Off-axis structures of spreading zones according to results of experimental modeling
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The off-axis topography of spreading ridges is a result of tectonic and magmatic processes occurring in the axial zone and operating off the ridge axis during further evolution of the crust. The results of physical and numerical simulations have shown that differences in topography roughness, rift valley depth, frequency and amplitude of normal faults, and geometric stability of the rift axis are determined by (a) the rate of extension and accretion of the new crust, (b) the thickness of the brittle lithospheric layer, and (c) the temperature of the underlying asthenosphere. Under conditions of the fast spreading, the stationary axial magma chamber in the crust predetermines the existence of the thinner and weakened lithosphere. As a result, the axis jumps for a short distance and the axis geometry remains almost rectilinear. The destruction of the thin axial lithosphere with a low mechanical strength results in formation of frequent and low-amplitude normal faultings. All these factors lead to the formation of the characteristic poorly dissected topography of fast-spreading ridges. Without a stationary axial magmatic chamber in the crust of slow-spreading ridges and with a thick and strong lithosphere, a deeply dissected axial and off-axis topography arises. The axis jumps for a significant distance within the rift valley, giving rise to geometric instability of the axis and development of transform and nontransform offsets.
Keyworsspreading ridge off-axis topography modeling transform and nontransform offsets
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- 1.Yu. I. Galushkin and E. P. Dubinin, “Thermal regime of the lithosphere by jump of spreading axis at the Mathematicians Ridge,” Fizika Zemli, No. 9, 59–69 (1992).Google Scholar
- 7.A. L. Grokholskii, E. P. Dubinin, K. T. Sevinyan, and Yu. I. Galushkin, “Experimental modeling of interaction between hotspot and spreading ridge, a case of the Southeast Indian Ridge,” in The Earth’s Life (MGU, Moscow, 2012), No. 34, pp. 24–35 [in Russian].Google Scholar
- 8.E. P. Dubinin and A. A. Sveshnikov, “Evolution of the lithosphere under extinct spreading ridges (results of mathematical modeling),” Geotectonics 34(3), 234–250 (2000).Google Scholar
- 9.E. P. Dubinin and S. A. Ushakov, Oceanic Rifting (GEOS, Moscow, 2001) [in Russian].Google Scholar
- 11.E. P. Dubinin, Yu. I. Galushkin, and A. A. Sveshnikov, “A model of oceanic crust accretion and its geodynamic implications,” in The Earth’s Life: Geology, Geodynamics, Ecology, and Museum Science (MGU, Moscow, 2010), pp. 53–82 [in Russian].Google Scholar
- 13.O. G. Sorokhtin, “Relationship between topography of mid-ocean ridges and rate of oceanic bottom spreading,” Dokl. AN SSSR 208(6), 1338–1341 (1973).Google Scholar
- 14.A. I. Shemenda, “Similarity criteria in mechanical modeling of tectonic processes,” Geol. Geofiz. 24(10), 10–19 (1983).Google Scholar
- 23.J. A. Goff, Y. Ma, A. Shah, and J. R. Cochran, “Stochastic analysis of seafloor morphology on the flank of the Southeast Indian Ocean Ridge. The influence of ridge morphology on the formation of abyssal hills,” J. Geophys. Res. 102, 521–534 (1997).Google Scholar
- 26.K. C. Macdonald, “Mid-ocean ridges: Fine scale tectonic, volcanic and hydrothermal processes within the plate boundary zone,” Ann. Rev. Earth Planet. Sci., No. 10, 155–190 (1982).Google Scholar
- 33.D. Sandwell and W. Smith, “Global marine gravity from retracked Geosat and ERS-1 altimetry: ridge segmentation versus spreading rate,” J. Geophys. Res. 114, 1–18 (2009).Google Scholar