The early tectono-magmatic evolution of the Southern Province: implications from the Agnew Intrusion, central Ontario, Canada

1998 ◽  
Vol 35 (7) ◽  
pp. 854-870 ◽  
Author(s):  
D C Vogel ◽  
R S James ◽  
R R Keays
Keyword(s):  
Parental Magma ◽  
Structural Data ◽  
Flood Basalt ◽  
Incompatible Trace Element ◽  
Superior Province ◽  
Magmatic Evolution ◽  
Layered Intrusions ◽  
Continental Flood Basalt ◽  
Southern Province ◽  
Field Evidence

The Palaeoproterozoic Southern Province comprises a thick, continental rift related volcanic-sedimentary sequence along the southern margin of the Archaean Superior Province. The Agnew Intrusion (50 km2), which is a member of the East Bull Lake suite of layered intrusions, occurs adjacent to the Superior Province - Southern Province boundary in central Ontario, Canada, and provides an opportunity to examine the early tectono-magmatic evolution of a Palaeoproterozoic rifting event. The Agnew Intrusion is a well-exposed, 2100 m thick, layered gabbronoritic to leucogabbronoritic pluton. It was the product of at least four recognizable, but chemically similar, high-Al2O3 and low-TiO2 magma pulses. Structural data, coupled with excellent stratigraphic correlations between the Agnew Intrusion and other East Bull Lake suite layered intrusions, suggest that these plutons are erosional remnants of one or more sill-like bodies that may originally have formed an extensive, subhorizontal mafic sheet. We argue on the basis of field evidence that the early evolution of the Southern Province was characterized by a large, mantle plume induced magmatic event that gave rise to a Palaeoproterozoic continental flood basalt province. However, the incompatible trace element characteristics of the Agnew Intrusion parental magma (i.e., large ion lithophile and light rare earth element enrichment and high field strength element depletion) are more typical of modern subduction-modified subcontinental lithospheric mantle. Given that this is a prevailing geochemical signature of mafic rocks in the Archaean-Palaeoproterozoic, we suggest that there was a fundamental difference in both the composition and structure between the ancient and more modern mantle. "Subduction-like" geochemical signatures may have been imparted to the entire developing mantle during early Earth differentiation.

Open-system evolution versus source control in basaltic magmas: Matachewan–Hearst dike swarm, Superior Province, Canada

1990 ◽  
Vol 27 (6) ◽  
pp. 767-783 ◽  
Author(s):  
Dennis O. Nelson ◽  
Donald A. Morrison ◽  
William C. Phinney
Keyword(s):  
Trace Element ◽  
Fractional Crystallization ◽  
Incompatible Trace Element ◽  
Source Control ◽  
Superior Province ◽  
Crustal Rock ◽  
Dike Swarm ◽  
Element Abundances ◽  
Field Evidence ◽  
Element Enrichment

The 2.45 Ga Matachewan–Hearst dike swarm was emplaced over 250 000 km2 in diverse granitoid–greenstone and metasedimentary terranes of the Superior Province of Canada. The Fe-rich tholeiitic dikes host large, uniform plagioclase megacrysts and display significant trace-element variations, e.g., (La/Sm)N = 0.62–2.23, not correlated to terrane lithologies.Fractional crystallization alone cannot produce these variations or simultaneously account for both major- and trace-element abundances. Combined periodic replenishment–fractional crystallization (RFC) in shallow magma chambers is consistent with major- and trace-element concentrations and with field evidence for periodic magma injection within the dikes. RFC cannot, however, produce the observed variation in incompatible-trace-element ratios, e.g., (La/Sm)N. Models invoking mixed mantle sources are unsuccessful at reproducing trace-element trends. Combined assimilation–fractional crystallization (AFC) models, assuming depleted parental magmas and using crustal rock data from xenoliths and from the Kapuskasing Structural Zone, can accommodate the trace-element variations, including the light-rare-earth-element enrichment and the observed relative depletions of the high-field-strength elements. The AFC process apparently took place in the lower crustal regions from where evolved magmas were periodically transported to shallow chambers dominated by RFC.

scholarly journals The Chief Joseph dike swarm of the Columbia River flood basalts, and the legacy data set of William H. Taubeneck

Geosphere ◽  
2020 ◽  
Vol 16 (4) ◽  
pp. 1082-1106
Author(s):  
Matthew C. Morriss ◽  
Leif Karlstrom ◽  
Morgan W.M. Nasholds ◽  
John A. Wolff
Keyword(s):  
Large Scale ◽  
Columbia River ◽  
Flood Basalt ◽  
Continental Flood Basalt ◽  
Data Set ◽  
Average Width ◽  
Near Surface ◽  
Surface Flows ◽  
Dike Swarm ◽  
Stress Changes

Abstract The Miocene Columbia River Basalt Group (CRBG) is the youngest and best studied continental flood basalt province on Earth. The 210,000 km3 of basaltic lava flows in this province were fed by a series of dike swarms, the largest of which is the Chief Joseph dike swarm (CJDS) exposed in northeastern Oregon and southwestern Washington. We present and augment an extensive data set of field observations, collected by Dr. William H. Taubeneck (1923–2016; Oregon State University, 1955–1983); this data set elucidates the structure of the CJDS in new detail. The large-scale structure of the CJDS, represented by 4279 mapped segments mostly cropping out over an area of 100 × 350 km2, is defined by regions of high dike density, up to ∼5 segments/km−2 with an average width of 8 m and lengths of ∼100–1000 m. The dikes in the CJDS are exposed across a range of paleodepths, from visibly feeding surface flows to ∼2 km in depth at the time of intrusion. Based on extrapolation of outcrops, we estimate the volume of the CJDS dikes to be 2.5 × 102–6 × 104 km3, or between 0.1% and 34% of the known volume of the magma represented by the surface flows fed by these dikes. A dominant NNW dike segment orientation characterizes the swarm. However, prominent sub-trends often crosscut NNW-oriented dikes, suggesting a change in dike orientations that may correspond to magmatically driven stress changes over the duration of swarm emplacement. Near-surface crustal dilation across the swarm is ∼0.5–2.7 km to the E-W and ∼0.2–1.3 km to the N-S across the 100 × 350 km region, resulting in strain across this region of 0.4%–13.0% E-W and 0.04%–0.3% N-S. Host-rock partial melt is rare in the CJDS, suggesting that only a small fraction of dikes were long-lived.

A simple recipe for red bole formation in continental flood basalt provinces: weathering of flow-top and flow-bottom breccias

2020 ◽  
Vol 13 (18) ◽  
Author(s):  
Raymond A. Duraiswami ◽  
Hetu Sheth ◽  
Purva Gadpallu ◽  
Nasrrddine Youbi ◽  
El Hassane Chellai
Keyword(s):  
Flood Basalt ◽  
Continental Flood Basalt

Field, petrographical and geochemical characterization of a layered anorthosite sequence in the Upper Main Zone of the Bushveld Complex

2020 ◽  
Vol 123 (3) ◽  
pp. 277-296
Author(s):  
J.E. Bourdeau ◽  
S.E. Zhang ◽  
B. Hayes ◽  
A. Logue
Keyword(s):  
Bushveld Complex ◽  
Major Element ◽  
Parental Magma ◽  
Incompatible Trace Element ◽  
Limpopo Province ◽  
Main Zone ◽  
Bulk Rock ◽  
Magmatic Differentiation ◽  
Slurry Injection

Abstract A sequence of eight poikilitic anorthosite layers (labeled 1 to 8), within the Upper Main Zone in the eastern lobe of the Bushveld Complex, are exposed along a road-cut, 5.3 km northeast of the town of Apel, Limpopo Province. The anorthosite layers are meter-scale in thickness (0.4 to 10 m), have sharp contacts and are defined on the size and shape of pyroxene oikocrysts they contain. The anorthosite sequence is bounded by typical Main Zone gabbronorites. Euhedral, zoned primocrystic laths of plagioclase (An62.5-80.6; 0.2 to 4 mm long) are morphologically identical throughout the anorthosite sequence and define a moderate to strong foliation that is typically aligned parallel to the plane of layering. Interstitial clinopyroxene and orthopyroxene typically occur as large (0.8 to 80 cm) oikocrysts enclosing numerous partly rounded plagioclase chadacrysts. Rarely, orthopyroxene appears as subophitic crystals enclosing few and significantly smaller (0.08 to 0.4 mm), equant plagioclase inclusions. Detailed plagioclase and pyroxene mineral compositions for layers 2 to 5 show minimal variations within layers (0.1 to 2.3 mol% An and 0.7 mol% Mg#), whereas compositional breaks occur between layers (0.5 to 3.8 mol% An and 1.3 mol% Mg#). In layers 2 to 5, the An-content of plagioclase cores and the Mg# of both clinopyroxene and orthopyroxene crystals decrease by 2.5 mol%, 8.6 mol% and 13.0 mol% upwards, respectively. Bulk-rock incompatible trace element concentrations and patterns are similar for all analyzed anorthosite layers indicating that they are related to the same parental magma. However, bulk-rock major element oxides (e.g. Al2O3, TiO2, K2O) and atomic Mg# become more evolved upwards, consistent with magmatic differentiation. Based on the consistent plagioclase crystal morphologies and relatively constant chemistries within each anorthosite layer, we propose that each layer was formed by the intrusion of a plagioclase slurry. The upwards-evolving mineral chemistries, bulk-rock major element oxides and atomic Mg# suggests that each plagioclase slurry injection, that yielded an anorthosite layer, was derived from a slightly more fractionated parental magma prior to emplacement.

Tectono-magmatic evolution of the Mesoproterozoic Singhora basin, central India: Evidence for compressional tectonics from structural data, AMS study and geochemistry of basic rocks

2013 ◽  
Vol 227 ◽  
pp. 276-294 ◽  
Author(s):  
Subhojit Saha ◽  
Kaushik Das ◽  
Partha Pratim Chakraborty ◽  
Priyabrata Das ◽  
Subrata Karmakar ◽  
...  
Keyword(s):  
Central India ◽  
Structural Data ◽  
Magmatic Evolution ◽  
Basic Rocks

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.

A comparison of Eastern North America and Coastal New England magma suites: implications for subcontinental mantle evolution and the broad-terrane hypothesis

2005 ◽  
Vol 42 (9) ◽  
pp. 1571-1587 ◽  
Author(s):  
Michael J Dorais ◽  
Matthew Harper ◽  
Susan Larson ◽  
Hendro Nugroho ◽  
Paul Richardson ◽  
...  
Keyword(s):  
North America ◽  
New England ◽  
Trace Element ◽  
Crustal Contamination ◽  
Flood Basalt ◽  
Incompatible Trace Element ◽  
Eastern North America ◽  
Mantle Evolution ◽  
Isotopic Compositions ◽  
Maritime Canada

New England and Maritime Canada host two major suites of Mesozoic diabase dykes. The oldest is the Coastal New England dykes that were emplaced between 225 and 230 Ma. These rocks are dominantly alkaline with trace element and isotopic compositions indicative of a high-238U/204Pb mantle (HIMU) source. The oldest of the ~200 Ma Mesozoic rift magmas is represented by the Talcott basalt of the Hartford basin and its feeder dykes. External to the basin is the compositionally equivalent Higganum dyke. The extension of the Higganum, the Onway dyke in New Hampshire, is identical in major and trace element and isotopic compositions indicating that the dyke system represented a feeder to flows of flood basalt proportions. The Talcott system rocks have some trace element similarities with arc basalts and have been interpreted as representing melts of a subduction zone modified mantle beneath the Laurentian- Gondwanan suture. Incompatible trace element ratios and Ba, Th, and U values are, however, unlike arc basalts and are more indicative of crustal contamination of the primary magma. The coastal New England magmas have oceanic island basalt signatures that are generally thought to represent plume-tail magmatism, which is antithetic to a plume-head origin for the younger eastern North America magmas. However, coastal New England rocks have the same trace element signatures as the alkaline rocks of the Loihi seamount, which represent the pre-shield stage to the voluminous tholeiitic magmatism in Hawaii.

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