Paleoproterozoic reworking of an Archean thrust fault in the Hearne domain, Western Churchill Province: U–Pb geochronological constraints

2005 ◽  
Vol 42 (7) ◽  
pp. 1313-1330 ◽  
Author(s):  
K MacLachlan ◽  
W J Davis ◽  
C Relf
Keyword(s):  
Shear Zone ◽  
Hanging Wall ◽  
Thrust Fault ◽  
Lake Area ◽  
High Grade ◽  
Facies Metamorphism ◽  
Minimum Age ◽  
Geochronological Constraints ◽  
Basement Deformation ◽  
And Control

The nature, timing and control of Archean crustal architecture on the distribution of Proterozoic reworking in Western Churchill Province are investigated in the Yathkyed Lake area, central Nunavut. The Tyrrell shear zone (TSZ) marks the boundary between the northwestern and central Hearne subdomains, respectively, in the hanging wall and footwall. Metamorphism and deformation in the hanging wall are ca. 2.66–2.50 Ga. Two episodes of metamorphism are recorded in a foliated granodiorite in the footwall, at 1818+5–2 and 1827 ± 5.6 Ma. The latter age is interpreted as the time of amphibolite-facies metamorphism and deformation in the footwall. A crosscutting dyke provides a minimum age of 1818 ± 2 Ma for this metamorphism and deformation. The TSZ is dominated by dextral oblique-slip shear fabrics. A suite of leucogranite dykes provide a maximum age of 1816 ± 2 Ma for dextral shearing. Dextral deformation is bracketed between 1815 ± 2 and 1811 ± 1 Ma, the ages of two other granitoid dykes. In an area of low dextral strain, there are proto-sheath folds related to Neoarchean thrusting. Paleoproterozoic transtensional shearing in the TSZ was localized along a preexisting late Archean thrust fault. The prior existence of this structure resulted in localization of penetrative Paleoproterozoic deformation in its footwall. This domain of high-grade Proterozoic deformation was uplifted in a regional, antiformal, metamorphic culmination, in part, by dextral-normal shearing along the TSZ. Penetrative basement deformation at depth played a role in transmitting farfield stresses related to the Trans-Hudson Orogen into its hinterland.

U/Pb geochronological constraints on Neoarchean tectonism: multiple compressional events in the northwestern Hearne Domain, Western Churchill Province, Canada

2005 ◽  
Vol 42 (1) ◽  
pp. 85-109 ◽  
Author(s):  
Kate MacLachlan ◽  
William J Davis ◽  
Carolyn Relf
Keyword(s):  
Shear Zone ◽  
Hanging Wall ◽  
Shear Zones ◽  
Crustal Thickening ◽  
Lake Area ◽  
Thermal Event ◽  
Grade Metamorphism ◽  
Geochronological Constraints

In the Yathkyed Lake area the Tyrrell shear zone (TSZ) marks the boundary between the northwestern and central Hearne subdomains of the Western Churchill Province. The TSZ is dominated by Proterozoic dextral strain, but in areas of low dextral strain, older shear fabrics are consistent with an earlier thrusting event. Four syntectonic granite sheets from within low-dextral-strain zones in the TSZ and contiguous shear zones at the base of the Yathkyed belt have ages of 2636–2629, 2652 ± 8, 2665–2639, and 2644 ± 3 Ma. The Yathkyed belt occurs in the hanging wall of these shear zones and comprises a greenschist- to amphibolite-grade, overturned panel that is overlain by an upper amphibolite-grade polydeformed panel. The geometry is consistent with a thrust-imbricated stack. Two episodes of deformation in the hanging wall are bracket between ca. 2660 and 2616 +6–4 Ma and between 2616 +6–4 Ma and ca. 2.60 Ga. The Yathkyed belt is interpreted to have initially been emplaced as a thick-skinned, thrust nappe along the TSZ, during 2.66–2.62 Ga tectonism, and reactivated at ca. 2.62–2.60 Ga, causing further crustal thickening. In the Upper Panel, protracted upper amphibolite-grade metamorphism and associated anatectic melting are recorded by zircon, titanite, and monazite ages ranging from ca. 2561 to 2492 Ma. This thermal event is in part attributed to burial in response to ca. 2.62–2.60 Ga thrust reactivation. The timing and means of emplacement of the Upper Panel on top of the Lower Panel is uncertain; however, ca. 2.50 Ga thrusting elsewhere in the northwestern Hearne subdomain provides one possible mechanism.

Mesoproterozoic sedimentation, magmatism, and metamorphism in the southern part of the Grenville Province (western Quebec): U–Pb geochronological constraints

1995 ◽  
Vol 32 (12) ◽  
pp. 2103-2114 ◽  
Author(s):  
R. M. Friedman ◽  
J. Martignole
Keyword(s):  
The Other ◽  
High Grade ◽  
Metamorphic Zircon ◽  
Grenville Province ◽  
Plutonic Complex ◽  
Minimum Age ◽  
High Grade Metamorphism ◽  
The One ◽  
Geochronological Constraints ◽  
Age Range

U–Pb data provide new constraints on the age of sedimentation, metamorphism, magmatism, and deformation in the Grenville Province of western Quebec. A metapelite, an alaskitic gneiss, and an amphibolite were sampled within an area of 1 km2 in the Mont-Laurier terrane. The metapelite yielded detrital-metamorphic zircons that gave 207Pb/206Pb ages of ca. 1205–2200 Ma. The youngest detrital components, between 1210 and 1300 Ma and possibly as old as [Formula: see text] Ma, provide a maximum age range for the deposition of this rock. Data for the alaskitic gneiss suggest that it is either derived from an igneous (volcanic) protolith with a minimum age of ca. 1250 Ma and a maximum age of [Formula: see text] Ma, or is a dyke emplaced at ca. 1140–1170 Ma. The amphibolite yielded zircon interpreted as metamorphic, with a minimum age of 1118 Ma, and a maximum age not likely older than ca. 1160 Ma. Zircons from charnockites and monzonites of the Morin plutonic complex gave zircon igneous ages between ca. 1157 and 1165 Ma. High-grade metapelites of the Réservoir Cabonga terrane yielded metamorphic zircon ages of 1140-1160 Ma. Metamorphic monazites from both the Réservoir Cabonga and the Mont-Laurier terranes yielded ages of 1138−1182 Ma, interpreted as the crystallization age or the time that significant Pb loss ceased. These ages indicate that the two terranes underwent the same long-lasting metamorphic event. The overlap between ages of metamorphic zircons and monazites on the one hand and the age of anorthosite–charnockite magmatism on the other hand suggests a long-lasting high-grade metamorphism with heat contribution from crystallizing plutons. A posttectonic aplite dyke from the interior of the Mont-Laurier terrane gives a zircon minimum age of 1054 Ma, considered a minimum age for penetrative deformation in this part of the Grenville Province. Rutile ages of 945–955 Ma record cooling through about 400 °C in both the Réservoir Cabonga and the Mont-Laurier terranes.

Metamorphism of high-grade pelites in the Brabant Lake area, eastern La Ronge Domain, northern Saskatchewan

1992 ◽  
Vol 29 (8) ◽  
pp. 1686-1700
Author(s):  
Syed A. F. Abbas-Hasanie ◽  
John F. Lewry ◽  
Dexter Perkins
Keyword(s):  
Experimental Data ◽  
Water Pressure ◽  
Lake Area ◽  
High Grade ◽  
Minor Components ◽  
Early Proterozoic ◽  
Garnet Core ◽  
Facies Metamorphism ◽  
Lower Temperature ◽  
Recent Version

The Brabant Lake area mostly comprises Early Proterozoic clastic metasediments of the MacLean Lake belt, eastern La Ronge Domain, Reindeer Zone. The belt underwent upper amphibolite facies metamorphism, with sillimanite occurring in both psammitic and pelitic gneisses. Biotite + garnet + sillimanite + cordierite + quartz + K-feldspar + plagioclase parageneses suggest peak metamorphic pressure–temperature (P–T) conditions of 650–750 °C at 4–6 kbar (1 bar = 100 kPa) and [Formula: see text]. Both psammitic and pelitic gneisses underwent anatexis, which may have caused a reduction in water pressure. P–T conditions were also calculated by applying thermometry on the basis of garnet–biotite Fe–Mg exchange and barometry on the basis of garnet + plagioclase + sillimanite + quartz assemblages. The most precise garnet–biotite thermometer yielded temperatures of 608–758 °C (mean 690 °C). A more recent version, which incorporates the effects of minor components and nonideal mixing in both garnet and biotite, yielded a wider range of temperatures (565–826 °C), suggesting that imprecision in garnet–biotite thermometry may be due to disparate closing temperatures or disequilibrium. Application of several recent calibrations of the grossular + anorthite + sillimanite + quartz barometer produced a range of pressure estimates: three of these calibrations gave results compatible with documented mineral parageneses and experimental data, yielding 6.1 ± 0.5,6.1 ± 0.8, and 6.8 ± 0.9 kbar, respectively. Estimated mean pressures from another calibration are about 1–2 kbar higher. Peak metamorphic conditions at Brabant Lake are comparable with those experienced by metasediments of the Kisseynew Domain in Saskatchewan and Manitoba and other portions of the Reindeer Zone. Of 19 analyzed garnets from metapelites, 4 showed distinct chemical zonation. Garnet core growth appears coeval with syn-D2 peak metamorphic conditions; such cores yield the highest temperature estimates. Lower temperature estimates from garnet rims (range 610–660 °C, mean 630 °C) reflect retrogression under postpeak metamorphic conditions.

New structural, metamorphic, and U–Pb geochronological constraints on the Blezardian Orogeny and Yavapai Orogeny in the Southern Province, Sudbury, Canada

2014 ◽  
Vol 51 (8) ◽  
pp. 750-774 ◽  
Author(s):  
Tsilavo Raharimahefa ◽  
Bruno Lafrance ◽  
Douglas K. Tinkham
Keyword(s):  
Inductively Coupled Plasma ◽  
Regional Metamorphism ◽  
Crustal Thickening ◽  
Lake Area ◽  
Southern Province ◽  
Inductively Coupled ◽  
Metasedimentary Rocks ◽  
Minimum Age ◽  
Plasma Mass Spectrometry ◽  
Geochronological Constraints

New structural and geochronological data are presented for two orogenic events, the Blezardian and Yavapai orogenies, which affected the Paleoproterozoic Southern Province near Sudbury, Ontario, Canada. The Southern Province comprises ca. 2452 Ma metavolcanic rocks and metasedimentary rocks of the Huronian Supergroup, which were deposited along the southern margin of the Archean Superior craton during its evolution from a rifted to passive continental margin. Emplacement of the ca. 2415 Ma Creighton pluton during rifting was followed by its deformation and the development of a penetrative gneissic fabric during the ca. 2415 − ca. 2219 Ma Blezardian Orogeny. New laser ablation – inductively coupled plasma – mass spectrometry (LA–ICP–MS) U–Pb zircon ages of 2343 ± 17 and 2344 ± 47 Ma on two granitic dikes that cut this fabric provide a new minimum age of ca. 2.34 Ga for the Blezardian Orogeny. The Sudbury area was then impacted by a large extraterrestrial bolide at ca. 1.85 Ga and deformed during the Penokean Orogeny. The southern part of the Southern Province was later reworked by regional folding and north-directed thrusting during the younger 1.7 Ga Yavapai Orogeny. The 1744 ± 29 Ma Eden Lake Complex was emplaced and deformed during this event, which produced a strong foliation overprinting the complex. The foliation formed at pressures of 2.8–4 kbar (1 kbar = 100 MPa) and temperatures of 540–565 °C and was intruded by a weakly deformed 1704 ± 13 Ma old granitic dike, bracketing the Yavapai event between 1744 ± 29 and 1704 ± 13 Ma in the Sudbury segment of the Southern Province. Crustal thickening associated with the Yavapai event resulted, locally, in minor pressure increases before or during regional metamorphism as revealed by phase equilibria modeling in the Raft Lake area; this evolution may be recorded elsewhere in the Ontario segment of the Southern Province.

High-pressure granulite facies metamorphism of Archean Bastar craton at the interface of Eastern Ghats Belt: Implications for cratonic subduction/underthrusting

2021 ◽  
Author(s):  
Padmaja Jayalekshmi ◽  
Tapabrato Sarkar ◽  
Somnath Dasgupta ◽  
Rajneesh Bhutani
Keyword(s):  
High Pressure ◽  
Shear Zone ◽  
Granulite Facies ◽  
Eastern Ghats ◽  
Mobile Belt ◽  
High Grade ◽  
Granulite Facies Metamorphism ◽  
Bastar Craton ◽  
High Pressure Granulite ◽  
Facies Metamorphism

<p>The Bastar Craton at the interface of Eastern Ghats Belt (EGB) contains a mélange of rocks from both the Archean cratonic domain and the adjacent Proterozoic mobile belt domain marking a broad shear zone, known as the Terrane Boundary Shear Zone (TBSZ). The TBSZ preserves a very rare occurrence of high-grade metamorphosed Archean cratonic rocks, whose ancestry has been constrained by Nd model ages. This study presents the petrological and geochemical characterization of mafic granulites and orthopyroxene bearing granitoids from the shear zone and its implications on the tectonic evolution of the craton – mobile belt boundary. Detailed petrographic, geothermobarometric and P-T pseudosection studies indicate that the Bastar cratonic rocks underwent high-pressure granulite facies metamorphism along a clockwise P-T path, reaching ~900°C and 9-10 kbar. The originally amphibolite facies rocks, metamorphosed through dehydration-melting of hornblende (mafic rocks) and biotite (felsic rocks), to attain the peak P-T conditions. We suggest that this high-grade metamorphism was due to the subduction/underthrusting of the Bastar Craton beneath the EGB, supported by the available seismic data, which resulted from far-field stress related to the Kuunga orogeny in an intraplate setting.</p>

U–Pb geochronology of the Raglan gabbro belt, Central Metasedimentary Belt, Ontario: implications for an ensialic marginal basin in the Grenville Orogen

1996 ◽  
Vol 33 (5) ◽  
pp. 691-702 ◽  
Author(s):  
Sally Pehrsson ◽  
Simon Hanmer ◽  
Otto van Breemen
Keyword(s):  
Shear Zone ◽  
Hanging Wall ◽  
Island Arc ◽  
Northwestern Part ◽  
Marginal Basin ◽  
Arc Model ◽  
Minimum Age ◽  
Thrust Zone ◽  
Stiff Material ◽  
Central Gneiss Belt

The Raglan gabbro belt of the Ontario Grenville Orogen is coincident with the top of the Central Metasedimentary Belt boundary thrust zone, a major mid-crustal shear zone separating the Central Gneiss Belt in the footwall from the Central Metasedimentary Belt in the hanging wall. It has been suggested that the gabbros making up the belt are coeval, that they formed in a marginal basin within the Central Metasedimentary Belt, and that they formed a horizon of Theologically stiff material that controlled the localization of the top of the boundary thrust zone during its initiation as the marginal basin closed at ca. 1190 Ma. U–Pb zircon dating of plutons within the Raglan gabbro belt was undertaken to test the coeval nature of intrusions in the belt. Magmatic crystallization ages for three of the gabbros fall in the range 1246–1227 Ma, and a fourth yields a minimum age of ca. 1175 Ma. The results are permissive of a common origin for the gabbros and allow that the Raglan gabbro belt may have been related to the marginal basin, at least with respect to the later stages of its evolution. Inherited 1440–1301 Ma zircons in the gabbros suggest interaction with underlying Central Gneiss Belt crust during magmatism and support an ensialic marginal-basin model, as opposed to an island-arc model, for the evolution of the northwestern part of the Central Metasedimentary Belt.

DIVING DEEPER INTO THE PICURIS OROGEN: UPPER AMPHIBOLITE FACIES METAMORPHISM AND BRITTLE DEFORMATION ALONG THE PLOMO SHEAR ZONE

2020 ◽  
Author(s):  
Adrian E. Castro ◽  
◽  
Chloe Bonamici ◽  
Christopher G. Daniel ◽  
Danielle Shannon Sulthaus
Keyword(s):  
Shear Zone ◽  
Amphibolite Facies ◽  
Brittle Deformation ◽  
Facies Metamorphism

Structural and geochronological constraints on the role of partial melting during the formation of the Shuswap metamorphic core complex at the latitude of the Thor-Odin dome, British Columbia

1999 ◽  
Vol 36 (6) ◽  
pp. 917-943 ◽  
Author(s):  
Olivier Vanderhaeghe ◽  
Christian Teyssier ◽  
Richard Wysoczanski
Keyword(s):  
Partial Melting ◽  
Metamorphic Core Complex ◽  
High Grade ◽  
Core Complex ◽  
Genetic Link ◽  
The Core ◽  
Lower Unit ◽  
Geochronological Constraints ◽  
Metamorphic Core ◽  
Middle Unit

At the latitude of the Thor-Odin dome, the Shuswap metamorphic core complex exposes a ~15 km thick structural section composed of an upper unit that preserved Mesozoic metamorphism, structures, and cooling ages, separated from the underlying high-grade rocks by low-angle detachment zones. Below the detachments, the core of the complex consists of an amphibolite-facies middle unit overlying a migmatitic lower unit exposed in the core of the Thor-Odin dome. Combined structural and super high resolution ion microprobe (SHRIMP) U-Pb geochronology studies indicate that the pervasive shallowly dipping foliation and east-west lineation developed in the presence of melt during Paleocene time. SHRIMP analyses of complexly zoned zircon grains suggest that the migmatites of the lower unit crystallized at ~56 Ma, and a syntectonic leucogranite at ~60 Ma. We suggest that leucogranite migrated upward from the migmatites through an array of dikes and sills that permeated the middle unit and ponded to form laccoliths spatially related to the detachment zones. The similarity in ages of inherited zircon cores in the two migmatite and the leucogranite samples suggests a genetic link consistent with the structural analysis. Following the crystallization of migmatites, the terrane cooled rapidly, as indicated by argon thermochronology. We propose that exhumation of the core of the Canadian Cordillera during the formation of the Shuswap metamorphic core complex occurred from ~60 to 56 Ma at a time when the crust was significantly partially molten. These structural and temporal relationships suggest a genetic link between mechanical weakening of the crust by partial melting, late-orogenic collapse, and exhumation of high-grade rocks in the hinterland of a thermally mature orogenic belt.

Exploration geochemistry of surficial media over the high-grade McArthur River uranium deposit, Saskatchewan, Canada

2021 ◽  
Vol 59 (5) ◽  
pp. 913-945
Author(s):  
Steve R. Beyer ◽  
Kurt Kyser ◽  
Tom G. Kotzer ◽  
Kevin Ansdell ◽  
David Quirt
Keyword(s):  
Pinus Banksiana ◽  
Hanging Wall ◽  
Coarse Fraction ◽  
Mining Activity ◽  
Alteration Zone ◽  
High Grade ◽  
Soil Geochemistry ◽  
Mine Site ◽  
Ore Body ◽  
Mine Effluent

ABSTRACT An orientation survey using surficial media was performed over the high-grade McArthur River unconformity-related U deposit (Saskatchewan, Canada) to test whether or not secondary dispersion of elements related to the ore body or alteration zone can be detected at the surface more than 500 m above the deposit. Organic-rich Ah-horizon soils, Fe-rich B-horizon soils, C-horizon soils, tree cores of Jack pine (Pinus banksiana), and glacially dispersed boulders of Manitou Falls Formation sandstone that host the U deposit were collected in four sampling grids near the mine site. Two of the grids overlaid the trace of the P2 fault that hosts the deposit and extends nearly to the surface, one grid overlaid both the P2 fault and one of the high-grade ore bodies (Zone 4), and one grid was located 2.5 km away from the ore body surface trace in the barren hanging wall of the P2 fault. The grid overlying the Zone 4 ore body had the highest proportion of samples with elevated U and low 207Pb/206Pb ratios, the latter indicative of radiogenic Pb from a high-U source, measured in two size fractions of Ah-horizon soils using Na pyrophosphate leach, pine tree cores using total digestion, and sandstone boulders using 2% HNO3 leach. A handful of pathfinder elements, such as As, Co, Ni, and Pb, are variably associated with the U and radiogenic Pb. Sandstone boulders with an assemblage of dravite + kaolinite ± illite, determined using shortwave infrared (SWIR) spectroscopy and matching the alteration mineralogy in the Manitou Falls Formation above the U deposit, were prevalent in the grid above the Zone 4 ore body and in the adjacent grid in the direction of glacial dispersion. A coarse fraction of the B-horizon soils, leached with 5% HNO3, highlighted the grid above the Zone 4 ore body to a lesser extent, whereas HNO3 leaches and aqua regia digests of C-horizon soil separates did not highlight the P2 fault or ore body trace due to influence by parent till mineralogy. Results of environmental monitoring at the mine site, which was active at the time of sampling, suggest that dust containing U, Pb, and radionuclides from waste rock piles and a ventilation shaft could influence A-horizon soil geochemistry near the mine site, and that U and radiogenic Pb anomalies in B- and C-horizon soils near the water table are close to a treated mine effluent discharge point. However, older trees that record elevated U and radiogenic Pb in annual rings that pre-date mining activity, and alteration mineralogy and geochemistry of boulders that are less susceptible to the influences of mining activity, add confidence that the geochemical anomaly in diverse surficial media above the Zone 4 ore body represents secondary dispersion from the underlying U deposit.

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