane. The Bras d'Or terrane and similar rocks in Newfoundland are interpreted to represent a peri-Gondwanan terrane where rocks of the Gander terrane were later formed. Hence this area is part of the Central Mobile Belt and distinct from Avalon terrane sensu stricto. The Aspy terrane is a complex area that may include fragments of Bras d'Or crust and components of the Gander, Exploits, and possibly Notre Dame terranes of Newfoundland. It formed by subduction and back-arc basin opening and closure during the Silurian to Early Devonian. The Blair River Inlier is a fragment of Grenvillian rocks, similar to those in the Grenvillian inliers in the Humber zone of western Newfoundland in terms of age, rock types, and isotopic composition. Silurian and Devonian promontory-promontory collision resulted in juxtaposition and stacking of these elements in Cape Breton Island, as in the Hermitage Flexure - Port aux Basques area of Newfoundland. Because the lower crust under Bras d'Or - Gander - Aspy terranes seems distinct from that under Avalon terrane sensu stricto, it is preferable to use the term peri-Gondwanan rather than Avalonian to refer to these areas.

The geochronology of some granitic bodies from eastern Newfoundland and its bearing on Appalachian evolution

1977 ◽  
Vol 14 (3) ◽  
pp. 456-476 ◽  
Author(s):  
Keith Bell ◽  
John Blenkinsop ◽  
D. F. Strong
Keyword(s):  
High Ratio ◽  
The Other ◽  
Mobile Belt ◽  
Magmatic Activity ◽  
Precambrian Basement ◽  
Isotopic Data ◽  
Late Cambrian ◽  
Appalachian Orogen ◽  
Leucocratic Granite ◽  
Geochronological Evidence

Whole-rock Rb–Sr isochron ages from nine granitic plutons that intrude the Central Mobile Belt and the Avalon Zone of Newfoundland are consistent with the view that most of the magmatic activity for this segment of the Appalachian Orogen is related to the Acadian Orogeny. Most of the granites are between 400 Ma and 340 Ma old, although two from the Avalon Zone are significantly different. One, the foliated Swift Current granite, is late Cambrian – early Ordovician (500 ± 30 Ma), whereas the other, the peralkaline St. Lawrence granite, is Carboniferous (315 ± 5 Ma).Several foliated granites from the Gander Zone of the Central Mobile Belt, formerly considered to be older than Mid-Ordovician, are Silurian or Devonian in age. Five megacrystic biotite granites have ages ranging between 420 ± 20 Ma and 340 ± 10 Ma, and a leucocratic granite, the Middle Ridge Pluton, gives an age of 370 ± 15 Ma. None of the granites from the Gander Zone is older than 420 ± 20 Ma, and geochronological evidence for a Precambrian basement in the Central Mobile Belt has still to be found.The initial 87Sr/86Sr ratios show no correlation with age, although the initial ratio of 0.722 for the St. Lawrence granite is much higher than the ratios of between 0.704 and 0.709 for the other granites; this high ratio is consistent with derivation of the granite by partial melting of the continental crust.The isotopic data impose certain constraints on models proposed for the evolution of Newfoundland, the most important being: (i) extensive Devonian magmatism; (ii) intense post-400 Ma cataclasis; (iii) generation of petrographically similar granites at different times; and (iv) Carboniferous magmatism.

Nd isotopic evidence for crustal recycling in the ca. 2.0 Ga subsurface of western Canada

1991 ◽  
Vol 28 (8) ◽  
pp. 1140-1147 ◽  
Author(s):  
R. J. Thériault ◽  
G. M. Ross
Keyword(s):  
Isotopic Data ◽  
Tectonic Zone ◽  
Isotopic Signatures ◽  
Crustal Recycling ◽  
The North ◽  
Tectonic History ◽  
Depleted Mantle ◽  
History Of ◽  
Mantle Component ◽  
Northern Alberta

Sm–Nd isotopic data are presented for 23 drill-core samples from five aeromagnetically and geochronologically (U–Pb zircon) distinct domains of the Precambrian basement of northern Alberta. The domains in question are the Taltson (1.96–1.94 Ga), Buffalo Head (2.32–1.99 Ga), Chinchaga (2.19–2.09 Ga), Ksituan (1.99–1.90 Ga), and Nova (2.81 Ga). These domains are truncated to the north and south by the Great Slave Lake shear zone and the Snowbird tectonic zone, respectively.Initial εNd values are −5.0 to −9.7 for the Taltson, +0.2 to −6.3 for the Buffalo Head, +0.6 to −1.8 for the Chinchaga, −1.8 to −2.1 for the Ksituan and +5.6 for the Nova. Crustal residence model ages fall in the 2.5–2.8 Ga range. The Nd isotopic signatures may be viewed in terms of mixing a minimum of 10% Archean continental crust with a depleted-mantle component. Speculations on the tectonic history of the basement domains in question involve the assembly of Archean crustal nuclei to form the Buffalo Head – Chinchaga composite domain. Arc magmatism resulting from plate subduction to the east and west of the Buffalo Head – Chinchaga composite domain would have generated the Taltson and Ksituan domains. The Nd isotopic data suggest that the basement of northern Alberta consists of crust of late Archean crustal residence age which has been extensively remobilized in the Early Proterozoic.

Esquisse geologique de l'Arabie seoudite

1957 ◽  
Vol S6-VII (6) ◽  
pp. 653-697 ◽  
Author(s):  
Roman Karpoff
Keyword(s):  
Saudi Arabia ◽  
Red Sea ◽  
Lava Flows ◽  
Precambrian Basement ◽  
Large Area ◽  
The North

Abstract An outline of the geology of Saudi Arabia. The Precambrian basement consists of two distinct series. The Medina series, the older, includes rocks metamorphosed to different stages (sericite schists, gneisses, and migmatites), with numerous lava flows, particularly in the western part. Various granites and dike rocks intrude the Medina but not the Wadi Fatima series lying discordantly above it. The Wadi Fatima is folded and contains three local stromatolitic zones. The Paleozoic is represented in the north by rocks exhibiting a typical Saharan facies. Marine Muschelkalk (Triassic) beds and Jurassic formations (beginning with Toarcian) cover a large area. The most important Cretaceous transgression occurred in the Maestrichtian, when a gulf extended to the Djeddah region. The grabens of central Arabia appear to be related to the formation of the Red Sea depression during Mio-Pliocene time.

scholarly journals Field work on the Nagssugtoqidian boundary north of Angmagssalik and Tertiary igneous rocks of Kialineq and Kap Gustav Holm, East Greenland

1979 ◽  
Vol 95 ◽  
pp. 82-85
Author(s):  
J.S Myers ◽  
H Austrheim ◽  
R.C.O Gill ◽  
B.E Gorman ◽  
D.C Rex
Keyword(s):  
Field Work ◽  
Igneous Rocks ◽  
Dyke Swarm ◽  
Mobile Belt ◽  
North Shore ◽  
Ice Cap ◽  
The North ◽  
Isotope Studies ◽  
Tycho Brahe ◽  
Inland Ice

Work was carried out from the 80 ton cutter Tycho Brahe using 16 ft inflatable rubber dinghies between 24th July and 31st August 1978. In addition, the Nagssugtoqidian boundary was mapped westwards from Kangerdlugssuatsiaq to the inland ice cap by Bell 204 helicopter and part of the Kialineq region was mapped from a Piper Navajo aircraft (fig. 28). The Nagssugtoqidian boundary was examined on the north shore of Kangerdlugssuatsiaq and a section through the northem part of the Nagssugtoqidian mobile belt was mapped along the shores of the upper part of Sermilik by rubber dinghy. Part of the Angmagssalik charnockite complex was examined in detail around Angmagssalik and Kap Dan. The Tertiary plutonic centres of Kialineq and Kap Gustav Holm were mapped in detail as well as the coastal dyke swarm in these regions, and samples were collected from all the main plutonic units for petrology and isotope studies.

scholarly journals On the Older Parian Formation in Trinidad

The Geologist ◽  
1863 ◽  
Vol 6 (6) ◽  
pp. 204-207
Author(s):  
R. Lechmere Guppy
Keyword(s):  
South America ◽  
Short Distance ◽  
East Coast ◽  
The South ◽  
Large Area ◽  
Main Band ◽  
The North ◽  
North Side ◽  
Line Parallel ◽  
The Government

In the Report on the Geology of Trinidad the Government geologists described a series of sandstones and shales extending across the island from east to west, and occupying an extent of about 97 square miles. The distribution of the formation, which has been named the “Older Parian,” is in the manner of an irregular band of from 1 to 4 miles in breadth, traversing the island in an easterly direction from the Gulf of Paria at Pointe à Pierre. This band terminates rather abruptly before reaching the east coast, but the formation reappears here and there near the south coast along a line parallel to the main band. The formation is only exposed for a short distance on the shores of the Gulf of Paria; but it has been found to cover a large area, and to be extensively developed on the continent of South America. The fossils found by the geologists in Trinidad seem to have been few, and for the most part indeterminable. They however obtained fossils from the same formation at Cumana, in Venezuela; and these remains led to the belief that the Older Parian was probably of Neocomian age. During a short visit to Pointe à Pierre I obtained several fossils, which have enabled me to make the observations detailed in the present paper.The section given by the Government geologists of the Older Parian deposits at Pointe à Pierre is taken on the south side of the point, which I have not had an opportunity of examining carefully. The geologists do not seem to be able to give much attention to that portion of the deposits which is exposed on the north side of the point, and I hope that the present paper, in so far at least as it relates to the fossils, may in some measure supply the deficiency.

scholarly journals Disko Bugt Project, central West Greenland

1990 ◽  
Vol 148 ◽  
pp. 21-24
Author(s):  
F Kalsbeek
Keyword(s):  
Mineral Resources ◽  
Precambrian Basement ◽  
Economic Potential ◽  
The West ◽  
North East ◽  
The North ◽  
North Eastern ◽  
Second Year ◽  
Proterozoic Basement ◽  
North Eastern Part

One of GGU’s major field activities in 1989 took place in July and August in the north-eastern part of the Disko Bugt region, mainly north of Illulissat (Jakobshavn) (fig. 1). This was the second year of the ‘Disko Bugt Project’, planned for 1988–1991, with one summer's break in 1990. The project spreads over various activities and over two very different geological provinces: the Archacan-Proterozoic basement east and north-east of Disko Bugt and in the eastern part of Nugssuaq, and the Cretaceous-Tertiary basin in the west, on Disko and the western part of Nugssuaq. The main aim of the project is to provide a background for the evaluation of the economic potential of the region mineral resources in the Precambrian basement, and the hydrocarbon potential of the basin.

A Radiocarbon-dated Collared Urn from Oban

2001 ◽  
Vol 23 (2) ◽  
pp. 105-118
Author(s):  
CHRISTOPHER LOWE ◽  
ANN MacSWEEN ◽  
KATHLEEN McSWEENEY
Keyword(s):  
The North ◽  
North Side ◽  
Funerary Ritual

A collared urn was found during the course of a watching-brief on the raised beach on the north side of Oban bay. Post-excavation analysis has succeeded in throwing some further light on the chronology of this type of urn and possibly on some elements of the funerary ritual associated with its burial. The same watching-brief also revealed the site of a truncated pit of medieval date, filled with fire-cracked stones.

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