Geochemistry, geochronology, and geodynamic setting of Ni–Cu ± PGE mineral prospects hosted by mafic and ultramafic intrusions in the Portneuf–Mauricie Domain, Grenville Province, QuebecGéologie Québec Contribution 8439-2008-2009-5. Geological Survey of Canada Contribution 20080511.

2009 ◽  
Vol 46 (5) ◽  
pp. 331-353 ◽  
Author(s):  
A.-A. Sappin ◽  
M. Constantin ◽  
T. Clark ◽  
O. van Breemen
Keyword(s):  
Trace Element ◽  
Crustal Contamination ◽  
Island Arc ◽  
Geodynamic Setting ◽  
Grenville Province ◽  
Magmatic Arc ◽  
Andean Type ◽  
Trace Element Signature ◽  
Arc Setting ◽  
Back Arc

The Portneuf–Mauricie Domain in the Grenville Province consists of the Montauban group rocks (1.45 Ga), intruded by the La Bostonnais complex plutons (1.40–1.37 Ga). This assemblage was formed in a magmatic arc setting. The sequence was intruded by mafic–ultramafic tholeiitic plutons, some of which host Ni–Cu ± PGE (platinum group element) prospects. U–Pb zircon ages determined from these plutons indicate that the mineralized intrusions were emplaced between 1.40 and 1.39 Ga and that they are coeval with the La Bostonnais complex plutons. The Ni–Cu ± PGE-bearing intrusions have mature island-arc trace element signatures, with strong chemical evidence for differentiation (Mg# and Cr content; MgO and TiO2 contents) and crustal contamination (enrichments in K2O, Rb, Ba, Th, and light rare-earth elements; Th/Yb and Ta/Yb ratios). However, one intrusion displays a back-arc trace element signature associated with evidence for weak crust assimilation. The evolution of the Portneuf–Mauricie Domain is interpreted as follows: (1) 1.45 Ga — Northwesterly directed Andean-type subduction beneath the Laurentian craton margin. Furthermore, northwest-dipping intraoceanic subduction offshore from the continent formed the Montauban island arc. (2) 1.45 to 1.40 Ga — Andean-type subduction led to the formation of a back-arc basin behind the Montauban arc. (3) 1.40 Ga — Emplacement of the La Bostonnais complex plutons, some hosting Ni–Cu ± PGE prospects, into the Montauban arc. (4) 1.39 Ga — Subduction beneath Laurentia led to arc–continent collision and to closure of the back-arc basin. Intrusion of the Ni–Cu ± PGE-bearing plutons ceased. (5) 1.37 Ga — Intrusion of all La Bostonnais complex plutons ceased.

New insights into the geologic evolution of the Grenvillian Trenton Prong inlier, Central Appalachian Piedmont, USA

2020 ◽  
Vol 57 (7) ◽  
pp. 840-854
Author(s):  
Richard A. Volkert
Keyword(s):  
Tectonic Setting ◽  
Hanging Wall ◽  
Sediment Source ◽  
Slow Cooling ◽  
Grenville Province ◽  
Magmatic Arc ◽  
Metamorphic History ◽  
Arc Setting ◽  
Appalachian Piedmont ◽  
Back Arc

New geochemical and 40Ar/39Ar hornblende and biotite data from the Grenvillian Trenton Prong inlier provide the first constraints for the identification of lithotectonic units, their tectonic setting, and their metamorphic to post-metamorphic history. Gneissic tonalite, diorite, and gabbro compose the Colonial Lake Suite magmatic arc that developed along eastern Laurentia prior to 1.2 Ga. Spatially associated low- and high-TiO2 amphibolites were formed from island-arc basalt proximal to the arc front and mid-ocean ridge basalt-like basalt in a back-arc setting, respectively. Supracrustal paragneisses include meta-arkose derived from a continental sediment source of Laurentian affinity and metagraywacke and metapelite from an arc-like sediment source deposited in a back-arc basin, inboard of the Colonial Lake arc. The Assunpink Creek Granite was emplaced post-tectonically as small bodies of peraluminous syenogranite produced through partial melting of a subduction-modified felsic crustal source. Prograde mineral assemblages reached granulite- to amphibolite-facies metamorphic conditions during the Ottawan phase of the Grenvillian Orogeny. Hornblende 40Ar/39Ar ages of 935–923 Ma and a biotite age of 868 Ma record slow cooling in the northern part of the inlier following the metamorphic peak. Elsewhere in the inlier, biotite 40Ar/39Ar ages of 440 Ma and 377–341 Ma record partial to complete thermal resetting or new growth during the Taconian and Acadian orogens. The results of this study are consistent with the Trenton Prong being the down-dropped continuation of the Grenvillian New Jersey Highlands on the hanging wall of a major detachment fault. The Trenton Prong therefore correlates to other central and northern Appalachian Grenvillian inliers and to parts of the Grenville Province proper.

Geodynamic setting, crustal architecture, and VMS metallogeny of ca. 2720 Ma greenstone belt assemblages of the northern Wawa subprovince, Superior Province

2015 ◽  
Vol 52 (3) ◽  
pp. 196-214 ◽  
Author(s):  
Robert W.D. Lodge ◽  
Harold L. Gibson ◽  
Greg M. Stott ◽  
James M. Franklin ◽  
George J. Hudak
Keyword(s):  
Trace Element ◽  
Greenstone Belt ◽  
Tectonic Setting ◽  
Geodynamic Setting ◽  
Trace Element Geochemistry ◽  
Superior Province ◽  
Suprasubduction Zone ◽  
Greenstone Belts ◽  
Arc Setting ◽  
Back Arc

The greenstone belts along the northern margin of the Wawa subprovince of the Superior Province (Vermilion, Shebandowan, Winston Lake, Manitouwadge) formed at ca. 2720 Ma and have been interpreted to be representative of a rifted-arc to back-arc tectonic setting. Despite a common inferred tectonic setting and broad similarities, these greenstone belts have a significantly different metallogeny as evidenced by different endowments in volcanogenic massive sulphide (VMS), magmatic sulphide, and orogenic gold deposits. In this paper, we examine differences in geodynamic setting and crustal architecture as they pertain to the metallogeny of each greenstone belt by characterizing the regional-scale trace-element and isotopic (Nd and Pb) geochemistry of each belt. The trace-element geochemistry of the Vermilion greenstone belt (VGB) shows evidence for a transition from arc-like to back-arc mafic rocks in the Soudan belt to plume-driven rifted arcs in the ultramafic-bearing Newton belt. The Shebandowan greenstone belt (SGB) has a significant proportion of calc-alkalic, arc-like basalts, intermediate lithofacies, and high-Mg andesites, which are characteristic of low-angle, “hot” subduction. Extensional settings within the SGB are plume-driven and associated with komatiitic ultramafic and mid-ocean ridge basalt (MORB)-like basalts. The Winston Lake greenstone belt (WGB) is characterized by a transition from calc-alkalic, arc-like basalts to back-arc basalts upward in the strata and is capped by alkalic ocean-island basalt (OIB)-like basalts. This association is consistent with plume-driven rifting of a mature arc setting. Each of the VGB, SGB, and WGB show some isotopic evidence for the interaction with a juvenile or slightly older differentiated crust. The Manitouwadge greenstone belt (MGB) is characterized by isotopically juvenile, bimodal, tholeiitic to transitional volcanic lithofacies in a back-arc setting. The MGB is the most isotopically juvenile belt and is also the most productive in terms of VMS mineralization. The Zn-rich VMS mineralization within the WGB suggests a relatively lower-temperature hydrothermal system, possibly within a relatively shallow-water environment. The Zn-dominated and locally Au-enriched VMS mineralization, as well as mafic lithofacies and alteration assemblages, are characteristic of relatively shallower-water deposition in the VGB and SGB, and indicate that the ideal VMS-forming tectonic condition may have been compromised by a shallower-water depositional setting. However, the thickened arc crust and compressional tectonics of the SGB suprasubduction zone during hot subduction may have provided a crustal setting more favourable for the magmatic Ni–Cu sulphide and relative gold endowment of this belt.

Convergent margin on southeastern Laurentia during the Mesoproterozoic: tectonic implications

2000 ◽  
Vol 37 (2-3) ◽  
pp. 359-383 ◽  
Author(s):  
Toby Rivers ◽  
David Corrigan
Keyword(s):  
Continental Crust ◽  
Continental Margin ◽  
Isotopic Signature ◽  
Convergent Margin ◽  
Grenville Province ◽  
Magmatic Arc ◽  
Marginal Basin ◽  
Arc Setting ◽  
Back Arc ◽  
Dyke Swarms

A continental-margin magmatic arc is inferred to have existed on the southeastern (present coordinates) margin of Laurentia from Labrador to Texas from ~1500-1230 Ma, with part of the arc subsequently being incorporated into the 1190-990 Ma collisional Grenville Orogen. Outside the Grenville Province, where the arc is known as the Granite-Rhyolite Belt, it is undeformed, whereas within the Grenville Province it is deformed and metamorphosed. The arc comprises two igneous suites, an inboard, principally quartz monzonitic to granodioritic suite, and an outboard tonalitic to granodioritic suite. The quartz monzonite-granodiorite suite was largely derived from continental crust, whereas the tonalitic-granodiorite suite is calc-alkaline and has a juvenile isotopic signature. Available evidence from the Grenville Province suggests that the arc oscillated between extensional and compressional settings several times during the Mesoproterozoic. Back-arc deposits of several ages, that formed during relatively brief periods of extension, include (1) mafic dyke swarms subparallel to the arc; (2) continental sediments, bimodal volcanics and plateau basalts; (3) marine sediments and volcanics formed on stretched continental crust; and (4) ocean crust in a marginal basin. Closure of the back-arc basins occurred during the accretionary Pinwarian (~1495-1445 Ma) and Elzevirian (~1250-1190 Ma) orogenies, as well as during three pulses of crustal shortening associated with the 1190-990 Ma collisional Grenvillian Orogeny. During the Elzevirian Orogeny, closure of the Central Metasedimentary Belt marginal basin in the southeastern Grenville Province was marked by subduction-related magmatism as well as by imbrication of back-arc deposits. The presence of a continental-margin magmatic arc on southeastern Laurentia during the Mesoproterozoic implies that other coeval magmatism inboard from the arc took place in a back-arc setting. Such magmatism was widespread and chemically diverse and included large volume "anorogenic" anorthosite-mangerite-charnockite-granite (AMCG) complexes as well as small volume alkaline, quartz-saturated and -undersaturated "within-plate" granitoids. Recognition of the ~300 million year duration of the Mesoproterozoic convergent margin of southeastern Laurentia suggests that there may be useful parallels with the evolution of the Andes, which has been a convergent margin since the early Paleozoic.

Geochemistry of Sainte-Marguerite volcanic rocks: implications for the evolution of Silurian–Devonian volcanism in the Gaspé Peninsula

2008 ◽  
Vol 45 (1) ◽  
pp. 15-29 ◽  
Author(s):  
Alan D’hulst ◽  
Georges Beaudoin ◽  
Michel Malo ◽  
Marc Constantin ◽  
Pierre Pilote
Keyword(s):  
Lower Devonian ◽  
Volcanic Rocks ◽  
Magma Source ◽  
Volcanic Arc ◽  
Lower Silurian ◽  
Trace Element Signature ◽  
Arc Setting ◽  
Back Arc ◽  
Gaspe Peninsula ◽  
Gaspé Peninsula

The Lower Devonian Sainte-Marguerite volcanic rocks are part of a Silurian–Devonian volcanic sequence deposited between the Taconian and Acadian orogenies in the Gaspé Peninsula, Quebec, Canada. The Sainte-Marguerite unit includes basaltic and dacitic lava flows with calc-alkaline and volcanic-arc affinities. Such affinities are also recorded by the trace-element signature in Lower Silurian and most Lower Devonian volcanic units of the Gaspé Peninsula. However, most of the other Silurian–Devonian volcanic rocks occurring in the Gaspé Peninsula have been previously interpreted to have erupted in an intracontinental setting. A back-arc setting for the Gaspé Peninsula between the Taconian and Acadian orogenies could account for these subduction volcanic-arc signatures, though a metasomatized lithospheric mantle magma source, unrelated to subduction, cannot be excluded. Lower Silurian and Lower Devonian volcanic rocks in the central part of the Gaspé Peninsula show an arc affinity, whereas Upper Silurian and Lower to Middle Devonian volcanic rocks, located in the south and north of the Gaspé Peninsula, respectively, show a within-plate affinity. The Lower Devonian Archibald Settlement and Boutet volcanic rocks of the southern and northern Gaspé Peninsula, respectively, show a trend toward a within-plate affinity. This suggests that within-plate volcanism migrated from south to north through time in an evolving back-arc environment and that the subduction signature of Lower Silurian and Lower Devonian rocks results from a source that melted only under the central part of the Gaspé Peninsula.

scholarly journals Trace Element and Isotope Systematics in Vent Fluids and Sulphides From Maka Volcano, North Eastern Lau Spreading Centre: Insights Into Three-Component Fluid Mixing

2021 ◽  
Vol 9 ◽  
Author(s):  
Lukas Klose ◽  
Manuel Keith ◽  
Daniel Hafermaas ◽  
Charlotte Kleint ◽  
Wolfgang Bach ◽  
...  
Keyword(s):  
Trace Element ◽  
Hydrothermal Activity ◽  
Fluid Composition ◽  
Black Smoker ◽  
Ph Values ◽  
The North ◽  
North Eastern ◽  
Trace Element Signature ◽  
Back Arc ◽  
Ree Patterns

Back-arc spreading centres and related volcanic structures are known for their intense hydrothermal activity. The axial volcanic edifice of Maka at the North Eastern Lau Spreading Centre is such an example, where fluids of distinct composition are emitted at the Maka hydrothermal field (HF) and at Maka South in 1,525–1,543 m water depth. At Maka HF black smoker-type fluids are actively discharged at temperatures of 329°C and are characterized by low pH values (2.79–3.03) and a depletion in Mg (5.5 mmol/kg) and SO4 (0.5 mmol/L) relative to seawater. High metal (e.g., Fe up to ∼6 mmol/kg) and rare Earth element (REE) contents in the fluids, are indicative for a rock-buffered hydrothermal system at low water/rock ratios (2–3). At Maka South, venting of white smoke with temperatures up to 301°C occurs at chimneys and flanges. Measured pH values range from 4.53 to 5.42 and Mg (31.0 mmol/kg), SO4 (8.2 mmol/L), Cl (309 mmol/kg), Br (0.50 mmol/kg) and Na (230 mmol/kg) are depleted compared to seawater, whereas metals like Li and Mn are typically enriched together with H2S. We propose a three-component mixing model with respect to the fluid composition at Maka South including seawater, a boiling-induced low-Cl vapour and a black smoker-type fluid similar to that of Maka HF, which is also preserved by the trace element signature of hydrothermal pyrite. At Maka South, high As/Co (>10–100) and Sb/Pb (>0.1) in pyrite are suggested to be related to a boiling-induced element fractionation between vapour (As, Sb) and liquid (Co, Pb). By contrast, lower As/Co (<100) and a tendency to higher Co/Ni values in pyrite from Maka HF likely reflect the black smoker-type fluid. The Se/Ge ratio in pyrite provides evidence for fluid-seawater mixing, where lower values (<10) are the result of a seawater contribution at the seafloor or during fluid upflow. Sulphur and Pb isotopes in hydrothermal sulphides indicate a common metal (loid) source at the two vent sites by host rock leaching in the reaction zone, as also reflected by the REE patterns in the vent fluids.

scholarly journals The Geon 14 arc-related mafic rocks from the central Grenville Province

2018 ◽  
Vol 55 (6) ◽  
pp. 545-570 ◽  
Author(s):  
Barun Maity ◽  
Aphrodite Indares
Keyword(s):  
Granulite Facies ◽  
Crustal Thickening ◽  
Grenville Province ◽  
Long Duration ◽  
Crustal Thinning ◽  
Isotopic Analyses ◽  
Southeastern Margin ◽  
Intermediate Unit ◽  
Arc Setting ◽  
Back Arc

The late Paleoproterozoic to Mesoproterozoic (ca. 1.7–1.2 Ga) evolution of the active southeastern margin of Laurentia terminated with the Grenvillian continental collision and the development of a large, hot, long-duration orogen at ca. 1.09–0.98 Ga. As a result, much of the hinterland of the Grenville Province consists of Paleoproterozoic and Mesoproterozoic rocks, mostly preserved as an imbricate stack of high-grade gneisses, that represent a potential repository of active-margin processes. This study presents geochronologic, geochemical, and isotopic analyses of two granulite-facies suites of ca. 1.45–1.40 Ga mafic tholeiites from the Canyon domain (Manicouagan area, central Grenville Province). One suite consists of 1439 +76/–68 Ma high-FeTi mafic sills with εNd values of –0.4 (TDM 2.57–2.72 Ga), indicate derivation from variably depleted to enriched MORB-type mantle sources, probably in an extensional back-arc setting, before intrusion in a ca. 1.5 Ga supracrustal metasedimentary sequence. The other, previously dated, 1410 ± 16 Ma Mafic to intermediate unit exhibits εNd values of 0.0 to +0.9 (TDM 2.02–2.25 Ga), and variably enriched MORB to arc geochemical signatures, for which formation in a transitional back-arc to arc setting is suggested. Integrated with published information, the new data support a model of a long-lived continental-margin arc and intermittent back-arc development on southeast Laurentia during the mid-Mesoproterozoic (ca. 1.5–1.4 Ga), in which repeated short periods of extension and crustal thinning in the back-arc or intra-arc regions were followed by compression and crustal thickening.

scholarly journals Geochemical and Sr-Nd-Pb-Hf Isotopic Characteristics of Muchen Pluton in Southeast China, Constrain the Petrogenesis of Alkaline A-Type Magma

Minerals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 80
Author(s):  
Haiyang Yan ◽  
Fangyue Wang ◽  
Hai-Ou Gu ◽  
He Sun ◽  
Can Ge
Keyword(s):  
Early Cretaceous ◽  
Lithospheric Mantle ◽  
Magma Ascent ◽  
Geodynamic Setting ◽  
Southeast China ◽  
Geochemical Properties ◽  
Arc Setting ◽  
Back Arc ◽  
T Values

We present comprehensive petrological, major-trace element, in situ zircon U-Pb dating and Sr-Nd-Pb isotopic data for Muchen granitoid (western Zhejiang Province, Southeast China), to constrain the petrogenesis of alkaline A-type granites and the geodynamic setting of Southeast China in the Early Cretaceous. The Early Cretaceous Muchen quartz monzonite yielded zircon U-Pb crystallization ages of 111.3 ± 0.7 Ma and is metaluminous to weakly peraluminous with SiO2 contents ranging from 59 to 69 wt.%, and can be classified as alkaline A-type granitoid. The quartz monzonites have low (87Sr/86Sr)i values (0.7052 to 0.7061) and high εNd(t) values (−2.6 to −2.0), similar to nearby coeval mafic rocks that have been proposed to be derived from the enriched lithospheric mantle. The high Nb/Ta ratios (16.7 to 30.1, average 21.8) and low Nb/U ratios (as low as 3.5) indicate the involvement of slab-derived melt and fluids in this mantle. These geochemical properties of the Muchen quartz monzonites indicated that they might be from a phlogopite-bearing and rutile-rich subduction-modified subcontinental lithospheric mantle, and underwent strong fractional crystallization of olivine + orthopyroxene + plagioclase during magma ascent. The low Mg# values of these alkaline rocks (<30 mostly) may indicate a low-pressure source in a back-arc setting. The early Cretaceous alkaline granitoids in Southeast China are related to the continental back-arc setting caused by deep angle subduction of the paleo-Pacific plate.

scholarly journals Evolution of Subduction Dynamics beneath West Avalonia in Middle to Late Ordovician Times

Lithosphere ◽  
2020 ◽  
Vol 2020 (1) ◽  
pp. 1-22
Author(s):  
Pierre Jutras ◽  
J. Brendan Murphy ◽  
Dennis Quick ◽  
Jaroslav Dostal
Keyword(s):  
Trace Element ◽  
Partial Melting ◽  
Volcanic Rocks ◽  
Upper Ordovician ◽  
The North ◽  
Trace Element Contents ◽  
Element Contents ◽  
Arc Setting ◽  
Back Arc ◽  
High Degree

Abstract Middle to Upper Ordovician volcanic rocks in the Arisaig area of Nova Scotia, Canada, constitute the only known record of volcanism in West Avalonia during that interval. Hence, they have been extensively studied to test paleocontinental reconstructions that consistently show Avalonia as a drifting microcontinent during that period. Identification of volcanic rocks with an intermediate composition (the new Seaspray Cove Formation) between upper Darriwilian bimodal volcanic rocks of the Dunn Point Formation and Sandbian felsic pyroclastic rocks of the McGillivray Brook Formation has led to a reevaluation of magmatic relationships in the Ordovician volcanic suite at Arisaig. Although part of the same volcanic construction, the three formations are separated by significant time-gaps and are shown to belong to three distinct magmatic subsystems. The tectonostratigraphic context and trace element contents of the Dunn Point Formation basalts suggest that they were produced by the high-degree partial melting of an E-MORB type source in a back-arc extensional setting, whereas trace element contents in intermediate rocks of the Seaspray Cove Formation suggest that they were produced by the low-degree partial melting of a subduction-enriched source in an arc setting. The two formations are separated by a long interval of volcanic quiescence and deep weathering, during which time the back-arc region evolved from extension to shortening and was eventually onlapped by arc volcanic rocks. Based on limited field constraints, paleomagnetic and paleontological data, this progradation of arc onto back-arc volcanic rocks occurred from the north, where an increasingly young Iapetan oceanic plate was being subducted at an increasingly shallow angle. Partial subduction of the Iapetan oceanic ridge is thought to have subsequently generated slab window magmatism, thus marking the last pulse of subduction-related volcanism in both East and West Avalonia.

scholarly journals Discovery of Ancient Volcanoes in the Okhotsk Sea (Russia): New Constraints on the Opening History of the Kurile Back Arc Basin

Geosciences ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 442
Author(s):  
Reinhard Werner ◽  
Boris Baranov ◽  
Kaj Hoernle ◽  
Paul van den Bogaard ◽  
Folkmar Hauff ◽  
...  
Keyword(s):  
Trace Element ◽  
Island Arc ◽  
Kurile Island ◽  
Geochemical Data ◽  
Magma Source ◽  
Published Data ◽  
Kurile Island Arc ◽  
History Of ◽  
Spreading Rates ◽  
Back Arc

Here we present the first radiometric age and geochemical (major and trace element and isotope) data for samples from the Hydrographer Ridge, a back arc volcano of the Kurile Island Arc, and a newly discovered chain of volcanoes (“Sonne Volcanoes”) on the northwestern continental slope of the Kurile Basin on the opposite side of the arc. The 40Ar/39Ar age and geochemical data show that Hydrographer Ridge (3.2–3.3 Ma) and the “Sonne Volcanoes” (25.3–25.9 Ma) have very similar trace element and isotope characteristics to those of the Kurile Island Arc, indicating derivation from a common magma source. We conclude that the age of the “Sonne Volcanoes” marks the time of opening of the Kurile Basin, implying slow back arc spreading rates of 1.3–1.8 cm/y. Combined with published data from the Kurile fore arc, our data suggest that the processes of subduction, Kurile Basin opening and frontal arc extension occurred synchronously and that extension in the rear part and in the frontal part of the Kurile Island Arc must have been triggered by the same mechanism.

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