Juxtaposition of Barrovian and migmatite domains in the Chinese Altai: a result of crustal thickening followed by doming of partially molten lower crust

2014 ◽  
Vol 33 (1) ◽  
pp. 45-70 ◽  
Author(s):  
Y. D. Jiang ◽  
P. Štípská ◽  
M. Sun ◽  
K. Schulmann ◽  
J. Zhang ◽  
...  
Keyword(s):  
Lower Crust ◽  
Crustal Thickening

scholarly journals Transversely isotropic lower crust of Variscan central Europe imaged by ambient noise tomography of the Bohemian Massif

Solid Earth ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 1051-1074
Author(s):  
Jiří Kvapil ◽  
Jaroslava Plomerová ◽  
Hana Kampfová Exnerová ◽  
Vladislav Babuška ◽  
György Hetényi ◽  
...  
Keyword(s):  
Bohemian Massif ◽  
Lower Crust ◽  
Ambient Noise ◽  
Regional Scale ◽  
Crustal Thickening ◽  
Scale Model ◽  
Significant Feature ◽  
Ambient Noise Tomography ◽  
North East ◽  
The North

Abstract. The recent development of ambient noise tomography, in combination with the increasing number of permanent seismic stations and dense networks of temporary stations operated during passive seismic experiments, provides a unique opportunity to build the first high-resolution 3-D shear wave velocity (vS) model of the entire crust of the Bohemian Massif (BM). This paper provides a regional-scale model of velocity distribution in the BM crust. The velocity model with a cell size of 22 km is built using a conventional two-step inversion approach from Rayleigh wave group velocity dispersion curves measured at more than 400 stations. The shear velocities within the upper crust of the BM are ∼0.2 km s−1 higher than those in its surroundings. The highest crustal velocities appear in its southern part, the Moldanubian unit. The Cadomian part of the region has a thinner crust, whereas the crust assembled, or tectonically transformed in the Variscan period, is thicker. The sharp Moho discontinuity preserves traces of its dynamic development expressed in remnants of Variscan subductions imprinted in bands of crustal thickening. A significant feature of the presented model is the velocity-drop interface (VDI) modelled in the lower part of the crust. We explain this feature by the anisotropic fabric of the lower crust, which is characterised as vertical transverse isotropy with the low velocity being the symmetry axis. The VDI is often interrupted around the boundaries of the crustal units, usually above locally increased velocities in the lowermost crust. Due to the north-west–south-east shortening of the crust and the late-Variscan strike-slip movements along the north-east–south-west oriented sutures preserved in the BM lithosphere, the anisotropic fabric of the lower crust was partly or fully erased along the boundaries of original microplates. These weakened zones accompanied by a velocity increase above the Moho (which indicate an emplacement of mantle rocks into the lower crust) can represent channels through which portions of subducted and later molten rocks have percolated upwards providing magma to subsequently form granitoid plutons.

scholarly journals Calculation of temperature distribution and rheological properties of the lithosphere along transect IV in the Western Carpathian-Pannonian Basin region

2019 ◽  
Vol 49 (4) ◽  
pp. 497-510
Author(s):  
Jana Dérerová ◽  
Miroslav Bielik ◽  
Igor Kohút ◽  
Dominika Godová
Keyword(s):  
Temperature Distribution ◽  
Lower Crust ◽  
Pannonian Basin ◽  
Strength Distribution ◽  
Crustal Thickening ◽  
Western Carpathians ◽  
Integrated Modelling ◽  
Rheological Parameters ◽  
Upper Crust ◽  
Rigid Deformation

Abstract 2D integrated modelling algorithm was used to calculate the temperature distribution in the lithosphere along the transect IV located in the Western Carpathian-Pannonian Basin area. Based on the determined temperature field and given rheological parameters of the rocks, it was possible to calculate the strength distribution for both compressional and extensional regimes, construct the strength envelopes for chosen columns of the main tectonic units of the model, and thus construct a simple rheological model of the lithosphere along transect IV. The obtained results indicate decrease of the lithospheric strength from the European platform and the Western Carpathians towards the Pannonian Basin. The largest strength (valid for all tectonic units) can be observed within the upper crust with its maxima on the boundary between upper and lower crust, decreasing towards lower crust and disappearing in the lithospheric mantle, suggesting mostly rigid deformation occurring in the upper crust. A local increase in the values of strength can be observed in the eastern segment of the Western Carpathians where crustal thickening accompanies the lithospheric thickening (formation of the lithospheric root), unlike the previous models along transects I and II, that pass through the western segment of the Western Carpathians and their lithosphere-asthenosphere boundary is almost flat and therefore no accompanying crustal thickening is observed and the decrease in strength is slow and steady.

Petrogenesis of Archaean granites in the Barberton region of South Africa as a guide to early crustal evolution

2021 ◽  
Vol 124 (1) ◽  
pp. 111-140
Author(s):  
L.J. Robb ◽  
F.M. Meyer ◽  
C.J. Hawkesworth ◽  
N.J. Gardiner
Keyword(s):  
South Africa ◽  
Continental Crust ◽  
Lower Crust ◽  
Plate Tectonics ◽  
Sedimentary Basins ◽  
Crustal Thickening ◽  
Gravity Inversion ◽  
Crustal Evolution ◽  
Broad Variety ◽  
Parallel Arrays

ABSTRACT The Barberton region of South Africa is characterized by a broad variety of granite types that range in age from ca. 3.5 Ga to 2.7 Ga and reflect the processes involved in the formation of Archaean continental crust on the Kaapvaal Craton. These granites are subdivided into three groups, as follows: A tonalite-trondhjemite-granodiorite (TTG) suite diapirically emplaced at 3 450 Ma and 3 250 Ma into pre-existing metamorphosed greenstone belt material. TTG melts were derived from melting amphibolite in the lower crust, with individual plutons being emplaced at various crustal levels. The dome-and-keel geometry that characterizes the TTG-greenstone dominated crust at this time is inconsistent with a plate tectonic domain and reworking was likely controlled by gravity inversion or ‘sagduction’; Regionally extensive potassic batholiths (the GMS suite) were emplaced at 3 110 Ma during a period of crustal thickening and melting of a TTG-dominated lower crust. Subsequent to emplacement of the voluminous GMS granites, the thickened continental crust had stabilized sufficiently for large sedimentary basins to form; Late granite plutons were emplaced along two distinct linear and sub-parallel arrays close to what might have been the edge of a Kaapvaal continent at 2 800 to 2 700 Ma. They are subdivided into high-Ca and low-Ca granites that resemble the I- and S-type granites of younger orogenic episodes. The high-Ca granites are consistent with derivation from older granitoids in the lower crust, whereas the low-Ca granites may have been derived by melting metasedimentary precursors in the lower-mid crust. Granites with similar characteristics are associated with a subduction zone in younger terranes, although the recognition of such a feature at Barberton remains unclear. The petrogenesis of granites in the Barberton region between 3.5 Ga and 2.7 Ga provides a record of the processes of Archaean crustal evolution and contributes to discussions related to the onset of plate tectonics.

scholarly journals Post-collisional crustal thickening and plateau uplift of southern Tibet: Insights from Cenozoic magmatism in the Wuyu area of the eastern Lhasa block

2020 ◽  
Author(s):  
Lu-Lu Hao ◽  
Qiang Wang ◽  
Andrew C. Kerr ◽  
Jin-Hui Yang ◽  
Lin Ma ◽  
...  
Keyword(s):  
Lower Crust ◽  
Temporal Distribution ◽  
Crustal Thickening ◽  
Indian Plate ◽  
Hf Isotopes ◽  
Southern Tibet ◽  
Tectonic Model ◽  
Surface Uplift ◽  
Thin Crust ◽  
Cenozoic Magmatism

The nature and timing of post-collisional crustal thickening and its link to surface uplift in the eastern Lhasa block of the southern Tibetan plateau remain controversial. Here we report on Cenozoic magmatism in the Wuyu area of the eastern Lhasa block. The Eocene (ca. 46 Ma) trachyandesites and trachydacites show slight fractionation of rare earth elements (REE), slightly negative Eu and Sr anomalies, and relatively homogeneous Sr-Nd and zircon Hf isotopes (87Sr/86Sr(i) = 0.7050−0.7063, εNd(t) = −0.92 to −0.03, εHf(t) = +2.6 to +4.8). Previous studies have suggested Neo-Tethys oceanic slab break-off at 50−45 Ma; thus, the Wuyu Eocene magmatism could represent a magmatic response to this slab break-off and originate from relatively juvenile Lhasa crust. The Miocene (ca. 15−12 Ma) dacites and rhyolites have adakitic affinities, e.g., high Sr (average 588 ppm), Sr/Y (29−136), and La/Yb (30−76) values, low Y (4−12 ppm) and Yb (0.4−0.9 ppm) contents, and variable Sr-Nd and zircon Hf isotopes (87Sr/86Sr(i) = 0.7064−0.7142, εNd(t) = −11.7 to −3.7, εHf(t) = −3.2 to +4.5). Their more enriched Sr-Nd-Hf isotopes relative to the Eocene lavas indicate that they should be derived from mixed Lhasa lower crust comprising juvenile crust, ultrapotassic rocks, and probably Indian lower crust-derived rocks. This study has also revealed the transformation from Eocene juvenile and thin crust with a thickness of <40 km to Miocene mixed and thickened crust with a thickness of >50 km. Combined with published tectonic data, we suggest that both lithospheric shortening and magma underplating contributed to eastern Lhasa block post-collisional crustal thickening. Given the spatial-temporal distribution of eastern Lhasa block magmatism and regional geology, we invoke a post-collisional tectonic model of steep subduction of the Indian plate and subsequent westward-propagating plate break-off beneath the eastern Lhasa block, which caused the surface uplift.

scholarly journals Vertical strain partitioning in hot Variscan crust: Syn-convergence escape of the Pyrenees in the Iberian-Armorican syntax

2017 ◽  
Vol 188 (6) ◽  
pp. 39 ◽  
Author(s):  
Bryan Cochelin ◽  
Dominique Chardon ◽  
Yoann Denèle ◽  
Charles Gumiaux ◽  
Benjamin Le Bayon
Keyword(s):  
Lower Crust ◽  
Shear Zones ◽  
Crustal Thickening ◽  
Upper Crust ◽  
Strain Partitioning ◽  
Kinematic Data ◽  
Mechanical Coupling ◽  
Gneiss Domes ◽  
Lateral Escape ◽  
Lower Crustal

A new structural map of the Paleozoic crust of the Pyrenees based on an extensive compilation and new kinematic data allows for the evaluation of the mechanical coupling between the upper and lower crust of the abnormally hot foreland of the Variscan orogen of SW Europe. We document partitioning between coeval lower crustal lateral flow and upper crustal thickening between 310 and 290 Ma under an overall dextral transpressive regime. Partitioning also involved syn-convergence transtensional gneiss domes emplacement during this period. Late orogen-normal shortening of the domes and strain localization in steep crustal-scale transpressive shear zones reflects increasing coupling between the lower crust and the upper crust. The combination of dextral transpression and eastward flow in the Pyrenees results from the shortening and lateral escape of a hot buoyant crust along the inner northern limb of the closing Cantabrian orocline at the core of the Iberian-Armorican arc between ca. 305 and 295 Ma. Delamination or thermal erosion of the lithosphere enhanced orocline closure and explains (1) the switch from crust- to mantle-derived magmatism in the Iberian-Armorican arc and (2) the abnormally hot and soft character of the Pyrenean crust that escaped the closing syntax.

Generation of the Early Cenozoic adakitic volcanism by partial melting of mafic lower crust, Eastern Turkey: Implications for crustal thickening to delamination

Lithos ◽  
2010 ◽  
Vol 114 (1-2) ◽  
pp. 109-120 ◽  
Author(s):  
Orhan Karsli ◽  
Abdurrahman Dokuz ◽  
İbrahim Uysal ◽  
Faruk Aydin ◽  
Raif Kandemir ◽  
...  
Keyword(s):  
Partial Melting ◽  
Lower Crust ◽  
Crustal Thickening ◽  
Eastern Turkey ◽  
Mafic Lower Crust ◽  
Early Cenozoic

scholarly journals Cenozoic uplift of the Central Andes in northern Chile and Bolivia—reconciling paleoaltimetry with the geological evolution

2016 ◽  
Vol 53 (11) ◽  
pp. 1227-1245 ◽  
Author(s):  
Simon Lamb
Keyword(s):  
Lower Crust ◽  
Central Andes ◽  
Crustal Thickening ◽  
Direct Result ◽  
Western Margin ◽  
Crustal Shortening ◽  
Eastern Cordillera ◽  
Surface Uplift ◽  
Geological Evolution ◽  
History Of

The Cenozoic geological evolution of the Central Andes, along two transects between ∼17.5°S and 21°S, is compared with paleo-topography, determined from published paleo-altimetry studies. Surface and rock uplift are quantified using simple 2-D models of crustal shortening and thickening, together with estimates of sedimentation, erosion, and magmatic addition. Prior to ∼25 Ma, during a phase of amagmatic flat-slab subduction, thick-skinned crustal shortening and thickening (nominal age of initiation ∼40 Ma) was focused in the Eastern and Western Cordilleras, separated by a broad basin up to 300 km wide and close to sea level, which today comprises the high Altiplano. Surface topography at this time in the Altiplano and the western margin of the Eastern Cordillera appears to be ∼1 km lower than anticipated from crustal thickening, which may be due to the pull-down effect of the subducted slab, coupled to the overlying lithosphere by a cold mantle wedge. Oligocene steepening of the subducted slab is indicated by the initiation of the volcanic arc at ∼27–25 Ma, and widespread mafic volcanism in the Altiplano between 25 and 20 Ma. This may have resulted in detachment of mantle lithosphere and possibly dense lower crust, triggering 1–1.5 km of rapid uplift (over ≪5 Myrs) of the Altiplano and western margin of the Eastern Cordillera and establishing the present day lithospheric structure beneath the high Andes. Since ∼25 Ma, surface uplift has been the direct result of crustal shortening and thickening, locally modified by the effects of erosion, sedimentation, and magmatic addition from the mantle. The rate of crustal shortening and thickening varies with location and time, with two episodes of rapid shortening in the Altiplano, lasting <5 Myrs, that are superimposed on a long-term history of ductile shortening in the lower crust, driven by underthrusting of the Brazilian Shield on the eastern margin.

Crustal thickening prior to 38Ma in southern Tibet: Evidence from lower crust-derived adakitic magmatism in the Gangdese Batholith

2012 ◽  
Vol 21 (1) ◽  
pp. 88-99 ◽  
Author(s):  
Qi Guan ◽  
Di-Cheng Zhu ◽  
Zhi-Dan Zhao ◽  
Guo-Chen Dong ◽  
Liang-Liang Zhang ◽  
...  
Keyword(s):  
Lower Crust ◽  
Crustal Thickening ◽  
Southern Tibet

Crustal thickening prior to 43 Ma in the Himalaya: Evidence from lower crust‐derived adakitic magmatism in Dala, eastern Tethyan Himalaya, Tibet

2019 ◽  
Vol 55 (5) ◽  
pp. 4021-4046 ◽  
Author(s):  
Zuowen Dai ◽  
Lei Dong ◽  
Guangming Li ◽  
Jan Marten Huizenga ◽  
Jun Ding ◽  
...  
Keyword(s):  
Lower Crust ◽  
Crustal Thickening ◽  
The Himalaya ◽  
Tethyan Himalaya
Sign in / Sign up

Export Citation Format

Share Document