scholarly journals Transitional amphibolite-granulite facies granites, diorites and metavolcanic amphibolites in the Isukasia map sheet, southern West Greenland

1982 ◽  
Vol 110 ◽  
pp. 46-49
Author(s):  
R.P Hall ◽  
D.J Hughes
Keyword(s):  
Granulite Facies ◽  
West Greenland ◽  
North West ◽  
The North ◽  
Geological Map

Detailed mapping of the north-west quadrant of the 1: 100 000 scale Isukasia geological map sheet was begun in 1981 (fig. 16). The area was previously visited during the 1977 helicopter reconnaissance mapping programme (Allaart et al., 1978) and from this work the stratigraphy was known only in the broadest of terms. The 1981 work has shown that the area is comprised of five principallithostratigraphic units, listed in Table 3.

scholarly journals I.—Microscopic Structure of Irish Granites. No. 2. Granite of Aillemore, Co. Mayo

1874 ◽  
Vol 1 (1) ◽  
pp. 1-2
Author(s):  
Edward Hull
Keyword(s):  
The Other ◽  
Microscopic Structure ◽  
South Side ◽  
North West ◽  
Fine Grained ◽  
Lower Silurian ◽  
The North ◽  
Geological Map ◽  
Vertical Walls ◽  
Dark Green

This granite forms an isolated mass, rising into two eminences a few miles south of Louisburg, called Corvock Brack (1287 feet) and Knockaskeheen (1288 feet). It is a greyish granite—generally fine—grained—consisting of quartz, two felspars,—one orthoclase, the other triclinic, probably oligoclase—and dark green mica. In some places there are patches in which the felspar assumes the appearance of “graphic granite.” Numerous boulders of this granite are strewn over the district to the north-west, and on the south side of Knockaskeheen; the rock is traversed by regular joints ranging N. 10 W., along which it splits off into nearly vertical walls. The position of the granite is shown on Griffith's Geological Map of Ireland, and it is surrounded by schistose beds, generally metamorphosed, and probably of Lower Silurian age. The granite itself is of older date than the Upper Llandovery beds, which lie to the southward.

scholarly journals Field work in the north of the Ivisârtoq region, inner Godthåbsfjord, southern West Greenland

1983 ◽  
Vol 115 ◽  
pp. 49-56
Author(s):  
B Chadwick ◽  
M.A Crewe ◽  
J.F.W Park
Keyword(s):  
Field Work ◽  
Geological Survey ◽  
West Greenland ◽  
North West ◽  
The North ◽  
Field Investigations ◽  
New Findings ◽  
Host Rocks

The programme of field investigations in the north of the Ivisartoq region begun in 1981 by Chadwick & Crewe (1982) was continued in 1982. Julia Park began mapping the Taserssuaq granodiorite, its host rocks and the Ataneq fault in the north-west. Dur team was joined by D. Bellur, Geological Survey of India, nominally as an assistant. In this report we present only summary notes of new findings relevant to the interpretation of the geometry and chronology of this segment of the Archaean crust in southern West Greenland. We use the established terminology for the Archaean rocks of the Godthåbsfjord region.

scholarly journals Explanatory notes to the Geological map of Greenland, 1:500 000, Thule, Sheet 5

2006 ◽  
pp. 1-100 ◽  
Author(s):  
Peter R. Dawes
Keyword(s):  
Raw Materials ◽  
Late Quaternary ◽  
Regional Metamorphism ◽  
Fault Reactivation ◽  
Detrital Zircons ◽  
Dyke Swarm ◽  
Baffin Bay ◽  
West Greenland ◽  
North West ◽  
Geological Map

Abstract Dawes, P.R. 2006: Explanatory notes to the Geological map of Greenland, 1:500 000, Thule, Sheet 5. Geological Survey of Denmark and Greenland Map Series 2, 97 pp. + map These explanatory notes cover part of North-West Greenland defined by latitudes 75°15'N and 78°N and longitudes 57°W and 73°W, a region with appreciable ice cover. The bedrock is dominated by two Precambrian provinces that extend across Baffin Bay into Canada: the highgrade Archaean-Palaeoproterozoic shield overlain by the intracratonic Mesoproterozoic-?Neoproterozoic Thule Basin. Map units are systematically described and introductory sections cover the physical environment, logistics, data sources and geoscientific research. The crystalline shield embraces seven complexes: three of Archaean age, two of Archaean-?Palaeoproterozoic age and two of Palaeoproterozoic age. Isotopic ages of c. 2900 Ma indicate that Neoarchaean orthogneisses are present in part of the region while the existence of Mesoarchaean crust is indicated by c. 3200 Ma detrital zircons. The high-grade orthogneisses and paragneisses of the Thule mixed-gneiss complex were intruded by two plutonic suites, the Kap York meta-igneous complex at c. 2700 Ma and the Smithson Bjerge magmatic association that includes a major anorthosite body. Subsequent deformation, metamorphism and migmatisation led to the formation of gneisses recognised within the Melville Bugt orthogneiss complex . Palaeoproterozoic sedimentation and volcanism represented by the Prudhoe Land supracrustal complex took place after c . 2250 Ma but had ceased by c. 1985 Ma when the Prudhoe Land granulite complex was emplaced. Rocks within the Lauge Koch Kyst supracrustal complex may correlate with the Palaeoproterozoic Karrat Group of West Greenland. Polyphase deformation with isoclinal folding, and regional metamorphism up to granulite-facies grade, affected the region c. 1900 Ma ago, with cooling until c . 1650 Ma. Extensional faulting, intracratonic basin formation and periods of basaltic magmatism occurred during the last 1000 million years of Proterozoic time. After regional dyking at c . 1630 Ma ( Melville Bugt dyke swarm ) followed by mature peneplanation, the Thule Basin developed as an interior fracture and sag depocentre across the area that is now northernmost Baffin Bay. Defined by the unmetmorphosed Thule Supergroup at least 6 km thick, the basin records fluvial to shallow-marine sedimentation and tholeiitic volcanism at least 1270 million years old. The basin is dissected by the Thule half-graben system dominated by WNW-ESE-trending faults thought to have developed during the final tectono-magmatic period dated at c. 700650 Ma. Conspicuous products of this are a major sill complex ( Steensby Land sill complex ) and a regional dyke swarm that parallels the half-grabens ( Thule dyke swarm ). Fault reactivation is probably related to the late Phanerozoic tectonic evolution of Baffin Bay. In addition to the four metallic commodities included on the map - magnetite, copper, iron suphides, ilmenite - there is potential for gold and other mineralisations. The Neoarchaean magnetite province, traceable for over 400 km through the map region, is spatially the largest in Greenland and it is a correlative of the Mary River iron deposits of Baffin Island, Canada. Several raw materials have potential for local handicraft industries, including soapstone and agate. The region hosts a multi-event glacial and marine Middle-Late Quaternary stratigraphy dating back to at least the Saalian/Illinoian (pre-130 ka B.P.). The entire region was probably overriden by the Inland Ice during the Weichselian/Wisconsinian glacial maximum and deglaciated in the early Holocene, 11 000 to 9000 years ago.

scholarly journals The structure of south Renland, Scoresby Sund. With special reference to the tectono-metamorphic evolution of a southern internal part of the Caledonides of East Greenland

1975 ◽  
Vol 112 ◽  
pp. 1-67
Author(s):  
B Chadwick
Keyword(s):  
Granulite Facies ◽  
Normal Faults ◽  
Mobile Belt ◽  
Minimum Thickness ◽  
East Greenland ◽  
North West ◽  
The North ◽  
South West ◽  
Igneous Activity ◽  
Group Form

Renland occupies an internal position within the southern extreme of the outcrop of the Caledonian mobile belt of East Greenland exposed between latitudes 70° and 82° N. In south-west Renland migmatised paragneisses derived from sediments comparable to the late Precambrian Lower Eleonore Bay Group form a multilayered sequence with a minimum thickness of 1500 m. The migmatites are interleaved with thick concordant sheets of garnetiferous augen granite, the formation of which may be linked with the low-pressure granulite or transitional amphibolite-granulite facies conditions attained during migmatisation of the paragneisses. These conditions persisted during the folding together of paragneisses and granites into regional structures of nappe dimensions which had a north or north-west direction of transport. Refolding of the nappes under continued high-grade conditions gave rise to structures locally coaxial with nappe axes. Reversals of facing of nappes occur in backfolds. Linear fabrics of sillimanite and biotite and prolate ellipsoidal augen of feldspar are parallel to fold axes and show that constrictional deformation dominated the later stages of the nappe phase and the refolding event. The constriction is attributed to compressing of rocks in south-west Renland between nappes advancing from the south and a rising mass of granite and basement gneisses in the north. Intrusion of concordant sheets of biotite-rich hypersthene monzonite (mangerite) followed the nappe deformation in south-east Renland. The principal sheet, which is 500 m thick, forms the rim to part of a lopolithic basin. Thinner sheets of monzonite injected into migmatites within the basin have been disrupted by further migmatisation and granitisation. Stable assemblages in pyribolite restite suggest this later event, which was restricted largely to the basin, attained conditions of hornblende-granulite facies. Open warps attributed to monzonite injection and the basin formation are superimposed on nappes west of the principal sheet. Normal faults with downthrow to east and west relate to the formation of troughs filled with Upper Palaeozoic and Mesozoic sediments in the Scoresby Sund region. The distribution of the faults suggests Renland was a horst area in Upper Palaeozoic times. Tertiary igneous activity in south Renland is represented by rare dykes of olivine dolerite and scattered plugs of pyroxenite which locally contain large blocks of host gneisses.

scholarly journals An ultrabasic pipe in the eastern Sukkertoppen region, southern West Greenland

1980 ◽  
Vol 100 ◽  
pp. 69-73
Author(s):  
R.P Hall
Keyword(s):  
Granulite Facies ◽  
The South ◽  
The West ◽  
West Side ◽  
West Greenland ◽  
North East ◽  
The North ◽  
South West ◽  
Unusual Occurrence ◽  
Anorthosite Complex

An unusual occurrence of ultrabasic material was located in the eastern Sukkertoppen region during the reconnaissance mapping programme of 1977, the findings of which were described by Allaart et al. (1978). It occurs on a small exposure on the west side of a north-pointing peninsula in the middle of the large nunatak Majorqap alangua (65°53'N, 50°40'W), to the north-east of the Majorqaq valley (Hall, 1978, fig. 21). The area is composed predominantly of a suite of granulite facies granitic gneisses which contain numerous enclaves of pyroxene-bearing amphibolites, and locally anorthositic and gabbroic rocks similar to those seen in the Fiskenæsset anorthosite complex (Myers, 1975). The gneisses in the centre af the nunatak are highly irregular in orient at ion, occupying the complex interseclion af closures af at least two major fold phases. A belt af amphibolitcs forms the cliff at the south-west tip af Majorqap alangua. Related rocks occur in arnphibolite facies in the acea around the lakc Qardlit taserssuat immediately to the soulh (Hall, 1978).

Late Labradorian metamorphism and anorthosite–granitoid intrusion, Cape Caribou River allochthon, Grenville Province, Labrador: evidence from U–Pb geochronology

1995 ◽  
Vol 32 (9) ◽  
pp. 1411-1425 ◽  
Author(s):  
François Bussy ◽  
Thomas E. Krogh ◽  
Richard J. Wardle
Keyword(s):  
Hanging Wall ◽  
Granulite Facies ◽  
Grenville Province ◽  
Mafic Dykes ◽  
North West ◽  
The North ◽  
Form Part ◽  
Thrust System ◽  
Granitoid Gneisses ◽  
New Generation

In the Cape Caribou River allochthon (CCRA), metaigneous and gneissic units occur as a shallowly plunging synform in the hanging wall of the Grand Lake thrust system (GLTS), a Grenvillian structure that forms the boundary between the Mealy Mountains and Groswater Bay terranes. The layered rocks of the CCRA are cut by a stockwork of monzonite dykes related to the Dome Mountain suite and by metadiabase–amphibolite dykes that probably form part of the ca. 1380 Ma Mealy swarm. The mafic dykes appear to postdate much of the development of subhorizontal metamorphic layering within the lower parts of the CCRA. The uppermost (least metamorphosed) units of the CCRA, the North West River anorthosite–metagabbro and the Dome Mountain monzonite suite, have been dated at 1625 ± 6 and 1626 ± 2 Ma, respectively. An amphibolite unit that concordantly underlies the anorthosite–metagabbro and is intruded discordantly by monzonite dykes has given metamorphic ages of 1660 ± 3 and 1631 ± 2 Ma. Granitoid gneisses that form the lowest level of the CCRA have given a migmatization age of 1622 ± 6 Ma. The effects of Grenvillian metamorphism become apparent in the lower levels of the allochthon where gneisses, amphibolite, and mafic dykes have given new generation zircon ages of 1008 ± 2, 1012 ± 3, and 1011 ± 3 Ma, respectively. A posttectonic pegmatite has also given zircon and monazite ages of [Formula: see text] and 1013 ± 3 Ma, respectively. Although these results indicate new growth of Grenvillian zircon, this process was generally not accompanied by penetrative deformation or melting. Thus, the formation of gneissic fabrics and the overall layered nature of the lower CCRA are a result primarily of Labradorian (1660–1620 Ma) tectonism and intrusion, and probably reflect early movement on an ancestral GLTS. Grenvillian heating and metamorphism (up to granulite facies) was strongly concentrated towards the base of the CCRA and probably occurred during northwestward thrusting of the allochthon over the Groswater Bay terrane.

scholarly journals NEW CHRONOSTRATIC SCHEME OF SOUTH-EASTERN FENNOSCANDIA AND ITS USE IN THE PREPARATION OF SMALL-SCALE GEOLOGICAL MAPS OF THE PRECAMBRIAN REGIONS

2017 ◽  
pp. 5-12
Author(s):  
V. S. Kulikov ◽  
V. V. Kulikova ◽  
A. K. Polin
Keyword(s):  
Russian Federation ◽  
Research Centre ◽  
Small Scale ◽  
North West ◽  
The North ◽  
Geological Maps ◽  
Geological Map ◽  
The Russian Federation ◽  
New Generation ◽  
Academy Of Sciences

A new chronostratic scheme of South-East (SE) Fennoscandia has been developed, based on the International Stratigraphie Scale, taking into account some elements of the Common Stratigraphic Scale of Russia and the regional stratigraphic scheme of the North-West (NW) of Russian Federation. A rank of Archean and Proterozoic stratons has been determined (including supersystems for Riphean and Archean geonotems), compatable in dutation to the Phanerozoic systems (Mesozoic and Paleozoic ones). An original coloring for the geological maps of the newly allocated systems and their analogues in the Precambrian, as well as the digital indexing of all stratons of the rank of systems instead of the traditional alphabetic one, have been proposed. Based on the extensive geological materials of the Institute of Geology of Karelian Research Centre of the Russian Academy of Sciences, in view of the new approaches and reliable geochronological data, an areal geological map of SE Fennoscandia in scale 1: 750 000 has been created, which includes the territory of Karelia and adjacent areas of the Russian Federation and eastern Finland. The proposed chronostratic scheme can serve as a basis for developing legends of small-scale state geological maps of the new generation, especially in the regions of the Precambrian development.

scholarly journals An investigation of the igneous rocks on Hareøen and western Nûgssuaq, West Greenland

1971 ◽  
Vol 35 ◽  
pp. 11-13
Author(s):  
N Hald
Keyword(s):  
East Coast ◽  
Geological Mapping ◽  
Igneous Rocks ◽  
South Coast ◽  
The South ◽  
West Greenland ◽  
North West ◽  
North East ◽  
The North ◽  
Basaltic Lavas

Hareøen is an island north-west of Disko in western Greenland. It has the form of a plateau, whose highest point - 512 metres - is found near the south coast. Like the neighbouring parts of Nugssuaq and Disko, Hareøen consists chiefly of Tertiary basaltic lavas. The island first attracted attention on account of the presence of interbasaltic, coal-bearing sediments on the north-east coast. These were already examined by Giesecke in 1811 (Giesecke, 1910) and later among others by Steenstrup (1874) and B.E. Koch (1959). A petrographie investigation of the basalts was first undertaken by Holmes (1919), who described loose fragments rich in K2O. Lavas from the south coast, colleeted and analysed by Pedersen (1970), also have a high content of potash. V. Miinther in the years 1948-49 untertook geological mapping of the island, on which the present investigation is supported (Miinther, in press).

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