Crustal thickening versus lateral extrusion during India–Asia continental collision: 3-D thermo-mechanical modeling

2021 ◽  
pp. 229081
Author(s):  
Qihua Cui ◽  
Zhong-Hai Li ◽  
Mian Liu
Keyword(s):  
Continental Collision ◽  
Crustal Thickening ◽  
Mechanical Modeling ◽  
Lateral Extrusion

scholarly journals Magmatic flare-up causes crustal thickening at the transition from subduction to continental collision

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Carlos E. Ganade ◽  
Pierre Lanari ◽  
Daniela Rubatto ◽  
Joerg Hermann ◽  
Roberto F. Weinberg ◽  
...  
Keyword(s):  
Production Rate ◽  
Continental Margin ◽  
Subduction Zones ◽  
Continental Collision ◽  
Crustal Thickening ◽  
Time Intervals ◽  
West Gondwana ◽  
Continental Arc ◽  
Order Of Magnitude

AbstractAbove subduction zones, magma production rate and crustal generation can increase by an order of magnitude during narrow time intervals known as magmatic flare-ups. However, the consequences of these events in the deep arc environment remain poorly understood. Here we use petrological and in-situ zircon dating techniques to investigate the root of a continental arc within the collisional West Gondwana Orogen that is now exposed in the Kabyé Massif, Togo. We show that gabbros intruded 670 million years ago at 20–25 km depth were transformed to eclogites by 620 million years ago at 65–70 km depth. This was coeval with extensive magmatism at 20–40 km depth, indicative of a flare-up event which peaked just prior to the subduction of the continental margin. We propose that increased H2O flux from subduction of serpentinized mantle in the hyper-extended margin of the approaching continent was responsible for the increased magma productivity and crustal thickening.

scholarly journals An anticlockwise metamorphic P-T path and nappe stacking in the Reisa Nappe Complex in the Scandinavian Caledonides, northern Norway: evidence for weakening of lower continental crust before and during continental collision

2018 ◽  
Author(s):  
Carly Faber ◽  
Holger Stünitz ◽  
Deta Gasser ◽  
Petr Jeřábek ◽  
Katrin Kraus ◽  
...  
Keyword(s):  
Partial Melting ◽  
Continental Crust ◽  
Large Scale ◽  
Structural Data ◽  
Geothermal Gradient ◽  
Continental Collision ◽  
Crustal Thickening ◽  
Northern Norway ◽  
Nappe Complex ◽  
T Path

Abstract. This study investigates the Caledonian metamorphic and tectonic evolution in northern Norway, examining the structure and tectonostratigraphy of the Reisa Nappe Complex (RNC; from bottom to top, Vaddas, Kåfjord and Nordmannvik nappes). Structural data, phase equilibrium modelling, and U-Pb zircon and titanite geochronology are used to constrain the timing and P-T conditions of deformation and metamorphism that formed the nappes and facilitated crustal thickening during continental collision. Five samples taken from different parts of the RNC reveal an anticlockwise P-T path attributed to the effects of early Silurian heating followed by thrusting. An early Caledonian S1 foliation in the Nordmannvik Nappe records kyanite-grade partial melting at ~ 760–790 °C and ~ 9.4–11 kbar. Leucosomes formed at 439 ± 2 Ma (U-Pb zircon) in fold axial planes in the Nordmannvik Nappe indicate that compressional deformation initiated while the rocks were still partially molten. This stage was followed by pervasive solid-state shearing as the rocks cooled and solidified, forming the S2 foliation at 680–730 °C and 9.5–10.9 kbar. Multistage titanite growth in the Nordmannvik Nappe records this extended metamorphism between 444 and 427 Ma. In the underlying Kåfjord Nappe, garnet cores record lower P-T (590–610 °C and 5.5–6.8 kbar) but a similar geothermal gradient as the S1 migmatitic event in the Nordmannvik Nappe, indicating formation at a higher relative position in the crust. S2 shearing in the Kåfjord Nappe occurred at 580–605 °C and 9.2–10.1 kbar, indicating a considerable pressure increase during nappe stacking. Gabbro intruded in the Vaddas Nappe at 439 ± 1 Ma, synchronously with migmatization in the Nordmannvik Nappe. In the Vaddas Nappe S2 shearing occurred at 630–640 ºC and 11.7–13 kbar. Titanite growth along the lower RNC boundary records S2-shearing at 432 ± 6 Ma. It emerges that early Silurian heating (~ 440 Ma), probably resulting from large-scale magma underplating, initiated partial melting that weakened the lower crust, which facilitated dismembering of the crust into individual nappe units. This tectonic style contrasts subduction of mechanically strong continental crust to great depths.

scholarly journals Anticlockwise metamorphic pressure–temperature paths and nappe stacking in the Reisa Nappe Complex in the Scandinavian Caledonides, northern Norway: evidence for weakening of lower continental crust before and during continental collision

Solid Earth ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 117-148 ◽  
Author(s):  
Carly Faber ◽  
Holger Stünitz ◽  
Deta Gasser ◽  
Petr Jeřábek ◽  
Katrin Kraus ◽  
...  
Keyword(s):  
Partial Melting ◽  
Continental Crust ◽  
Large Scale ◽  
Structural Data ◽  
Continental Collision ◽  
Crustal Thickening ◽  
Western Gneiss Region ◽  
Nappe Complex ◽  
T Path ◽  
Tectonic Style

Abstract. This study investigates the tectonostratigraphy and metamorphic and tectonic evolution of the Caledonian Reisa Nappe Complex (RNC; from bottom to top: Vaddas, Kåfjord, and Nordmannvik nappes) in northern Troms, Norway. Structural data, phase equilibrium modelling, and U-Pb zircon and titanite geochronology are used to constrain the timing and pressure–temperature (P–T) conditions of deformation and metamorphism during nappe stacking that facilitated crustal thickening during continental collision. Five samples taken from different parts of the RNC reveal an anticlockwise P–T path attributed to the effects of early Silurian heating (D1) followed by thrusting (D2). At ca. 439 Ma during D1 the Nordmannvik Nappe reached the highest metamorphic conditions at ca. 780 ∘C and ∼9–11 kbar inducing kyanite-grade partial melting. At the same time the Kåfjord Nappe was at higher, colder, levels of the crust ca. 600 ∘C, 6–7 kbar and the Vaddas Nappe was intruded by gabbro at > 650 ∘C and ca. 6–9 kbar. The subsequent D2 shearing occurred at increasing pressure and decreasing temperatures ca. 700 ∘C and 9–11 kbar in the partially molten Nordmannvik Nappe, ca. 600 ∘C and 9–10 kbar in the Kåfjord Nappe, and ca. 640 ∘C and 12–13 kbar in the Vaddas Nappe. Multistage titanite growth in the Nordmannvik Nappe records this evolution through D1 and D2 between ca. 440 and 427 Ma, while titanite growth along the lower RNC boundary records D2 shearing at 432±6 Ma. It emerges that early Silurian heating (ca. 440 Ma) probably resulted from large-scale magma underplating and initiated partial melting that weakened the lower crust, which facilitated dismembering of the crust into individual thrust slices (nappe units). This tectonic style contrasts with subduction of mechanically strong continental crust to great depths as seen in, for example, the Western Gneiss Region further south.

A lifetime of the Variscan orogenic plateau from uplift to collapse as recorded by the Prague Basin, Bohemian Massif

2017 ◽  
Vol 156 (3) ◽  
pp. 485-509 ◽  
Author(s):  
FRANTIŠEK VACEK ◽  
JIŘÍ ŽÁK
Keyword(s):  
Bohemian Massif ◽  
Three Dimensional ◽  
Plate Boundary ◽  
Early Carboniferous ◽  
Shear Zones ◽  
Crustal Thickening ◽  
Variscan Orogeny ◽  
Prague Basin ◽  
Lateral Extrusion ◽  
Orogenic Plateau

AbstractThe Ordovician to Middle Devonian Prague Basin, Bohemian Massif, represents the shallowest crust of the Variscan orogen corresponding toc.1–4 km palaeodepth. The basin was inverted and multiply deformed during the Late Devonian to early Carboniferous Variscan orogeny, and its structural inventory provides an intriguing record of complex geodynamic processes that led to growth and collapse of a Tibetan-type orogenic plateau. The northeastern part of the Prague Basin is a simple syncline cross-cut by reverse/thrust faults and represents a doubly vergent compressional fan accommodatingc.10–19 % ~NW–SE shortening, only minor syncline axis-parallel extension and significant crustal thickening. The compressional structures were locally overprinted by vertical shortening, kinematically compatible with ductile normal shear zones that exhumed deep crust in the orogen's interior atc. 346–337 Ma. On a larger scale, the deformation history of the Prague Syncline is consistent with building significant palaeoelevation during Variscan plate convergence. Based on a synthesis of finite deformation parameters observed across the upper crust in the centre of the Bohemian Massif, we argue for a differentiated within-plateau palaeotopography consisting of domains of local thickening alternating with topographic depressions over lateral extrusion zones. The plateau growth, involving such complex three-dimensional internal deformations, was terminated by its collapse driven by multiple interlinked processes including gravity, voluminous magma emplacement and thermal softening in the hinterland, and far-field plate-boundary forces resulting from the relative dextral motion of Gondwana and Laurussia.

An early metamorphic stage for the Variscan Ulten Zone gneiss (NE Italy): evidence from mineral inclusions in kyanite

2007 ◽  
Vol 71 (06) ◽  
pp. 691-702 ◽  
Author(s):  
R. Braga ◽  
H.-J. Massonne ◽  
L. Morten
Keyword(s):  
Continental Collision ◽  
Crustal Thickening ◽  
Variscan Orogeny ◽  
Thermal Decay ◽  
Metamorphic Stage ◽  
Mineral Inclusions ◽  
Ne Italy

Abstract The early P-T evolution of a garnet-kyanite gneiss from the Variscan Ulten Zone has been defined by detailed petrographic observations leading to the detection of chlorite-epidote- and staurolite-bearing assemblages enclosed in kyanite porphyroblasts. Calculations of P-T pseudosections in the system NaCaKFeMgAlSiHO allowed us to constrain the evolution of these relics to the earliest metamorphic stages. The overall path shows a P-T increase to a peak of 11–12 kbar and 600–650°C followed by decompressional heating to 720°C and 9–10 kbar and final cooling at 7 kbar, 550–600°C. This clockwise P-T path reflects crustal thickening and subsequent thermal decay related to the continental collision of the Variscan orogeny 330–340 Ma ago. Our study demonstrates that large kyanite porphyroblasts may preserve assemblages related to prograde metamorphic stages. As a result, the detection of mineral inclusions in kyanite can complement many similar studies on mineral suites hosted in garnet and zircon.

scholarly journals Crustal deformation and exhumation within the India-Eurasia oblique convergence zone: New insights from the Ailao Shan-Red River shear zone

2021 ◽  
Author(s):  
B. Zhang ◽  
S.Y. Chen ◽  
Y. Wang ◽  
P.W. Reiners ◽  
F.L. Cai ◽  
...  
Keyword(s):  
Shear Zone ◽  
Middle Miocene ◽  
Shear Zones ◽  
Strike Slip ◽  
Red River ◽  
Crustal Thickening ◽  
The Core ◽  
Early Oligocene ◽  
Lateral Extrusion ◽  
Tectonic Boundaries

During the collision of India and Eurasia, regional-scale strike-slip shear zones played a key role in accommodating lateral extrusion of blocks, block rotation, and vertical exhumation of metamorphic rocks as presented by deformation on the Ailao Shan-Red River shear zone (ARSZ) in the Eastern Himalayan Syntaxis region and western Yunnan, China. We report structural, mica Ar/Ar, apatite fission-track (AFT), and apatite (U-Th)/He (AHe) data from the Diancangshan massif in the middle segment of the ARSZ. These structural data reveal that the massif forms a region-scale antiform, bordered by two branches of the ARSZ along its eastern and western margins. Structural evidence for partial melting in the horizontal mylonites in the gneiss core document that the gneiss experienced a horizontal shear deformation in the middle crust. Muscovite Ar/Ar ages of 36−29 Ma from the core represent cooling ages. Muscovite Ar/Ar ages of 25 and 17 Ma from greenschist-facies mylonites along the western and southern shear zones, respectively, are interpreted as recording deformation in the ARSZ. The AFT ages, ranging from 15 to 5 Ma, represent a quiescent gap with a slow cooling/exhumation in the massif. AHe results suggest that a rapid cooling and final exhumation episode of the massif could have started before 3.2 Ma, or likely ca. 5 Ma, and continue to the present. The high-temperature horizontal shearing layers of the core were first formed across the Indochina Block, locally antiformed along the tectonic boundaries, and then cooled through the mica Ar-Ar closure temperature during Eocene or early Oligocene, subsequently reworked and further exhumed by sinistral strike-slip movement along the ARSZ during the early Oligocene (ca. 29 Ma), lasting until ca. 17 Ma, then final exhumation of the massif occurred by dextral normal faulting on the Weixi-Qiaohou and Red River faults along the limbs of the ARSZ since ca. 5 Ma. The formation of the antiform could indicate local crustal thickening in an early transpressional setting corresponding to India-Asia convergence. Large-scale sinistral ductile shear along the ARSZ in the shallow crust accommodated lateral extrusion of the Indochina Block, and further contributed to the vertical exhumation of the metamorphic massif from the late Oligocene to the middle Miocene. Furthermore, the change of kinematic reversal and associated cooling episodes along the ARSZ since the middle Miocene or early Pliocene imply a tectonic transfer from strain localization along the major tectonic boundaries to continuous deformation corresponding to plateau growth and expansion.

Continental collision including a weak zone: the vise model and its application to the Newfoundland Appalachians

1998 ◽  
Vol 35 (11) ◽  
pp. 1323-1346 ◽  
Author(s):  
Susan Ellis ◽  
Christopher Beaumont ◽  
Rebecca A Jamieson ◽  
Garry Quinlan
Keyword(s):  
Pure Shear ◽  
Indirect Evidence ◽  
Shear Thickening ◽  
Continental Collision ◽  
Relative Strength ◽  
Crustal Thickening ◽  
Weak Zone ◽  
Cross Sectional ◽  
Mantle Dynamics ◽  
Tectonic Style

Continental collision generally occurs after a protracted history of rifting, sedimentation, and subduction. Inherited material heterogeneities and thermal effects from terrane accretion and amalgamation may control subsequent collisional deformation. Such strength contrasts may have played an important role in the Silurian evolution of the Newfoundland Appalachians. A cross-sectional plane-strain numerical model is used to investigate the effect of a weak zone embedded between stronger model crust (the "vise") on the deformation style of orogens. In contrast to collision of uniform strong crust in which deformation is directly related to the underlying subduction of mantle lithosphere, deformation in vise models can propagate out to the ends of the vise in a diffuse manner. This distributed tectonic style depends on the relative strength of the embedded weak zone, the degree of coupling of this zone to underlying layers, and the effect of gravity acting on thickened crust. For weak coupling at the base of the crust, results are insensitive to the behaviour of the underlying model mantle (e.g., subduction, subduction retreat, or pure-shear thickening). Vise model results are in first-order agreement with the following characteristics of Newfoundland Silurian tectonics: (i) a diffuse deformation style distributed over a weak core zone more than 100 km wide, (ii) lack of indirect evidence of mantle dynamics from crustal reflectivity fabric, and (iii) lack of clear evidence for significant crustal thickening during orogeny.

scholarly journals PETROGRAFIA, GEOQUÍMICA E GEOCRONOLOGIA DO LEUCOGRANITO PERALUMINOSO DO COMPLEXO DE GOUVEIA-MG

2013 ◽  
Author(s):  
Alexandre de Oliveira Chaves ◽  
Raphael Martins Coelho
Keyword(s):  
Shear Zones ◽  
Continental Collision ◽  
Geochemical Characteristics ◽  
Amphibolite Facies ◽  
Crustal Thickening ◽  
High Grade ◽  
Mean Values

As características petrográficas e geoquímicas do leucogranito peraluminoso do Complexo de Gouveia (MG), sua relaçãogeológica a migmatitos deste complexo arqueano e a zonas de cisalhamento, bem como sua intensa milonitização, aproximam sua gêneseà dos granitos de ambiente de colisão continental ou da tectônica transcorrente a ela associada. Idades químicas U-Th-Pb em cristaishomogêneos de monazita inclusos em K-feldspato do leucogranito mostram valor médio em torno de 1811 +/- 32 Ma, que marca acristalização do magma leucogranítico derivado da anatexia dos migmatitos. Esta anatexia teria se dado em ambiente hidratado e emcondições de alto grau metamórfico (fácies anfibolito alto) atingidas em função do espessamento crustal e cisalhamentos regionaisrelacionados às fases sin- a tardi-colisionais do evento Transamazônico. Além disso, esta rocha foi submetida ao retrabalhamentoBrasiliano sob fácies xisto-verde, identificado pela cloritização da biotita e da granada e por processos de turmalinização. A monazitaassociada aos corpos tardios de turmalinitos apresenta idade química U-Th-Pb de 634 +/- 20 Ma.Palavras-chave: leucogranito peraluminoso, gouveia, tectônica colisional, transamazônico, brasiliano ABSTRACTThe petrographic and geochemical characteristics of the peraluminous leucogranite of the Gouveia Complex (MG), their association to migmatites of such archean complex and to shear zones and their intense mylonitization approach their genesis to thegranites of continental collision setting or linked transcurrent tectonics. U-Th-Pb chemical ages of 0monazite grains included in K-feldsparof the leucogranite show mean values around 1811 +/- 32 Ma, which reveal its magmatic crystallization from anatexis of the migmatites.The anatexis that generated the leucogranites has been given in hydrated environment and high-grade metamorphic conditions(amphibolite facies) reached during crustal thickening and regional shear related to the syn- to late-collisional phases of theTransamazonian event. However, this rock has been subjected to Brasiliano reworking under green-schist facies, identified by chloritizationof biotite and garnet and by tourmalinization processes. Monazite associated with late tourmalinite bodies has U-Th-Pb chemical age of634 +/- 20 Ma.Keywords: peraluminous leucogranite, gouveia, collisional tectonics, transamazonian, brasiliano.

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