Numerical analysis and simulation experiment of lithospheric thermal structures in the South China Sea and the Western Pacific

Abstract

The asthenosphere upwelled on a large scale in the western Pacific and South China Sea during the Cenozoic, which formed strong upward throughflow and caused the thermal structure to be changed obviously. The mathematical analysis has demonstrated that the upward throughflow velocity may have varied from 3×10¹¹ to 6×10¹² m/s. From the relationship between the lithospheric thickness and the conductive heat flux, the lithospheric heat flux in the western Pacific should be above 30 mW/m², which is consistent with the observed data. The huge low-speed zone within the upper mantle of the marginal sea in the western Pacific reflects that the upper mantle melts partially, flows regionally in the regional stress field, forms the upward heat flux at its bottom, and causes the change of the lithospheric thermal structure in the region. The numerical simulation result of the expansion and evolution in the South China Sea has demonstrated that in the early expansion, the upward throughflow velocity was relatively fast, and the effect that it had on the thickness of the lithosphere was relatively great, resulting in the mid-ocean basin expanding rapidly. After the formation of the ocean basin in the South China Sea, the upward throughflow velocity decreased, but the conductive heat flux was relatively high, which is close to the actual situation. Therefore, from the heat transfer point of view, this article discusses how the upward heat flux affects the lithospheric thermal structure in the western Pacific and South China Sea. The conclusions show that the upward heat throughflow at the bottom of the lithospheric mantle resulted in the tectonic deformation at the shallow crust. The intensive uplifts and rifts at the crust led to the continent cracks and the expansion in the South China Sea.

Keywords

numerical analysis / lithospheric thermal structure / heat transfer / South China Sea

References

[1] Andreescu M., Demetrescu C.. Rheological Implications of the Thermal Structure of the Lithosphere in the Convergence Zone of the Eastern Carpathians. Journal of Geodynamics, 2001, 31(4): 373-391.

[2] Ashi J., Tokuyama H., Taira A.. Distribution of Methane Hydrate BSRs and Its Implication for the Prism Growth in the Nankai Trough. Marine Geology, 2002, 187(1–2): 177-191.

[3] Braitenberg, C., Wienecke, S., Wang, Y., 2006. Basement Structures from Satellite-Derived Gravity Field: South China Sea Ridge. Journal of Geophysical Research, 111: B05407, doi: 10.1029/2005JB003938

[4] Briais A., Patriat P., Tapponnier P.. Updated Interpretation of Magnetic Anomalies and Seafloor Spreading Stages in the South China Sea: Implications for the Tertiary Tectonics of Southeast Asia. J. Geophysical Research, 1993, 98(B4): 6299-6328.

[5] Chen G.. An Explanation on the Origin-Mechanism of Formation of the Cenozoic Basins in the Post-Platform Orogenic Belts of East China. Geotectonica et Metallogenia, 1988, 12(1): 5-16.

[6] Clift P., Lin J.. Preferential Mantle Lithospheric Extension under the South China Margin. Marine and Petroleum Geology, 2001, 18(8): 929-945.

[7] Clift P., Lin J., Barckhausen U.. Evidence of Low Flexural Rigidity and Low Viscosity Lower Continental Crust during Continental Break-up in the South China Sea. Marine and Petroleum Geology, 2002, 19: 951-970.

[8] Fang N. Q., Yao B. C., Wang L., . The Velocity Structure of the Lithosphere and the Origin of Sedimentary Basins in the South China and Northern Margin of the South China Sea. Earth Science—Journal of China University of Geosciences, 2007, 32(2): 147-154.

[9] Fowler, C. M. R., Nisbet, E. G., Pandit, B. I., 1998. The Transform of Heat by Conduction in the Earth’s Crust: Physical Constraints. In: Nisbet, E. G., Fowler, C. M. R., eds., Heat, Metamorphism and Tectonics Mineralogical Association of Canada, l–33

[10] Karig D. E.. Origin and Development of Marginal Basins in the Western Pacific. Journal of Geophysical Research, 1971, 76(11): 2542-2561.

[11] Li S. T., Lin C. S., Zhang Q. M., . Dynamic Process of Episodic Rifting in Continental Marginal Basin and Tectonic Events since 10 Ma in South China Sea. Chinese Science Bulletin, 1998, 43(8): 797-810.

[12] Lin G., Wang Y. H.. The P-Wave Velocity Structure of the Crust-Mantle Transition Zone in the Continent of China. Journal of Geophysics and Engineering, 2005, 2(3): 268-276.

[13] Lin G., Zhang Y. H., Guo F., . Numerical Modelling of Lithosphere Evolution in the North China Block: Thermal Thinning versus Tectonic Extension Thinning. Journal of Geodynamics, 2005, 40: 92-103.

[14] Lin G., Zhao C. B., Hobbs B. E., . Theoretical and Numerical Analyses of Convective Instability in Porous Media with Temperature-Dependent Viscosity. Communications in Numerical Methods in Engineering, 2003, 19: 787-799.

[15] Lin G., Zhao C. B., Hobbs B. E., . Potential Effects of Upward Throughflow on Thermal Structure Models within the Continental Lithospheric Mantle-Crust. Chinese Journal of Geophysics, 2008, 51(2): 393-401.

[16] Luedmann T., Wong H. K.. Neotectonic Regime on the Passive Continental Margin of the Northern South China Sea. Tectonophysics, 1999, 311(1–4): 113-138.

[17] Qiu X. L., Ye S. Y., Wu S. M., . Crustal Structure across the Xisha Trough, Northwestern South China Sea. Tectonophysics, 2001, 341(1–4): 179-193.

[18] Ren J. Y., Li S. T.. Spreading and Dynamic Setting of Marginal Basins of the West Pacific. Earth Science Frontiers, 2000, 7(3): 203-213.

[19] Sandiford, M., Hand, M., McLaren, S., 2001. Tectonic Feedback, Intraplate Orogeny and the Geochemical Structure of the Crust: A Central Australian Perspective. In: Miller, J., Holdsworth, R., Buick, I., et al., eds., Continental Reactivation and Reworking. Geological Society Special Publication, 184: 195–218

[20] Sandiford M., McLaren S.. Tectonic Feedback and the Ordering of Heat Producing Elements within the Continental Lithosphere. Earth Planet. Sci. Lett., 2002, 204(1–2): 133-150.

[21] Sandiford M., McLaren S., Neumann N.. Long-Term Thermal Consequences of the Redistribution of Heat-Producing Elements Associated with Large-Scale Granitic Complexes. J. Metamorph. Geol., 2002, 20(1): 87-98.

[22] Schlueter H. U., Hinz K., Block M.. Tectonostratigraphic Terranes and Detachment Faulting of the South China Sea and Sulu Sea. Marine Geology, 1996, 130(1–2): 39-78.

[23] Shi X. B., Qiu X. L., Xia K. Y., . Characteristics of Surface Heat Flow in the South China Sea. Journal of Asian Earth Sciences, 2003, 22(3): 265-277.

[24] Shyu C. T., Hsu S. K., Liu C. S.. Heat Flows off Southwest Taiwan: Measurements over Mud Diapers and Estimated from Bottom Simulating Reflectors. Terrestrial Atmospheric Ocean Sciences, 1998, 9: 795-812.

[25] Song H. B., Wu S. G., Jiang W.. The Characteristics of BSRs and Their Derived Heat Flow on the Profile 973 in the Northeastern South China Sea. Chinese Journal of Geophysics, 2007, 50(5): 1321-1331.

[26] Tapponnier P.. On the Mechanics of the Collision between India and Asia. Geol. Soc. Spec. Publ., 1986, 19: 115-157.

[27] Taylor B., Hayers D. E.. Hayers D. E.. The Tectonic Evolution of the South China Sea. The Tectonic and Geologic Evolution of Southeast Asian Seas and Islands, 1980, Washington DC.: Am. Geophys. Union 89-104.

[28] Taylor B., Hayers D. E.. Hayers D. E.. The Tectonic Evolution of the South China Sea. The Tectonic and Geologic Evolution of Southeast Asian Seas and Islands, 1983, Washington DC.: Am. Geophys. Union 23-56.

[29] Wang J., Li L.. Geothermics in China, 1996, Beijing: Seismological Press

[30] Wang J., Yao B. C., Wan L., . Characteristics of Tectonic Dynamics of the Cenozoic Sedimentary Basins and the Petroleum Resources in the South China Sea. Marine Geology & Quaternary Geology, 2005, 25(2): 91-100.

[31] Wang P. L., Lo C. H., Chung S. L., . Onset Timing of Left-Lateral Movement along the Ailao Shan Red River Shear Zone: ⁴⁰Ar/³⁹Ar Dating Constraint from the Nam Dinh Area, Northeastern Vietnam. Journal of Asian Earth Sciences, 2000, 18(3): 281-292.

[32] Wei B. Z., Chung W. Y.. Strike-Slip Faulting on the Northern Margin of the South China Sea: Evidence from Two Earthquakes Offshore of Hainan Island, China, in December 1969. Tectonophysics, 1995, 241(1–2): 55-66.

[33] Xia B., Zhang Y., Cui X. J., . Understanding of the Geological and Geodynamic Controls on the Formation of the South China Sea: A Numerical Modelling Approach. Journal of Geodynamics, 2006, 42(1–3): 63-84.

[34] Xia K. Y., Huang C. L., Jiang S. R., . Comparison of the Tectonics and Geophysics of the Major Structural Belts between the Northern and Southern Continental Margins of the South China Sea. Tectonophysics, 1994, 235(1–2): 99-116.

[35] Xu Y., Li Z. W., Hao T. Y., . Pn Wave Velocity and Anisotropy in the Northeastern South China Sea and Adjacent Region. Chinese Journal of Geophysics, 2007, 50(5): 1473-1479.

[36] Yan P., Zhou D., Liu Z. S.. A Crustal Structure Profile across the Northern Continental Margin of the South China Sea. Tectonophysics, 2001, 338(1): 1-21.

[37] Yao B. C., Wan L., Wu N.. Cenozoic Tectonic Evolution and the 3D Structure of the Lithosphere of the South China Sea. Geological Bulletin of China, 2005, 24(1): 1-8.

[38] Yoder H. S.. Generation of Basaltic Magma, 1976, Washington DC.: National Academy of Sciences 165

[39] Yuan Y. S., Ma Y. S., Hu S. B., . Present-Day Geothermal Characteristics in South China. Chinese Journal of Geophysics, 2006, 49(4): 1118-1126.

[40] Zhang J., Shi Y.. Thermal Structure of Central Basin in South China Sea and Their Geodynamic Implications. Journal of the Graduate School of the Chinese Academy of Sciences, 2004, 21(3): 407-412.

[41] Zhang J., Song H.. The Thermal Structure of Main Sedimentary Basins in the Northern Margin of the South China Sea. Journal of Geomechanics, 2001, 7(3): 238-244.

[42] Zhang J., Wang J.. Geodynamical Characteristics of Deep Part of Spreading in Northern Continental Margin of the South China Sea. Science in China (Series D), 2000, 30(6): 561-567.

[43] Zhao C. B., Hobbs B. E., Muhlhaus H. B.. Finite Element Modelling of Temperature Gradient Driven Rock Alteration and Mineralization in Porous Rock Masses. Computer Methods in Applied Mechanics and Engineering, 1998, 165: 175-187.

[44] Zhao C. B., Hobbs B. E., Muhlhaus H. B., . Finite Element Analysis of Flow Patterns near Geological Lenses in Hydrodynamic and Hydrothermal Systems. Geophysical Journal International, 1999, 138(1): 146-158.

[45] Zhao C. B., Hobbs B. E., Muhlhaus H. B.. Finite Element Analysis of Heat Transfer and Mineralization in Layered Hydrothermal Systems with Upward Throughflow. Computer Methods in Applied Mechanics and Engineering, 2000, 186: 49-64.

[46] Zhao C. B., Hobbs B. E., Ord A., . Theoretical and Numerical Analysis of Large-Scale Heat Transfer Problems with Temperature-Dependent Pore-Fluid Densities. Engineering Computations, 2005, 22: 232-252.

[47] Zhao C. B., Lin G., Hobbs B. E., . Finite Element Modelling of Heat Transfer through Permeable Cracks in Hydrothermal Systems with Upward Throughflow. Engineering Computations, 2001, 18: 996-1011.

[48] Zhao C. B., Lin G., Hobbs B. E., . Finite Element Modelling of Reactive Fluids Mixing and Mineralization in Pore-Fluid Saturated Hydrothermal/Sedimentary Basins. Engineering Computations, 2002, 19: 364-387.

[49] Zhao C. B., Muhlhaus H. B., Hobbs B. E.. Finite Element Analysis of Steady-State Natural Convection Problems in Fluid-Saturated Porous Media Heated from Below. International Journal for Numerical and Analytical Methods in Geomechanics, 1997, 21(12): 863-881.

[50] Zhao C. B., Peng S. L., Liu L. M., . Potential Mechanisms of Pore-Fluid Movement from the Continental Lithospheric Mantle into the Upper Continental Crust. Journal of Central South University of Technology, 2008, 15(1): 81-88.

[51] Zhao C. B., Valliappan S.. Finite Element Modelling of Methane Gas Migration in Coal Seams. Computers and Structures, 1995, 55(4): 625-629.

[52] Zhao C. B., Xu T. P., Valliappan S.. Numerical Modelling of Mass Transport Problems in Porous Media: A Review. Computers and Structures, 1994, 53: 849-860.

[53] Zhou D., Ru K., Chen H. Z.. Kinematics of Cenozoic Extension on the South China Sea Continental Margin and Its Implications for the Tectonic Evolution of the Region. Tectonophysics, 1995, 251(1–4): 161-177.

[54] Zhu B. Q., Wang H. F., Chen Y. W., . Geochronological and Geochemical Constraint on the Cenozoic Extension of Cathaysian Lithosphere and Tectonic Evolution of the Border Sea Basins in East Asia. Journal of Asian Earth Sciences, 2004, 24(2): 163-175.

[55] Zienkiewicz O. C.. The Finite Element Method, 1977, London: McGraw-Hill