Fracture Zones of the Doldrams Megatrasform System (Equatorial Atlantic)

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Abstract

This article presents results of the structural and morphological analysis of the fracture zones which are part of Doldrums Megatransform System (MTS), located in the northern part of the Equatorial Atlantic (6.5°–9° N) that include Vernadskiy and Bogdanov transform faults and the Doldrums and Pushcharovskiy megatransforms. Bathymetric map, based on the multibeam echo sounding data, collected during 45 cruise of the R/V Akademik Nikolaj Strakhov was used for this analysis. It was established that large-scale variations in the width of fracture zone valleys are determined by the distribution of stresses perpendicular to the fracture zone. In the areas with compressive stresses, the fracture zone valleys are narrower, and the in extension areas are wider. The difference in geodynamic settings within the MTS is due to the difference in spreading directions, which change from \(\perp \)89° to \(\perp \)93° when moving from south to north. The depth of fracture zone valleys consistently increases from the periphery of the MTS (Bogdanov and Doldrums faults) to the center (Pushcharovskiy fracture zone) in accordance with a decrease in the upper mantle temperature. In each fracture zone, the valley depth decreases from the rift- fracture zone intersections towards the center of the active part to a certain background depth. It is assumed that this phenomenon is the result of the uplift of the valley bottom, which occurred due to the decompaction of the lithosphere, caused by the serpentinization of ultramafic rocks. The violation of the revealed variations in the width and depth of fracture zone valley patterns occurs as a result of various ridges and uplifts formation in the fracture zone. In the axial zones of the active parts of the fracture zone valleys median ridges are widespread, extending parallel to the fracture zone and representing serpentinite diapirs squeezed out above the bottom surface. Transversal ridges which were formed 10‒11 million years ago as a result of the lithospheric plate edge flexural bending under extensional conditions are now located in the western passive parts on the southern sides of the of Doldrums and Pushcharovskiy fracture zone valleys. The transverse ridge on the northern side of the Vernadskiy fracture zone, which includes Mount Peyve, was formed between 3.65‒2.4 Ma. Due to the frequent jumps of the spreading axis in this region, it was divided into three segments. There are interfracture zone ridges in megatransforms, which in the active part consist of two fracture zone valleys. Time of their formation: in Pushcharovskiy megatransform ‒ 30‒32 million years ago and in Doldrums megatransform ‒ about 4 million years ago. Due to the curvilinearity of the outlines and under the pressure of moving lithospheric plates, the interfracture zone ridges experience longitudinal (along the fault) compressive and tensile stresses, which are compensated by vertical uplifts of their separate blocks and the formation of depressions, pull apart depressions, and spreading centers (the latter are only in Pushcharovskiy megatransform). Structure-forming processes that determine pattern and morphology of the fracture zones as a part of the MTS are related by their origin to the spreading and transform geodynamic systems.

About the authors

S. G. Skolotnev

Geological Institute RAS

Email: sysokolov@yandex.ru
Russia, 119017, Moscow, Pyzhevsky per., bld. 7

K. O. Dobrolyubova

Geological Institute RAS

Email: sysokolov@yandex.ru
Russia, 119017, Moscow, Pyzhevsky per., bld. 7

A. A. Peyve

Geological Institute RAS

Email: sysokolov@yandex.ru
Russia, 119017, Moscow, Pyzhevsky per., bld. 7

S. Yu. Sokolov

Geological Institute RAS

Author for correspondence.
Email: sysokolov@yandex.ru
Russia, 119017, Moscow, Pyzhevsky per., bld. 7

N. P. Chamov

Geological Institute RAS

Email: sysokolov@yandex.ru
Russia, 119017, Moscow, Pyzhevsky per., bld. 7

M. Ligi

Istituto di Scienze Marine (CNR)

Email: sysokolov@yandex.ru
Italy, 40129, Bologna, Via Gobetti, bld. 101

References

  1. Дубинин Е.П. Трансформные разломы океанической литосферы. ‒ Под ред. С. А. Ушакова ‒ М.: МГУ, 1987. 179 с.
  2. Мазарович А.О. Геологическое строение Центральной Атлантики: разломы, вулканические сооружения и деформации океанского дна. ‒ М.: Научный Мир, 2000. 176 с.
  3. Пейве А.А. О вертикальных тектонических движениях земной коры в зонах трансформных разломов Центральной Атлантики // Геотектоника. 2006. № 1. С. 31‒43.
  4. Пущаровский Ю.М., Разницин Ю.Н., Мазарович А.О. и др. Строение зоны разлома Долдрамс: Центральная Атлантика. ‒ Под ред. Ю.М. Пущаровского ‒ М.: Наука. 1991. 224 с. (Тр. ГИН АН СССР. 1991. Вып. 459).
  5. Пущаровский Ю.М., Пейве А.А., Разницин Ю.Н., Базилевская Е.С. Разломные зоны Центральной Атлантики. ‒ Под ред. Ю.М. Пущаровского ‒ М.: ГЕОС, 1995. 160 с. (Тр. ГИН РАН. 1995. Вып. 495).
  6. Пущаровский Ю.М., Сколотнев С.Г., Пейве А.А. и др. Геология и металлогения Срединно-Атлантиче1ского хребта. 5°–7° с.ш. ‒ Под ред. Ю.М. Пущаровского ‒ М.: ГЕОС, 2004. 152 с. (Тр. ГИН РАН. 2004. Вып. 562).
  7. Разницин Ю.Н. Тектоническая расслоенность литосферы молодых океанов и палеоокеанических бассейнов. ‒ Под ред. Ю.М. Пущаровского ‒ М.: Наука, 2004. 270 с. (Тр. ГИН РАН. 2004. Вып. 560).
  8. Сколотнев С.Г., Бельтенев В.Е., Лепехина Е.Н. и др. Молодые и древние цирконы из пород океанической литосферы в Центральной Атлантике, геотектонические следствия // Геотектоника. 2010. № 6. С. 24‒59.
  9. Сколотнев С.Г., Добролюбова К.О., Пейве А.А., Соколов С.Ю., Чамов Н.П., Ligi M. Строение спрединговых сегментов Срединно-Атлантического хребта между трансформными разломами Архангельского и Богданова (Приэкваториальная Атлантика) // Геотектоника. 2022. № 1. С. 3‒26
  10. Сколотнев С.Г., Санфилиппо А., Пейве А.А. и др. Новые данные по строению мегатрансформной системы Долдрамс (Центральная Атлантика) // ДАН. 2020. Т. 491. № 1. С. 29–32.
  11. Balmino G., Vales N., Bonvalot S., Briais A. Spherical harmonic modeling to ultra-high degree of Bouguer and isostatic anomalies // J. Geodes. 2012. Vol. 86. P. 499‒520.
  12. Bedard J.H. The opening the Atlantic, the Mesozoic New England igneous province and mechanisms of continental breakup // Tectonophysics. 1985. Vol. 113. No. 34. P. 209‒232.
  13. Bonatti E., Brunelli D., Buck W.R. et al. Flexural uplift of a lithospheric slab near the Vema transform (Central Atlantic): Timing and mechanisms // EPSL. 2005. Vol. 240. P. 642–655.
  14. Bonatti E., Ligi M., Gasperini L., Carrara G., Vera E. Imaging crustal uplift, emersion and subsidence at the Vema fracture zone // EOS. 1994. No. 9. P. 371‒372.
  15. Bonatti E., Sarnthein M., Boersma A. et al. Neogen crustal emersion and subsidence of the Romanche fracture zone, Equatorial Atlantic// EPSL. 1997. Vol. 35. P. 369‒383.
  16. Cande S.C., Kent D.V. A new geomagnetic polarity time scale for the Late Cretaceous and Cenozoic // J. Geophys. Res. 1992. Vol. 97. No. B10. P. 13 917‒13 951.
  17. Cande S.C., LaBrecque J.L., Haxby W.F. Plate kinematics of the South Atlantic: Chron 34 to present // J. Geophys. Res. 1988. Vol. 93. No. B11. P. 13479‒13492.
  18. Chen Y.J. Thermal model of oceanic transform faults // J. Geophys. Res. 1988. Vol. 93. P. 8839‒8851.
  19. Christensen N.I., Salisbury M.H. Structure and constitution of the lower oceanic crust // Rev. Geophys and Space Physics 1975. Vol. 13. No. 1. P. 57–85.
  20. De Mets C., Gordon R.G., Argus D.F., Stein S. Effect of recent revisions to the geomagnetic reversal time scale on estimates of current plate motions // Geophys. Res. Lett. 1994. Vol. 21. P. 2191–2194.
  21. GEBCO 30" Bathymetry Grid. ‒ Vers. 20141103. 2014. http://www.gebco.net.
  22. Hooft E.E.E., Detrick R.S., Toomey D.R. et al. Crustal thickness and structure along three contrasting spreading segments of the Mid-Atlantic Ridge, 33.5°–35° N // J. Geophys. Res. 2000. Vol. 105. No. B4. P. 8205–8226.
  23. Klitgoard K.D., Shouten H. Plate kinematics of the central Atlantic. ‒ In: The Geology of North America. ‒ Vol. M ‒ The Western North Atlantic Region. ‒ GSA. 1986. Vol. 3. P. 351–373.
  24. Ligi M., Bonatti E., Gasperini L. and Poliakov A.N.B. Oceanic broad multi-fault transform plate boundaries // Geology. 2002. Vol. 30. P. 11‒14.
  25. Maia M., Sichel S., Briais A. et al. Extreme mantle uplift and exhumation along a transpressive transform fault // Nature Geoscience. 2016. V. 9 P. 619–624. https://doi.org/10.1038/NGEO2759
  26. Nürnberg D., Müller R.D. The tectonic evolution of the South Atlantic from Late Jurassic to present // Tectonophysics. 1991. No. 191. P. 27‒53.
  27. Pockalny R.A., Gente P., Buck W.R. Oceanic transversive ridges; a flexural response to fracture zone‒normal extension // Geology. 1996. No. 24. P. 71‒74.
  28. Sandwell D.T., Smith W.H.F. Global marine gravity from retracked Geosat and ERS-1 altimetry: Ridge segmentation versus spreading rate // J.Geophys. Res. 2009. Vol. 114. No. B1. P. 1‒18.
  29. Sclater J.G., Anderson R.N. and Bell M.L. Elevation of ridges and evolution of the Central‒ Eastern Pacific // J. Geophys. Res. 1971. Vol. 76. P. 7888–7915.
  30. Skolotnev S.G., Sanfilippo A., Peyve A.A. et al. Large-scale structure of the Doldrums multi-fault transform system (7°‒8° N Equatorial Atlantic): Preliminary results from the 45th expedition of the R/V A.N. Strakhov // Ofioliti. 2020. Vol. 45. No. 1. P. 25‒41.
  31. USGS earthquake catalogue. URL: https://earthquake.usgs.gov/earthquakes/ (Accessed April 27, 2021).
  32. Wilson J.T. A new class of faults and their bearing on continental drift // Nature. 1965. Vol. 207. No. 4995. P. 343‒347.
  33. PDS2000 (RESON), vers.3.7.0.53, http://www.teledynemarine.com/reson

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Copyright (c) 2023 С.Г. Сколотнев, К.О. Добролюбова, А.А. Пейве, С.Ю. Соколов, Н.П. Чамов, M. Ligi