地壳放射性生热效应对大陆俯冲过程影响的数值模拟研究
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摘要
岩体中的放射性生热是地幔对流和地壳变质作用的关键热源之一,但地壳放射性生热率是如何影响大陆俯冲-碰撞的动力学过程,尤其是大陆碰撞区域的热结构演化,尚未获得共识。本文使用热-力学数值模拟方法对上、下地壳放射性生热率进行系统的模拟实验,以研究其对大陆俯冲动力学演化过程的影响。模型实验表明,由于大陆上地壳富集U、Th和K等主要放射性生热元素,且放射性生热率的变化区间较大(1.0~3.0μW/m~3),导致其对大陆俯冲碰撞动力学演化过程的影响较为显著,主要包括进入俯冲通道内的上地壳体积大小、碰撞区域内地壳熔融范围、俯冲下地壳物质折返的规模和两大陆的耦合程度等四个方面。而大陆下地壳则以中-基性岩为主,相对亏损U、Th、K等主要放射性生热元素,且放射性生热率的变化区域较小(0.2~0.8μW/m~3),致使其对大陆俯冲演化过程的影响相对有限,主要通过控制俯冲下地壳以及大陆板片的粘滞度和流变强度的大小,进而制约大陆俯冲过程下地壳物质折返的规模以及板片倾角的大小。
Radiogenic heat production is a key energy source for convection in the Earth's mantle and for metamorphic reactions in the continental crust. However, its effects on continental subduction remain a poorly resolved aspect of plate tectonics. Based on 2D thermo-mechanical modeling, the sensitivity of model results to radiogenic heat production rates in the continental upper crust and lower crust is thoroughly investigated. The granodioritic upper crust usually concentrates radioactive isotopes(e.g., U, Th and K) with a wide range of radiogenic heat production rate, i.e., roughly from 1.0 μW/m3 to 3.0 μW/m~3. The radiogenic heat significantly effects the continental subduction evolution including the volume of subducted continental upper crust, the distribution and evolution of crustal melting in the collision zone, exhumation of subducted lower crust along the subduction channel, and coupling of the subducting continent with the overriding continent. In contrast, the mafic lower crust is depleted in radioactive isotopes(e.g., U, Th and K), resulting in a low radiogenic heat production rate(0.2-0.8 μW/m~3) and relatively limited influences on the geodynamic processes of continual subduction. Specifically, the radiogenic heating of the continental lower crust mainly regulates the viscosity and rheological strength of the continental slab to further affect the degree of the lower crust exhumation and the continental slab dip angle.
Radiogenic heat production is a key energy source for convection in the Earth's mantle and for metamorphic reactions in the continental crust. However, its effects on continental subduction remain a poorly resolved aspect of plate tectonics. Based on 2D thermo-mechanical modeling, the sensitivity of model results to radiogenic heat production rates in the continental upper crust and lower crust is thoroughly investigated. The granodioritic upper crust usually concentrates radioactive isotopes(e.g., U, Th and K) with a wide range of radiogenic heat production rate, i.e., roughly from 1.0 μW/m3 to 3.0 μW/m~3. The radiogenic heat significantly effects the continental subduction evolution including the volume of subducted continental upper crust, the distribution and evolution of crustal melting in the collision zone, exhumation of subducted lower crust along the subduction channel, and coupling of the subducting continent with the overriding continent. In contrast, the mafic lower crust is depleted in radioactive isotopes(e.g., U, Th and K), resulting in a low radiogenic heat production rate(0.2-0.8 μW/m~3) and relatively limited influences on the geodynamic processes of continual subduction. Specifically, the radiogenic heating of the continental lower crust mainly regulates the viscosity and rheological strength of the continental slab to further affect the degree of the lower crust exhumation and the continental slab dip angle.
引文
李忠海,许志琴.2015.大洋俯冲和大陆碰撞沿走向的转换动力学及流体?熔体活动的作用.岩石学报,31(12):3524-3530.
Bea F.2012.The sources of energy for crustal melting and the geochemistry of heat-producing elements.Lithos,153:278-291.
Bittner D and Schmeling H.1995.Numerical modeling of melting processes and induced diapirism in the lower crust.Geophysical Journal International,123:59-70.
Brace W F and Kohlstedt D L.1980.Limits on lithospheric stress imposed by laboratory experiments.Journal of Geophysical Research,85:6248-6252.
Brady R J,Ducea M N,Kidder S B and Saleeby J B.2006.The distribution of radiogenic heat production as a function of depth in the Sierra Nevada Batholith,California.Lithos,86:229-244.
Burg J P and Gerya T V.2005.The role of viscous heating in Barrovian metamorphism of collisional orogens:Thermomechanical models and application to the Lepontine Dome in the Central Alps.Journal of Metamorphic Geology,23:75-95.
Chamberlain C P and Sonder L J.1990.Heat-producing elements and the thermal and Baric Patterns of metamorphic belts.Science,250:763-769.
Clauser C and Huenges E.1995.Thermal conductivity of rocks and minerals.AGU Reference Shelf,3:105-126.
Faccenda M,Gerya T V and Chakraborty S.2008.Styles of post-subduction collisional orogeny:Influence of convergence velocity,crustal rheology and radiogenic heat production.Lithos,103:257-287.
Gerya T V and Yuen D A.2003a.Characteristics-based marker-in-cell method with conservative finite-differences schemes for modeling geological flows with strongly variable transport properties.Physics of the Earth and Planetary Interiors,140:293-318.
Gerya T V and Yuen D A.2003b.Rayleigh-Taylor instabilities from hydration and melting propel‘cold plumes’at subduction zones.Earth and Planetary Science Letters,212:47-62.
Gerya T V and Yuen D A.2007.Robust characteristics method for modelling multiphase visco-elasto-plastic thermo-mechanical problems.Physics of the Earth and Planetary Interiors,163:83-105.
Goffe B,Bousquet R,Henry P and Le Pichon X.2003.Effect of the chemical composition of the crust on the metamorphic evolution of orogenic wedges.Journal of Metamorphic Geology,21:123-141.
Green D H and Ringwood A.1967.An experimental investigation of the gabbro to eclogite transformation and its petrological applications.Geochimica et Cosmochimica Acta,31:767-833.
Heier K S and Lambert I B.1978.A Compilation of Potassium,Uranium and Thorium Abundances and Heat Productivities of Australian Rocks.Department of Geophysics and Geochemistry,Australian National University.
Hermann J.2002.Experimental constraints on phase relations in subducted continental crust.Contributions to Mineralogy and Petrology,143:219-235.
Huerta A D,Royden L H and Hodges K V.1998.The thermal structure of collisional orogens as a response to accretion,erosion,and radiogenic heating.Journal of Geophysical Research:Solid Earth,103:15287-15302.
Jamieson R A,Beaumont C,Fullsack P and Lee B.1998.Barrovian regional metamorphism:Where’s the heat?Geological Society,London,Special Publications,138:23-51.
Jaupart C and Mareschal J C.2003.Constraints on crustal heat production from heat flow data//Treatise on Geochemistry:The Crust,3:65-84.
Jaupart C and Mareschal J C.2010.Heat Generation and Transport in the Earth.Cambridge University Press.
Ji S C and Zhao P L.1993.Flow laws of multiphase rocks calculated from experimental-data on the constituent phases.Earth and Planetary Science Letters,117:181-187.
Kirby S H.1983.Rheology of the lithosphere.Reviews of Geophysics,21:1458-1487.
Kirby S H and Kronenberg A K.1987.Rheology of the lithosphere:Selected topics.Reviews of Geophysics,25:1219-1244.
Li Z H.2014.A review on the numerical geodynamic modeling of continental subduction,collision and exhumation.Science China:Earth Sciences,57:47-69.
Li Z H,Gerya T V and Burg J P.2010.Influence of tectonic overpressure on P-T paths of HP-UHP rocks in continental collision zones:Thermomechanical modelling.Journal of Metamorphic Geology,28:227-247.
Macfarlane A M.1992.The tectonic evolution of the core of the Himalaya,Langtang National Park,central Nepal.Massachusetts Institute of Technology.
Neumann N,Sandiford M and Foden J.2000.Regional geochemistry and continental heat flow:Implications for the origin of the South Australian heat flow anomaly.Earth and Planetary Science Letters,183:107-120.
Ranalli G.1995.Rheology of the Earth.Springer.
Ranalli G and Murphy D C.1987.Rheological stratification of the lithosphere.Tectonophysics,132:281-295.
Rudnick R L and Fountain D M.1995.Nature and composition of the continental-crust:A lower crustal perspective.Reviews of Geophysics,33:267-309.
Rudnick R L and Gao S.2003.Composition of the continental crust//Treatise on Geochemistry,3:1-64.
Scaillet B,Francelanord C and Lefort P.1990.BadrinathGangotri plutons(Garhwal,India)-Petrological and geochemical evidence for fractionation processes in a High Himalayan leucogranite.Journal of Volcanology and Geothermal Research,44:163-188.
Turcotte D L and Schubert G.2002.Geodynamics.Cambridge University Press.
Ueda K,Gerya T V and Sobolev S V.2008.Subduction initiation by thermal-chemical plumes:Numerical studies.Physics of the Earth and Planetary Interiors,171:296-312.
Vidal P,Cocherie A and Lefort P.1982.Geochemical investigations of the origin of the Manaslu leucogranite(Himalaya,Nepal).Geochimica et Cosmochimica Acta,46:2279-2292.
Bea F.2012.The sources of energy for crustal melting and the geochemistry of heat-producing elements.Lithos,153:278-291.
Bittner D and Schmeling H.1995.Numerical modeling of melting processes and induced diapirism in the lower crust.Geophysical Journal International,123:59-70.
Brace W F and Kohlstedt D L.1980.Limits on lithospheric stress imposed by laboratory experiments.Journal of Geophysical Research,85:6248-6252.
Brady R J,Ducea M N,Kidder S B and Saleeby J B.2006.The distribution of radiogenic heat production as a function of depth in the Sierra Nevada Batholith,California.Lithos,86:229-244.
Burg J P and Gerya T V.2005.The role of viscous heating in Barrovian metamorphism of collisional orogens:Thermomechanical models and application to the Lepontine Dome in the Central Alps.Journal of Metamorphic Geology,23:75-95.
Chamberlain C P and Sonder L J.1990.Heat-producing elements and the thermal and Baric Patterns of metamorphic belts.Science,250:763-769.
Clauser C and Huenges E.1995.Thermal conductivity of rocks and minerals.AGU Reference Shelf,3:105-126.
Faccenda M,Gerya T V and Chakraborty S.2008.Styles of post-subduction collisional orogeny:Influence of convergence velocity,crustal rheology and radiogenic heat production.Lithos,103:257-287.
Gerya T V and Yuen D A.2003a.Characteristics-based marker-in-cell method with conservative finite-differences schemes for modeling geological flows with strongly variable transport properties.Physics of the Earth and Planetary Interiors,140:293-318.
Gerya T V and Yuen D A.2003b.Rayleigh-Taylor instabilities from hydration and melting propel‘cold plumes’at subduction zones.Earth and Planetary Science Letters,212:47-62.
Gerya T V and Yuen D A.2007.Robust characteristics method for modelling multiphase visco-elasto-plastic thermo-mechanical problems.Physics of the Earth and Planetary Interiors,163:83-105.
Goffe B,Bousquet R,Henry P and Le Pichon X.2003.Effect of the chemical composition of the crust on the metamorphic evolution of orogenic wedges.Journal of Metamorphic Geology,21:123-141.
Green D H and Ringwood A.1967.An experimental investigation of the gabbro to eclogite transformation and its petrological applications.Geochimica et Cosmochimica Acta,31:767-833.
Heier K S and Lambert I B.1978.A Compilation of Potassium,Uranium and Thorium Abundances and Heat Productivities of Australian Rocks.Department of Geophysics and Geochemistry,Australian National University.
Hermann J.2002.Experimental constraints on phase relations in subducted continental crust.Contributions to Mineralogy and Petrology,143:219-235.
Huerta A D,Royden L H and Hodges K V.1998.The thermal structure of collisional orogens as a response to accretion,erosion,and radiogenic heating.Journal of Geophysical Research:Solid Earth,103:15287-15302.
Jamieson R A,Beaumont C,Fullsack P and Lee B.1998.Barrovian regional metamorphism:Where’s the heat?Geological Society,London,Special Publications,138:23-51.
Jaupart C and Mareschal J C.2003.Constraints on crustal heat production from heat flow data//Treatise on Geochemistry:The Crust,3:65-84.
Jaupart C and Mareschal J C.2010.Heat Generation and Transport in the Earth.Cambridge University Press.
Ji S C and Zhao P L.1993.Flow laws of multiphase rocks calculated from experimental-data on the constituent phases.Earth and Planetary Science Letters,117:181-187.
Kirby S H.1983.Rheology of the lithosphere.Reviews of Geophysics,21:1458-1487.
Kirby S H and Kronenberg A K.1987.Rheology of the lithosphere:Selected topics.Reviews of Geophysics,25:1219-1244.
Li Z H.2014.A review on the numerical geodynamic modeling of continental subduction,collision and exhumation.Science China:Earth Sciences,57:47-69.
Li Z H,Gerya T V and Burg J P.2010.Influence of tectonic overpressure on P-T paths of HP-UHP rocks in continental collision zones:Thermomechanical modelling.Journal of Metamorphic Geology,28:227-247.
Macfarlane A M.1992.The tectonic evolution of the core of the Himalaya,Langtang National Park,central Nepal.Massachusetts Institute of Technology.
Neumann N,Sandiford M and Foden J.2000.Regional geochemistry and continental heat flow:Implications for the origin of the South Australian heat flow anomaly.Earth and Planetary Science Letters,183:107-120.
Ranalli G.1995.Rheology of the Earth.Springer.
Ranalli G and Murphy D C.1987.Rheological stratification of the lithosphere.Tectonophysics,132:281-295.
Rudnick R L and Fountain D M.1995.Nature and composition of the continental-crust:A lower crustal perspective.Reviews of Geophysics,33:267-309.
Rudnick R L and Gao S.2003.Composition of the continental crust//Treatise on Geochemistry,3:1-64.
Scaillet B,Francelanord C and Lefort P.1990.BadrinathGangotri plutons(Garhwal,India)-Petrological and geochemical evidence for fractionation processes in a High Himalayan leucogranite.Journal of Volcanology and Geothermal Research,44:163-188.
Turcotte D L and Schubert G.2002.Geodynamics.Cambridge University Press.
Ueda K,Gerya T V and Sobolev S V.2008.Subduction initiation by thermal-chemical plumes:Numerical studies.Physics of the Earth and Planetary Interiors,171:296-312.
Vidal P,Cocherie A and Lefort P.1982.Geochemical investigations of the origin of the Manaslu leucogranite(Himalaya,Nepal).Geochimica et Cosmochimica Acta,46:2279-2292.