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Vlaha DR, Zuza AV, Chen L, Harlaux M. Hot Cordilleran hinterland promoted lower crust mobility and decoupling of Laramide deformation. Nat Commun 2024; 15:3750. [PMID: 38704380 PMCID: PMC11069518 DOI: 10.1038/s41467-024-48182-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Accepted: 04/23/2024] [Indexed: 05/06/2024] Open
Abstract
The Late Cretaceous to Paleogene Laramide orogen in the North American Cordillera involved deformation >1,000 km from the plate margin that has been attributed to either plate-boundary end loading or basal traction exerted on the upper plate from the subducted Farallon flat slab. Prevailing tectonic models fail to explain the relative absence of Laramide-aged (ca. 90-60 Ma) contractional deformation within the Cordillera hinterland. Based on Raman spectroscopy of carbonaceous material thermometry and literature data from the restored upper 15-20 km of the Cordilleran crust we reconstruct the Late Cretaceous thermal architecture of the hinterland. Interpolation of compiled temperature data (n = 200) through a vertical crustal column reveals that the hinterland experienced a continuous but regionally elevated, upper-crustal geothermal gradient of >40 °C/km during Laramide orogenesis, consistent with peak metamorphic conditions and synchronous peraluminous granitic plutonism. The hot and partially melted hinterland promoted lower crust mobility and crust-mantle decoupling during flat-slab traction.
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Affiliation(s)
- Dominik R Vlaha
- Nevada Bureau of Mines and Geology, University of Nevada, Reno, NV, USA.
- Department of Geological Sciences and Engineering, University of Nevada, Reno, NV, USA.
- Nevada Geosciences, University of Nevada, Reno, NV, USA.
| | - Andrew V Zuza
- Nevada Bureau of Mines and Geology, University of Nevada, Reno, NV, USA
- Nevada Geosciences, University of Nevada, Reno, NV, USA
| | - Lin Chen
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
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The Current Crustal Vertical Deformation Features of the Sichuan–Yunnan Region Constrained by Fusing the Leveling Data with the GNSS Data. REMOTE SENSING 2022. [DOI: 10.3390/rs14051139] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
This study uses the least squares collocation method to fuse the leveling vertical deformation velocity in the Sichuan–Yunnan region with the GNSS observations of this region from 320 stations in the China Crustal Movement Observation Network (CMONOC) and the China Continental Tectonic Environment Monitoring Network (CMTEMN) from 1999 to 2017. Such fusion is to improve the accuracy of the vertical deformation rates in large spatial scales. The fused vertical deformation results show that: (1) the fused deformation field has a uniform spatial distribution, and shows detailed change characteristics of key regions; (2) the current vertical crustal motion in this region is featured by the contemporaneous occurrence of crustal compression, shortening and uplift and basin extensional subsidence; (3) most areas in this region experience uplifts, as the lateral push of the Qinghai–Tibet Plateau was blocked by the Sichuan Basin. The areas on the northwest side of the Longmenshan fault and the Lijiang-Xiaojinhe fault are dominated by uplifts, with the velocity of 1.5 mm/a–5.5 mm/a, and the region on the southeast side has slight uplifts, with the velocity of 1.0 mm/a–1.5 mm/a; (4) many areas have high gradient vertical deformation, especially the region close to the Wenshan fault and on the two sides of the Yarlung Zangbo fault that has the value of 3.0–4.0 × 10−8/a, deserving further attention to be paid to the long-term earthquake hazards.
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The Hindu Kush slab break-off as revealed by deep structure and crustal deformation. Nat Commun 2021; 12:1685. [PMID: 33727553 PMCID: PMC7966371 DOI: 10.1038/s41467-021-21760-w] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Accepted: 02/04/2021] [Indexed: 11/24/2022] Open
Abstract
Break-off of part of the down-going plate during continental collision occurs due to tensile stresses built-up between the deep and shallow slab, for which buoyancy is increased because of continental-crust subduction. Break-off governs the subsequent orogenic evolution but real-time observations are rare as it happens over geologically short times. Here we present a finite-frequency tomography, based on jointly inverted local and remote earthquakes, for the Hindu Kush in Afghanistan, where slab break-off is ongoing. We interpret our results as crustal subduction on top of a northwards-subducting Indian lithospheric slab, whose penetration depth increases along-strike while thinning and steepening. This implies that break-off is propagating laterally and that the highest lithospheric stretching rates occur during the final pinching-off. In the Hindu Kush crust, earthquakes and geodetic data show a transition from focused to distributed deformation, which we relate to a variable degree of crust-mantle coupling presumably associated with break-off at depth. Here, the authors document active slab break-off and the crustal response during continental collision under the Hindu Kush, a rarely observed process since it happens over geologically short time spans.
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Lithospheric delamination and upwelling asthenosphere in the Longmenshan area: insight from teleseismic P-wave tomography. Sci Rep 2019; 9:6967. [PMID: 31061519 PMCID: PMC6503211 DOI: 10.1038/s41598-019-43476-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 04/25/2019] [Indexed: 11/22/2022] Open
Abstract
We apply teleseismic P-wave tomography to reconstruct the velocity structure of the Longmenshan area. Our results show possible large-scale delamination beneath the Songpan-Ganzi and Qiangtang terranes, which induced upwelling asthenosphere. Upwelling asthenosphere might have led to lower crust heating, facilitating eastward extrusion of the Songpan Ganzi terrane resulting in localized deformation and uplift along the Longmenshan orogenic belt. We suggest that the eastward extrusion of the Songpan-Ganzi terrane against the rigid lithospheric root of the Sichuan Basin results in stress accumulation and release, leading to large earthquakes in the Longmenshan area.
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Cao J, Shi Y, Zhang H, Wang H. Numerical simulation of GPS observed clockwise rotation around the eastern Himalayan syntax in the Tibetan Plateau. Sci Bull (Beijing) 2009. [DOI: 10.1007/s11434-008-0588-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Royden LH, Burchfiel BC, van der Hilst RD. The Geological Evolution of the Tibetan Plateau. Science 2008; 321:1054-8. [DOI: 10.1126/science.1155371] [Citation(s) in RCA: 1054] [Impact Index Per Article: 65.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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Cook KL, Royden LH. The role of crustal strength variations in shaping orogenic plateaus, with application to Tibet. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2007jb005457] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Kristen L. Cook
- Department of Earth, Atmospheric and Planetary Science; Massachusetts Institute of Technology; Cambridge Massachusetts USA
| | - Leigh H. Royden
- Department of Earth, Atmospheric and Planetary Science; Massachusetts Institute of Technology; Cambridge Massachusetts USA
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Medvedev S, Beaumont C. Growth of continental plateaus by channel injection: models designed to address constraints and thermomechanical consistency. ACTA ACUST UNITED AC 2006. [DOI: 10.1144/gsl.sp.2006.268.01.06] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AbstractWeak, possibly partially molten, middle crust may exist and deform by channel flow beneath continental plateaus, thereby significantly influencing their dynamics. The role of channel flows in the transition zone between the plateau and the foreland is, however, unclear. We develop successively more complete approximate models for the channel injection (CI) mode in which differential pressure pumps channel material from beneath the plateau into the transitional crust, which thickens it and widens the plateau. The motivation is to improve our understanding of the controls on the growth of continental plateaus and the interactions in the transition zone, and to gain more insight into the results of more complex numerical models. In model CI-1, a channel with constant viscosity and thickness exists in the transitional crust and the pumped material accretes/freezes above and below the channel. Although results compare favourably with the geometry of some natural examples, this model is incomplete because the connection between the transition zone and the plateau is not considered. Model CI-2 includes a decrease in channel viscosity when the channel depth exceeds a critical value, D*, a proxy for onset of melt weakening or low viscosities at high temperatures. The model completes the connection to the plateau, but relies on the arbitrary choice of D*. Model CI-3 is more physically based, and considers the channel viscosity and thickness to depend on temperature, calculated by an associated thermal model that includes radioactive self-heating, and advection of heat by channel material. This model demonstrates self-consistent plateau widening if the channel viscosity decreases at the critical temperature, T*. Acceptable comparisons with the topography of Tibet are achieved with transition zone viscosities that decrease from 1019−1022 Pa s to subplateau values of 1018–1019 Pa s, with T* of 700−750°C. Additional analyses and tests are used to determine the range of parameter values for which CI models are both internally consistent and compatible with observations. Additional modes of deformation in the transition zone, viscous thickening (VT) and plastic translation (PT), may also be important.
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Affiliation(s)
- S. Medvedev
- Department of Oceanography, Dalhousie University
Halifax, NS, B3H4J1 Canada
- Fachrichtung Geologie, Freie Universität Berlin
Malteserstrasse 74-100, Berlin, 12249 Germany
- Physics of Geological Processes, University of Oslo
PO Box 1048 Blindern, 0316 Oslo, Norway
| | - C. Beaumont
- Department of Oceanography, Dalhousie University
Halifax, NS, B3H4J1 Canada
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Abstract
AbstractCrustal-scale channel flow numerical models support recent interpretations of Himalayan—Tibetan tectonics proposing that gravitationally driven channel flows of low-viscosity, melt-weakened, middle crust can explain both outward growth of the Tibetan Plateau and ductile extrusion of the Greater Himalayan Sequence. We broaden the numerical model investigation to explore three flow modes: homogeneous channel flow (involving laterally homogeneous crust); heterogeneous channel flow (involving laterally heterogeneous lower crust that is expelled and incorporated into the mid-crustal channel flow); and the hot fold nappes style of flow (in which mid-/lower crust is forcibly expelled outward over a lower crustal indentor to create fold nappes that are inserted into the mid-crust). The three flow modes are members of a continuum in which the homogeneous mode is driven by gravitational forces but requires very weak channel material. The hot fold nappe mode is driven tectonically by, for example, collision with a strong crustal indentor and can occur in crust that is subcritical for homogeneous flows. The heterogeneous mode combines tectonic and gravitationally driven flows. Preliminary results also demonstrate the existence and behaviour of mid-crustal channels during advancing and retreating dynamical mantle lithosphere subduction. An orogen temperature—magnitude (T-M) diagram is proposed and the positions of orogens in T-M space that may exhibit the flow modes are described, together with the characteristic positions of a range of other orogen types.
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Affiliation(s)
- C. Beaumont
- Oceanography Department, Dalhousie University
Halifax, Nova Scotia, Canada B3H 4J1
| | - M. H. Nguyen
- Oceanography Department, Dalhousie University
Halifax, Nova Scotia, Canada B3H 4J1
- Department of Earth Sciences, Dalhousie University
Halifax, Nova Scotia, Canada B3H 3J5
| | - R. A. Jamieson
- Department of Earth Sciences, Dalhousie University
Halifax, Nova Scotia, Canada B3H 3J5
| | - S. Ellis
- Institute for Geological and Nuclear Sciences
Lower Hutt, New Zealand
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Godin L, Grujic D, Law RD, Searle MP. Channel flow, ductile extrusion and exhumation in continental collision zones: an introduction. ACTA ACUST UNITED AC 2006. [DOI: 10.1144/gsl.sp.2006.268.01.01] [Citation(s) in RCA: 212] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AbstractThe channel flow model aims to explain features common to metamorphic hinterlands of some collisional orogens, notably along the Himalaya-Tibet system. Channel flow describes a protracted flow of a weak, viscous crustal layer between relatively rigid yet deformable bounding crustal slabs. Once a critical low viscosity is attained (due to partial melting), the weak layer flows laterally due to a horizontal gradient in lithostatic pressure. In the Himalaya-Tibet system, this lithostatic pressure gradient is created by the high crustal thicknesses beneath the Tibetan Plateau and ‘normal’ crustal thickness in the foreland. Focused denudation can result in exhumation of the channel material within a narrow, nearly symmetric zone. If channel flow is operating at the same time as focused denudation, this can result in extrusion of the mid-crust between an upper normal-sense boundary and a lower thrust-sense boundary. The bounding shear zones of the extruding channel may have opposite shear sense; the sole shear zone is always a thrust, while the roof shear zone may display normal or thrust sense, depending on the relative velocity between the upper crust and the underlying extruding material. This introductory chapter addresses the historical, theoretical, geological and modelling aspects of channel flow, emphasizing its applicability to the Himalaya-Tibet orogen. Critical tests for channel flow in the Himalaya, and possible applications to other orogenic belts, are also presented.
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Affiliation(s)
- L. Godin
- Department of Geological Sciences & Geological Engineering, Queen’s University
Kingston, Ontario, K7L 3N6, Canada
| | - D. Grujic
- Department of Earth Sciences, Dalhousie University
Halifax, Nova Scotia, B3H 4J1, Canada
| | - R. D. Law
- Department of Geological Sciences, Virginia Tech.
Blacksburg, VA 24061, USA
| | - M. P. Searle
- Department of Earth Sciences, Oxford University
Oxford, OX1 3PR, UK
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11
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Dimanov A. Rheology of synthetic anorthite-diopside aggregates: Implications for ductile shear zones. ACTA ACUST UNITED AC 2005. [DOI: 10.1029/2004jb003431] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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12
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Kapp JLD. Nyainqentanglha Shan: A window into the tectonic, thermal, and geochemical evolution of the Lhasa block, southern Tibet. ACTA ACUST UNITED AC 2005. [DOI: 10.1029/2004jb003330] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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13
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Jamieson RA, Beaumont C, Medvedev S, Nguyen MH. Crustal channel flows: 2. Numerical models with implications for metamorphism in the Himalayan-Tibetan orogen. ACTA ACUST UNITED AC 2004. [DOI: 10.1029/2003jb002811] [Citation(s) in RCA: 273] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Rebecca A. Jamieson
- Department of Earth Sciences; Dalhousie University; Halifax, Nova Scotia Canada
| | | | - Sergei Medvedev
- Department of Oceanography; Dalhousie University; Halifax, Nova Scotia Canada
| | - Mai H. Nguyen
- Department of Earth Sciences; Dalhousie University; Halifax, Nova Scotia Canada
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Beaumont C, Jamieson RA, Nguyen MH, Medvedev S. Crustal channel flows: 1. Numerical models with applications to the tectonics of the Himalayan-Tibetan orogen. ACTA ACUST UNITED AC 2004. [DOI: 10.1029/2003jb002809] [Citation(s) in RCA: 459] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
| | - Rebecca A. Jamieson
- Department of Earth Sciences; Dalhousie University; Halifax Nova Scotia Canada
| | - Mai H. Nguyen
- Department of Oceanography; Dalhousie University; Halifax Nova Scotia Canada
| | - Sergei Medvedev
- Department of Oceanography; Dalhousie University; Halifax Nova Scotia Canada
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Dupont-Nivet G, Horton BK, Butler RF, Wang J, Zhou J, Waanders GL. Paleogene clockwise tectonic rotation of the Xining-Lanzhou region, northeastern Tibetan Plateau. ACTA ACUST UNITED AC 2004. [DOI: 10.1029/2003jb002620] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- G. Dupont-Nivet
- Department of Earth and Space Sciences; University of California; Los Angeles California USA
| | - B. K. Horton
- Department of Earth and Space Sciences; University of California; Los Angeles California USA
| | - R. F. Butler
- Department of Geosciences; University of Arizona; Tucson Arizona USA
| | - J. Wang
- Institute of Geochemistry; Chinese Academy of Sciences; Guangzhou China
| | - J. Zhou
- Faculty of Earth Sciences; China University of Geosciences; Wuhan China
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Hilley GE, Strecker MR. Steady state erosion of critical Coulomb wedges with applications to Taiwan and the Himalaya. ACTA ACUST UNITED AC 2004. [DOI: 10.1029/2002jb002284] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- G. E. Hilley
- Institut für Geowissenschaften; Universität Potsdam; Potsdam Germany
| | - M. R. Strecker
- Institut für Geowissenschaften; Universität Potsdam; Potsdam Germany
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17
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Kastrup U, Zoback ML, Deichmann N, Evans KF, Giardini D, Michael AJ. Stress field variations in the Swiss Alps and the northern Alpine foreland derived from inversion of fault plane solutions. ACTA ACUST UNITED AC 2004. [DOI: 10.1029/2003jb002550] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Ulrike Kastrup
- Institute of Geophysics, ETH-Hönggerberg; Zürich Switzerland
| | - Mary Lou Zoback
- Western Region Earthquake Hazard Team, U.S. Geological Survey; Menlo Park California USA
| | | | - Keith F. Evans
- Institute of Geophysics, ETH-Hönggerberg; Zürich Switzerland
| | | | - Andrew J. Michael
- Western Region Earthquake Hazard Team, U.S. Geological Survey; Menlo Park California USA
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Cowgill E, Yin A, Harrison TM, Xiao-Feng W. Reconstruction of the Altyn Tagh fault based on U-Pb geochronology: Role of back thrusts, mantle sutures, and heterogeneous crustal strength in forming the Tibetan Plateau. ACTA ACUST UNITED AC 2003. [DOI: 10.1029/2002jb002080] [Citation(s) in RCA: 230] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Eric Cowgill
- Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics; University of California; Los Angeles California USA
| | - An Yin
- Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics; University of California; Los Angeles California USA
| | - T. Mark Harrison
- Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics; University of California; Los Angeles California USA
| | - Wang Xiao-Feng
- Institute of Geomechanics; Chinese Academy of Geological Sciences; Beijing China
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19
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Sobel ER, Hilley GE, Strecker MR. Formation of internally drained contractional basins by aridity-limited bedrock incision. ACTA ACUST UNITED AC 2003. [DOI: 10.1029/2002jb001883] [Citation(s) in RCA: 196] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Edward R. Sobel
- Institut für Geowissenschaften; Universität Potsdam; Potsdam Germany
| | - George E. Hilley
- Institut für Geowissenschaften; Universität Potsdam; Potsdam Germany
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20
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Klepeis KA, Clarke GL, Rushmer T. Magma transport and coupling between deformation and magmatism in the continental lithosphere. ACTA ACUST UNITED AC 2003. [DOI: 10.1130/1052-5173(2003)013<0004:mtacbd>2.0.co;2] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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21
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Liu M. Extensional collapse of the Tibetan Plateau: Results of three-dimensional finite element modeling. ACTA ACUST UNITED AC 2003. [DOI: 10.1029/2002jb002248] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Affiliation(s)
- Susan L. Beck
- Department of Geosicences and Southern Arizona Seismological Observatory; University of Arizona; Tucson Arizona USA
| | - George Zandt
- Department of Geosicences and Southern Arizona Seismological Observatory; University of Arizona; Tucson Arizona USA
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23
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Medvedev S. Mechanics of viscous wedges: Modeling by analytical and numerical approaches. ACTA ACUST UNITED AC 2002. [DOI: 10.1029/2001jb000145] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Abstract
AbstractThe tectonic evolution of Archaean granite-greenstone terranes remains controversial. Here this subject is reviewed and illustrated with new data from the Slave craton. These data show that a thick, c. 2.7Ga, pillow basalt sequences extruded across extended sialic basement of the Slave craton at a scale comparable with that of modern large igneous provinces. The pillow basalts do not represent obducted oceanic allochthons. Basement-cover relationships argue for autochthonous to parautochthonous development of the basaltic greenstone belts of the west-central Slave craton, an interpretation that is further supported by geochemical and geochronological data. Similar data exist for several other cratons and granite-greenstone terrains, including the Abitibi greenstone belt of the Superior craton, where stratigraphic and subtle zircon inheritance data are equally incompatible with accretion of oceanic allochthons. Many classical granite-greenstone terrains, including most well-documented komatiite occurrences, thus appear to have formed in extensional environments within or on the margins of older continental crust. Closest modern analogues for such basalt-komatiite-rhyolite-dominated greenstone successions are rifts, marginal basins and volcanic rifted margins. Indeed, these environments have high preservation potential compared with fully oceanic settings. Collapse and structural telescoping of these highly extended volcano-sedimentary basins would allow for the complex structural development seen in granite-greenstone terrains while maintaining broadly autochthonous to parautochthonous tectonostratigraphic relationships. Seismic reflection profiles cannot discriminate between these telescoped autochthonous to parautochthonous settings and truly allochthonous accretionary complexes. Only carefully constructed structural-stratigraphic cross-sections, allowing some degree of palinspastic reconstruction, and underpinned by sufficient U-Pb zircon dating, can address the degree of allochthoneity of greenstone packages. Furthermore, seismic reflection profiles are essentially blind for the steep structures produced by multiple phases of upright folding and buoyant rise of mid- to lower-crustal, composite, granitoid and gneiss domes. Such structures are ubiquitous in granite-greenstone terrains and, indeed, most of these terrains appear to have experienced at least one phase of convective overturn to re-establish a stable density configuration, irrespective of the complexities of the pre-doming structural history. Buoyant rise of mid- to lower-crustal granitoid and gneiss domes can explain the typical size and spacing characteristics of such domes in granite-greenstone terranes, and the coeval deposition of late-kinematic, ‘Timiskaming-type’ conglomerate-sandstone successions in flanking basins. The extensional and subsequent contractional evolution of granite-greenstone terrains may have occurred in the overall context of a plate tectonic regime (e.g. volcanic rifted margins, back-arc basins) but highly extended, intraplate, rift-like settings seem equally plausible. Explaining the evolution of the latter in terms of Wilson cycles is misguided. Periods of intense rifting and flood volcanism (e.g. 2.73–2.70 Ga) may have been related to increased mantle plume activity or perhaps catastrophic mantle overturn events. Although there is evidence for plate-like lateral movement in late Archaean time (e.g. lateral heterogeneity of cratons, arc-like volcanism, cratonscale deformation patterns, strike-slip faults, etc.), the details of how these plate-like crustal blocks interacted and how they responded to rifting and collision appear to have differed significantly from those in Phanerozoic time. The most productive approach for Archaean research is probably to more fully understand and quantify these differences rather than the common emphasis on the superficial similarities with modern plate tectonics.
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Affiliation(s)
- Wouter Bleeker
- Continental Geoscience Division, Geological Survey of Canada
601 Booth Street, Ottawa, Ontario K1A 0E8, Canada
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25
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Beaumont C, Jamieson RA, Nguyen MH, Lee B. Himalayan tectonics explained by extrusion of a low-viscosity crustal channel coupled to focused surface denudation. Nature 2001; 414:738-42. [PMID: 11742396 DOI: 10.1038/414738a] [Citation(s) in RCA: 1189] [Impact Index Per Article: 51.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Recent interpretations of Himalayan-Tibetan tectonics have proposed that channel flow in the middle to lower crust can explain outward growth of the Tibetan plateau, and that ductile extrusion of high-grade metamorphic rocks between coeval normal- and thrust-sense shear zones can explain exhumation of the Greater Himalayan sequence. Here we use coupled thermal-mechanical numerical models to show that these two processes-channel flow and ductile extrusion-may be dynamically linked through the effects of surface denudation focused at the edge of a plateau that is underlain by low-viscosity material. Our models provide an internally self-consistent explanation for many observed features of the Himalayan-Tibetan system.
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Affiliation(s)
- C Beaumont
- Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, Canada, B3H 4J1
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26
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Shen F, Royden LH, Burchfiel BC. Large-scale crustal deformation of the Tibetan Plateau. ACTA ACUST UNITED AC 2001. [DOI: 10.1029/2000jb900389] [Citation(s) in RCA: 192] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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27
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Abstract
The crustal remnants of Earth's Archean continents have been shielded from mantle convection by thick roots of ancient mantle lithosphere. The precise time of crust-root coupling (tectosphere birth) is poorly known but is needed to test competing theories of continental plate genesis. Our mapping and geochronology of an impact-generated section through the Mesoarchean crust of the Kaapvaal craton indicates tectosphere birth at 3.08 +/- 0.01 billion years ago, roughly 0.12 billion years after crust assembly. Growth of the southern African mantle root by subduction processes occurred within about 0.2 billion years. The assembly of crust before mantle may be common to the tectosphere.
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Affiliation(s)
- D E Moser
- Geology and Geophysics Department, University of Utah, 135S 1460E, Salt Lake City, UT 84112-0111, USA.
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Royden LH, Burchfiel BC, King RW, Wang E, Chen Z, Shen F, Liu Y. Surface Deformation and Lower Crustal Flow in Eastern Tibet. Science 1997; 276:788-90. [PMID: 9115202 DOI: 10.1126/science.276.5313.788] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Field observations and satellite geodesy indicate that little crustal shortening has occurred along the central to southern margin of the eastern Tibetan plateau since about 4 million years ago. Instead, central eastern Tibet has been nearly stationary relative to southeastern China, southeastern Tibet has rotated clockwise without major crustal shortening, and the crust along portions of the eastern plateau margin has been extended. Modeling suggests that these phenomena are the result of continental convergence where the lower crust is so weak that upper crustal deformation is decoupled from the motion of the underlying mantle. This model also predicts east-west extension on the high plateau without convective removal of Tibetan lithosphere and without eastward movement of the crust east of the plateau.
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Affiliation(s)
- LH Royden
- L. H. Royden, B. C. Burchfiel, R. W. King, E. Wang, Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. Z. Chen, F. Shen, Y. Liu, Chengdu Institute of Geology and Mineral Resources, Chengdu, China
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