scholarly journals A metamorphosed basic dyke swarm in the vicinity of Sarqarigsup nunâ (Ravns Storø area), Fiskenæsset, southern West Greenland

1976 ◽  
Vol 73 ◽  
pp. 22-30
Author(s):  
C.R.L Friend
Keyword(s):  
Significant Part ◽  
Dyke Swarm ◽  
Basic Dyke ◽  
West Greenland ◽  
Plutonic Rocks ◽  
Dyke Swarms

Ancient dyke swarms have been used successfully as time markers throughout the Archaean of West Greenland, particularly in subdividing the early Archaean in the Godthåb region (McGregor, 1973). This paper describes a swarm of metamorphosed basic dykes which cut across the lithologicallayering and an early tectonic fabric in the Ravns Storø group of metavo1canic and plutonic rocks. Previously only sporadic occurrences of metamorphosed basic dykes have been noted in the Fiskenæsset region. The Sarqarigsup nuna swarm may thus have a significant part to play in the division of the events which have taken place in the area from the Frederikshåbs Isblink to Bjørnesund and perhaps even further north.

scholarly journals Ti-rich plagioclase-phyric dykes of southern West Greenland

1987 ◽  
Vol 135 ◽  
pp. 46-52
Author(s):  
R.P Hall ◽  
D.J Hughes ◽  
C.R.L Friend
Keyword(s):  
World Wide ◽  
Entire Region ◽  
Basic Dyke ◽  
Systematic Mapping ◽  
Late Archaean ◽  
West Greenland ◽  
Mantle Evolution ◽  
The World ◽  
Geological Map ◽  
Dyke Swarms

The investigation of Proterozoic basic dykes in southern West Greenland stemmed from the programme of systematic mapping of the Archaean craton in that region by the Geological Survey of Greenland (GGU). This work began in the southern Frederikshåb region in the early 1960s (Jensen, 1968, 1969) and progressed northwards, from bases in the Fiskenæsset (Kalsbeek & Myers, 1973; GGU, 1976), Godthåb (Allaart et al., 1977) and Sukkertoppen areas (Allaart et al., 1978). The results of most of this mapping work were summarized by Bridgwater et al. (1976) and compiled onto a 1:500 000 scale geological map sheet by Allaart (1982). The distribution of the major Proterozoic dykes which cut the entire region is shown on this map. While the basic dykes are individually minor intrusions, many are up to 50 metres wide and continuous for several tens of kilometres, and collectively they represent a major magmatic event. As many of the Archaean terrains of the world possess Proterozoic basic dyke swarms, their compositions are crucial to a correlation of events from one craton to another and to an understanding of crustal and mantle evolution after the world-wide late Archaean sialic crust-forming event.

scholarly journals Field relations of some Precambrian basic dykes in the vicinity of Sukkertoppen, central West Greenland

1978 ◽  
Vol 90 ◽  
pp. 54-57
Author(s):  
C.R.L Friend
Keyword(s):  
Central Portion ◽  
Garnet Amphibolite ◽  
Basic Dyke ◽  
West Greenland ◽  
Dyke Swarms

Various field relations of the basic dyke swarms near Sukkertoppen have been described (Ramberg, 1948; Berthelsen & Bridgwater, 1960; Windley, 1970) and a preliminary chronology suggested (Bridgwater et al., 1976). The Kangâmiut dykes are noteable in that the central portion of some of the dykes has been converted into amphibolite and garnet amphibolite (Ramberg, 1948; Windley, 1970). Otherwise they appear as normal dolerites.

The gabbro–dyke transition zone demonstrated on Tviberg, Solund–Stavfjord Ophiolite Complex

1996 ◽  
Vol 133 (5) ◽  
pp. 573-582 ◽  
Author(s):  
K. P. Skjerlie ◽  
H. Furnes
Keyword(s):  
Transition Zone ◽  
Basaltic Magma ◽  
Source Region ◽  
Geochemical Evolution ◽  
Dyke Swarm ◽  
Gradual Transition ◽  
Ophiolite Complex ◽  
Plutonic Complex ◽  
Plutonic Rocks ◽  
High Level

AbstractThe transition zone between 100 % dykes and high-level plutonic rocks of the Solund-Stavfjord Ophiolite Complex is complex due to the existence of many lithologies with different and variable contact relationships. The rocks of the plutonic complex vary in composition from FeTi basaltic to quartz dioritic, and the grain sizes vary from fine to pegmatitic. Felsic varieties are produced by fractional crystallization of basaltic magma as demonstrated by geochemical evolution and by gradual transition from gabbro to quartz diorite. Patches of fractionated dioritic rocks may show both gradual and intrusive relationships with the surrounding host gabbro. This demonstrates that late-stage liquids commonly left the source region and locally intruded the surrounding parent rocks. The high-level plutonic rocks are thoroughly epidotized and are cut by dykes consisting of granoblastic epidote and quartz. The high-level plutonic complex is associated with irregular bodies of fine- to medium-grained plagioclase-porphyritic diabase of high MgO content. These diabase bodies are intruded by dykes that become progressively more regular in shape. The plutonic complex locally shows intrusive relationships with the overlying 100% dyke complex, but is itself cut by two dyke swarms. The dykes of the first swarm formed while the plutonic complex experienced sinistral shear strain, and the dykes are generally less regular and thinner than the dykes of the second swarm. This indicates that the dykes of the first swarm intruded while the rocks of the plutonic complex were still hot, while the next dyke swarm intruded later when the rock complex was colder. Dykes of both swarms range in composition from slightly to strongly fractionated, suggesting that the magma chambers they were expelled from underwent significant fractionation in between magma replenishment. Numerous dykes of both swarms carry large quantities of glomeroporphyritic aggregates of plagioclase and altered clinopyroxene, indicating that the source area to the dykes very often was a crystal mush.

scholarly journals Seismic reflection data reveal the 3D structure of the newly discovered Exmouth Dyke Swarm, offshore NW Australia

2020 ◽  
Author(s):  
Craig Magee ◽  
Christopher A.-L. Jackson
Keyword(s):  
Seismic Reflection ◽  
Surface Deformation ◽  
3D Structure ◽  
Sedimentary Basins ◽  
Dyke Swarm ◽  
Normal Faults ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Dyke Swarms ◽  
Nw Australia

Abstract. Dyke swarms are common on Earth and other planetary bodies, comprising arrays of dykes that can extend for 10's to 1000's of kilometres. The vast extent of such dyke swarms, and their rapid emplacement, means they can significantly influence a variety of planetary processes, including continental break-up, crustal extension, resource accumulation, and volcanism. Determining the mechanisms driving dyke swarm emplacement is thus critical to a range of Earth Science disciplines. However, unravelling dyke swarm emplacement mechanics relies on constraining their 3D structure, which is extremely difficult given we typically cannot access their subsurface geometry at a sufficiently high enough resolution. Here we use high-quality seismic reflection data to identify and examine the 3D geometry of the newly discovered Exmouth Dyke Swarm, and associated structures (i.e. dyke-induced normal faults and pit craters), in unprecedented detail. The latest Jurassic dyke swarm is located on the Gascoyne Margin offshore NW Australia and contains numerous dykes that are > 170 km long, potentially > 500 km long. The mapped dykes are distributed radially across a 39° arc centred on the Cuvier Margin; we infer this focal area marks the source of the dyke swarm, which was likely a mantle plume. We demonstrate seismic reflection data provides unique opportunities to map and quantify dyke swarms in 3D in sedimentary basins, which can allow us to: (i) recognise dyke swarms across continental margins worldwide and incorporate them into models of basin evolution and fluid flow; (ii) test previous models and hypotheses concerning the 3D structure of dyke swarms; (iii) reveal how dyke-induced normal faults and pit craters relate to dyking; and (iv) unravel how dyking translates into surface deformation.

scholarly journals Seismic reflection data reveal the 3D structure of the newly discovered Exmouth Dyke Swarm, offshore NW Australia

Solid Earth ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 579-606 ◽  
Author(s):  
Craig Magee ◽  
Christopher Aiden-Lee Jackson
Keyword(s):  
Seismic Reflection ◽  
Surface Deformation ◽  
3D Structure ◽  
Dyke Swarm ◽  
Normal Faults ◽  
Borehole Data ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Dyke Swarms ◽  
Nw Australia

Abstract. Dyke swarms are common on Earth and other planetary bodies, comprising arrays of dykes that can extend laterally for tens to thousands of kilometres. The vast extent of such dyke swarms, and their presumed rapid emplacement, means they can significantly influence a variety of planetary processes, including continental break-up, crustal extension, resource accumulation, and volcanism. Determining the mechanisms driving dyke swarm emplacement is thus critical to a range of Earth Science disciplines. However, unravelling dyke swarm emplacement mechanics relies on constraining their 3D structure, which is difficult given we typically cannot access their subsurface geometry at a sufficiently high enough resolution. Here we use high-quality seismic reflection data to identify and examine the 3D geometry of the newly discovered Exmouth Dyke Swarm, and associated structures (i.e. dyke-induced normal faults and pit craters). Dykes are expressed in our seismic reflection data as ∼335–68 m wide, vertical zones of disruption (VZD), in which stratal reflections are dimmed and/or deflected from sub-horizontal. Borehole data reveal one ∼130 m wide VZD corresponds to an ∼18 m thick, mafic dyke, highlighting that the true geometry of the inferred dykes may not be fully captured by their seismic expression. The Late Jurassic dyke swarm is located on the Gascoyne Margin, offshore NW Australia, and contains numerous dykes that extend laterally for > 170 km, potentially up to > 500 km, with spacings typically < 10 km. Although limitations in data quality and resolution restrict mapping of the dykes at depth, our data show that they likely have heights of at least 3.5 km. The mapped dykes are distributed radially across a ∼39∘ wide arc centred on the Cuvier Margin; we infer that this focal area marks the source of the dyke swarm. We demonstrate that seismic reflection data provide unique opportunities to map and quantify dyke swarms in 3D. Because of this, we can now (i) recognise dyke swarms across continental margins worldwide and incorporate them into models of basin evolution and fluid flow, (ii) test previous models and hypotheses concerning the 3D structure of dyke swarms, (iii) reveal how dyke-induced normal faults and pit craters relate to dyking, and (iv) unravel how dyking translates into surface deformation.

Paleomagnetism and U-Pb geochronology of diabase dyke swarms of Minto block, Superior Province, Quebec, Canada

1998 ◽  
Vol 35 (9) ◽  
pp. 1054-1069 ◽  
Author(s):  
Kenneth L Buchan ◽  
James K Mortensen ◽  
Kenneth D Card ◽  
John A Percival
Keyword(s):  
Collaborative Study ◽  
Sedimentary Rocks ◽  
Dyke Swarm ◽  
Superior Province ◽  
Mafic Dyke ◽  
Magnetization Direction ◽  
Virtual Geomagnetic Pole ◽  
Southern Province ◽  
Geomagnetic Pole ◽  
Dyke Swarms

In the first collaborative study of paleomagnetism and precise U-Pb geochronology in the Minto block of the Superior Province, mafic dyke swarms with three widely divergent paleomagnetic signatures and isotopic ages have been identified. The 2505 ± 2 Ma Ptarmigan dykes trend north to northeast and have a virtual geomagnetic pole at 42°S, 220°E, similar to that of 2473-2446 Ma Matachewan dykes of the southern Superior Province. The ca. 2230 Ma Maguire dykes trend west to northwest and yield a paleopole at 9°S, 267°E, similar to those for 2216+8-4 Ma Senneterre dykes and 2217-2210 Ma Nipissing sills of the southern Superior and Southern provinces, respectively. The 2209 ± 1 Ma Klotz dykes trend west-northwest, but do not carry a consistent magnetization direction. Finally, 1998 ± 2 Ma Minto dykes of west-northwest to northwest trend, identical in age to the 1998 Ma ± 2 Ma Purtuniq ophiolite of the Cape Smith Belt, have a paleopole at 38°N, 174°E. The similarity of paleopoles for the ca. 2.23-2.21 Ga Maguire dykes of the Minto block, Senneterre dykes of the southern Superior, and Nipissing sills of the Southern Province demonstrates that these regions were in their present relative latitudes and orientations at that time. Likewise, the similarity of the Ptarmigan virtual geomagnetic pole and the Matachewan paleopole suggests little relative latitudinal movement or rotation of the two regions since ca. 2.5 Ga. The Maguire, Senneterre, and Klotz dykes form a roughly radiating pattern and may represent one quadrant of a giant radiating dyke swarm centred southeast of Ungava Bay, whose focus marks the location of a mantle plume responsible for ca. 2.22 Ga breakup along the eastern margin of the Superior Province. If so, the coeval Nipissing sills that intrude sedimentary rocks of the Huronian Supergroup of the Southern Province may have been fed laterally by Senneterre dykes from the Ungava plume centre.

PALAEOMAGNETISM OF THE ABITIBI DYKE SWARM

1966 ◽  
Vol 3 (5) ◽  
pp. 671-683 ◽  
Author(s):  
A. Larochelle
Keyword(s):  
Long Range ◽  
Dyke Swarm ◽  
Relative Importance ◽  
Angular Dispersion ◽  
Range Correlation ◽  
Dyke Swarms

Previous data published on the palaeomagnetism of a group of Precambrian diabase dykes, referred to as the Abitibi swarm, were characterized by considerable angular dispersion attributed to a number of possible factors. The relative importance of these factors was investigated in the light of data obtained for an independent suite of samples from the same group of dykes. Most of the previous interpretation is probably no longer valid because the magnetization of the swarm was found to be distributed tightly about three mean directions rather than dispersed widely about one mean direction, as originally thought. It is concluded that the dykes forming the swarm were injected intermittently during several widely distinct periods and that, accordingly, long-range correlation of diabase dyke swarms on the sole basis of their palaeomagnetism may be more hazardous than was realized earlier.

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 Preliminary Rb-Sr whole-rock data for Archean and Nagssugtoqidian rocks from the Søndre Strømfjord area, West Greenland

1978 ◽  
Vol 90 ◽  
pp. 129-134
Author(s):  
F Kalsbeek ◽  
H.P Zeck
Keyword(s):  
Dyke Swarm ◽  
Mobile Belt ◽  
West Greenland

The boundary between the Archaean gneiss block and the Nagssugtoqidian mobile belt (Escher et al., 1976) runs through the area south-east of the inner part of Søndre Strømfjord (fig. 42). The Archaean block here is mainly composed ofbrownish hypersthene gneisses cut by numerous basic dykes, the Kangåmiut dyke swarm. The Nagssugtoqidian mobile belt consists mainly of light grey biotite gneisses, formed by shearing and recrystallisation of gneisses from the Archaean block, together with numerous amphibolite layers, derived from the Kangâmiut dykes.

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