太平洋-纳兹卡洋中脊扩张速率研究及其对板块动力学的启示

洋中脊扩张会形成新的海洋地壳。洋中脊扩张速率具有一阶的全球性变化规律：当洋中脊所处洋盆存在俯冲带时，扩张速率较快，如太平洋-纳兹卡洋中脊、太平洋-科科斯洋中脊等；当洋中脊所处洋盆不存在俯冲带时，洋中脊扩张速率较慢，如西南印度洋中脊、大西洋中脊等。然而，学界对其成因与动力学机制尚未形成统一的认识。

为揭示扩张速率变化的成因，本研究以太平洋-纳兹卡洋中脊为研究对象，使用最新的全球板块运动速率、全球水深、Slab 2.0全球俯冲板片俯冲形态以及全球板块边界等关键数据，定量计算全球主要洋中脊的扩张速率。随后，以纳兹卡板块为例，精细测算该板块边界单位长度上洋中脊推力与俯冲板片拖曳力的关系，探索洋中脊扩张规律的动力学机制等问题。

本研究的主要创新结果如下：洋中脊扩张存在两种驱动模式，即洋中脊推挤-俯冲板片拖曳共同驱动扩张以及单一洋中脊推挤驱动扩张。存在俯冲板片的洋盆中，洋中脊平均扩张速率较大，为8.79 cm/yr，板块边界单位长度上的驱动力为7.30×10¹² N/m；而不存在俯冲板片的洋盆中，洋中脊平均扩张速率较小，为2.46 cm/yr，板块边界单位长度上驱动力为0.79×10¹² N/m。快速-中速扩张洋中脊的扩张速率受控于洋中脊推力与俯冲板片拖曳力的共同作用，其中俯冲板片拖曳力对扩张速率起主要作用，洋中脊推力起次要作用。由于俯冲板片向地幔更深处运动，加速了洋中脊的被动扩张。而慢速-超慢速扩张的洋中脊仅由洋中脊推力单独驱动，则无法形成高数量级的板块驱动力。

The mid-ocean ridge is a place where new oceanic crust is formed. It is worth nothing that the spreading rates of ridges have a first-order global variation pattern: when a mid-ocean ridge is located in a plate with subduction zones, its spreading is fast, such as the Pacific-Nazca Ridge and the Pacific-Cocos Ridge. In contrast, spreading rate of the ridge is much smaller when the ridge is located in the plate without subduction zone, such as the Southwest Indian ridge and Mid-Atlantic ridge. However, there is no unified understanding of its causes and geodynamical mechanisms.

To reveal the causes of spreading rates variations, this study focused on the Pacific-Nazca ridge, using key datasets such as GPlates global plate motion rate, GMT global bathymetry, Slab 2.0 global subduction slab and morphology, and global plate boundaries data, to quantitatively calculate distribution of spreading rates of major global ridge systems (with accuracy of 50 km). Subsequently, we quantitatively computed the relationship between ridge push and slab pull per unit length at the boundary of the Nazca Plate, to reveal the dynamical mechanism of mid-ocean ridge spreading pattern.

The main innovative results of this study are as follows: there are two driving modes for ridge spreading, i.e., the joint effect of ridge push and slab pull, as well as the single effect of ridge push. In the plate with subduction zones, the average spreading rate of ridge is 8.79 cm/yr and the driving force per unit length of the plate boundary is 7.30×10¹² N/m, while in the plate without subduction zones, the average spreading rate of mid-ocean ridge is 2.46 cm/yr and the driving force per unit length of the plate boundary is 0.79×10¹² N/m. The spreading rate of fast-intermediate spreading system is controlled by the combined effect of the ridge push and slab pull, where the slab pull plays a major role and the ridge push plays a secondary role in controlling the spreading rates. The passive spreading of mid-ocean ridge is accelerated by the subduction of plate into deeper mantle. For the slow-ultraslow spreading ridge system, it is only driven by ridge push and cannot generate a plate driving force with sufficient large order of magnitude.

[1] WEGENER A. The origin of continents and oceans[M]. Courier Corporation, 1966:268-270.
[2] HESS H H. History of ocean basins[J]. Geological Society of America, 1962: 599- 620.
[3] MORGAN, W J. Rise, trenches, great faults, and crustal[J]. Journal of GeophysicalResearch, 1968, 73(6): 1959-1982.
[4] FRISCH W, MESCHEDE M, BLAKEY R. Plate Tectonic: Contiental Drift and Mountain Building[M]. Heidelberg: Springer, 2011: 6.
[5] MORGAN, W J. Palte Motions and Deep Mantle Convection[J]. Geological Societyof America Memoirs, 1972, 132: 7-22.
[6] MACDONALD K C. Mid-ocean ridges: Fine scale tectonic, volcanic and hydrothemal processes within the palte boundary zone[J]. Annual Review of Earth and Planetary Sciences, 1982, 10: 155.
[7] MACDONALD K C, FOX P J, PERRAM L J. et al. A new view of the mid-ocean ridge from the behaviour of ridge-axis discontinuities[J]. Nature, 1988, 335(6187): 217-225.
[8] MACDONALD K C, SCHEIRER D S, CARBOTTE S M. Mid-ocean ridges: Discontinuities, segments and giant cracks[J].Science, 1991, 253(5023): 986-994.
[9] SMALL C. Global systematics of mid-ocean ridge morphology[J]. Geophysical Monogrph, 1998, 106: 1-25.
[10] 李江海,刘持恒,韩喜球.全国洋中脊系统的构造特征及其运动学意义[J].地学前缘,2019,26(3): 155-162.
[11] FUKAO Y, OBAYASHI M. Subducted slabs stagnant above, penetrating through, and through, and trapped below the 660 km discontinuity[J]. Journal of GeophysicalResearch: Solid Earth, 2013, 118(11): 5920-5938.
[12] CHEN Y J, MORGAN J P. A nonlinear rheology model for mid-ocean ridge axis topography[J]. Journal of Geophysical Research, 1990, 95(B11): 17583-17604.
[13] MORGAN J P, CHEN Y J. The genesis of oceanic crust: magma injection, hydrothermal circulation, and crustal flow[J].Journal of Geophysical Research: Solid Earth, 1993, 98(B4): 6283-6297.
[14] MORGAN J P, CHHEN Y J. Dependence of ridge-axis morphology on magmasupply and spreading rate[J]. Nature, 1993, 364: 706-708.
[15] BAKER E, Chen Y J, MORGAN J P. The relationship between near-axis hydrothermal cooling and the spreading rate of mid-ocean ridges[J]. Earth and Planetary Science Letter, 1996, 142(1-2): 137-145.
[16]BECKER T W, BOSCHI L. A comparison of tomographic and geodynamic mantle models[J]. Geochemistry, Geophysics, Geosystems, 2002, 3(1): 2001GC000171.
[17]NIU Y L, GREEN D H. The petrological control on the lithosphere-asthenosphere boundary (LAB) beneath ocean basins[J]. Earth-Science Reviews, 2018, 185: 301-307.
[18]PUTHE C, GERYA T. Dependence of mid-ocean ridge morphology on spreading rate in numerical 3-D models[J]. Gondwana Research, 2014, 25(1): 270-283.
[19]CARBOTTE S M, SMITH D K, CANNAT M, et al. Tectonic and magmatic segmentation of the Global Ocean Ridge System: a synthesis of observations[J]. Geologcal Society, 2015, 420(1): 249-295.
[20]TOLSTOY M. Mid-ocean ridge eruption as a climate value[J].Geophysical Research Letters, 2015, 42(5): 1346-1351.
[21]GERMAN C R, PETERSEN S, HANNINGTON M D. Hydrothermal exploration of mid-ocean ridges: Where might the largest sulfied deposits be forming?[J]. Chemical Geology, 2016, 420: 114-126.
[22]ANDERSEN C, RUPKE L, HASENCLEVER J, et al. Fault geometry and permeability contrast contrast control vent temperatures at the Logatchev 1 hydrothermal field, Mid-Atlantic Ridge[J]. Geology, 2016, 43: 51-54.
[23]李龑,牛雄伟,阮爱国,等.洋中脊扩张速率对洋壳速度结构的约束[J].地球物理学报,2020,63(5):1913-1926.
[24]CHEN Y J. Oceanic crustal thickness versus spreading rate[J]. Geophysical Research Letters, 1992, 19(8): 753-756.
[25]MAGDE L S, SPARKS D W, DETRICK R S. The relationship between buoyant mantl flow, melt migration, and gravity bull’s eyes at the mid-Atlantic ridge between 33°N and 35°N[J]. Earth and Planetary Science Letters, 1997, 148(1-2): 59-67.
[26]RABINOWICZ M, ROUZO S, SEMPERE J C, et al. Three-dimensional mantle flow beneath mid-ocean ridges[J]. Journal of Geophysical Research: Solid Earth, 1993, 91(B3): 3739-3762.
[27]LANGMUIR C, FORSYTH D. Thermodynamic modeling of post-entrapment crystallization in igneous phases[J]. Journal of Volcanology and Geothermal Research, 2004, 137(4): 247-260.
[28]KLEIN E M, LANGMUIR C H. Global correlations of ocean ridge basalt chemistry with axial depth and crustal thickness[J]. Journal of Geophysical Research: Solid Earth, 1987, 92(B8): 8089-8115.
[29]NIU Y L, BATIZA R. In situ densities of MORB melts and residual mantle: Implication for buoyancy forces beneath mid-ocean ridges[J]. The journal of Geology, 1991, 99(5): 767-775.
[30]宋珏琛,李江海,冯博.慢速-超慢速扩张洋中脊热液活动及其机理[J].地质学报,2021,95(8):2274-2282.
[31]李三忠,索艳慧,余珊,等.西南印度洋构造地貌与构造过程[J].大地构造与成矿学,2015,39(1):15-29.
[32]MORGAN W J. Convection Plumes in the Lower Mantle[J]. Nature, 1971, 230.
[33]OSEI T A, SOBOLEV S V, STEINBERGER B, et al. Evaluating the influence of plate boundary friction and mantle viscosity on plate velocities[J]. Geochemistry, Geophysics, Geosystems, 2018, 19: 642-666.
[34]KOELEMEIJER P, DEUSS A, RITSEMA J. Density structure of Earth’s lowermost mantle from Stoneley mode splitting observations[J].Nature Communication, 2017, 8.
[35]LI X, KIND R, PRIESTLEY K, et al. Mapping the Hawaiian plume conduit with converted seismic waves[J]. Nature, 2000, 405: 938-941.
[36]WOLFE C J, SOLOMON S C, LASKE G, et al. Mantle shear-wave velocity structure beneath the Hawaiian hot spot[J]. Science, 2009, 326: 1388-1390.
[37]GERYA T. Precambrian geodynamics: Concepts and models[J]. Gondwana Research, 2014, 25: 442-463.
[38]ROWLEY D B, FORTE A M, ROWAN C J, et al. Kinematics and dynamics of the east Pacific rise linked to a stable, deep-mantle upwelling[J]. Science Advances, 2016, 2: 18.
[39]BURKE K, STEINBERGER B, TORSVIK T H, et al. Plume generation zones at the margins of large low shear velocity provinces on the core-mantle boundary[J]. Earth and Planetary Science Letters, 2008, 265: 49-60
[40]MULLER R D, SETON M, ZAHIROVIC S, et al. Ocean basin evolution and global-scale plate reorganization events since Pangea breakup[J]. Annual Review of Earth and Planetary Sciences, 2016, 44: 107-138.
[41]ZAHIROVIC S, MATTHEWS K J, FLAMENT N, et al. Tectonic evolution and deep mantle structure of the eastern Tethys since the latest Jurassic[J]. Earth-Science Reviews, 2016, 162: 293-337.
[42]SETON M, MULLER R D, ZAHIROVIC S, et al. Global continental and ocean basin reconstructions since 200 Ma[J]. Earth-Science Reviews, 2012, 113(3-4): 212-270.
[43]SUN X, SUN W, HU Y, et al. Major Miocene geological events in southern Tibet and eastern Asia induced by the subduction of the Ninetyeast Ridge[J]. Acta Geochimica, 2018, 37: 395-401.
[44]孙卫东.“岩浆引擎”与板块运动驱动力[J].科学通报, 2019, 64: 2988-3006.
[45]NIU Y, HEKINIAN R. Spreading-rate dependence of the extent of mantle melting beneath ocean ridges[J]. Nature, 1997, 385: 326-329.
[46]FORSYTH D, UYEDA S. On the relative importance of the driving forces of plate motion[J]. Geophysical Journal International, 1975, 43(1): 163-200.
[47]CARLSON R L, HILDE T W C, UYEDA S. The driving mechanism of plate tectonics: relation to age of the lithosphere at trenches[J]. Geophysical Research Letters, 1983, 10(4): 297-300.
[48]PACANOVSKY K M, DAVIS D M, RICHARDSON R M, et al. Intraplate stresses and plate-driving forces in the Philippine Sea Plate[J]. Journal of Geophysical Research: Solid Earth, 1999, 104(B1): 1095-1110.
[49]VAN BENTHEM S, GOVERS R. The Caribbean plate: Pulled, pushed, or dragged?[J]. Journal of Geophysical Research: Solid Earth, 2010, 115(B10).
[50]GRAEME E, AFFELIA D W. Ridge push, mantle plumes and the speed of the Indian plate[J]. Geophysical Journal International, 2013, 194: 670-677.
[51]郑群凡,石耀霖.印度板块持续向北运动的驱动力来源[J]. 中国科学院大学学报: 2021, 38(6): 722-728.
[52]MULLER R D, ZAHIROVIC S, WILLIAMS S E, et al. A global plate model including lithospheric deformation along major rifts and orogens since the Triassic[J]. Tectonics, 2019, 38: 1884-1907.
[53]MATTHEWS K J, MALONEY K T, ZAHIROVIC S, et al. Global plate boundary evolution and kinematics since the late Paleozoic[J]. Global and Planetary Change, 2016, 146: 226-250.
[54]GEE J, KENT D. Source of oceanic magnetic anomalies and the geomagnetic polarity timescale[J]. Treatrise Geophys, 2007, 5: 455-507.
[55]HANDY M, USTASZEWSKI K, KISSLING E. Reconstructing the Alps-Carpathians-Dinarides as a key to understanding switches in subduction polarity, slab gaps and surface motion[J]. International Journal of Earth Sciences,2015, 104(1): 1-26.
[56]LEPICHON X. Sea-floor spreading and continental drift[J]. Journal of Geophysical Research, 1968, 73: 3661-3697.
[57]MINSTER J B, JORDAN T H, MOLNAR P, et al. Numerical modelling of instantaneous plate tectonics[J]. Geophysical Journal Royal Astronomical Society, 1974, 36: 541-576.
[58]LI S Z, SUO Y H, LI X Y, et al. Microplate tectonics: new insights from micro-blocks in the global oceans, continental margins and deep mantle[J]. Earth-Science Reviews, 2018, 185: 1029-1064.
[59]李三忠,索艳慧,周洁,等.微板块与大板块:基本原理与范式转换[J].地质学报,2022,96(10):3542-6558.
[60]SAGER W W, HUANG Y M, TOMINAGA M, et al. Oceanic plateau formation by seafloor spreading implied by Tamu Massif magnetic anomalies[J]. Nature Geoscience, 2019, 12: 661-666.
[61]BURKE K, STEINBERGER B, TORSVIK T H, et al.Plume generation zones at the margins of large low shear velocity provinces on the core-matle boundary[J]. Earth and Planetary Science Letters, 2008, 265(1-2): 49-60.
[62]TORSVIK T H, SMETHURST M A, BURKE K, et al. Large igneous provinces general from the margins of the large low-velocity provinces in the deep mantle[J]. Geophysical Journal International, 2010, 167: 1447-1460.
[63]TORSVIK T H, VOO R V D, PREEDEN U, et al. Phanerozoic polar wander, palaeogrography and dynamics[J]. Earth-Science Reviews, 2012, 114(3): 32-658.
[64]BOYDEN J A, MULLER R D, GRUNIS M, et al. Next-generation Plate-Tectonic Reconstructions Using Gplates[M]. Cambridge:Cambridge University Press, 2011: 95-114.
[65]GURNIS M, TURNER M, ZAHIROVIC S, et al.Plate tectonic reconstructions with continuously closing plate[J]. Computers and Geosciences, 2012, 38(1): 35-42.
[66]GURNIS M, YANG T, CANNON J, et al. Global tectonic reconstructions with continuously deforming and evolving rigid plates[J].Computers and Geosciences, 2018, 116: 32-41.
[67]MULLER R D , CANNON J, QIN X D, et al. GPlates:Buiding a virtual earth through deep time[J]. Geochemistry, Geophysics, Geosystems, 2018, 19(7): 2243-2261.
[68]LIU S F, GURNIS M, MA P, et al. Reconstruction of northeast Asian deformation integraed with western Pacific plate subduction since 200 Ma[J]. Earth-Science Revies, 2017, 175: 114-142.
[69]OROWAN E. Continental drift and the origin of mountains: Hot creep and creep fracture are crucial factors in the formation of continents and mountains[J]. Science, 1964, 146: 1003-1010.
[70]TURCOTTE D L, SCHUBERT G. Geodynamics[M]. Cambridge University Press, 1982: 440-475.
[71]HARLAND W B, COX A V, LEWELLYN P G et al. A Geologic Time Scale[M]. Cambridge University Press, 1982: 131-133.
[72]RUBEY W W, HUBBERT M K. Role of fluid pressure in mechanics of overthrust faulting. 2. Overthrust belt in geosynclinal area of western Wyoming in light of fluid-pressure hypothesis[J]. Geological Society of America Bulletin, 1959, 70: 167−205.
[73]HALES A L. Gravitational sliding and continental drift[J]. Earth and Planetary Science Letters, 1969, 6: 31-34.
[74]DAVIS D M, SOLOMON S C. True polar wander and plate-driving forces[J]. Journal of Geophysical Research[J]: Solid Earth, 1985, 90(B2): 1837-1841.
[75]PENNINGTON W D. The effect of oceanic crustal structure on phase changes and subduction[J]. Tectonophysics, 1984, 102: 377-398.
[76]LI J, WANG X, WANG X, et al. P and SH velocity structure in the upper mantle beneath northeast China: Evidence for a stagnant slab in hydrous mantle transition zone[J]. Earth and Planetary Science Letters, 2013, 367: 71-81.
[77]李江海,刘仲兰.地幔内板片俯冲运动模式及其大地构造意义[J]. 地质论评, 2019, 65(2): 454-463.
[78]WENG H H, AMPUERO J P. Integrated rupture mechanics for slow slip events and earthquakes[J]. Nature Communication, 2022, 13(1): 7321.
[79]ZHU R X, FAN H R, LI J W, et al. Decratonic gold deposits[J]. Science China-earth Sciences, 2015, 58: 1523-1537.
[80]ARTYUSHKOV E V. Stresses in the lithosphere caused by crustal thickness inhomogeneities[J]. Journal of Geophysical Research, 1973, 78: 7675-7708.
[81]ZHOU Z, LIN J. Elasto-plastic deformation and plate weakening due to normal faulting in the subducting plate along the Mariana Trench[J]. Tectonophysics, 2018, 734: 59-68.
[82]WESSEL P, SMITH W H F. NEW, improved version of Generic Mapping Tools released[J]. Eos, Transactions American Geophysical Union, 1998, 79(47): 579.
[83]TOZER B, SANDWELL D T, SMITH W H F, et al. Global Bathymetry and Topography at 15 Arc Sec: SRTM15+[J]. Earth and Space Science, 2019, 6: 1847-1864.
[84]HAYES G P, WALD D J, JOHNSON R L. Slab1.0: A three-dimensional model of global subduction zone geometries[J]. Journal of Geophysical Research, 2012, 117 (B01302).
[85]HAYES G P, MOORE G L, PORTNER D, et al. Slab2, a comprehensive subductionzone geometry model[J]. Science, 2018, 362(6410).HERRON E M. Sea-floor spreading and the Cenozoic history of the east-central Pacific[J].Geological Society of America Bulletin, 1972, 83: 1671-1692.