Occurrence of a sheeted dolerite dyke complex in the Ballantrae ophiolite, Scotland

1998 ◽  
Vol 135 (4) ◽  
pp. 509-517 ◽  
Author(s):  
G. J. H. OLIVER ◽  
R. R. McALPINE
Keyword(s):  
Dyke Swarm ◽  
Dolerite Dyke ◽  
Early Ordovician ◽  
Marginal Basin ◽  
Geological Setting ◽  
Back Arc

A sheeted dolerite dyke swarm has been discovered at Duniewick Fort, Ballantrae. It forms part of the Early Ordovician Ballantrae Complex of Ayrshire, southwest Scotland. Asymmetric chilled margins, parallel to sub-parallel dykes and multiple dykes (dykes within dykes) are found. Although the mineralogy has been altered by metamorphism, the geochemistry is comparable with modern day back-arc marginal basin basalt. Cross-cutting sills have the chemistry of within-plate basalt. The regional geological setting suggests that an ophiolite sequence has been dismembered and incorporated into a serpentinite mélange. This is the first description of a 100% sheeted dyke complex (senso stricto) from the Ballantrae ophiolite.

scholarly journals The dolerite dyke swarm of Mongo, Guéra Massif (Chad, Central Africa): Geological setting, petrography and geochemistry

2017 ◽  
Vol 9 (1) ◽  
Author(s):  
Oumarou Faarouk Nkouandou ◽  
Jacques-Marie Bardintzeff ◽  
Oumar Mahamat ◽  
Aminatou Fagny Mefire ◽  
Alembert Alexandre Ganwa
Keyword(s):  
Central Africa ◽  
Dyke Swarm ◽  
Dolerite Dyke ◽  
Geological Setting ◽  
Pan African ◽  
Basement Rocks

AbstractDolerite dykes are widespread in the Mongo area within the granitic Guéra Massif (Chad, Central Africa). Dykes are several hundred metres to several kilometres long, a metre to decametre thick, and vertical, crosscutting the Pan-African granitic basement rocks. They are controlled by major Pan-African NNE-SSW, NE-SW and ENE-WSW faults. Rocks constituting the dykes exhibit typical doleritic textures (

Composition, structure and tectonic analysis of the Shangrimuce arc-continent collision zone on the northern margin of the Central Qilian, NW China

2021 ◽  
Author(s):  
Hongyuan Zhang ◽  
Zhibin Lei ◽  
Bo Yang ◽  
Qing Liu ◽  
Haijun Zhang ◽  
...  
Keyword(s):  
Shear Zones ◽  
Oceanic Lithosphere ◽  
Late Ordovician ◽  
Island Arc ◽  
Qilian Mountain ◽  
Northern Margin ◽  
Early Ordovician ◽  
Collision Zone ◽  
Two Stages ◽  
Back Arc

<p>A 1:50000 regional survey, covering an area of about 2000 km<sup>2</sup>, was carried out in the Shangrimuce area of Qilian Mountain in Northwest China. The results show that during Caledonian, the northern margin of the Central Qilian block experienced collision with mature island arcs and subsequently northward expansion. In the Shangrimuce study area, five geological units have been identified; they are, form south to north, back-arc basin, early Ordovician island arc, inter arc basin, middle Late Ordovician island arc, and fore-arc and oceanic lithosphere amalgamation zone. </p><p>(1) back-arc basin. In the Yangyuchi- Shule River- Cuorigang- Wawusi area, there may be a back-arc spreading basin, and there should be spreading basins in this area. It is speculated that there was a northward reverse subduction in the late Ordovician, accompanied by a syenite body, a broad spectrum dyke swarms and an accretionary wedge zone in the whole area.</p><p>(2) early Ordovician island arc. In the Shangrimuce-Dander area, the Proterozoic basement granitic gneiss, the early Ordovician island arc block and the high-pressure geological body all occur in the form of thrust horses, forming a double metamorphic belt, which reveals the existence of ocean subduction to south in the early Ordovician. </p><p>(3) inter arc basin. On both banks of Tuolai River to the east of Yanglong Township, there are early Middle Ordovician inter-arc basins with oceanic crust. </p><p>(4) middle Late Ordovician island arc. To the north of Tuolai River, there is a middle Late Ordovician island arc belt. Both sides of the island arc zone experienced strong ductile shear deformation, which recorded a complex arc-continent collision. </p><p>(5) fore-arc and oceanic lithosphere amalgamation zone (Fig.1). The Yushigou area has developed a fore-arc and oceanic lithospheric amalgamation zone, with weakly deformed fore-arc flysch basin, strongly deformed siliceous rocks, pillow Basalt, diabase, gabbro, peridotite and other rock assemblages.</p><p>Combined with the characteristics of arc-continent collision zone in the Western Pacific, there are two stages of shear zone series (Fig.2). One is ductile shear zones formed by the South dipping gneissic belt, revealing the existence of oceanic subduction accretion wedge and emplacement of high-pressure rocks. Another superimposed one is north dipping. This indicates that the arc-continent collision caused by back-arc reverse subduction, which ultimately controls the overall geometric and kinematic characteristics of the shear zones in the region.</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gepj.8219836ca50067454890161/sdaolpUECMynit/12UGE&app=m&a=0&c=40b3389c641f2d0ca723e1527c32927e&ct=x&pn=gepj.elif&d=1" alt=""></p><p>Figure 1 United sections showing a Caledonian trench-arc system in the Qilian Mountain, NW China.</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gepj.8def566da50066084890161/sdaolpUECMynit/12UGE&app=m&a=0&c=e82258ecc235c4e618abd6c035b58232&ct=x&pn=gepj.elif&d=1" alt=""></p><p>Figure 2 Structural analysis at Hongyahuo, indicating two stages of deformation.</p><p>The research has been supported by projects from the Ministry of Land and Resources (No.201211024-04; 1212011121188) and the 2020 undergraduate class construction project from China University of Geosciences (Beijing) (No. HHSKE202003).</p><p> </p>

Baltica-Laurentia link during the Mesoproterozoic: 1.27 Ga development of continental basins in the Sveconorwegian Orogen, southern Norway

2002 ◽  
Vol 39 (9) ◽  
pp. 1425-1440 ◽  
Author(s):  
Bernard Bingen ◽  
Joakim Mansfeld ◽  
Ellen MO Sigmond ◽  
Holly Stein
Keyword(s):  
Secondary Ion Mass Spectrometry ◽  
Active Continental Margin ◽  
Dyke Swarm ◽  
Quartz Porphyry ◽  
Extensional Tectonic ◽  
Basin Formation ◽  
Sveconorwegian Orogen ◽  
Southern Norway ◽  
Back Arc ◽  
Secondary Ion

Recent models suggest that Laurentia and Baltica were contiguous during the Mesoproterozoic and shared a long-lived active continental margin, subsequently reworked during the Grenvillian orogeny. Around 1.25 Ga, the geological record is dominated by dyke-swarm intrusion, continental rift basin formation, A-type felsic magmatism, and arc – back-arc basin development. It points to a dominantly extensional tectonic regime over most of the craton and the Grenvillian margin, suggesting a retreating subduction boundary at that time. In the westernmost allochthonous domain of the Sveconorwegian Orogen, southern Norway, the Sæsvatn–Valldal supracrustal sequences are interpreted as rift or pull-apart basins. They formed at and after 1.27 Ga, in a continental setting, at the margin of Baltica. This interpretation is based on geological, geochemical, and new secondary ion mass spectrometry (SIMS) zircon U–Pb data. A subvolcanic quartz porphyry at the base of the Sæsvatn sequence yields a 1275 ± 8 Ma intrusion age. Metarhyolite samples in the lower part of the sequences yield equivalent extrusion ages of 1264 ± 4 Ma (Sæsvatn sequence) and 1260 ± 8 Ma (Valldal sequence). The metarhyolite units are overlain by sequences of metabasalt and metasandstone. An angular unconformity between the metarhyolites and overlying rocks is locally observed and possibly reflects rift tectonics during formation of the basin. A sample of arkosic metasandstone at the top of the exposed Sæsvatn sequence yields a few Archaean detrital zircon grains and a large spectrum of 2.2–1.2 Ga Proterozoic grains. These data point to a varied continental provenance and constrain sedimentation to later than 1211 ± 18 Ma.

A Devonian >2000-km-long dolerite dyke swarm-belt and associated basalts along the Urals-Novozemelian fold-belt: part of an East-European (Baltica) LIP tracing the Tuzo Superswell

GFF ◽  
2016 ◽  
Vol 138 (1) ◽  
pp. 6-16 ◽  
Author(s):  
Victor Puchkov ◽  
Richard E. Ernst ◽  
Michael A. Hamilton ◽  
Ulf Söderlund ◽  
Nina Sergeeva
Keyword(s):  
Dyke Swarm ◽  
Fold Belt ◽  
The Urals ◽  
Dolerite Dyke ◽  
East European

The Oman ophiolite as a Cretaceous arc-basin complex: evidence and implications

1981 ◽  
Vol 300 (1454) ◽  
pp. 299-317 ◽  
Keyword(s):  
Subduction Zone ◽  
Oceanic Crust ◽  
Significant Proportion ◽  
Dyke Swarm ◽  
Geochemical Analysis ◽  
Oman Ophiolite ◽  
Geochemical Evidence ◽  
Tectonic Development ◽  
High Level ◽  
Back Arc

Geological and geochemical evidence suggest that the Oman ophiolite is a fragment of a submarine arc-basin complex formed above a short-lived subduction zone in the mid-Cretaceous. Detailed studies of the lava stratigraphy and the intrusive relationships of dykes, sills and high-level plutons provide further evidence for the magmatic and tectonic development of the complex in question. Four consecutive events can be recognized to have taken place before emplacement: (1) eruption of basalts of island arc affinity onto pre-existing (Triassic) oceanic crust; (2) creation of new oceanic crust by backarc spreading; (3) intrusion of magma into this back-arc oceanic crust accompanied by eruption of basalts and andesites from discrete volcanic centres; (4) further intrusion of magma accompanied by uplift and eruption of basalts and rhyolites in submarine graben. A combined structural and geochemical analysis of the dyke swarm indicates that extension took place in approximately a N-S (ridge) and an ESE-WNW (leaky transform) direction relative to an inferred direction of subduction to the NE, and that a small but significant proportion of the sheeted dykes were injected during the ‘arc’ rather than the earlier ‘back-arc spreading’ episode. These various observations can be explained in terms of the progressive response of a non-isotropic lithosphere to the stresses induced during subduction.

Origin of Fe-Ni-Cu (Co) sulfide and Fe-Ti oxide minerals in the c. 1.77 Ga dolerite dyke, Singhbhum Craton (eastern India)

2021 ◽  
pp. SP518-2021-46
Author(s):  
Arnab Dey ◽  
Sisir K. Mondal
Keyword(s):  
Dyke Swarm ◽  
Sulfide Liquid ◽  
Eastern India ◽  
Content Type ◽  
Dolerite Dyke ◽  
Singhbhum Craton ◽  
Ti Oxides ◽  
Supplementary Material ◽  
Oxide Minerals ◽  
Dyke Swarms

AbstractDolerite dyke swarms are widespread within the Singhbhum Craton (eastern India) that emplaced from the Neoarchean to Paleoproterozoic era just after the stabilization of crust before c. 3 Ga. These dyke swarms are oriented in NE - SW to NNE - SSW, NW - SE to WNW - ESE, E - W, and N - S directions. The WNW - ESE trending c. 1.77 Ga Pipilia dyke swarm is sampled from the Satkosia area of the Orissa state. The dyke shows a noticeable disparity in terms of the modal proportion and grain size of pyroxenes, plagioclase, Fe-Ti-oxide minerals and texture across the trend. At places the primary silicates are altered to secondary hydrated mineral assemblages of amphibole, chlorite and sericite. Primary silicates are clinopyroxene (augite: Mg# = 65.7 - 82.6; En37-48Fs11-17Wo36-41), orthopyroxene (clinoenstatite: Mg# = 68.5 − 78; En63-70Fs20-29Wo4-5), plagioclase (An11-39Ab44-82Or1-7) and Fe-Ti oxides are titanomagnetite (FeO = 34.38 − 39.50 wt%, Fe2O3 = 48.26 − 56.21 wt%, TiO2 = 5.05 − 9.60 wt%) and ilmenite (FeO = 40.75 − 43.79 wt%, Fe2O3 = 3.54 − 10.03 wt%, TiO2 = 47.82 − 50.87 wt%). Application of two-pyroxene thermometry yields an equilibration temperature range of 1065oC to 978oC, and coexisting titanomagnetite-ilmenite pairs reveal 731.39oC to 573.37oC at the oxygen fugacity (fO2) condition NNO+0.3 to FMQ-1.03. The dyke contains disseminated sulfides at the interstices of Fe-Ti-oxides, and silicates. Major sulfide minerals are pyrite, chalcopyrite, and vaesite; Pyrite-vaesite assemblages occur in association with secondary silicate minerals. Pyrite grains contain variable concentration of Co = 0.01 − 5.70 wt% and Ni = 0.02 − 1.95 wt%. Coexisting vaesite contains Co = 2.42 − 10.44 wt%, Ni = 26.40 − 47.88 wt%, and Fe = 7.32 − 26.55 wt%. Texture, sulfide-silicate assemblage, and presence of low metal/S sulfides such as the pyrite-vaesite assemblage indicate primary Fe-Ni- sulfides (pyrrhotite-pentlandite) that segregated from immiscible sulfide liquid at high temperature is modified by late magmatic/hydrothermal fluid activities. Numerous sulfide-bearing deposits hosted in ultramafic-mafic intrusions of Paleoproterozoic age have been recorded globally and the occurrence of Fe-Ni-sulfides in the c. 1.77 Ga Pipilia dyke swarm in the Singhbhum Craton enhances the exploration potential of this craton in eastern India.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5643989

The Ordovician volcanics of the Elmtree–Belledune inlier and their relationship to volcanics of the northern Miramichi Highlands, New Brunswick

1992 ◽  
Vol 29 (7) ◽  
pp. 1430-1447 ◽  
Author(s):  
J. A. Winchester ◽  
C. R. van Staal ◽  
J. P. Langton
Keyword(s):  
New Brunswick ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Late Ordovician ◽  
Igneous Rocks ◽  
Volcanic Arc ◽  
Middle Ordovician ◽  
Marginal Basin ◽  
Tectonic Mélange ◽  
Back Arc

An investigation of the geology and chemistry of the basic igneous rocks in the Elmtree and Belledune inliers in northern New Brunswick shows that the bulk of the Middle Ordovician rocks of the ophiolitic Fournier Group are best interpreted as the products of volcanism and sedimentation in an extensive ensimatic back-arc basin southeast of a volcanic arc. The oceanic back-arc-basin igneous rocks form the basement to renewed arc-related basaltic volcanism in late Middle to Late Ordovician time. The Fournier Group is separated from the structurally-underlying, shale-dominated Elmtree Formation of the Tetagouche Group by an extensive tectonic melange, which incorporates lenses of serpentinite, mafic volcanic rocks, and sedimentary rocks of both the Tetagouche and Fournier groups. The mafic volcanic rocks in the Elmtree Formation correlate best with those intercalated with the lithologically similar sediments of the Llandeilian–Caradocian Boucher Brook Formation in the northern Miramichi Highlands. The melange and the present structural amalgamation of the Tetagouche and Fournier groups result from closure of the marginal basin by northward-directed subduction at the end of the Ordovician. Most mafic suites in the Elmtree and Belledune inliers can be chemically correlated with similar suites in the northern Miramichi Highlands, showing that the two areas are not separated by a terrane boundary.

Parallel geological development in the Dunnage Zone of Newfoundland and the Lower Palaeozoic terranes of southern Scotland: an assessment

1992 ◽  
Vol 83 (3) ◽  
pp. 571-594 ◽  
Author(s):  
S. P. Colman-Sadd ◽  
P. Stone ◽  
H. S. Swinden ◽  
R. P. Barnes
Keyword(s):  
Volcanic Rocks ◽  
Foreland Basin ◽  
Late Ordovician ◽  
Marine Transgression ◽  
Early Ordovician ◽  
Sedimentary Sequences ◽  
Structural Regime ◽  
Lower Palaeozoic ◽  
Back Arc ◽  
Combined Data

AbstractThe Notre Dame and Exploits subzones of Newfoundland's Dunnage Zone are correlated with the Midland Valley and Southern Uplands of Scotland, using detailed comparisons of two key Lower Palaeozoic successions which record similar histories of extension and compression. It follows that the Baie Verte Line, Red Indian Line and Dover Fault are equivalent to the Highland Boundary Fault, Southern Upland Fault and Solway Line, respectively.The Betts Cove Complex and overlying Snooks Arm Group of the Notre Dame Subzone are analogous to the Ballantrae Complex of the Midland Valley, both recording the Arenig evolution and subsequent obduction of an arc and back-arc system. The Early Ordovician to Silurian sequence unconformably overlying the Ballantrae Complex is poorly represented in the Notre Dame Subzone but important similarities can still be detected suggesting corresponding histories of continental margin subsidence and marine transgression.In the Exploits Subzone, Early Ordovician back-arc volcanic rocks are overlain by Llandeilo mudstones and Late Ordovician to Early Silurian turbidites. A similar stratigraphy occurs in the Northern and Central Belts of the Southern Uplands and both areas have matching transpressive structural histories. Deeper erosion in the Exploits Subzone reveals Cambrian and Early Ordovician volcano-sedimentary sequences structurally emplaced on the Gander Zone, and such rocks are probably present beneath the Southern Uplands. Combined data from the Notre Dame Subzone and Midland Valley suggest an Arenig southeast-dipping subduction zone. Early Ordovician volcanic rocks in the Exploits Subzone and Southern Uplands have back-arc basin geochemistry and support the model of the Southern Uplands as a transition from back-arc to foreland basin. Preferential emergence of the Dunnage Zone and contrasts between Exploits Subzone and Southern Uplands turbidite basins are attributed to collision of Newfoundland with a Laurentian promontory and Scotland with a re-entrant. This hypothesis also explains the transpressive structural regime common to both areas.

scholarly journals Baddeleyite U–Pb ages and gechemistry of the 1875–1835 Ma Black Hills Dyke Swarm across north-eastern South Africa: part of a trans-Kalahari Craton back-arc setting?

GFF ◽  
2015 ◽  
Vol 138 (1) ◽  
pp. 183-202 ◽  
Author(s):  
J.R. Olsson ◽  
M.B. Klausen ◽  
M.A. Hamilton ◽  
N. März ◽  
U. Söderlund ◽  
...  
Keyword(s):  
South Africa ◽  
Black Hills ◽  
Dyke Swarm ◽  
Kalahari Craton ◽  
North Eastern ◽  
Arc Setting ◽  
Back Arc

Geochemical aspects of back-arc spreading in the Scotia Sea and western Pacific

1981 ◽  
Vol 300 (1454) ◽  
pp. 263-285 ◽  
Keyword(s):  
Island Arc ◽  
Calc Alkaline ◽  
Volcanic Arc ◽  
Scotia Sea ◽  
Marginal Basin ◽  
Early Stages ◽  
Enriched Mantle ◽  
Mantle Sources ◽  
History Of ◽  
Back Arc

The results of recent geochemical investigations of several island arc - marginal basin systems in the Scotia Sea area and in the western Pacific are outlined. Marginal basins in different stages of evolution are represented, from those in the initial stages of formation to those with an extensive and multiple history of back-arc spreading. Some are completely intraoceanic, others have developed at continental margins. Basalts erupted at back-arc spreading centres seem to be as geochemically varied as those from normal mid-ocean ridges, and record evidence for similar processes of partial melting, fractional crystallization and magma mixing in their genesis. They appear to have been derived from mantle sources with incompatible trace element characteristics ranging from ‘depleted’ to ‘enriched’, but with the ‘enriched’ mantle sources being sampled during the earlier stages of back-arc spreading. Submarine back-arc basalts are more vesicular than their normal ocean ridge equivalents, and their corresponding glasses have higher water contents. This, together with other geochemical features such as the higher ratios of lithophile to high field strength elements in some back-arc basalts, suggests that a component from the subducted slab may be involved in their petrogenesis. The chemistry of the corresponding arc volcanics is described in relation to the subduction and extensions history of marginal basin development. In intraoceanic arcs the early stages of arc magmatism are dominated by the eruption of large volumes of island arc tholeiites and subsidiary high-Mg andesites. In the Mariana region, after the initial volcanic arc is split and separated by back-arc spreading, the later frontal arc volcanics have calc-alkaline characteristics. Basalts erupted during the early stages of back-arc spreading more commonly have arc-like geochemical features when the marginal basin has developed through splitting of a calc-alkaline volcanic arc. The secular variation in the geochemistry of the arc volcanics may be related to the progressive development of a lithophile element enriched mantle source beneath the arc. This source contributes to the basalts produced during the early stages of arc rifting and back-arc spreading. Ophiolite complexes which represent marginal basin floor may well carry these arc-like geochemical features.

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