scholarly journals Middle Triassic trachytic lava flows associated with coeval dyke swarm in the North Patagonian Massif: A postorogenic magmatism related to extensional collapse of the Gondwanide orogen

2017 ◽  
Vol 75 ◽  
pp. 134-143 ◽  
Author(s):  
Santiago N. González ◽  
Gerson A. Greco ◽  
Ana M. Sato ◽  
Eduardo J. Llambías ◽  
Miguel A.S. Basei ◽  
...  
Keyword(s):  
Middle Triassic ◽  
Lava Flows ◽  
Dyke Swarm ◽  
The North ◽  
Extensional Collapse

scholarly journals Stratigraphy and age of the Eocene Igtertivâ Formation basalts, alkaline pebbles and sediments of the Kap Dalton Group in the graben at Kap Dalton, East Greenland

2013 ◽  
Vol 61 ◽  
pp. 1-18 ◽  
Author(s):  
Lotte Melchior Larsen ◽  
Erik Vest Sørensen ◽  
W. Stuart Watt ◽  
Asger Ken Pedersen ◽  
Robert A. Duncan
Keyword(s):  
Field Work ◽  
Lava Flows ◽  
Radiometric Dating ◽  
Dyke Swarm ◽  
Geological Time ◽  
Geological Time Scale ◽  
The North ◽  
Northward Propagation ◽  
Volcanic Succession ◽  
Good Agreement

A NE–SW-trending graben at Kap Dalton on the Blosseville Kyst contains an at least 600 m thick succession of Eocene basalt lavas and sediments. The succession has been investigated by new field work, geochemical analysis and radiometric dating by the 40Ar-39Ar incremental heating method. The results show that the volcanic succession comprises about 220 m of the uppermost plateau basalt formation, the Skrænterne Formation. This is separated from the overlying lava flows of the Igtertivâ Formation by 7 m of sediments that represent a period of around six million years. The two formations can be distinguished by different trace element ratios. The Igtertivâ Formation comprises an at least 300 m thick main succession of flows dated to 49.09 ± 0.48 Ma, overlain by sediments of the Bopladsdalen Formation. A basal conglomerate in the sediments contains pebbles of alkaline igneous rocks of which three were dated at 49.17 ± 0.35 Ma, 47.60 ± 0.25 Ma, and 46.98 ± 0.24 Ma. The sediments are thus younger than 47 Ma. Above 30 m of sediments occur two Igtertivâ Formation lava flows dated to 43.77 ± 1.08 Ma. The overlying sediments of the Bopladsdalen and Krabbedalen Formations are therefore not older than about 44 Ma and palynological evidence shows that they are also not much younger than this. Use of the Geological Time Scale 2012 has resulted in good agreement between radiometric and palynological ages. The Igtertivâ Formation lava flows were fed from a regional coast-parallel dyke swarm indicating a new rifting episode at 49–44 Ma. This coincides with a major mid-Eocene plate reorganisation event in the North Atlantic and the start of northward-propagation of the Reykjanes Ridge through the continent. The Igtertivâ rift may have been directly instrumental for the initiation of this process.

scholarly journals Tectono-magmatic evolution of the younger Gardar southern rift, South Greenland

2013 ◽  
Vol 29 ◽  
pp. 1-24 ◽  
Author(s):  
Brian G.J. Upton
Keyword(s):  
Mafic Magma ◽  
Dyke Swarm ◽  
Small Scale ◽  
Alkaline Magmatism ◽  
East African ◽  
The North ◽  
Intrusive Rocks ◽  
Alkali Granites ◽  
African Rift ◽  
Very High

The 1300–1140 Ma Gardar period in South Greenland involved continental rifting, sedimentation and alkaline magmatism. The latest magmatism was located along two parallel rift zones, Isortoq–Nunarsuit in the north and the Tuttutooq–Ilimmaasaq–Narsarsuaq zone in the south addressed here. The intrusive rocks crystallised at a depth of troctolitic gabbros. These relatively reduced magmas evolved through marked iron enrichment to alkaline salic differentiates. In the Older giant dyke complex, undersaturated augite syenites grade into sodalite foyaite. The larger, c . 1163 Ma Younger giant dyke complex (YGDC) mainly consists of structureless troctolite with localised developments of layered cumulates. A layered pluton (Klokken) is considered to be coeval and presumably comagmatic with the YGDC. At the unconformity between the Ketilidian basement and Gardar rift deposits, the YGDC expanded into a gabbroic lopolith. Its magma may represent a sample from a great, underplated mafic magma reservoir, parental to all the salic alkaline rocks in the southern rift. The bulk of these are silica undersaturated; oversaturated differentiates are probably products of combined fractional crystallisation and crustal assimilation. A major dyke swarm 1–15 km broad was intruded during declining crustal extension, with decreasing dyke widths and increasing differentiation over time. Intersection of the dyke swarm and E–W-trending sinistral faults controlled the emplacement of at least three central complexes (Narssaq, South Qôroq and early Igdlerfigssalik). Three post-extensional complexes (Tugtutôq, Ilímaussaq and late Igdlerfigssalik) along the former rift mark the end of magmatism at c . 1140 Ma. The latter two complexes have oblate plans reflecting ductile, fault-related strain. The Tugtutôq complex comprises quartz syenites and alkali granites. The Ilímaussaq complex mainly consists of nepheline syenite crystallised from highly reduced, Fe-rich phonolitic peralkaline (agpaitic) magma, and resulted in rocks with very high incompatible element concentrations. Abundant anorthositic xenoliths in the mafic and intermediate intrusions point to a large anorthosite protolith at depth which is considered of critical importance in the petrogenesis of the salic rocks. Small intrusions of aillikite and carbonatite may represent remobilised mantle metasomites. The petrological similarity between Older and Younger Gardar suites implies strong lithospheric control of their petrogenesis. The parental magmas are inferred to have been derived from restitic Ketilidian lithospheric mantle, metasomatised by melts from subducting Ketilidian oceanic crust and by small-scale melt fractions associated with Gardar rifting. There are numerous analogies between the southern Gardar rift and the Palaeogene East African rift.

Paleomagnetism and U–Pb geochronology of the Clarence Head dykes, Arctic Canada: orthogonal emplacement of mafic dykes in a large igneous province

2009 ◽  
Vol 46 (3) ◽  
pp. 155-167 ◽  
Author(s):  
Steven W. Denyszyn ◽  
Don W. Davis ◽  
Henry C. Halls
Keyword(s):  
Remanent Magnetization ◽  
High Arctic ◽  
Large Igneous Province ◽  
Dyke Swarm ◽  
Canadian High Arctic ◽  
The North ◽  
Igneous Province ◽  
The Difference ◽  
Age Range ◽  
Chemical Remanent Magnetization

The north–south-trending Clarence Head dyke swarm, located on Devon and Ellesmere Islands in the Canadian High Arctic, has a trend orthogonal to that of the Neoproterozoic Franklin swarm that surrounds it. The Clarence Head dykes are dated by the U–Pb method on baddeleyite to between 716 ± 1 and 713 ± 1 Ma, ages apparently younger than, but within the published age range of, the Franklin dykes. Alpha recoil in baddeleyite is considered as a possible explanation for the difference in ages, but a comparison of the U–Pb ages of grains of equal size from both swarms suggests that recoil distances in baddeleyite are lower than those in zircon and that the Clarence Head dykes are indeed a distinctly younger event within the period of Franklin magmatism. The Clarence Head dykes represent a large swarm tangential to, and cogenetic with, a giant radiating dyke swarm ∼800 km from the indicated source. The preferred mechanism for the emplacement of the Clarence Head dykes is the exploitation of concentric zones of extension around a depleting and collapsing plume source. While the paleomagnetism of most Clarence Head dykes agrees with that of the Franklin dykes, two dykes have anomalous remanence directions, interpreted to be a chemical remanent magnetization carried by pyrrhotite. The pyrrhotite was likely deposited from fluids mobilized southward from the Devonian Ellesmerian Orogeny to the north that used the interiors of the dykes as conduits and precipitated pyrrhotite en route.

Le horst suggarien de Timg'aouine

1961 ◽  
Vol S7-III (2) ◽  
pp. 156-158
Author(s):  
Michel Bouvet ◽  
C. Reboul
Keyword(s):  
Lava Flows ◽  
Structural Development ◽  
The West ◽  
The North

Abstract The north-south fault along the 4 degrees 50' meridian is one of the major structural trends of the Ahaggar mountains, Algeria. It separates Suggarian (Precambrian) deposits on the east from Pharusian (Precambrian) deposits on the west. A north-northeast-south-southwest- trending horst, the Timg'aouine horst, about 120 kilometers long and averaging 15 kilometers in width, lies west of the fault. Large lava flows are associated with the faults bounding the horst. The presence of this Suggarian unit played an important role in the structural development of the surrounding Pharusian basin.

scholarly journals Geochemistry of a Triassic dyke swarm in the North Patagonian Massif, Argentina. Implications for a postorogenic event of the Permian Gondwanide orogeny

2016 ◽  
Vol 70 ◽  
pp. 69-82 ◽  
Author(s):  
Santiago N. González ◽  
Gerson A. Greco ◽  
Pablo D. González ◽  
Ana M. Sato ◽  
Eduardo J. Llambías ◽  
...  
Keyword(s):  
Dyke Swarm ◽  
The North

Inversion tectonics during post-orogenic extensional collapse: a comparison between ancient (North Sea, UK) and recent (Fucino Basin, central Apennines Apennines) intermontane systems

2020 ◽  
Author(s):  
Stefano Patruno ◽  
Vittorio Scisciani
Keyword(s):  
Gravitational Collapse ◽  
Western Europe ◽  
Central Italy ◽  
Middle Pleistocene ◽  
Coupled Analysis ◽  
Inversion Tectonics ◽  
Central Apennines ◽  
The North ◽  
Fucino Basin ◽  
Extensional Collapse

<p>Post-orogenetic extensional/gravitational collapse events constitute a relatively poorly understood tectonic process, which is responsible for the quick and effective dismantling of the thickened crust and topographic bulge of fold-and-thrust belt edifices. These events are also responsible for the accumulation of very thick post-orogenetic successions and, in case of active extension, may trigger moderate to strong earthquakes resulting in obvious seismic hazards (e.g., the 1915 Mg 7.0 Fucino earthquake in Central Italy, which caused 30,000 victims)</p><p>Here, we combine seismic interpretation coupled with well analyses, basin modelling and a thorough literature review, in order to compare an ancient and a modern example of study areas subject to post-orogenetic collapse. The Devonian-age Old Red Sandstones of north-western Europe and ?Plio-Quaternary fill of the Fucino intramontane extensional basin in the central Apennines (Italy) share several stratigraphic, depositional and tectonic characteristics. Both are characterized by remarkably similar seismic-stratigraphic architecture (with syn-depositional half-grabens) and maximum thickness of >1,500 metres. In the Fucino, the border faults associated to the main tectonic depocentres achieved maximum throw rates of 1,000-1,400 mm/kyr.</p><p>Both units comprise thick continental siliciclastic successions, dominated by lacustrine and alluvial to fluvio-deltaic facies. The facies architecture reveals a progressive transition from localized, fault-bounded depocentres to transgressive lacustrine successions in wider basins that are less reliant on the sole fault-driven subsidence. The studied units were deposited due to high and quick tectonic subsidence which took place very shortly after the end (or during?) of crustal shortening processes (respectively Caledonian and Apenninic orogenesis) and in a post-orogenic collapse context.</p><p>In both study areas, the sedimentation of the thick continental units are intimately associated to a polyphase inversion tectonics, with pre-existing inherited deep-seated discontinuities affected, in places, first by a positive and subsequently by a negative reactivation during the extensional collapse. A further element common in the two study areas, is a strike-slip or oblique tectonics occurring during or immediately prior to the extensional collapse achieved by the normal faulting. This has been interpreted as a consequence of the gradual rotation of the stress vectors around their axes, culminating in the relaxation of the horizontal compressive stress and the onset of the post-orogenetic extensional/gravitational collapse process itself. For example, in the Fucino Basin, maximum Plio-Quaternary sediment thicknesses of >1700 m occur in two tectonic depocentres, situated respectively to the north and east of the basin. In contrast, the south-eastern striking dip-slip border faults bounding the eastern edge of the Fucino show maximum slip rates in the Lower-Middle Pleistocene, with evidence (e.g., Gioia dei Marsi) for a very recent activity, possibly linked with the 1915 seismic event.</p><p>The study of post-orogenic extensional collapse by comparison of ancient and recent basins suggest that in these settings poly-phase tectonic inversion commonly occurs and promote multiple reactivation of inherited zones of weakness. The comprehension of the common and dissimilar features, may be fundamental to better understand the mechanism and evolution of post-orogenic chain reworking and for natural resources and geological hazards assessment, including earthquakes. The coupled analysis of an ancient and recent example enables just that.</p>

A 1.78 Ga large igneous province in the North China craton: The Xiong'er Volcanic Province and the North China dyke swarm

Lithos ◽  
2008 ◽  
Vol 101 (3-4) ◽  
pp. 260-280 ◽  
Author(s):  
Peng Peng ◽  
Mingguo Zhai ◽  
Richard E. Ernst ◽  
Jinghui Guo ◽  
Fu Liu ◽  
...  
Keyword(s):  
North China Craton ◽  
North China ◽  
Large Igneous Province ◽  
Dyke Swarm ◽  
Volcanic Province ◽  
The North ◽  
Igneous Province

scholarly journals The Petrogenesis of Mid-Cretaceous Continental  Intraplate Volcanism in Marlborough, New Zealand,  during the Break-up of Gondwana

2021 ◽  
Author(s):  
◽  
Alexander Joseph McCoy-West
Keyword(s):  
New Zealand ◽  
Lithospheric Mantle ◽  
Volcanic Rocks ◽  
Oceanic Lithosphere ◽  
Small Degree ◽  
Lava Flows ◽  
Dyke Swarm ◽  
Subcontinental Lithospheric Mantle ◽  
Igneous Complex ◽  
Volcanic Material

<p>The Lookout Volcanics are the remnants of an extensive sheet of mid-Cretaceous (ca. 96 Ma) continental intraplate volcanic rocks erupted just prior to the rifting of New Zealand from Gondwana. Preserved in a fault angle depression bounded by the Awatere Fault located in Marlborough, South Island, New Zealand, the volcanic rocks cover an area of ca. 50 km2 with exposed thicknesses up to 1000 m. On the basis of stratigraphic evidence the dominantly terrestrial lavas flows are inferred to have erupted from dykes of a coeval radial dyke swarm. A detailed sampling of the lava flows of the Lookout Volcanics has been undertaken with a ca. 700 m composite stratigraphic section being constructed, largely based on a continuous sequence of lava flows outcropping in Middlehurst Stream. New Rb-Sr age constraints for the Lookout Volcanics (97.6 plus or minus 3.4 Ma) and Blue Mountain Igneous Complex (97.1 plus or minus 0.7 Ma) are consistent with previous radiometric dates of plutonic complexes in the Central Marlborough Igneous Complex, and suggest a rapid accumulation of volcanic material from ca. 98-96 Ma during the initial extension of proto-New Zealand. The predominantly mafic and alkaline samples include basalt, picrobasalt, basanite, trachybasalt and basaltic trachyandesite rock types. No samples represent primary magmas with all samples having undergone fractionation (or accumulation) of olivine plus clinopyroxene plus or minus plagioclase plus or minus Fe-Ti oxides. Initial Sr-Nd-Hf-Pb isotopic variations (87Sr/86Sr = 0.7030-0.7039; 143Nd/144Nd = 0.51272-0.51264; 176Hf/177Hf = 0.28283-0.28278; 206Pb/204Pb = 20.32-18.82) reflect mixing between melts of a HIMUlike mantle component with up to 25-30% of an Early Cretaceous upper crustal component. Oxygen isotope ratios determined by laser fluorination analysis from 6 lava flows yielded delta 18O = 4.7-5.0 per thousand for olivine, 4.8-5.4 per thousand in clinopyroxene cores, 3.9-5.5 per thousand in clinopyroxene rims. Average olivine (4.8 per thousand) and clinopyroxene core (5.1 per thousand) values are 0.4-0.5 per thousand lower than those of average mantle peridotite but comparable to those of HIMU OIB, and are consistent with New Zealand intraplate magmas being generated by a low delta 18O mantle. However, oxygen isotopic disequilibrium between clinopyroxene cores and rims (Delta 18O = -1.4 to +0.3) records the overprinting of this signature by crustal processes. Negative disequilibrium between clinopyroxene rims and cores in primitive samples suggests these phenocrysts grew in a shallow crustal magma chamber with an active meteoric water system. The effects of crustal assimilation can also be observed with clinopyroxene phenocrysts from the most evolved sample exhibiting coupled elevated delta 18O and 87Sr/86Sr. Variations in incompatible trace element ratios are consistent with the Lookout Volcanics being the small degree (2-5%) partial melts of an amphibole-bearing garnet pyroxenite. Furthermore, the elevated NiO contents of olivine phenocrysts are consistent with melting of a pyroxenitic mantle source. The presence of residual amphibole constrains melting to the hydrous subcontinental lithospheric mantle. The Lookout Volcanics and coeval plutonic complexes are the oldest occurrences of HIMU magmatism in Zealandia. This source was generated by small degree silicate melts from recycled oceanic lithosphere that metasomatised the base of the subcontinental lithospheric mantle beneath East Gondwana over 200 Ma ago.</p>

Sign in / Sign up

Export Citation Format

Share Document