The supposed Lewisian inlier Of Scardroy, Central Ross-Shire, And its relations with the surrounding Moine rocks

1952 ◽  
Vol 108 (1-4) ◽  
pp. 99-126 ◽  
Author(s):  
J. Sutton ◽  
J. Watson
Keyword(s):  
Moine Rocks

Field and isotopic evidence for a c. 750 Ma tectonothermal event in Moine rocks in the Central Highland region of the Scottish Caledonides

1983 ◽  
Vol 73 (3) ◽  
pp. 119-134 ◽  
Author(s):  
M. A. J. Piasecki ◽  
O. van Breemen
Keyword(s):  
Crustal Rocks ◽  
Highland Region ◽  
Ductile Shearing ◽  
Central Highland ◽  
Isotopic Studies ◽  
Previous Hypothesis ◽  
Moine Rocks ◽  
Early Palaeozoic ◽  
Similar Vein ◽  
Tectonothermal Event

ABSTRACTEvidence is presented for a late Proterozoic, tectonothermal event which affected the rocks of the Moine assemblage in the Central Highland region of the Scottish Caledonides c. 750 Ma ago. This is about 200 Ma before the early Palaeozoic Grampian orogeny, whose effects are superimposed on the Moine rocks as well as dominating the tectonism in the Dalradian Supergroup.Field and isotopic studies are integrated in zones of ductile thrusting (sliding) which are typified by belts of tectonic schists with related swarms of quartz and muscovite-bearing pegmatite veins. Of particular significance is a ductile thrust (the Grampian slide) which separates deeper crustal rocks (the Central Highland division), interpreted as showing the imprint of the Grenville orogeny, from shallower rocks (the Grampian division) representing a supracrustal assemblage formed between the Grenville and the c. 750 Ma events.The Grampian slide is the structurally highest member of a system of related, previously unrecorded slides affecting the Central Highland division. New structural, petrographic and Rb-Sr isotopic data, obtained largely from a recently recognised inlier of the Central Highland division at Laggan, bear out that the quartz and pegmatite veins are segregations formed during ductile shearing under amphibolite facies conditions. Muscovites from these veins yield ages between 780 and 730 Ma, and a regression analysis of tectonic schists and the muscovites gives an age of 740 ± 40 Ma. These data substantiate our previous hypothesis that the deeper-seated Moine rocks were affected by a distinct orogenic event at 750 ± 30 Ma.In the Northern Highlands, similar vein swarms are related to the Sgurr Beag slide and to belts of previously unrecorded tectonic schists in the Glenfinnan division of the Moine assemblage. A new, 755 ± 8 Ma age obtained from such a tectonic schist at Kinloch Hourn, combined with previous, similar age data from lensoid pegmatites, imply that the c. 750 Ma event may have also affected the Morar and Glenfinnan divisions.

Moine─Dalradian relationships and their palaeotectonic significance

1984 ◽  
Vol 395 (1809) ◽  
pp. 185-202 ◽  
Keyword(s):  
Thick Layer ◽  
High Heat ◽  
Source Rocks ◽  
Mineral Deposits ◽  
Common Source ◽  
Calc Alkaline ◽  
Isotopic Data ◽  
Moine Rocks ◽  
Southeastern Margin ◽  
Southern Highland

Regional geochemical and lithogeochemical data, when reviewed in relation to the development of the Caledonian orogen in Scotland, indicate that the Moine-Dalradian boundary coincides with a long-lived crustal discontinuity. It is suggested that this boundary follows the original southeastern margin of an old continental slab in which the Lewisian basement was overlain by a thick layer of ‘Old Moine’ metasediments affected by pre-Caledonian (750 Ma or over) deformation and metamorphism. Early Caledonian ‘Young Moine’ sediments on this slab resemble the underlying metasediments in lithofacies but are somewhat poorer in Zr and Y. To the southeast of the boundary, a thick Dalradian succession accumulated in a marine ensialic basin on a thinned basement of granulites and gneisses. In the Dalradian, elements of basic-ultrabasic association are high, especially in the upper Argyll and Southern Highland Groups where they are associated with products of basic volcanicity. Stratabound Ba, Pb and Zn mineral deposits occur widely not far below the volcanic horizon, and magmatism and mineralization are attributed to the opening of a palaeo-oceanic rift within the Dalradian basin. The geochemistry of the Torridonian, Old Moine and Young Moine detrital sediments suggests derivation from a common source dominated by intermediate-acid calc-alkaline rocks. Low to moderate large-ion litho-phile (l. i. l.) element levels suggest variable degrees of depletion caused by deep metamorphism of the source rocks. Isotopic data show that the sourceland was Archaean and early Proterozoic, and suggest that it may have resembled the Ketilidian and pre-Ketilidian of southern Greenland. The geochemical influence of this ancient western sourceland can be recognized throughout the Dalradian succession, constraining models that involve the availability of young island arc or exotic tectonic materials during the filling of the Dalradian basin. The mechanical strength, relatively low density and high heat production of the Old Moine rocks enhanced the contrast between the crustal slab incorporating a thick Moine layer and the main Dalradian basin beneath which this layer is absent. Tectonic and metamorphic develop­ments differed in the adjacent regions during orogeny, and deep discon­tinuities at the Moine-Dalradian boundary acted as conduits for Late Caledonian appinitic and metalliferous granites rising from sub-crustal sources.

scholarly journals IV.—Moine Pebbles in Torridonian Conglomerates

1915 ◽  
Vol 2 (10) ◽  
pp. 447-450 ◽  
Author(s):  
J. W. Gregory
Keyword(s):  
Good Evidence ◽  
British Association ◽  
Remarkable Feature ◽  
North West ◽  
Scottish Highlands ◽  
The North ◽  
Moine Rocks ◽  
North Western

The relation of the Torridon Sandstone to the Moine Gneiss or ‘Eastern Schists’ is one of the primary questions in thegeology of the Scottish Highlands. These two widespread series ofrocks occur on opposite sides of the great overthrusts in North-Western Scotland; and another remarkable feature of their distributionis that though the Torridon Sandstone often rests directly upon theLewisian Gneiss, it never occurs on the Moine Gneiss. The view hastherefore been suggested that the Moine rocks are the easternmetamorphosed continuation of the Torridonian. Some altered Torridon Sandstones certainly resemble the rocks of the Moine Series.Dr. Home, in his address to the British Association in 1901, quotedthe authority of Dr. Teall and Dr. Peach for the resemblance ofaltered Torridon Sandstone to the Moine; and he again remarked thisresemblance in the memoir on the North-West Highlands. The lateW. Gunn went further, and in the same work claimed (p. 612) that “east of Dundonnell good evidence can be adduced that alteredTorridon Sandstone has entered largely into the composition of the Eastern schists”. The recent memoir on the Fannich Mountains represents some of the flaggy granulites of that district as due “to the crushing of Torridonn grit”.

The structural age and possible origin of the Vagastie Bridge granite and associated intrusions, central Sutherland

1988 ◽  
Vol 125 (6) ◽  
pp. 613-620 ◽  
Author(s):  
R. E. Holdsworth ◽  
R. A. Strachan
Keyword(s):  
Igneous Intrusions ◽  
Moine Rocks ◽  
Thrust Zone ◽  
Isotope Systematics ◽  
Granite Suite

AbstractThe Vagastie Bridge granite, central Sutherland, belongs to a regional suite of igneous intrusions within Moine psammites adjacent to the base of the east Sutherland migmatite complex. An isotopic date of 405 ± 11 Ma, obtained using U–Pb determinations on zircon and sphene taken from the granite, has previously been interpreted as an intrusion age. However, a reassessment of the field relationships demonstrates that intrusion was syn-tectonic with respect to the later stages of ductile Caledonian deformation affecting the Moine rocks. It is suggested that the granite suite magmas originated at depth and that they were channelled into the still active Caledonian ductile thrust zone (the Naver Thrust) which forms the tectonic base of the Naver Nappe. On regional grounds, the interpretation of the c. 405 Ma date as an intrusion age is untenable, which implies that the isotope systematics of the Vagastie Bridge granite require re-investigation.

Two arfvedsonitic rhyolite intrusions from Cloghaneely, Co. Donegal

1954 ◽  
Vol 30 (225) ◽  
pp. 393-399 ◽  
Author(s):  
E. H. Timothy Whitten
Keyword(s):  
Moine Rocks

Many of the Dalradian and 'Moine' rocks of Donegal, and the Caledonian granites associated with them, have been shown to bear structural and petrographic resemblance to the rocks of similar age in Scotland. In Scotland riebeckite-bearing minor intrusions occur at many localities and include Ordovician, Caledonian, Carboniferous, and Tertiary intrusions. There appears to be no record of analogous rocks containing sodic amphiboles occurring in situ in NW. Ireland. The purpose of this paper is to record the existence of two small intrusions of such rocks in western Cloghaneely, Co. Donegal.

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