U–Pb geochronology of a Paleoproterozoic continental magmatic arc on the western margin of the Archean Nain craton, northern Labrador, Canada

1995 ◽  
Vol 32 (11) ◽  
pp. 1870-1882 ◽  
Author(s):  
David J. Scott
Keyword(s):  
Shear Zone ◽  
Calc Alkaline ◽  
Western Margin ◽  
Magmatic Arc ◽  
Eastern Margin ◽  
Two Samples ◽  
Plutonic Rocks ◽  
Continental Magmatic Arc

The Paleoproterozoic Torngat Orogen, in northernmost Labrador and northeastern Quebec, records the collision between the western margin of the Nain Province and the eastern margin of the Rae Province. Six samples from a suite of calc-alkaline plutonic rocks that intrude the Nain craton have been dated using the U–Pb method at 1895 ± 2, 1888 ± 2, [Formula: see text], 1885 ± 2 (two samples), and >1859 Ma, and support the interpretation that east-dipping subduction occurred below the Nain craton during this interval. A granitic dyke that truncates the sinistral shear fabric in the Abloviak shear zone is 1824 ± 2 Ma, placing a younger limit on the timing of this deformation in the area. A second granitic dyke, emplaced synchronously with dextral deformation in the bend in the Abloviak shear zone, is 1798 ± 3 Ma. A model is proposed in which subduction occurred beneath the Nain craton along its entire exposed length from 1.91 to 1.86 Ga, and collision occurred between 1.86 and 1.84 Ga, followed by oblique uplift of the southern part of the Rae craton from 1.80 to 1.71 Ga.

scholarly journals An Early Ordovician tonalitic–granodioritic belt along the Schistose-Greywacke Domain of the Central Iberian Zone (Iberian Massif, Variscan Belt)

2012 ◽  
Vol 149 (5) ◽  
pp. 927-939 ◽  
Author(s):  
A. RUBIO-ORDÓÑEZ ◽  
P. VALVERDE-VAQUERO ◽  
L. G. CORRETGÉ ◽  
A. CUESTA-FERNÁNDEZ ◽  
G. GALLASTEGUI ◽  
...  
Keyword(s):  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Variscan Belt ◽  
Iberian Massif ◽  
Calc Alkaline ◽  
Central Iberian Zone ◽  
Magmatic Arc ◽  
Early Ordovician ◽  
Icp Ms ◽  
Continental Magmatic Arc

AbstractThe Zarza la Mayor and Zarza de Montánchez tonalites and Arroyo de la Luz granodiorite are part of a tonalitic–granodioritic belt located along the Schistose-Greywacke Domain of the Central Iberian Zone. These intrusions are also part of the Central Extremadura Batholith, a set of plutons ranging from tonalite to leucogranite that have been considered a prime example of Variscan syn-kinematic plutonism. New LA-ICP-MS and CA-ID-TIMS U–Pb dating reveals that the Zarza la Mayor tonalite–granodiorite is an Early Ordovician intrusion. The LA-ICP-MS data show that there is an absence of inherited cores, despite some complex internal zoning with obvious resorption features in some of the zircon crystals. Dating of monazite and zircon by CA-ID-TIMS provides a concordant age of 478.1 ± 0.8 Ma. This age coincides with electron microprobe analysis (EMPA) monazite chemical ages for the Zarza de Montánchez (482 ± 10 Ma) and Arroyo de la Luz (470 ± 15 Ma) intrusions. These new data indicate the presence of an Early Ordovician belt of calc-alkaline tonalite–granodiorite in the Schistose-Greywacke Domain – the Beira Baixa–Central Extremadura tonalite–granodiorite belt – which resembles a continental magmatic arc. This belt is contemporaneous with the Ollo de Sapo magmatic event further north in the Central Iberian Zone.

Crustal-scale flexural slip folding during late tectonic amplification of an orogenic boundary perturbation in the Paleoproterozoic Torngat Orogen, northeastern Canada

1997 ◽  
Vol 34 (12) ◽  
pp. 1545-1565 ◽  
Author(s):  
M. J. Van Kranendonk ◽  
R. J. Wardle
Keyword(s):  
Shear Zone ◽  
Plate Boundary ◽  
Granulite Facies ◽  
Boundary Perturbation ◽  
Magmatic Arc ◽  
Tectonic Events ◽  
Deep Crust ◽  
High Grade Metamorphism ◽  
Continental Magmatic Arc ◽  
Northern Segment

Large variations in metamorphic grade over short distances, disparate orientations and diverse kinematics of contemporaneous structures, and a previously unexplained, 90° counterclockwise bend in the orogenic boundary of the amphibolite- to granulite-facies northern segment of the Paleoproterozoic Torngat Orogen are shown to be the result of multiple tectonic events acting upon an orogenic boundary perturbation. The perturbation was initiated when a promontory on the Nain Province margin, composed of a 1910–1885 Ma continental magmatic arc (Burwell domain), indented the Rae Province hinterland during the onset of collisional orogeny at ca. 1870 Ma (Dn+1). Sinistral transpression at ca. 1845–1822 Ma (Dn+2) caused formation of the orogen-parallel Abloviak shear zone and oblique burial of the Nain Province margin beneath a tilted section of the hot, buoyant magmatic arc. Reactivation of the orogen at ca. 1798–1770 Ma (Dn+3) involved crustal-scale flexural slip folding of the perturbation and simultaneous exhumation of the Burwell domain and the previously buried Nain crust across the Komaktorvik shear zone, which represents a sheared, tightened fold train localized along the western limit of thinned Nain crust affected by preorogenic rifting, but which does not represent a fundamental plate boundary. The along-strike heterogeneities in the Torngat Orogen document the influence of geometrical and competency heterogeneities in the colliding margins on subsequent deformation and the fact that heterogeneities in the deep crust persist through high-grade metamorphism.

Geochronological and kinematic constraints on crustal shortening and escape in a two-sided oblique-slip collisional and magmatic orogen, Paleoproterozoic Taltson magmatic zone, northeastern Alberta

2000 ◽  
Vol 37 (11) ◽  
pp. 1549-1573 ◽  
Author(s):  
Michael R McDonough ◽  
Vicki J McNicoll ◽  
Ernst M Schetselaar ◽  
Timothy W Grover
Keyword(s):  
Shear Zone ◽  
Shear Zones ◽  
Remotely Sensed Data ◽  
Kinematic Data ◽  
Magmatic Arc ◽  
Magmatic Rocks ◽  
Ductile Shear Zones ◽  
Continental Magmatic Arc ◽  
Northeastern Alberta ◽  
Lower Crustal

The southern Taltson magmatic zone (south of 60°N) is a composite continental magmatic arc and collisional orogen resulting from the convergence of the Buffalo Head terrane with the Archean Churchill craton. Taltson basement (ca. 3.2–3.0 Ga and 2.4–2.14 Ga) and Rutledge River supracrustal gneisses (2.13–2.09 Ga) were intruded by voluminous I- and S-type magmatic rocks between 1.99 and 1.92 Ga. Taltson magmatic zone was deformed by three ductile shear zones: Leland Lakes, Charles Lake, and Andrew Lake, exhibiting both strike- and dip-lineated mylonitic domains. Kinematic data for shear zones are reported at microscopic, mesoscopic, and macroscopic (remotely sensed data) scale. We present field and U–Pb isotopic data (zircon and monazite) for magmatic and metamorphic rocks that constrain the timing of granulite to upper amphibolite-grade shearing in the Leland Lakes and Charles Lake (formerly Allan) shear zones to ca. 1938–1934 Ma. Foreland (easterly) vergent thrusting on the Andrew Lake shear zone is ca. 1932 Ma. Taltson shear zones were overprinted by widespread amphibolite- to greenschist-grade shearing, which is constrained by published 40Ar–39Ar and K–Ar dates on hornblende and muscovite to between ca. 1900 and 1800 Ma. We propose a crustal architecture, resembling a crustal-scale asymmetric flower structure, in which the Charles Lakes shear zone formed the fundamental shear zone of a middle to lower crustal sinistral transpression system that accommodated southward escape of crust in the upper plate of an oblique continental subduction–collision zone, with shortening partitioned into synchronous outwardly vergent thrust systems to the east and west of the main shear zone.

Laramide to Miocene syn-extensional plutonism in the Puerta del Sol area, central Sonora, Mexico

2017 ◽  
Vol 34 (1) ◽  
pp. 45 ◽  
Author(s):  
Elizard González-Becuar ◽  
Efrén Pérez-Segura ◽  
Ricardo Vega-Granillo ◽  
Luigi Solari ◽  
Carlos Manuel González-León ◽  
...  
Keyword(s):  
Metamorphic Core Complex ◽  
Primitive Mantle ◽  
Isotopic Ratios ◽  
Magmatic Evolution ◽  
Calc Alkaline ◽  
Core Complex ◽  
High K ◽  
Sierra Madre ◽  
Plutonic Rocks ◽  
Metamorphic Core

Plutonic rocks of the Puerta del Sol area, in central Sonora, represent the extension to the south of the El Jaralito batholith, and are part of the footwall of the Sierra Mazatán metamorphic core complex, whose low-angle detachment fault bounds the outcrops of plutonic rocks to the west. Plutons in the area record the magmatic evolution of the Laramide arc and the Oligo-Miocene syn-extensional plutonism in Sonora. The basement of the area is composed by the ca. 1.68 Ga El Palofierral orthogneiss that is part of the Caborca block. The Laramide plutons include the El Gato diorite (71.29 ± 0.45 Ma, U-Pb), the El Pajarito granite (67.9 ± 0.43 Ma, U-Pb), and the Puerta del Sol granodiorite (49.1 ± 0.46 Ma, U-Pb). The younger El Oquimonis granite (41.78 ± 0.32 Ma, U-Pb) is considered part of the scarce magmatism that in Sonora records a transition to the Sierra Madre Occidental magmatic event. The syn-extensional plutons are the El Garambullo gabbro (19.83 ± 0.18 Ma, U-Pb) and the Las Mayitas granodiorite (19.2 ± 1.2 Ma, K-Ar). A migmatitic event that affected the El Palofierral orthogneiss, El Gato diorite, and El Pajarito granite between ca. 68 and 59 Ma might be related to the emplacement of the El Pajarito granite. The plutons are metaluminous to slightly peraluminous, with the exception of El Oquimonis granite, which is a peraluminous two-mica, garnet-bearing granite. They are mostly high-K calc-alkaline with nearly uniform chondrite-normalized REE and primitive-mantle normalized multielemental patterns that are characteristic of continental margin arcs and resemble patterns reported for other Laramide granites of Sonora. The Laramide and syn-extensional plutons also have Sr, Nd and Pb isotopic ratios that plot within the fields reported for Laramide granites emplaced in the Caborca terrane in northwestern and central Sonora. Nevertheless, and despite their geochemical affinity to continental magmatic arcs, the El Garambullo gabbro and Las Mayitas granodiorite are syn-extensional plutons that were emplaced at ca. 20 Ma during development of the Sierra Mazatán metamorphic core complex. The 40Ar/39Ar and K-Ar ages obtained for the El Palofierral orthogneiss, the Puerta del Sol granodiorite, the El Oquimonis granite, and the El Garambullo gabbro range from 26.3 ± 0.6 to 17.4 ± 1.0 Ma and are considered cooling ages associated with the exhumation of the metamorphic core complex.

Felsic plutonic rocks from the southern portion of the New Caledonian Ultramafic Belt

1973 ◽  
Vol 110 (5) ◽  
pp. 431-446 ◽  
Author(s):  
K. A. Rodgers
Keyword(s):  
New Caledonia ◽  
Ultramafic Rocks ◽  
Calc Alkaline ◽  
Mafic Rocks ◽  
Alkaline Magma ◽  
Southwest Pacific ◽  
Plutonic Rocks

SummaryGranodiorite stocks were intruded into the alpine peridotites of southern New Caledonia in the Eocene following overthrusting of the ultramafics onto the sialic core of the island. Strong zoning, from mela-diorite to granodiorite, is developed in one pluton and is believed to be the result of assimilation of ultramafic and mafic rocks by the calc-alkaline magma. Evidence in favour of a consanguineous relationship between the felsic and ultramafic rocks is largely circumstantial. In their petrography, mineralogy and chemistry, the rocks show few differences from other felsic plutonics of Tertiary age in the southwest Pacific.

Lower Palaeozoic and Precambrian igneous rocks from eastern England, and their bearing on late Ordovician closure of the Tornquist Sea: constraints from U-Pb and Nd isotopes

1993 ◽  
Vol 130 (6) ◽  
pp. 835-846 ◽  
Author(s):  
S. R. Noble ◽  
R. D. Tucker ◽  
T. C. Pharaoh
Keyword(s):  
Volcanic Rocks ◽  
Igneous Rocks ◽  
Calc Alkaline ◽  
Nd Isotopes ◽  
Nd Isotope ◽  
Magmatic Arc ◽  
The North ◽  
Basement Rocks ◽  
Continental Arc ◽  
Lower Palaeozoic

AbstractThe U-Pb isotope ages and Nd isotope characteristics of asuite of igneous rocks from the basement of eastern England show that Ordovician calc-alkaline igneous rocks are tectonically interleaved with late Precambrian volcanic rocks distinct from Precambrian rocks exposed in southern Britain. New U-Pb ages for the North Creake tuff (zircon, 449±13 Ma), Moorby Microgranite (zircon, 457 ± 20 Ma), and the Nuneaton lamprophyre (zircon and baddeleyite, 442 ± 3 Ma) confirm the presence ofan Ordovician magmatic arc. Tectonically interleaved Precambrian volcanic rocks within this arc are verified by new U-Pb zircon ages for tuffs at Glinton (612 ± 21 Ma) and Orton (616 ± 6 Ma). Initial εNd values for these basement rocks range from +4 to - 6, consistent with generation of both c. 615 Ma and c. 450 Ma groups of rocksin continental arc settings. The U-Pb and Sm-Nd isotope data support arguments for an Ordovician fold/thrust belt extending from England to Belgium, and that the Ordovician calc-alkaline rocks formed in response to subductionof Tornquist Sea oceanic crust beneath Avalonia.

Jurassic Arc: Reconstructing the Lost World of eastern Gondwana

Geology ◽  
2021 ◽  
Author(s):  
Elliot K. Foley ◽  
R.A. Henderson ◽  
E.M. Roberts ◽  
A.I.S. Kemp ◽  
C.N. Todd ◽  
...  
Keyword(s):  
Detrital Zircon ◽  
Tectonic Setting ◽  
Magmatic Arc ◽  
Continental Arc ◽  
Key Factor ◽  
Igneous Activity ◽  
Competing Models ◽  
Juvenile Crust ◽  
Sedimentary Fill ◽  
Continental Magmatic Arc

The tectonic setting of the Australian sector of the eastern Gondwanan margin during the Jurassic and Cretaceous is enigmatic. Whether this involved convergent tectonism and a long-lived continental magmatic arc or rift-related extension unrelated to subduction is debated. The paucity of Australian Jurassic–Cretaceous igneous outcrops makes resolving these competing models difficult. We used the detrital zircon record of the Jurassic–Cretaceous Great Australian Superbasin (GAS) as a proxy for igneous activity. We attribute the persistent magmatism recorded in GAS sedimentary fill throughout the Mesozoic to ca. 95 Ma to continuation of the established Paleozoic continental arc system. The detrital zircon record signals short (~10 m.y.) pulses of elevated Jurassic and Cretaceous magmatic activity and strongly positive εHf values, indicating juvenile crust or mantle-derived magmatism. Margin reconstruction indicates sustained continental growth at rates of at least ~55 km3 km–1 m.y.–1, mainly to the tract now represented by submerged northern Zealandia, due to the retreat of this arc system. We posit that arc retreat was a key factor in rapid crust generation and preservation, and that continental sedimentary systems globally may host cryptic records of juvenile crustal addition that must be considered in estimating crustal growth rates along convergent plate margins.

New age constraints on magmatism and metamorphism in the Morin terrane (Grenville Province, Quebec)

2022 ◽  
Author(s):  
William H Peck ◽  
Matthew P Quinan
Keyword(s):  
Shear Zone ◽  
Granulite Facies ◽  
Western Boundary ◽  
Grenville Province ◽  
Granulite Facies Metamorphism ◽  
Metamorphic History ◽  
Crustal Block ◽  
Two Samples ◽  
Western Side ◽  
Age Constraints

The Morin terrane is an allochthonous crustal block in the southwestern Grenville Province with a relatively poorly-constrained metamorphic history. In this part of the Grenville Province, some terranes were part of the ductile middle crust during the 1.09–1.02 Ga collision of Laurentia with the Amazon craton (the Ottawan phase of the Grenvillian orogeny), while other terranes were part of the orogen’s superstructure. New U-Pb geochronology suggests that the Morin terrane experienced granulite-facies metamorphism during the accretionary Shawinigan orogeny (1.19–1.14 Ga) and again during the Ottawan. Seven zircon samples from the 1.15 Ga Morin anorthosite suite were dated to confirm earlier age determinations, and Ottawan metamorphic rims (1.08–1.07 Ga) were observed in two samples. U-Pb dating of titanite in nine marble samples surrounding the Morin anorthosite suite yielded mixed ages spanning between the Shawinigan and Ottawan metamorphisms (n=7), and predominantly Ottawan ages (n=2). Our results show that Ottawan zircon growth and resetting of titanite ages is spatially heterogeneous in the Morin terrane. Ages with a predominantly Ottawan signature are recognized in the Morin shear zone, which deforms the eastern lobe of the anorthosite, in an overprinted skarn zone on the western side of the massif, and in the Labelle shear zone that marks its western boundary. In the rest of the Morin terrane titanite with Shawinigan ages appear to have been only partially reset during the Ottawan. Further work is needed to better understand the relationship between the character of Ottawan metamorphism and resetting in different parts of the Morin terrane.

scholarly journals Petrogenesis and U-Pb and Sm-Nd geochronology of the Taquaral granite: record of an orosirian continental magmatic arc in the region of Corumba - MS

2015 ◽  
Vol 45 (3) ◽  
pp. 431-451 ◽  
Author(s):  
Letícia Alexandre Redes ◽  
Maria Zélia Aguiar de Sousa ◽  
Amarildo Salina Ruiz ◽  
Jean-Michel Lafon
Keyword(s):  
Geochemical Data ◽  
Alkaline Magmatism ◽  
Alluvial Deposits ◽  
Mato Grosso ◽  
Microgranular Enclave ◽  
Magmatic Arc ◽  
Rock Types ◽  
High K ◽  
Continental Magmatic Arc ◽  
Shrimp Zircon

The Taquaral Granite is located on southern Amazon Craton in the region of Corumbá, westernmost part of the Brazilian state of Mato Grosso do Sul (MS), near Brazil-Bolivia frontier. This intrusion of batholitic dimensions is partially covered by sedimentary rocks of the Urucum, Tamengo Bocaina and Pantanal formations and Alluvial Deposits. The rock types are classified as quartz-monzodiorites, granodiorites, quartz-monzonites, monzo and syenogranites. There are two groups of enclaves genetically and compositionally different: one corresponds to mafic xenoliths and the second is identified as felsic microgranular enclave. Two deformation phases are observed: one ductile (F1) and the other brittle (F2). Geochemical data indicate intermediate to acidic composition for these rocks and a medium to high-K, metaluminous to peraluminous calk-alkaline magmatism, suggesting also their emplacement into magmatic arc settings. SHRIMP zircon U-Pb geochronological data of these granites reveals a crystallization age of 1861 ± 5.3 Ma. Whole rock Sm-Nd analyses provided εNd(1,86 Ga) values of -1.48 and -1.28 and TDM model ages of 2.32 and 2.25 Ga, likely indicating a Ryacian crustal source. Here we conclude that Taquaral Granite represents a magmatic episode generated at the end of the Orosirian, as a part of the Amoguija Magmatic Arc.

scholarly journals Geochemical Significance of Clay Minerals and Elements in Paleogene Sandstones in the Center of the Northern Margin of the Qaidam Basin, China

Minerals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 505 ◽  
Author(s):  
Guoqiang Sun ◽  
Meng Wang ◽  
Jiajia Guo ◽  
Yetong Wang ◽  
Yongheng Yang
Keyword(s):  
Clay Minerals ◽  
Chemical Weathering ◽  
Qaidam Basin ◽  
Sedimentary Environment ◽  
Climatic Conditions ◽  
Northern Margin ◽  
Magmatic Arc ◽  
Average Value ◽  
Geochemical Significance ◽  
Continental Magmatic Arc

The average thickness of Paleogene sandstones reaches about 3000–4000 m at the northern margin of the Qaidam Basin. However, the provenance and sedimentary environment of these sandstones are uncertain; thus, more comprehensive research is needed. Integrated research is conducted on the provenance and weathering process based on petrographic characteristics, clay minerals, and geochemical compositions of sandstones in the center of the northern Qaidam Basin. The results of lithofacies analysis show that the Paleogene sandstones were mainly derived from an active continental magmatic arc, subduction accretion, or a fold-thrust belt. The average illite content in the Paleogene clay minerals is more than 50%, followed by chlorite and smectite, which reflect climatic and environmental characteristics that were arid to semi-arid, whereas the characteristics of carbon–oxygen isotopes reveal a mainly freshwater sedimentary environment. The corrected chemical index of alteration (CIAcorr) is between 56.3 and 75.7, with an average value of 66.5. These results indicate that the provenance of the Paleogene sandstones in the center of the northern Qaidam Basin mainly formed under cold and dry climatic conditions and experienced limited chemical weathering with a small amount that underwent intermediate chemical weathering under warm and humid conditions.

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