Ophiolite obduction in the Quebec Appalachians, Canada — 40Ar/39Ar age constraints and evidence for syn-tectonic erosion and sedimentation1Geological Survey of Canada Contribution 20100430.2GEOTOP (Centre de recherche en géochimie et géodynamique) Contribution 2011-0002.3This article is one of a series of papers published in this CJES Special Issue: In honour of Ward Neale on the theme of Appalachian and Grenvillian geology.

2012 ◽  
Vol 49 (1) ◽  
pp. 91-110 ◽  
Author(s):  
Stéphane De Souza ◽  
Alain Tremblay ◽  
Gilles Ruffet ◽  
Nicolas Pinet
Keyword(s):  
Field Work ◽  
Metamorphic Rocks ◽  
Special Issue ◽  
Lower Paleozoic ◽  
Ophiolitic Mélange ◽  
Orogenic Wedge ◽  
Ultramafic Complex ◽  
Tectonic Erosion ◽  
Laurentian Margin ◽  
Age Constraints

Detailed field work conducted in the Dunnage zone of the Quebec Appalachians, is herein combined with 40Ar/39Ar dating on a series of ophiolitic massifs, crosscutting granites, and associated metamorphic rocks occurring along the Baie Verte–Brompton line, the Taconian suture between Laurentia and Lower Paleozoic peri-Laurentian oceanic terranes. Studied massifs are the Lac-Brompton ophiolite and the Rivière-des-Plante Ultramafic Complex in southern Quebec, and the Nadeau Ophiolitic Mélange in the Gaspé Peninsula. Our work suggests that these massifs form remnants of eroded ophiolitic nappes, which are unconformably overlain by the Saint-Daniel and Rivière-Port-Daniel mélanges, and correlate with the Thetford-Mines and Mont-Albert ophiolitic complexes. Our 40Ar/39Ar data and compiled regional age constraints indicate that ophiolite obduction was diachronous along the strike of the orogen. The timing of obduction and mélange formation varies according to the irregular geometry of the Early Paleozoic Laurentian margin, with earlier collision occurring along, or at the margins of promontories. Obduction was initiated with the formation of infraophiolitic metamorphic soles between ca. 479 and 472 Ma in southern Quebec and the Nadeau Ophiolitic Mélange, and possibly as late as ca. 470–466 Ma for the Mont-Albert Complex. These sole rocks were later exhumed and translated onto the Laurentian margin with the overlying ophiolites between 475 and 460–457 Ma. The uplifting and erosion of the orogenic wedge during the waning stages of obduction, has resulted in the sedimentation of olistostromal mélanges and onlapping flysch units above the ophiolitic nappes, as well as foredeep flysch successions during the latest Arenig(?) to earliest Caradoc.

scholarly journals Stratigraphic and tectonic control of deep-water scarp accumulation in Paleogene synorogenic basins: a case study of the Súľov Conglomerates (Middle Váh Valley, Western Carpathians)

2017 ◽  
Vol 68 (5) ◽  
pp. 403-418 ◽  
Author(s):  
Ján Soták ◽  
Zuzana Pulišová ◽  
Dušan Plašienka ◽  
Viera Šimonová
Keyword(s):  
Deep Water ◽  
Fault Scarp ◽  
Submarine Landslides ◽  
Orogenic Wedge ◽  
Calcite Veins ◽  
Tectonic Erosion ◽  
Mass Flow Deposits ◽  
Miocene Tectonics ◽  
Mass Transport Deposits

Abstract The Súľov Conglomerates represent mass-transport deposits of the Súľov-Domaniža Basin. Their lithosomes are intercalated by claystones of late Thanetian (Zones P3 - P4), early Ypresian (Zones P5 - E2) and late Ypresian to early Lutetian (Zones E5 - E9) age. Claystone interbeds contain rich planktonic and agglutinated microfauna, implying deep-water environments of gravity-flow deposition. The basin was supplied by continental margin deposystems, and filled with submarine landslides, fault-scarp breccias, base-of-slope aprons, debris-flow lobes and distal fans of debrite and turbidite deposits. Synsedimentary tectonics of the Súľov-Domaniža Basin started in the late Thanetian - early Ypresian by normal faulting and disintegration of the orogenic wedge margin. Fault-related fissures were filled by carbonate bedrock breccias and banded crystalline calcite veins (onyxites). The subsidence accelerated during the Ypresian and early Lutetian by gravitational collapse and subcrustal tectonic erosion of the CWC plate. The basin subsided to lower bathyal up to abyssal depth along with downslope accumulation of mass-flow deposits. Tectonic inversion of the basin resulted from the Oligocene - early Miocene transpression (σ1 rotated from NW-SE to NNW-SSE), which changed to a transpressional regime during the Middle Miocene (σ1 rotated from NNE-SSW to NE-SW). Late Miocene tectonics were dominated by an extensional regime with σ3 axis in NNW-SSE orientation.

scholarly journals Renewed tectonic extrusion of high-grade metamorphic rocks in the MCT footwall since Late Miocene (Sutlej Valley, India)

2008 ◽  
Vol 2 (4) ◽  
pp. 102-103 ◽  
Author(s):  
Vincent Baudraz ◽  
Jean-Claude Vannay ◽  
Elizabeth Catlos ◽  
Mike Cosca ◽  
Torsten Vennemann
Keyword(s):  
Late Miocene ◽  
Metamorphic Rocks ◽  
High Grade ◽  
Special Issue ◽  
Tectonic Extrusion

Himalayan Journal of Sciences Vol.2(4) Special Issue 2004 pp. 102-3

New Albian (Cretaceous) radiolarian age constraints for the Dumak ophiolitic mélange from the Shuru area, Eastern Iran

2020 ◽  
Vol 111 ◽  
pp. 104451
Author(s):  
Péter Ozsvárt ◽  
Elham Bahramnejad ◽  
Sasan Bagheri ◽  
Mortaza Sharifi
Keyword(s):  
Ophiolitic Mélange ◽  
Eastern Iran ◽  
Age Constraints

scholarly journals Out-of-sequence deformation and expansion of the Himalayan orogenic wedge: insight from the Changgo culmination, south-central Tibet

1970 ◽  
Vol 5 (7) ◽  
pp. 84
Author(s):  
Kyle P Larson ◽  
Laurent Godin
Keyword(s):  
Special Issue ◽  
South Central ◽  
Orogenic Wedge ◽  
Central Tibet

DOI = 10.3126/hjs.v5i7.1279 Himalayan Journal of Sciences Vol.5(7) (Special Issue) 2008 p.84

Lower Paleozoic stratigraphic and biostratigraphic correlations in the Canadian Cordillera: implications for the tectonic evolution of the Laurentian margin

2003 ◽  
Vol 40 (12) ◽  
pp. 1739-1753 ◽  
Author(s):  
Leanne J Pyle ◽  
Christopher R Barnes
Keyword(s):  
Tectonic Evolution ◽  
Passive Margin ◽  
Lower Paleozoic ◽  
Early Devonian ◽  
Southern Rocky Mountains ◽  
Peace River ◽  
Regional Correlation ◽  
Laurentian Margin ◽  
Peace River Arch ◽  
Early Late

The ancient Laurentian margin rifted in the latest Neoproterozoic to early Cambrian but appears not to have developed as a simple passive margin through a long, post-rift, drift phase. Stratigraphic and conodont biostratigraphic information from four platform-to-basin transects across the margin has advanced our knowledge of the early Paleozoic evolution of the margin. In northeastern British Columbia, two northern transects span the Macdonald Platform to Kechika Trough and Ospika Embayment, and a third transect spans the parautochthonous Cassiar Terrane. In the southern Rocky Mountains, new conodont biostratigraphic data for the Ordovician succession of the Bow Platform is correlated to coeval basinal facies of the White River Trough. In total, from 26 stratigraphic sections, over 25 km of strata were measured and > 1200 conodont samples were collected that yielded over 100 000 conodont elements. Key zonal species were used for regional correlation of uppermost Cambrian to Middle Devonian strata along the Cordillera. The biostratigraphy temporally constrains at least two periods of renewed extension along the margin, in the latest Cambrian and late Early Ordovician. Alkalic volcanics associated with abrupt facies changes across the ancient shelf break, intervals of slope debris breccia deposits, and distal turbidite flows suggest the margin was characterized by intervals of volcanism, basin foundering, and platform flooding. Siliciclastics in the succession were sourced by a reactivation of tectonic highs, such as the Peace River Arch. Prominent hiatuses punctuate the succession, including unconformities of early Late Ordovician, sub-Llandovery, possibly Early to Middle Silurian and Early Devonian ages.

Evidence for seamount accretion to a peri-Laurentian arc during closure of Iapetus 1This article is one of a series of papers published in CJES Special Issue: In honour of Ward Neale on the theme of Appalachian and Grenvillian geology.2 Geological Survey of Canada Contribution 20100465.

2012 ◽  
Vol 49 (1) ◽  
pp. 147-165 ◽  
Author(s):  
A. Zagorevski ◽  
V. McNicoll
Keyword(s):  
Accretionary Prism ◽  
Special Issue ◽  
Volcanic Arc ◽  
Bay Area ◽  
Mylonite Zone ◽  
Iapetus Ocean ◽  
Subduction Erosion ◽  
Area Preserve ◽  
Laurentian Margin ◽  
Accretionary Prisms

The Red Indian Line is the fundamental Iapetus suture zone in the Newfoundland Appalchians along which the main tract of the Iapetus Ocean was consumed. Despite being the site of the closure of a wide ocean, few vestiges of the Iapetus plate have been accreted along Red Indian Line. Ordovician rocks in the Notre Dame Bay area preserve the only evidence for accretion of a seamount in Newfoundland. The seamount is characterized by alkali basalt and hypabyssal rocks that are juxtaposed with Darriwilian peri-Laurentian volcanic arc rocks (466 ± 4 and 467 ± 4 Ma) along a major mylonite zone. The mylonite zone lacks sedimentary rocks suggesting that the seamount was accreted to the arc along a sediment-starved interface and that significant subduction erosion took place along the Laurentian margin. Identification of subduction erosion indicates that an accretionary prism did not exist outboard of Laurentia in Newfoundland, in contrast to the well developed accretionary prisms of the Caledonides.

scholarly journals MODELAGEM DE DADOS AEROMAGNÉTICOS PARA ESTIMAR LARGURA E ESPESSURA DO COMPLEXO MÁFICO/ULTRAMÁFICO DE CAMPO FORMOSO-BA

2003 ◽  
Vol 52 ◽  
Author(s):  
Francisco José Fonseca Ferreira ◽  
Raimundo Almeida Filho ◽  
Francisco Valdyr Da Silva
Keyword(s):  
Geological Mapping ◽  
Magnetic Data ◽  
Ultramafic Rocks ◽  
Metamorphic Rocks ◽  
Simple Geometry ◽  
Ultramafic Complex ◽  
Northern Portion ◽  
Depth Extent ◽  
Best Fit ◽  
Airborne Magnetic

O complexo máfico/ultramáfico Campo Formoso, no estado da Bahia, é constituído por rochas metamórficas de alto grau, derivadas de peridotitos e piroxenitos do Proterozóico Inferior. Em superfície, ele estende-se por cerca de 40 km, com larguras variando entre 100 e 1.100 metros. A despeito de encerrar as mais importantes mineralizações de cromo conhecidas no Brasil, os conhecimentos geológicos sobre o complexo ainda são bastante limitados. O profundo intemperismo e a presença de coberturas aluviais e coluviais dificultam o mapeamento geológico dessas rochas. Estimativas sobre largura e espessura do complexo em subsuperfície são importantes, visto que, por tratar-se de um corpo estratiforme, níveis mineralizados em superfície podem prolongar-se até grandes profundidades. Neste estudo, dados aeromagnéticos são analisados visando a obter informações sobre a extensão do complexo em subsuperfície. Para isso, um método interativo de modelagem de corpos magnéticos tabulares por processo de inversão foi empregado em uma área selecionada, onde ocorrem alguns dos mais importantes depósitos de cromo conhecidos no complexo. A técnica de modelagem empregada permite o cálculo de parâmetros tais como mergulho, largura e espessura de corpos de geometria simples, magnetizados por indução, remanência, ou ambos. O algoritmo empregado usa valores iniciais para cada parâmetro do corpo a ser modelado, os quais podem ser modificados pelo analista, de modo a incorporar dados reais. Esses dados são manipulados interativamente na busca de um "melhor ajuste", de modo que os parâmetros ajustados caiam dentro de limites de tolerância especificados pelo usuário. A qualidade do ajuste é medida pela relação da soma ponderada dos desvios quadráticos entre valores observados e calculados. Tomando-se como base a geologia da área de estudo, selecionou-se o modelo de dique espesso finito tabular 2 (2¾-D) como o mais apropriado para representar o complexo. Os resultados de modelagens em três perfis indicaram corpos magnéticos com larguras variando entre 264 e 374 metros, espessuras entre 432 e 470 metros e mergulhos entre 52o e 68o para SE. MODELING AIRBORNE MAGNETIC DATA TO ESTIMATE WIDTH AND THICKNESS OF THE MAFIC/ULTRAMAFIC COMPLEX OF CAMPO FORMOSO, BAHIA STATE, BRAZIL Abstract The Campo Formoso complex is located in the Bahia State, in the northeastern part of Brazil. The complex comprises high-grade metamorphic rocks derived from peridotite and pyroxenite of Early Proterozoic age. Mafic/ultramafic rocks cover an area approximately 40 km long and 100 to 1100 m wide, with a general NE-SW direction, dipping to the southeast. This complex hosts the most important chromium deposit of Brazil. This deposit occurs in the southern portion of the complex which makes up a lower structural block, better preserved by the erosion than the northern portion. In spite of its economic importance, geological knowledge of the complex is still very limited. The deep weathering of the mafic/ultramafic rocks and the presence of alluvial and colluvial deposits difficult geological mapping. It is a stratiform complex and the mineralized layers may extend down to great depths. Therefore it is important do know the width and thickness of its rocks in subsurface. In this study airborne magnetic data were analyzed to obtain information of the subsurface extent of the Campo Formoso complex. In order to do that an interactive modeling method of tabular magnetic bodies with inversion process was applied in a selected area of the southern portion of the complex. The used model calculates depth, thickness, and dip of a simple geometry body, magnetized by induction, remanence, or both. This procedure helps to find the best possible match between a theoretical anomaly and a given set of magnetic data. The best fit is found when the adjusted parameters fall within a user-specified tolerance of values which minimize the weighted sum of squared deviations between the observed and the theoretical magnetic anomaly. When a set of parameters satisfies the best-fit criterion, confidence ranges are calculated for all parameters. According to geological data, the best model assumed for the ore body was a thick, flat-topped dyke of finite strike length 2 (2¾-D) and a finite variable depth extent. The modeling results of three profiles of the study area indicate magnetized bodies varying width from 264 to 374 m, thickness from 432 to 473m, and dipping from 52o to 68o SE.

How Himalayan collision stems from subduction

Geology ◽  
2021 ◽  
Author(s):  
M. Soret ◽  
K.P. Larson ◽  
J. Cottle ◽  
A. Ali
Keyword(s):  
Foreland Basin ◽  
Continental Collision ◽  
Ultrahigh Pressure ◽  
Metamorphic Rocks ◽  
Conductive Heat ◽  
Plate Interface ◽  
Continental Subduction ◽  
Metamorphic History ◽  
Orogenic Wedge ◽  
History Of

The mechanisms and processes active during the transition from continental subduction to continental collision at the plate interface are largely unknown. Rock records of this transition are scarce, either not exposed or obliterated during subsequent events. We examine the tectono-metamorphic history of Barrovian metamorphic rocks from the western Himalayan orogenic wedge. We demonstrate that these rocks were buried to amphibolite-facies conditions from ≤47 Ma to 39 ± 1 Ma, synchronously with the formation (46 Ma) and partial exhumation (45–40 Ma) of the ultrahigh-pressure eclogites. This association indicates that convergence during continental subduction was accommodated via development of a deep orogenic wedge built through successive underplating of continental material, including the partially exhumed eclogites, likely in response to an increase in interplate coupling. This process resulted in the heating of the subduction interface (from ~7 to ~20 °C/km) through advective and/or conductive heat transfer. Rapid cooling of the wedge from 38 Ma, coeval with the formation of a foreland basin, are interpreted to result from indentation of a promontory of thick Indian crust.

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