Crustal evolution along a seismic section across the Grenville Province (western Quebec)

2000 ◽  
Vol 37 (2-3) ◽  
pp. 291-306 ◽  
Author(s):  
J Martignole ◽  
A J Calvert ◽  
R Friedman ◽  
P Reynolds
Keyword(s):  
Shear Zone ◽  
Large Scale ◽  
Seismic Profile ◽  
Detrital Zircons ◽  
Seismic Section ◽  
Grenville Province ◽  
Good Definition ◽  
Metasedimentary Rocks ◽  
Thin Crust ◽  
Front Zone

Results of deep seismic reflection survey along a 375 km long transect of the Grenville Province in western Quebec are combined with a review of geological observations and published isotopic ages. The seismic profile offers a remarkably clear image of the crust-mantle boundary and a good definition of the various crustal blocks. Crust about 44 km thick beneath the Grenville Front zone thins abruptly to ca. 36 km southeastward, perhaps the result of extension on southeast-dipping surfaces extending to the Moho. Other zones of relatively thin crust, although less pronounced, occur where Proterozoic crust overlies Archean crust, and beneath the Morin anorthosite complex. The thickest crust is found at the extreme southeast of the transect, east of the Morin anorthosite. From northwest to southeast, three main crustal subdivisions are (1) deformed Archean rocks with southeast-dipping reflectors in the Grenville Front zone, (2) an Archean parautochthon with northwest-dipping reflectors extending to the lower crust, and (3) an overlying three-layer crust interpreted as accreted Proterozoic terranes. The boundary between (2) and (3) is a major, southeast-dipping, crustal-scale ramp (Baskatong ramp) interpreted to have accommodated strain during and after accretion. U-Pb and Pb-Pb ages on detrital zircons show that metasedimentary rocks of the allochthons (Mont-Laurier, Réservoir Cabonga, and Lac Dumoine terranes) range from Archean to as young as 1.21 Ga. A single zone with 1.4 Ga old Sm-Nd model ages appears to lack Archean components and may be considered as a fragment of juvenile Mesoproterozoic crust pinched in a shear zone (Renzy shear zone) that could be raised to the status of terrane (Renzy terrane). In the allochthons, U-Pb ages of metamorphic zircon and monazite cluster around 1.17 Ga (Mont-Laurier and Réservoir Cabonga terrane) and 1.07 Ga (Renzy and Lac Dumoine terrane) and are interpreted to record late and post-accretion crustal reworking, a common feature of the Grenville orogen. A final high-grade metamorphic event (ca. 1.0 Ga) documented only in the parautochthon and the Grenville Front zone records large-scale, piggyback-style thrusting of allochthonous slabs onto the parautochthon. The age of transcurrent displacement following peak metamorphism affecting both the allochthons and the parautochthon decreases northwestward from 1.07 to 1.00 Ga. Dating thus shows that Grenvillian deformation in western Quebec occurred in pulses over an interval of 180 million years, with a tendency to propagate from the inner part of the orogen toward the Grenville Front. Reworked migmatites from the parautochthon cooled from the ca. 1.0 Ga peak of metamorphism through about 450°C (Ar closure in hornblende) at ca. 0.96 Ga with calculated cooling rates of about 6°C per million years, and unroofing rates of 0.33 km per million years. The cooling-unroofing history of the allochthons is not so straightforward, probably due to tectonic disturbances related to allochthon emplacement. Cooling through 450°C occurred between 1.04 and 1.01 Ga, at least 50 million years earlier than cooling in the parautochthon; this contrast agrees with the northwestward propagation of the orogen.

U–Pb geochronology of Late Cretaceous and early Tertiary plutons in the northern Coast Mountains batholith

1991 ◽  
Vol 28 (6) ◽  
pp. 899-911 ◽  
Author(s):  
George E. Gehrels ◽  
William C. McClelland ◽  
Scott D. Samson ◽  
P. Jonathan Patchett ◽  
David A. Brew
Keyword(s):  
Shear Zone ◽  
Late Cretaceous ◽  
Detrital Zircons ◽  
Northern Coast ◽  
Coast Mountains ◽  
Western Margin ◽  
Early Proterozoic ◽  
Isotopic Signatures ◽  
Metasedimentary Rocks ◽  
Early Tertiary

U–Pb geochronologic studies demonstrate that steeply dipping, sheetlike tonalitic plutons along the western margin of the northern Coast Mountains batholith were emplaced between ~83 and ~57 (perhaps ~55) Ma. Less elongate tonalitic–granodioritic bodies in central portions of the batholith yield ages of 59–58 Ma, coeval with younger phases of the tonalitic sheets. Large granite–granodiorite bodies in central and eastern portions of the batholith were emplaced at 51–48 Ma. Trends in ages suggest that the tonalitic bodies generally become younger southeastward and that, at the latitude of Juneau, plutonism migrated northeastward across the batholith at ~0.9 km/Ma. Variations in the age, shape, location, and degree of fabric development among the various plutons indicate that Late Cretaceous – Paleocene tonalitic bodies were emplaced into a steeply dipping, dip-slip shear zone that was active along the western margin of the batholith. Postkinematic Eocene plutons were emplaced at shallow crustal levels. Inherited zircon components in these plutons range in age from mid-Paleozoic to Early Proterozoic and are coeval with detrital zircons in adjacent metasedimentary rocks. These old zircons, combined with evolved Nd isotopic signatures for most plutons, record assimilation of continental crustal or supracrustal rocks during the generation and (or) ascent of the plutons.

U–Pb age constraints for deposition of clastic metasedimentary rocks and late-tectonic plutonism, Michipicoten Belt, Superior Province

1992 ◽  
Vol 29 (8) ◽  
pp. 1640-1651 ◽  
Author(s):  
F. Corfu ◽  
R. P. Sage
Keyword(s):  
Isotopic Composition ◽  
Greenstone Belt ◽  
Nepheline Syenite ◽  
Large Scale ◽  
Sedimentary Rocks ◽  
Detrital Zircons ◽  
Metasedimentary Rocks ◽  
Enriched Mantle ◽  
The Matrix ◽  
Age Constraints

The study investigates the ages of clastic metasedimentary rocks and of late-tectonic alkalic to calc-alkalic intrusions and puts constraints on the timing of major deformation in the Michipicoten greenstone belt of the Wawa Subprovince. A trondhjemitic boulder in the Doré conglomerate of the southern metasedimentary belt is dated at 2698 ± 2 Ma. This is a maximum age of sedimentation that is also supported by ages of detrital zircons in the matrix and may directly reflect the time of synvolcanic deposition. Detrital zircons in metapsammites of the central and northern sedimentary belts yield younger ages of 2682 ± 3 and 2680 ± 3 Ma, respectively, suggesting that sedimentation occurred significantly later in the northern than in the southern parts of the greenstone belt. The ≤2682 Ma sedimentary rocks were affected by multiphase deformation that is related to the development of a large-scale recumbent fold and superimposed folds and faults. This tectonism was followed by the emplacement of the granodioritic Troupe Lake and Maskinonge Lake stocks that yield identical zircon and titanite ages of 2671 ± 2 Ma. The structurally older and deformed Herman Lake nepheline syenite has an imprecise titanite age of [Formula: see text]. The isotopic composition of Pb in feldspar of these intrusions is relatively evolved and, in light of geochemical considerations, may reflect provenance of the melts from enriched mantle reservoirs.

scholarly journals Age and Origin of Silicocarbonate Pegmatites of the Adirondack Region

Minerals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 508 ◽  
Author(s):  
Jeffrey Chiarenzelli ◽  
Marian Lupulescu ◽  
George Robinson ◽  
David Bailey ◽  
Jared Singer
Keyword(s):  
Fluid Flow ◽  
Shear Zone ◽  
Isotopic Ratios ◽  
Large Crystal ◽  
Grenville Province ◽  
Orogenic Collapse ◽  
Metasedimentary Rocks ◽  
Granitic Magmatism ◽  
Oxygen Isotopic ◽  
Sedimentary Carbonates

Silicocarbonate pegmatites from the southern Grenville Province have provided exceptionally large crystal specimens for more than a century. Their mineral parageneses include euhedral calc–silicate minerals such as amphibole, clinopyroxene, and scapolite within a calcite matrix. Crystals can reach a meter or more in long dimension. Minor and locally abundant phases reflect local bedrock compositions and include albite, apatite, perthitic microcline, phlogopite, zircon, tourmaline, titanite, danburite, uraninite, sulfides, and many other minerals. Across the Adirondack Region, individual exposures are of limited aerial extent (<10,000 m2), crosscut metasedimentary rocks, especially calc–silicate gneisses and marbles, are undeformed and are spatially and temporally associated with granitic pegmatites. Zircon U–Pb results include both Shawinigan (circa 1165 Ma) and Ottawan (circa 1050 Ma) intrusion ages, separated by the Carthage-Colton shear zone. Those of Shawinigan age (Lowlands) correspond with the timing of voluminous A-type granitic magmatism, whereas Ottawan ages (Highlands) are temporally related to orogenic collapse, voluminous leucogranite and granitic pegmatite intrusion, iron and garnet ore development, and pervasive localized hydrothermal alteration. Inherited zircon, where present, reflects the broad range of igneous and detrital ages of surrounding rocks. Carbon and oxygen isotopic ratios from calcite plot within a restricted field away from igneous carbonatite values to those of typical sedimentary carbonates and local marbles. Collectively, these exposures represent a continuum between vein-dyke and skarn occurrences involving the anatexis of metasedimentary country rocks. Those of Ottawan age can be tied to movement and fluid flow along structures accommodating orogenic collapse, particularly the Carthage-Colton shear zone.

Geology and age of the Precambrian basement in the Windsor, Chatham, and Sarnia area, southwestern Ontario

1982 ◽  
Vol 19 (8) ◽  
pp. 1627-1634 ◽  
Author(s):  
A. Turek ◽  
R. N. Robinson
Keyword(s):  
Oil And Gas ◽  
Precambrian Basement ◽  
Grenville Province ◽  
Metasedimentary Rocks ◽  
Gas Drilling ◽  
Arch System ◽  
Grenvillian Orogeny ◽  
Anomaly Map ◽  
Paleozoic Rocks ◽  
Basement Surface

Precambrian basement in the Windsor–Chatham–Sarnia area is covered by Paleozoic rocks that are up to 1300 m thick. The basement surface is characterized by a northeast–southwest arch system with a relief of about 350 m. Extensive oil and gas drilling has penetrated and sampled this basement, and an examination of core and chip samples from 133 holes and an assessment of the magnetic anomaly map of the area have been used to produce a lithologic map of the Precambrian basement. The predominant rocks are granite gneisses and syenite gneisses but also significant are gabbros, granodiorite gneisses, and metasedimentary rocks. The average foliation dips 50° and is inferred to have a northeasterly trend. The Precambrian basement has been regarded as part of the Grenville Province. An apparent Rb–Sr whole rock isochron, for predominantly meta-igneous rocks, yields an age of 1560 ± 140 Ma. This we interpret as pre-Grenvillian, surviving the later imprint of the Grenvillian Orogeny. Points excluded from the isochron register ages of 1830, 915, and 670 Ma, and can be interpreted as geologically meaningful.

scholarly journals Monazite U–Th–Pb geochronology of the Central Metasedimentary Belt Boundary Zone (CMBbz), Grenville Province, Ontario Canada

2018 ◽  
Vol 55 (9) ◽  
pp. 1063-1078 ◽  
Author(s):  
Michelle J. Markley ◽  
Steven R. Dunn ◽  
Michael J. Jercinovic ◽  
William H. Peck ◽  
Michael L. Williams
Keyword(s):  
Shear Zone ◽  
Crustal Thickening ◽  
Boundary Zone ◽  
Grenville Province ◽  
Metamorphic History ◽  
Crustal Thinning ◽  
Tectonic Significance ◽  
History Of ◽  
Central Gneiss Belt ◽  
Scale Shear

The Central Metasedimentary Belt boundary zone (CMBbz) is a crustal-scale shear zone that juxtaposes the Central Gneiss Belt and the Central Metasedimentary Belt of the Grenville Province. Geochronological work on the timing of deformation and metamorphism in the CMBbz is ambiguous, and the questions that motivate our study are: how many episodes of shear zone activity did the CMBbz experience, and what is the tectonic significance of each episode? We present electron microprobe data from monazite (the U–Th–Pb chemical method) to directly date deformation and metamorphism recorded in five garnet–biotite gneiss samples collected from three localities of the CMBbz of Ontario (West Guilford, Fishtail Lake, and Killaloe). All three localities yield youngest monazite dates ca. 1045 Ma; most of the monazite domains that yield these dates are high-Y rims. In comparison with this common late Ottawan history, the earlier history of the three CMBbz localities is less clearly shared. The West Guilford samples have monazite grain cores that show older high-Y domains and younger low-Y domains; these cores yield a prograde early Ottawan (1100–1075 Ma) history. The Killaloe samples yield a well-defined prograde, pre- to early Shawinigan history (i.e., 1220–1160 Ma) in addition to some evidence for a second early Ottawan event. In other words, the answers to our research questions are: three events; a Shawinigan event possibly associated with crustal thickening, an Ottawan event possibly associated with another round of crustal thickening, and a late Ottawan event that resists simple interpretation in terms of metamorphic history but that coincides chronologically with crustal thinning at the base of an orogenic lid.

Oxygen, hydrogen, and strontium isotope constraints on the origin of granites

1988 ◽  
Vol 79 (2-3) ◽  
pp. 317-338 ◽  
Author(s):  
Hugh P. Taylor
Keyword(s):  
Large Scale ◽  
Wide Spectrum ◽  
Volcanic Field ◽  
Parent Material ◽  
Rock Interaction ◽  
Metasedimentary Rocks ◽  
Clear Cut ◽  
End Members ◽  
Type 3

ABSTRACTOxygen isotope data are very useful in determining the source rocks of granitic magmas, particularly when used in combination with Sr, Pb, and Nd isotope studies. For example, unusually high δ18O values in magmas (δ18O> +8) require the involvement of some precursor parent material that at some time in the past resided on or near the Earth's surface, either as sedimentary rocks or as weathered or hydrothermally altered rocks. The isotopic systematics which are preserved in the Mesozoic and Cenozoic batholiths of western North America can be explained by grand-scale mixing of three broadly defined end-members: (1) oceanic island-arc magmas derived from a “depleted” (MORB-type?) source in the upper mantle (δ18O c. +6 and 87Sr/86Sr c. 0·703); (2) a high-18O (c. +13 to +17) source with a very uniform 87Sr/86Sr (c. 0·708 to 0·712), derived mainly from eugeosynclinal volcanogenic sediments and (or) hydrothermally altered basalts; and (3) a much more heterogeneous source (87Sr/86Sr c. 0·706 to 0·750, or higher) with a high δ18O (c. +9 to +15) where derived from supracrustal metasedimentary rocks and a much lower δ18O (c. +7 to +9) where derived from the lower continental crust of the craton. These end-members were successively dominant from W to E, respectively, within three elongate N–S geographic zones that can be mapped from Mexico all the way N to Idaho.18O/16O studies (together with D/H analyses) can, however, play a more important and certainly a unique role in determining the origins of the aqueous fluids involved in the formation of granitic and rhyolitic magmas. Fluid-rock interaction effects are most clear-cut when low-18O, low-D meteoric waters are involved in the isotopic exchange and melting processes, but the effects of other waters such as seawater (with a relatively high δD c. 0) can also be recognised. Because of these hydrothermal processes, rocks that ultimately undergo partial melting may exhibit isotopic signatures considerably different from those that they started with. We discuss three broad classes of potential source materials of such “hydrothermal-anatectic” granitic magmas, based mainly on water/rock (w/r), temperature (T), and the length of time (t) that fluid-rock interaction proceeds: (Type 1) epizonal systems with a wide variation in whole-rock δ18O and extreme 18O/16O disequilibrium among coexisting minerals (e.g. quartz and feldspar); (Type 2) deeper-seated and (or) longer-lived systems, also with a wide spectrum of whole-rock δ18O, but with equilibrated 18O/16O ratios among coexisting minerals; (Type 3) thoroughly homogenised and equilibrated systems with relatively uniform δ18O in all lithologies. Low-18O magmas formed by melting of rocks altered in a Type 2 or a Type 3 meteoric-hydrothermal system are the only kinds of “hydrothermal-anatectic” granitic magmas that are readily recognisable in the geological record. Analogous effects produced by other kinds of aqueous fluids may, however, be quite common, particularly in areas of extensional tectonics and large-scale rifting. The greatly enhanced permeabilities in such fractured terranes make possible the deep convective circulation of ground waters and sedimentary pore fluids. The nature and origin of low-18O magmas in the Yellowstone volcanic field and the Seychelles Islands are briefly reviewed in light of these concepts, as is the development of high-D, peraluminous magmas in the Hercynian of the Pyrenees.

scholarly journals Crustal thickness of the Grenville orogen: A Mesoproterozoic Tibet?

Geology ◽  
2021 ◽  
Author(s):  
Adam Brudner ◽  
Hehe Jiang ◽  
Xu Chu ◽  
Ming Tang
Keyword(s):  
Crustal Thickness ◽  
Detrital Zircons ◽  
Crustal Thickening ◽  
Geochemical Data ◽  
Geochronological Data ◽  
Grenville Province ◽  
Crustal Thinning ◽  
Paleoenvironmental Evolution ◽  
Orogenic Plateau ◽  
St Lawrence River

The Grenville Province on the eastern margin of Laurentia is a remnant of a Mesoproterozoic orogenic plateau that comprised the core of the ancient supercontinent Rodinia. As a protracted Himalayan-style orogen, its orogenic history is vital to understanding Mesoproterozoic tectonics and paleoenvironmental evolution. In this study, we compared two geochemical proxies for crustal thickness: whole-rock [La/Yb]N ratios of intermediate-to-felsic rocks and europium anomalies (Eu/Eu*) in detrital zircons. We compiled whole-rock geochemical data from 124 plutons in the Laurentian Grenville Province and collected trace-element and geochronological data from detrital zircons from the Ottawa and St. Lawrence River (Canada) watersheds. Both proxies showed several episodes of crustal thickening and thinning during Grenvillian orogenesis. The thickest crust developed in the Ottawan phase (~60 km at ca. 1080 Ma and ca. 1045 Ma), when the collision culminated, but it was still up to 20 km thinner than modern Tibet. We speculate that a hot crust and several episodes of crustal thinning prevented the Grenville hinterland from forming a high Tibet-like plateau, possibly due to enhanced asthenosphere-lithosphere interactions in response to a warm mantle beneath a long-lived supercontinent, Nuna-Rodinia.

The oxygen isotope composition of the surface crystalline rocks of the Canadian Shield

1978 ◽  
Vol 15 (11) ◽  
pp. 1773-1782 ◽  
Author(s):  
Yuch-Ning Shieh ◽  
Henry P. Schwarcz
Keyword(s):  
Isotope Composition ◽  
Crystalline Rocks ◽  
Canadian Shield ◽  
Granitic Rocks ◽  
Baffin Island ◽  
Grenville Province ◽  
Metasedimentary Rocks ◽  
Rock Types ◽  
Northern District ◽  
Basic Rocks

The average 18O/16O ratios of the major rock types of the surface crystalline rocks in different parts of the Canadian Precambrian Shield have been determined, using 47 composite samples prepared from 2221 individual rock specimens. The sampling areas include Baffin Island, northern and southwestern Quebec, Battle Harbour – Cartwright, northern District of Keewatin, Fort Enterprise, Snowbird Lake, Kasmere Lake, and Saskatchewan, covering approximately 1 400 000 km2. The granitic rocks from the Superior, Slave, and Churchill Provinces vary only slightly from region to region (δ18O = 6.9–8.4‰) and are significantly lower in 18O than similar rock types from the younger Grenville Province (δ = 9.2–10.0‰). The sedimentary and metasedimentary rocks have δ18O = 9.0–11.7‰ and hence are considerably lower than their Phanerozoic equivalents, possibly reflecting the presence of a high percentage of little-altered igneous rock detritus in the original sediments. The basic rocks in most regions fall within a δ18O range of 6.8–7.6‰, except in northern and southwestern Quebec where the δ-values are abnormally high (8.5–8.9‰). The overall average 18O/16O ratio of the surface crystalline rocks of the Canadian Shield is estimated to be 8.0‰, which represents an enrichment with respect to probable mantle derived starting materials by about 2‰.

The Parry Sound domain: a far-travelled allochthon? New evidence from U–Pb zicon geochronology

1996 ◽  
Vol 33 (7) ◽  
pp. 1087-1104 ◽  
Author(s):  
N. Wodicka ◽  
R. A. Jamieson ◽  
R. R. Parrish
Keyword(s):  
Source Region ◽  
Detrital Zircons ◽  
Absolute Maximum ◽  
Present Position ◽  
Mafic Dyke ◽  
Metasedimentary Rocks ◽  
Thrust Zone ◽  
Tonalitic Gneiss ◽  
Central Gneiss Belt ◽  
New Evidence

We report U–Pb zircon ages for metaplutonic and metasedimentary rocks from three lithotectonic assemblages within the Parry Sound allochthon of the Central Gneiss Belt, southwestern Grenville Orogen: the basal Parry Sound, interior Parry Sound, and Twelve Mile Bay assemblages. Magmatic crystallization ages for granitic to tonalitic gneisses from the basal Parry Sound assemblage fall in the range 1400–1330 Ma. Younger intrusions include the Parry Island anorthosite dated at 1163 ± 3 Ma and a crosscutting mafic dyke bracketed between 1151 and 1163 Ma. Dated at [Formula: see text] a tonalitic gneiss from the overlying interior Parry Sound assemblage is slightly younger than the older group of rocks from the basal Parry Sound assemblage. 207Pb/206Pb ages for zircons from a quartzite of the basal Parry Sound assemblage range from 1385 Ma to the Neoarchaean. An absolute maximum age for this quartzite is 1436 ± 17 Ma. In contrast, detrital zircons from a quartzite of the Twelve Mile Bay assemblage constrain the age of deposition at post-ca. 1140–1120 Ma. We speculate that Grenvillian-age zircons within this quartzite were derived from rocks in the Adirondack Highlands and Frontenac terrane, implying that part of the Parry Sound domain and these terranes were contiguous during deposition of the quartzite. Our data support previous interpretations that the Parry Sound domain is allochthonous with respect to its surroundings, and suggest that the most likely source region of the basal Parry Sound domain lies southeast of the Central Gneiss Belt, within the Central Metasedimentary Belt boundary thrust zone or the Adirondack Highlands. This implies the possibility of 100–300 km of displacement of the domain. Emplacement of the Parry Sound domain into its present position must have occurred relatively late in the orogen's history, by about 1080 Ma.

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