Bedrock Geology UK North: Archaean and Palaeoproterozoic - Revision history

Dbk at 14:19, 29 January 2015

2015-01-29T14:19:22Z

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	'''The Rhinns Complex of western Islay''' (and a small outcrop on Colonsay) consists of Palaeoproterozoic, felsic gneisses, the igneous protoliths of which were generated at about 1.8 Ga, probably in a subduction-related magmatic arc. Deformation and metamorphism then occurred prior to the intrusion of further felsic and mafic igneous rocks, generated in the same tectonic regime, at about 1.7 Ga. The Rhinns Complex may be the surface expression of a unique Islay–Colonsay terrane that extends south-west towards Northern Ireland (where Lewisian-like rocks form Inishtrahull island, off the north coast) but similar Palaeoproterozoic rocks could also underlie much of the Neoproterozoic succession south of the Great Glen.		'''The Rhinns Complex of western Islay''' (and a small outcrop on Colonsay) consists of Palaeoproterozoic, felsic gneisses, the igneous protoliths of which were generated at about 1.8 Ga, probably in a subduction-related magmatic arc. Deformation and metamorphism then occurred prior to the intrusion of further felsic and mafic igneous rocks, generated in the same tectonic regime, at about 1.7 Ga. The Rhinns Complex may be the surface expression of a unique Islay–Colonsay terrane that extends south-west towards Northern Ireland (where Lewisian-like rocks form Inishtrahull island, off the north coast) but similar Palaeoproterozoic rocks could also underlie much of the Neoproterozoic succession south of the Great Glen.

			==Bedrock Geology UK North - contents==
			{{bedrockNorth}}


	[[Category:Bedrock Geology UK North\| 01]]		[[Category:Bedrock Geology UK North\| 01]]

Dbk at 08:00, 19 June 2014

2014-06-19T08:00:13Z

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	{{BedN}}		{{BedN}}
	==More than 1600 million years ago==		==More than 1600 million years ago==
	[[Image:P785805.jpg\|thumb\|~~300px~~\|P785805. ]]		[[Image:P785805.jpg\|thumb\|200px\|P785805. ]]
	[[image:P008322.jpg\|right\|thumb\|300px\|The characteristic scenery produced by Archaean gneiss of the Lewisian Complex seen here at Castlebay, Barra, Outer Hebrides. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=7037&index=0&total=1&view=viewSearchItem P008322.]]]		[[image:P008322.jpg\|right\|thumb\|300px\|The characteristic scenery produced by Archaean gneiss of the Lewisian Complex seen here at Castlebay, Barra, Outer Hebrides. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=7037&index=0&total=1&view=viewSearchItem P008322.]]]
	'''The crystalline, metamorphic rocks''' of the Hebridean terrane originated as part of a continental assemblage of Archaean cratons and Palaeoproterozoic deformation belts that had been brought together by about 1.7 billion years ago (i.e. 1700 million years ago or 1.7 Ga). The dispersed fragments of this assemblage can now be recognised along the length of a vast tectonic zone (Caledonian Orogen) that stretches from Scandinavia, through Scotland to Greenland and North America. In Britain, the Hebridean terrane consists principally of the various high-grade metamorphic rocks that make up the Lewisian Gneiss Complex (A1–3 & Z1)†. This forms the north-west extremity of Scotland, cropping out in a coastal strip on the mainland, from Cape Wrath to the Sound of Sleat, and extending westward across the Outer Isles ('''Plate P008322'''). Its eastern margin is the Moine Thrust Belt, on which rocks of the Northern Highlands terrane have been carried westward over the Lewisian gneisses. East of the Moine Thrust, inliers are formed from Lewisian-like (or Lewisianoid) gneisses caught up in the folding and thrusting of the overlying, younger Proterozoic strata. Geophysical evidence suggests that Lewisian-like rocks underlie the younger Proterozoic sequences at least as far south as the Great Glen Fault. To the south of that structure, a distinctive Palaeoproterozoic gneiss assemblage is seen in the Rhinns Complex of western Islay.		'''The crystalline, metamorphic rocks''' of the Hebridean terrane originated as part of a continental assemblage of Archaean cratons and Palaeoproterozoic deformation belts that had been brought together by about 1.7 billion years ago (i.e. 1700 million years ago or 1.7 Ga). The dispersed fragments of this assemblage can now be recognised along the length of a vast tectonic zone (Caledonian Orogen) that stretches from Scandinavia, through Scotland to Greenland and North America. In Britain, the Hebridean terrane consists principally of the various high-grade metamorphic rocks that make up the Lewisian Gneiss Complex (A1–3 & Z1)†. This forms the north-west extremity of Scotland, cropping out in a coastal strip on the mainland, from Cape Wrath to the Sound of Sleat, and extending westward across the Outer Isles ('''Plate P008322'''). Its eastern margin is the Moine Thrust Belt, on which rocks of the Northern Highlands terrane have been carried westward over the Lewisian gneisses. East of the Moine Thrust, inliers are formed from Lewisian-like (or Lewisianoid) gneisses caught up in the folding and thrusting of the overlying, younger Proterozoic strata. Geophysical evidence suggests that Lewisian-like rocks underlie the younger Proterozoic sequences at least as far south as the Great Glen Fault. To the south of that structure, a distinctive Palaeoproterozoic gneiss assemblage is seen in the Rhinns Complex of western Islay.

Dbk at 07:58, 19 June 2014

2014-06-19T07:58:28Z

← Older revision		Revision as of 08:58, 19 June 2014
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	{{BedN}}		{{BedN}}
	==More than 1600 million years ago==		==More than 1600 million years ago==
			[[Image:P785805.jpg\|thumb\|300px\|P785805. ]]
	[[image:P008322.jpg\|right\|thumb\|300px\|The characteristic scenery produced by Archaean gneiss of the Lewisian Complex seen here at Castlebay, Barra, Outer Hebrides. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=7037&index=0&total=1&view=viewSearchItem P008322.]]]		[[image:P008322.jpg\|right\|thumb\|300px\|The characteristic scenery produced by Archaean gneiss of the Lewisian Complex seen here at Castlebay, Barra, Outer Hebrides. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=7037&index=0&total=1&view=viewSearchItem P008322.]]]
	'''The crystalline, metamorphic rocks''' of the Hebridean terrane originated as part of a continental assemblage of Archaean cratons and Palaeoproterozoic deformation belts that had been brought together by about 1.7 billion years ago (i.e. 1700 million years ago or 1.7 Ga). The dispersed fragments of this assemblage can now be recognised along the length of a vast tectonic zone (Caledonian Orogen) that stretches from Scandinavia, through Scotland to Greenland and North America. In Britain, the Hebridean terrane consists principally of the various high-grade metamorphic rocks that make up the Lewisian Gneiss Complex (A1–3 & Z1)†. This forms the north-west extremity of Scotland, cropping out in a coastal strip on the mainland, from Cape Wrath to the Sound of Sleat, and extending westward across the Outer Isles ('''Plate P008322'''). Its eastern margin is the Moine Thrust Belt, on which rocks of the Northern Highlands terrane have been carried westward over the Lewisian gneisses. East of the Moine Thrust, inliers are formed from Lewisian-like (or Lewisianoid) gneisses caught up in the folding and thrusting of the overlying, younger Proterozoic strata. Geophysical evidence suggests that Lewisian-like rocks underlie the younger Proterozoic sequences at least as far south as the Great Glen Fault. To the south of that structure, a distinctive Palaeoproterozoic gneiss assemblage is seen in the Rhinns Complex of western Islay.		'''The crystalline, metamorphic rocks''' of the Hebridean terrane originated as part of a continental assemblage of Archaean cratons and Palaeoproterozoic deformation belts that had been brought together by about 1.7 billion years ago (i.e. 1700 million years ago or 1.7 Ga). The dispersed fragments of this assemblage can now be recognised along the length of a vast tectonic zone (Caledonian Orogen) that stretches from Scandinavia, through Scotland to Greenland and North America. In Britain, the Hebridean terrane consists principally of the various high-grade metamorphic rocks that make up the Lewisian Gneiss Complex (A1–3 & Z1)†. This forms the north-west extremity of Scotland, cropping out in a coastal strip on the mainland, from Cape Wrath to the Sound of Sleat, and extending westward across the Outer Isles ('''Plate P008322'''). Its eastern margin is the Moine Thrust Belt, on which rocks of the Northern Highlands terrane have been carried westward over the Lewisian gneisses. East of the Moine Thrust, inliers are formed from Lewisian-like (or Lewisianoid) gneisses caught up in the folding and thrusting of the overlying, younger Proterozoic strata. Geophysical evidence suggests that Lewisian-like rocks underlie the younger Proterozoic sequences at least as far south as the Great Glen Fault. To the south of that structure, a distinctive Palaeoproterozoic gneiss assemblage is seen in the Rhinns Complex of western Islay.

Dbk at 07:55, 19 June 2014

2014-06-19T07:55:14Z

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			__NOTOC__
	{{BedN}}		{{BedN}}
	==More than 1600 million years ago==		==More than 1600 million years ago==

Jeth1 at 12:04, 12 June 2014

2014-06-12T12:04:28Z

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	~~'''~~More than 1600 million years ago~~'''~~		==More than 1600 million years ago==
	[[image:P008322.jpg\|right\|thumb\|300px\|The characteristic scenery produced by Archaean gneiss of the Lewisian Complex seen here at Castlebay, Barra, Outer Hebrides. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=7037&index=0&total=1&view=viewSearchItem P008322.]]]		[[image:P008322.jpg\|right\|thumb\|300px\|The characteristic scenery produced by Archaean gneiss of the Lewisian Complex seen here at Castlebay, Barra, Outer Hebrides. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=7037&index=0&total=1&view=viewSearchItem P008322.]]]
	'''The crystalline, metamorphic rocks''' of the Hebridean terrane originated as part of a continental assemblage of Archaean cratons and Palaeoproterozoic deformation belts that had been brought together by about 1.7 billion years ago (i.e. 1700 million years ago or 1.7 Ga). The dispersed fragments of this assemblage can now be recognised along the length of a vast tectonic zone (Caledonian Orogen) that stretches from Scandinavia, through Scotland to Greenland and North America. In Britain, the Hebridean terrane consists principally of the various high-grade metamorphic rocks that make up the Lewisian Gneiss Complex (A1–3 & Z1)†. This forms the north-west extremity of Scotland, cropping out in a coastal strip on the mainland, from Cape Wrath to the Sound of Sleat, and extending westward across the Outer Isles ('''Plate P008322'''). Its eastern margin is the Moine Thrust Belt, on which rocks of the Northern Highlands terrane have been carried westward over the Lewisian gneisses. East of the Moine Thrust, inliers are formed from Lewisian-like (or Lewisianoid) gneisses caught up in the folding and thrusting of the overlying, younger Proterozoic strata. Geophysical evidence suggests that Lewisian-like rocks underlie the younger Proterozoic sequences at least as far south as the Great Glen Fault. To the south of that structure, a distinctive Palaeoproterozoic gneiss assemblage is seen in the Rhinns Complex of western Islay.		'''The crystalline, metamorphic rocks''' of the Hebridean terrane originated as part of a continental assemblage of Archaean cratons and Palaeoproterozoic deformation belts that had been brought together by about 1.7 billion years ago (i.e. 1700 million years ago or 1.7 Ga). The dispersed fragments of this assemblage can now be recognised along the length of a vast tectonic zone (Caledonian Orogen) that stretches from Scandinavia, through Scotland to Greenland and North America. In Britain, the Hebridean terrane consists principally of the various high-grade metamorphic rocks that make up the Lewisian Gneiss Complex (A1–3 & Z1)†. This forms the north-west extremity of Scotland, cropping out in a coastal strip on the mainland, from Cape Wrath to the Sound of Sleat, and extending westward across the Outer Isles ('''Plate P008322'''). Its eastern margin is the Moine Thrust Belt, on which rocks of the Northern Highlands terrane have been carried westward over the Lewisian gneisses. East of the Moine Thrust, inliers are formed from Lewisian-like (or Lewisianoid) gneisses caught up in the folding and thrusting of the overlying, younger Proterozoic strata. Geophysical evidence suggests that Lewisian-like rocks underlie the younger Proterozoic sequences at least as far south as the Great Glen Fault. To the south of that structure, a distinctive Palaeoproterozoic gneiss assemblage is seen in the Rhinns Complex of western Islay.

Dbk: Protected "Bedrock Geology UK North: Archaean and Palaeoproterozoic" ([Edit=Allow only administrators] (indefinite) [Move=Allow only administrators] (indefinite)) [cascading]

2014-06-11T12:19:30Z

Protected "Bedrock Geology UK North: Archaean and Palaeoproterozoic" ([Edit=Allow only administrators] (indefinite) [Move=Allow only administrators] (indefinite)) [cascading]

← Older revision		Revision as of 13:19, 11 June 2014
(No difference)

Dbk at 08:19, 20 May 2014

2014-05-20T08:19:55Z

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	'''The majority of the Lewisian gneisses''' originated during the Archaean as broadly tonalitic, intrusive plutons, but they had already been reworked by tectonothermal events prior to the intrusion of the mafic and ultramafic Scourie dyke suite in mid Palaeoproterozoic times. The Archaean rocks are typically coarse-grained, banded or streaky, grey felsic gneisses, which commonly enclose dark layers and lenses composed mostly of hornblende. In places, these mafic rocks are sufficiently abundant to form substantial belts of spectacularly banded gneisses ('''Plate P008309'''). A few large mafic enclaves may represent relict oceanic crust and are locally in association with more pelitic gneisses of sedimentary origin.		'''The majority of the Lewisian gneisses''' originated during the Archaean as broadly tonalitic, intrusive plutons, but they had already been reworked by tectonothermal events prior to the intrusion of the mafic and ultramafic Scourie dyke suite in mid Palaeoproterozoic times. The Archaean rocks are typically coarse-grained, banded or streaky, grey felsic gneisses, which commonly enclose dark layers and lenses composed mostly of hornblende. In places, these mafic rocks are sufficiently abundant to form substantial belts of spectacularly banded gneisses ('''Plate P008309'''). A few large mafic enclaves may represent relict oceanic crust and are locally in association with more pelitic gneisses of sedimentary origin.

	[[Image:P008309.jpg\|thumb\|300px\|Banded mafic and feldspathic Archaean gneiss, Lewisian Complex, South Uist, Outer Hebrides. [http://geoscenic.bgs.ac.uk/asset-bank/action/~~viewFullSizedImage~~?id=7024&~~size~~=~~1000~~ P008309.]]]		[[Image:P008309.jpg\|thumb\|300px\|Banded mafic and feldspathic Archaean gneiss, Lewisian Complex, South Uist, Outer Hebrides. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=7024&index=0&total=1&view=viewSearchItem P008309.]]]

	'''The oldest of the Archaean rocks''' are the felsic gneisses of the Outer Hebrides, which yield protolith ages of 3.2 to 2.8 Ga. The oldest gneisses on the mainland have protolith ages of about 3.0 Ga but differences in the detail of the age range from different parts of the complex suggest a complicated early history prior to the amalgamation of the component parts. High-grade metamorphism occurred at about 2.7 Ga, with an additional metamorphic episode at about 2.5 Ga recorded in the northern part of the mainland. This metamorphism, together with deformation and the formation of wide shear zones, preceded intrusion of the earliest Scourie dykes. These were intruded, predominantly as quartz-dolerites, in two swarms; the main one was emplaced at about 2.4 Ga with subsidiary intrusion at about 2.0 Ga.		'''The oldest of the Archaean rocks''' are the felsic gneisses of the Outer Hebrides, which yield protolith ages of 3.2 to 2.8 Ga. The oldest gneisses on the mainland have protolith ages of about 3.0 Ga but differences in the detail of the age range from different parts of the complex suggest a complicated early history prior to the amalgamation of the component parts. High-grade metamorphism occurred at about 2.7 Ga, with an additional metamorphic episode at about 2.5 Ga recorded in the northern part of the mainland. This metamorphism, together with deformation and the formation of wide shear zones, preceded intrusion of the earliest Scourie dykes. These were intruded, predominantly as quartz-dolerites, in two swarms; the main one was emplaced at about 2.4 Ga with subsidiary intrusion at about 2.0 Ga.

Dbk at 08:19, 20 May 2014

2014-05-20T08:19:12Z

← Older revision		Revision as of 09:19, 20 May 2014
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	{{BedN}}		{{BedN}}
	'''More than 1600 million years ago'''		'''More than 1600 million years ago'''
	[[image:P008322.jpg\|right\|thumb\|300px\|The characteristic scenery produced by Archaean gneiss of the Lewisian Complex seen here at Castlebay, Barra, Outer Hebrides. [http://geoscenic.bgs.ac.uk/asset-bank/action/~~search~~?~~newSearch~~=~~true~~&~~quickSearch~~=~~true~~&~~includeImplicitCategoryMembers~~=~~true~~&~~keywords~~=~~P008322~~ P008322.]]]		[[image:P008322.jpg\|right\|thumb\|300px\|The characteristic scenery produced by Archaean gneiss of the Lewisian Complex seen here at Castlebay, Barra, Outer Hebrides. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=7037&index=0&total=1&view=viewSearchItem P008322.]]]
	'''The crystalline, metamorphic rocks''' of the Hebridean terrane originated as part of a continental assemblage of Archaean cratons and Palaeoproterozoic deformation belts that had been brought together by about 1.7 billion years ago (i.e. 1700 million years ago or 1.7 Ga). The dispersed fragments of this assemblage can now be recognised along the length of a vast tectonic zone (Caledonian Orogen) that stretches from Scandinavia, through Scotland to Greenland and North America. In Britain, the Hebridean terrane consists principally of the various high-grade metamorphic rocks that make up the Lewisian Gneiss Complex (A1–3 & Z1)†. This forms the north-west extremity of Scotland, cropping out in a coastal strip on the mainland, from Cape Wrath to the Sound of Sleat, and extending westward across the Outer Isles ('''Plate P008322'''). Its eastern margin is the Moine Thrust Belt, on which rocks of the Northern Highlands terrane have been carried westward over the Lewisian gneisses. East of the Moine Thrust, inliers are formed from Lewisian-like (or Lewisianoid) gneisses caught up in the folding and thrusting of the overlying, younger Proterozoic strata. Geophysical evidence suggests that Lewisian-like rocks underlie the younger Proterozoic sequences at least as far south as the Great Glen Fault. To the south of that structure, a distinctive Palaeoproterozoic gneiss assemblage is seen in the Rhinns Complex of western Islay.		'''The crystalline, metamorphic rocks''' of the Hebridean terrane originated as part of a continental assemblage of Archaean cratons and Palaeoproterozoic deformation belts that had been brought together by about 1.7 billion years ago (i.e. 1700 million years ago or 1.7 Ga). The dispersed fragments of this assemblage can now be recognised along the length of a vast tectonic zone (Caledonian Orogen) that stretches from Scandinavia, through Scotland to Greenland and North America. In Britain, the Hebridean terrane consists principally of the various high-grade metamorphic rocks that make up the Lewisian Gneiss Complex (A1–3 & Z1)†. This forms the north-west extremity of Scotland, cropping out in a coastal strip on the mainland, from Cape Wrath to the Sound of Sleat, and extending westward across the Outer Isles ('''Plate P008322'''). Its eastern margin is the Moine Thrust Belt, on which rocks of the Northern Highlands terrane have been carried westward over the Lewisian gneisses. East of the Moine Thrust, inliers are formed from Lewisian-like (or Lewisianoid) gneisses caught up in the folding and thrusting of the overlying, younger Proterozoic strata. Geophysical evidence suggests that Lewisian-like rocks underlie the younger Proterozoic sequences at least as far south as the Great Glen Fault. To the south of that structure, a distinctive Palaeoproterozoic gneiss assemblage is seen in the Rhinns Complex of western Islay.

Dbk at 08:18, 20 May 2014

2014-05-20T08:18:32Z

← Older revision		Revision as of 09:18, 20 May 2014
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	{{BedN}}		{{BedN}}
	'''More than 1600 million years ago'''		'''More than 1600 million years ago'''
	[[image:P008322.jpg\|right\|thumb\|300px\|The characteristic scenery produced by Archaean gneiss of the Lewisian Complex seen here at Castlebay, Barra, Outer Hebrides. [http://geoscenic.bgs.ac.uk/asset-bank/action/search?newSearch=true&quickSearch=true&includeImplicitCategoryMembers=true&keywords=P008322.]]]		[[image:P008322.jpg\|right\|thumb\|300px\|The characteristic scenery produced by Archaean gneiss of the Lewisian Complex seen here at Castlebay, Barra, Outer Hebrides. [http://geoscenic.bgs.ac.uk/asset-bank/action/search?newSearch=true&quickSearch=true&includeImplicitCategoryMembers=true&keywords=P008322 P008322.]]]
	'''The crystalline, metamorphic rocks''' of the Hebridean terrane originated as part of a continental assemblage of Archaean cratons and Palaeoproterozoic deformation belts that had been brought together by about 1.7 billion years ago (i.e. 1700 million years ago or 1.7 Ga). The dispersed fragments of this assemblage can now be recognised along the length of a vast tectonic zone (Caledonian Orogen) that stretches from Scandinavia, through Scotland to Greenland and North America. In Britain, the Hebridean terrane consists principally of the various high-grade metamorphic rocks that make up the Lewisian Gneiss Complex (A1–3 & Z1)†. This forms the north-west extremity of Scotland, cropping out in a coastal strip on the mainland, from Cape Wrath to the Sound of Sleat, and extending westward across the Outer Isles ('''Plate P008322'''). Its eastern margin is the Moine Thrust Belt, on which rocks of the Northern Highlands terrane have been carried westward over the Lewisian gneisses. East of the Moine Thrust, inliers are formed from Lewisian-like (or Lewisianoid) gneisses caught up in the folding and thrusting of the overlying, younger Proterozoic strata. Geophysical evidence suggests that Lewisian-like rocks underlie the younger Proterozoic sequences at least as far south as the Great Glen Fault. To the south of that structure, a distinctive Palaeoproterozoic gneiss assemblage is seen in the Rhinns Complex of western Islay.		'''The crystalline, metamorphic rocks''' of the Hebridean terrane originated as part of a continental assemblage of Archaean cratons and Palaeoproterozoic deformation belts that had been brought together by about 1.7 billion years ago (i.e. 1700 million years ago or 1.7 Ga). The dispersed fragments of this assemblage can now be recognised along the length of a vast tectonic zone (Caledonian Orogen) that stretches from Scandinavia, through Scotland to Greenland and North America. In Britain, the Hebridean terrane consists principally of the various high-grade metamorphic rocks that make up the Lewisian Gneiss Complex (A1–3 & Z1)†. This forms the north-west extremity of Scotland, cropping out in a coastal strip on the mainland, from Cape Wrath to the Sound of Sleat, and extending westward across the Outer Isles ('''Plate P008322'''). Its eastern margin is the Moine Thrust Belt, on which rocks of the Northern Highlands terrane have been carried westward over the Lewisian gneisses. East of the Moine Thrust, inliers are formed from Lewisian-like (or Lewisianoid) gneisses caught up in the folding and thrusting of the overlying, younger Proterozoic strata. Geophysical evidence suggests that Lewisian-like rocks underlie the younger Proterozoic sequences at least as far south as the Great Glen Fault. To the south of that structure, a distinctive Palaeoproterozoic gneiss assemblage is seen in the Rhinns Complex of western Islay.

Dbk at 08:18, 20 May 2014

2014-05-20T08:18:13Z

← Older revision		Revision as of 09:18, 20 May 2014
Line 1:		Line 1:
	{{BedN}}		{{BedN}}
	'''More than 1600 million years ago'''		'''More than 1600 million years ago'''
	[[image:P008322.jpg\|right\|thumb\|300px\|The characteristic scenery produced by Archaean gneiss of the Lewisian Complex seen here at Castlebay, Barra, Outer Hebrides. [http://geoscenic.bgs.ac.uk/asset-bank/action/~~viewFullSizedImage~~?id=~~7037~~&~~size~~=~~1000~~ P008322.]]]		[[image:P008322.jpg\|right\|thumb\|300px\|The characteristic scenery produced by Archaean gneiss of the Lewisian Complex seen here at Castlebay, Barra, Outer Hebrides. [http://geoscenic.bgs.ac.uk/asset-bank/action/search?newSearch=true&quickSearch=true&includeImplicitCategoryMembers=true&keywords=P008322.]]]
	'''The crystalline, metamorphic rocks''' of the Hebridean terrane originated as part of a continental assemblage of Archaean cratons and Palaeoproterozoic deformation belts that had been brought together by about 1.7 billion years ago (i.e. 1700 million years ago or 1.7 Ga). The dispersed fragments of this assemblage can now be recognised along the length of a vast tectonic zone (Caledonian Orogen) that stretches from Scandinavia, through Scotland to Greenland and North America. In Britain, the Hebridean terrane consists principally of the various high-grade metamorphic rocks that make up the Lewisian Gneiss Complex (A1–3 & Z1)†. This forms the north-west extremity of Scotland, cropping out in a coastal strip on the mainland, from Cape Wrath to the Sound of Sleat, and extending westward across the Outer Isles ('''Plate P008322'''). Its eastern margin is the Moine Thrust Belt, on which rocks of the Northern Highlands terrane have been carried westward over the Lewisian gneisses. East of the Moine Thrust, inliers are formed from Lewisian-like (or Lewisianoid) gneisses caught up in the folding and thrusting of the overlying, younger Proterozoic strata. Geophysical evidence suggests that Lewisian-like rocks underlie the younger Proterozoic sequences at least as far south as the Great Glen Fault. To the south of that structure, a distinctive Palaeoproterozoic gneiss assemblage is seen in the Rhinns Complex of western Islay.		'''The crystalline, metamorphic rocks''' of the Hebridean terrane originated as part of a continental assemblage of Archaean cratons and Palaeoproterozoic deformation belts that had been brought together by about 1.7 billion years ago (i.e. 1700 million years ago or 1.7 Ga). The dispersed fragments of this assemblage can now be recognised along the length of a vast tectonic zone (Caledonian Orogen) that stretches from Scandinavia, through Scotland to Greenland and North America. In Britain, the Hebridean terrane consists principally of the various high-grade metamorphic rocks that make up the Lewisian Gneiss Complex (A1–3 & Z1)†. This forms the north-west extremity of Scotland, cropping out in a coastal strip on the mainland, from Cape Wrath to the Sound of Sleat, and extending westward across the Outer Isles ('''Plate P008322'''). Its eastern margin is the Moine Thrust Belt, on which rocks of the Northern Highlands terrane have been carried westward over the Lewisian gneisses. East of the Moine Thrust, inliers are formed from Lewisian-like (or Lewisianoid) gneisses caught up in the folding and thrusting of the overlying, younger Proterozoic strata. Geophysical evidence suggests that Lewisian-like rocks underlie the younger Proterozoic sequences at least as far south as the Great Glen Fault. To the south of that structure, a distinctive Palaeoproterozoic gneiss assemblage is seen in the Rhinns Complex of western Islay.