Developing plate tectonics theory from oceanic subduction zones to collisional orogens

Science China-earth Sciences, Volume 58, Issue 7, 2015, Pages 1045-1069.

Cited by: 84|Views34
Weibo:
The first stage was evolved from continental drift, through seafloor spreading, to oceanic subduction, laying a physical foundation of the plate tectonics theory

Abstract:

Crustal subduction and continental collision is the core of plate tectonics theory. Understanding the formation and evolution of continental collision orogens is a key to develop the theory of plate tectonics. Different types of subduction zones have been categorized based on the nature of subducted crust. Two types of collisional orogens...More

Code:

Data:

0
Introduction
  • The plate tectonics theory is a geotectonic theory that was established in terms of studies on continental drift and seafloor spreading.
Highlights
  • The plate tectonics theory is a geotectonic theory that was established in terms of studies on continental drift and seafloor spreading
  • Some of them may be exhumed together with the ultrahigh pressure (UHP) metamorphic rocks to form orogenic peridotites, which can contain both the serpentinized and chloritized peridotites due to fluid alteration derived from dehydration of subducted continental crust, and olivine-poor mantle metasomatites such as hornblendite and pyroxenite due to melt metasomatism derived from anatexis of the subducted crustal rocks; (3) internal tectonic mélanges, composed of sediment cover, volcanics and underlying plutonic and metamorphic rocks that have been offscraped from the subducting slab, with minor amounts of peridotites offscraped from the bottom of the subcontinental lithospheric mantle (SCLM) wedge
  • For the crust-mantle interaction in oceanic subduction zones beneath continental margins and the resulted andesitic magmatism, it involves a series of subcontinental subduction channel processes in different stages and styles. This has been outlined by a SARSH model (Chen et al, 2014): (1) subduction: subduction of the oceanic crust with abundant trench sediments beneath continental margins, without significant dehydration at shallow forearc mantle depths (<60 km); (2) anatexis: dehydration melting of the subducting trench sediments and their underlying oceanic basalts at subarc depths (60–130 km) during eclogite- to granulite-facies metamorphism due to the heating of the overlying mantle wedge, producing felsic melts with enrichment of lithophile elements (LILE), Pb and LREE but depletion of high field strength elements (HFSE) and heavy rare earth elements (HREE); (3) reaction: the felsic melts would react with the overlying mantle wedge peridotite in the subcontinental subduction channel, generating heterogenous and fertile mantle metasomatites that are composed of ultramafic rocks like olivine-poor pyroxenite and hornblendite, and mafic rocks like garnet pyroxenite and garnet amphibolite; (4) storage: the mantle metasomatites are stored in the SCLM wedge for a while to keep stable without partial melting, and the timespan for the storage may vary from million years to hundred million years; (5) heating: by heating the bottom of the mantle wedge, the mantle metasomatites become partially melts to produce basalt-andesiterhyolitic volcanic assemblages with arc-type trace element distribution patterns inside orogens and overlying continental margins
  • The first stage was evolved from continental drift, through seafloor spreading, to oceanic subduction, laying a physical foundation of the plate tectonics theory
  • The second stage was evolved from oceanic subduction, through continental subduction, to collisional orogeny, with the recognition of continental deep subduction to mantle depths that is regarded as the first revolution of plate tectonics applied to continents
  • The deeply subducted oceanic crust was mainly submerged into the mantle, with minor brought back to the surface by mafic magmas, whereas deeply subducted continental crust underwent UHP metamorphism at mantle depths and was exhumed to the surface as coherent mélanges
Results
  • Some of them may be exhumed together with the UHP metamorphic rocks to form orogenic peridotites, which can contain both the serpentinized and chloritized peridotites due to fluid alteration derived from dehydration of subducted continental crust, and olivine-poor mantle metasomatites such as hornblendite and pyroxenite due to melt metasomatism derived from anatexis of the subducted crustal rocks; (3) internal tectonic mélanges, composed of sediment cover, volcanics and underlying plutonic and metamorphic rocks that have been offscraped from the subducting slab, with minor amounts of peridotites offscraped from the bottom of the SCLM wedge.
  • The thermal structure of subduction zones controls whether the subducted oceanic crust can release abundant fluids to metasomatize the mantle wedge at the subarc depths, and the key to the formation of island arc basalts is the generation of ultramafic mantle metasomatites with fertile and enriched geochemical compositions at the bottom of the mantle wedge.
  • This has been outlined by a SARSH model (Chen et al, 2014): (1) subduction: subduction of the oceanic crust with abundant trench sediments beneath continental margins, without significant dehydration at shallow forearc mantle depths (<60 km); (2) anatexis: dehydration melting of the subducting trench sediments and their underlying oceanic basalts at subarc depths (60–130 km) during eclogite- to granulite-facies metamorphism due to the heating of the overlying mantle wedge, producing felsic melts with enrichment of LILE, Pb and LREE but depletion of HFSE and HREE; (3) reaction: the felsic melts would react with the overlying mantle wedge peridotite in the subcontinental subduction channel, generating heterogenous and fertile mantle metasomatites that are composed of ultramafic rocks like olivine-poor pyroxenite and hornblendite, and mafic rocks like garnet pyroxenite and garnet amphibolite; (4) storage: the mantle metasomatites are stored in the SCLM wedge for a while to keep stable without partial melting, and the timespan for the storage may vary from million years to hundred million years; (5) heating: by heating the bottom of the mantle wedge, the mantle metasomatites become partially melts to produce basalt-andesiterhyolitic volcanic assemblages with arc-type trace element distribution patterns inside orogens and overlying continental margins.
  • The depletion of HFSE and HREE in arc volcanics can inherit from the metasomatic agents released from the subducting oceanic crust, rather than the result from the partial melting of subarc mantle wedge in the rutile and garnet stability fields.
Conclusion
  • These shed some new lights on developing the plate tectonics theory to encompass continental tectonics, and directing further study toward solutions to such questions as how thinning of the orogenic lithosphere and upwelling of the asthenospheric mantle affect postcollisional reworking of the intracontinental materials
Summary
  • The plate tectonics theory is a geotectonic theory that was established in terms of studies on continental drift and seafloor spreading.
  • Some of them may be exhumed together with the UHP metamorphic rocks to form orogenic peridotites, which can contain both the serpentinized and chloritized peridotites due to fluid alteration derived from dehydration of subducted continental crust, and olivine-poor mantle metasomatites such as hornblendite and pyroxenite due to melt metasomatism derived from anatexis of the subducted crustal rocks; (3) internal tectonic mélanges, composed of sediment cover, volcanics and underlying plutonic and metamorphic rocks that have been offscraped from the subducting slab, with minor amounts of peridotites offscraped from the bottom of the SCLM wedge.
  • The thermal structure of subduction zones controls whether the subducted oceanic crust can release abundant fluids to metasomatize the mantle wedge at the subarc depths, and the key to the formation of island arc basalts is the generation of ultramafic mantle metasomatites with fertile and enriched geochemical compositions at the bottom of the mantle wedge.
  • This has been outlined by a SARSH model (Chen et al, 2014): (1) subduction: subduction of the oceanic crust with abundant trench sediments beneath continental margins, without significant dehydration at shallow forearc mantle depths (<60 km); (2) anatexis: dehydration melting of the subducting trench sediments and their underlying oceanic basalts at subarc depths (60–130 km) during eclogite- to granulite-facies metamorphism due to the heating of the overlying mantle wedge, producing felsic melts with enrichment of LILE, Pb and LREE but depletion of HFSE and HREE; (3) reaction: the felsic melts would react with the overlying mantle wedge peridotite in the subcontinental subduction channel, generating heterogenous and fertile mantle metasomatites that are composed of ultramafic rocks like olivine-poor pyroxenite and hornblendite, and mafic rocks like garnet pyroxenite and garnet amphibolite; (4) storage: the mantle metasomatites are stored in the SCLM wedge for a while to keep stable without partial melting, and the timespan for the storage may vary from million years to hundred million years; (5) heating: by heating the bottom of the mantle wedge, the mantle metasomatites become partially melts to produce basalt-andesiterhyolitic volcanic assemblages with arc-type trace element distribution patterns inside orogens and overlying continental margins.
  • The depletion of HFSE and HREE in arc volcanics can inherit from the metasomatic agents released from the subducting oceanic crust, rather than the result from the partial melting of subarc mantle wedge in the rutile and garnet stability fields.
  • These shed some new lights on developing the plate tectonics theory to encompass continental tectonics, and directing further study toward solutions to such questions as how thinning of the orogenic lithosphere and upwelling of the asthenospheric mantle affect postcollisional reworking of the intracontinental materials
Funding
  • This study is supported by funds from the National Basic Research Program of China (Grant No 2015CB856100) and the National Natural Science Foundation of China (Grant No 41221062)
Reference
  • 212 Gao T S, Chen J F, Xie Z, Yan J, Qian H. 2004. Geochemistry of Triassic igneous complex at Shidao in the Sulu UHP metamorphic belt (in Chinese with English abstract). Acta Petrol Sin, 20: 1025–1038 Gao P, Zhao Z-F, Zheng Y-F. 2014. Petrogenesis of Triassic granites from the Nanling Range in South China: Implications for geochemical diversity in granites. Lithos, 210-211: 40–56 Gerya T V, Stöckhert B, Perchuk A L. 2002. Exhumation of high-pressure metamorphic rocks in a subduction channel: A numerical simulation. Tectonics, 21: 1056, doi: 10.1029/2002TC001406
    Findings
  • 424 Peacock S M, Wang K. 1999. Seismic consequences of warm versus cool subduction metamorphism: Examples from southwest and northeast Japan. Science, 286: 937–939 Plank T, Langmuir C H. 1998. The chemical composition of subducting sediment and its consequences for the crust and mantle. Chem Geol, 145: 325–394 Plank T. 2014. The Chemical composition of subducting sediments. Treatise Geochem, 4: 607–629 Platt J P. 1986. Dynamics of orogenic wedges and the uplift of high-pressure metamorphic rocks. Geol Soc Am Bull, 97: 1037–1053 Rubatto D, Hermann J. 2003. Zircon formation during fluid circulation in eclogites (Monviso, Western Alps): Implications for Zr and Hf budget in subduction zones. Geochim Cosmochim Acta, 67: 2173–2187 Rubatto D, Hermann J. 2007. Experimental zircon/melt and zircon/garnet trace element partitioning and implications for the geochronology of crustal rocks. Chem Geol 241, 62–87 Rudnick R L, Barth M G, Horn I, McDonough W F. 2000. Rutile-bearing refractory eclogites: Missing link between continents and depleted mantle. Science, 287: 278–281 Rudnick R L, Gao S. 2003. Composition of the continental crust. Treatise Geochem, 3: 1–64 Runcorn S K. 196Towards a theory of continental drift. Nature, 193: 313–314 Ryan P D, Mac Niocaill C. 1999. Continental tectonics: An introduction. Geol Soc Spec Publ, 164: 1–5 Ryerson F J, Watson E B. 1987. Rutile saturation in magmas: Implications for Ti-Nb-Ta depletion in island-arc basalts. Earth Planet Sci Lett, 86: 225–239 Schiano P, Clocchiatti R, Shimizu N, Maury R C, Jochum K P, Hofmann A W. 1995.
    Google ScholarLocate open access versionFindings
  • 101 Turner S, Caulfield J, Turner M, van Keken P, Maury R, Sandiford M, Prouteau G. 2011. Recent contribution of sediments and fluids to the mantle’s volatile budget. Nature Geosci, 5: 50–54 Uyeda S. 1982. Subduction zones: An introduction to comparative subductology. Tectonophysics, 81: 133–159 Uyeda S. 198Comparative subductology. Episodes, 5: 19–24 van Keken P E, Hacker B R, Syracuse E M, et al. 2011. Subduction factory: 4. Depth-dependent flux of H2O from subducting slabs worldwide. J Geophys Res, 116: B01401 van Westrenen W, Blundy J, Wood B. 1999. Crystal-chemical controls on trace element partitioning between garnet and anhydrous silicate melt. Am Mineral, 84: 838–847 Vine F J, Matthews D H. 1963. Magnetic anomalies over ocean ridges.
    Google ScholarLocate open access versionFindings
Your rating :
0

 

Tags
Comments