Preprints
https://doi.org/10.5194/se-2017-142
https://doi.org/10.5194/se-2017-142

  30 Jan 2018

30 Jan 2018

Review status: this preprint has been withdrawn by the authors.

3D numerical modelling of the re-distribution of partially molten lower crust rocks in relay zones between faults during transtension: Implications for the Sefwi terrane, SW Ghana

Xiaojun Feng1,2,3, Enyuan Wang1,2, Jérôme Ganne3, Roland Martin3, and Mark W. Jessell3,4 Xiaojun Feng et al.
  • 1Key Laboratory of Gas and Fire Control for Coal Mines, China University of mining and Technology, Ministry of Education, Xuzhou, 221116, China
  • 2School of Safety Engineering, China University of Mining and Technology, Xuzhou, 221116, China
  • 3Geosciences Environnement Toulouse, Observatoire Midi Pyrénées, Toulouse, 31400, France
  • 4Centre for Exploration Targeting, The University of Western Australia, Perth, WA 6009, Australia

Abstract. High-grade tectono-metamorphic domains in the Sefwi terrane of Ghana are separated from adjacent low-grade greenstone belts by two main shear zones. The high-grade rocks are thought to have been exhumed along sinistral shear zones during the D2 ENE-WSW transtension. To better understand the role boundary conditions and the spatial relationship of faults play in the re-distribution of partially molten lower crust, ten 3D thermo-mechanical models have been constructed. The results show that the normal component of velocity boundary conditions mainly controls the exhumation of the lower crust which occurred along pre-existing faults, while the exhumation in the relay zones between faults is controlled by the ratio of extension rate to shear rate applied at the boundaries. The strike of the exhumation belt made of partially molten lower crust rocks in the relay zone is sub-orthogonal to the transtension direction. The isostatic compensation from low-density upper mantle to overlying crust (thinning) is higher under transtension than under extension.

The lower crust exhumation influenced by inherited shear zones can be used to better understand the loci of the high-grade rocks in the Sefwi terrane. We suggest that the Kukuom-Juaboso domain composed of up to amphibolite-migmatite facies probably resulted from the concentration of partially molten rocks in the relay zone between the Ketesso and Kenyase shear zones during the D2 ENE-WSW transtension. The two shear zones probably underwent two main stages for growth and maturation from the D1 to D2 deformation phases. The regional exhumation of the high-grade rocks in the Sefwi terrane probably occurred within a duration of less than 5Ma.

This preprint has been withdrawn.

Xiaojun Feng et al.

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Status: closed
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Xiaojun Feng et al.

Xiaojun Feng et al.

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