气候变化领域集成服务门户(CCPortal): Geophysical evidences for large-scale mullion-type structures at the mantle–crust interface in southern Madagascar: implications for Neoproterozoic orogeny

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DOI	10.1007/s00531-020-01840-w
	Geophysical evidences for large-scale mullion-type structures at the mantle–crust interface in southern Madagascar: implications for Neoproterozoic orogeny
	Martelat J.-E.; Cardon H.; Lardeaux J.-M.; Nicollet C.; Schulmann K.; Pili E.
发表日期	2020
ISSN	14373254
起始页码	1487
结束页码	1500
卷号	109 期号:4
英文摘要	This study uses gravimetric data integrated with recent seismic data published on south Madagascar to investigate geometry of crust–mantle interface. The regional tectonic framework of Madagascar is characterised by anastomosing network of up to 15-km-wide, 600-km-long and north-oriented high-strain zones, which originated during Neoproterozoic convergence. The studied Bouguer anomalies obtained from the International Gravimetric Bureau were high-pass filtered to emphasise short-wavelength gravimetric variations (shorter than 200 km). The Pan-African high-strain zones coincide with the positive gravimetric anomalies suggesting a link with deep seated high-density material. Considering the present-day thickness of the crust (35 km) and its seismic velocity record, the gravimetric anomalies can be visualised as narrow vertical tabular bodies located at the base of the Moho. Modelling further confirmed that such narrow vertical bodies could be stable over geologic time scale since these structures are relatively small (10 to 30 km wide). The vertical tabular bodies possibly reflect material transfer such as vertical motion of sub-crustal weak and possibly partially molten mantle along vertical deformation zones. It is proposed that these structures were initiated by folding of weak mantle–crust interface characterised by low-viscosity contrast between weak mantle and stronger granulitized lower crust during bulk pure shear-dominated horizontal shortening. It is proposed that the cuspate-lobate “mullion-type” geometry mimics rheological inversions of mafic and felsic rocks and shape of folds of variable scale observed in southern Madagascar. The formation of such mega-mullion structures is possibly an expression of “crème brulée” rheological model, where the deformation of the lithosphere is governed by stronger granulitic lower crust and weaker partially molten and/or hydrated mantle. © 2020, Geologische Vereinigung e.V. (GV).
英文关键词	Crust–mantle coupling; Hot-orogen; Madagascar; Transpressive shear zone
语种	英语
scopus关键词	Bouguer anomaly; crustal structure; gravity anomaly; mantle structure; Moho; orogeny; Proterozoic; seismic data; seismic velocity; Madagascar
来源期刊	International Journal of Earth Sciences
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/147671
作者单位	UCBL, ENSL, CNRS, Laboratoire de Géologie LGL-TPE, Université de Lyon, Villeurbanne, 69622, France; GEOAZUR, Université Nice, UMR 6526, 250 rue Albert Einstein Sophia, Antipolis, Valbonne, 06560, France; Laboratoire Magmas et Volcans, Université Clermont Auvergne, CNRS, IRD, OPGC, Clermont-Ferrand, 63000, France; Institut de Physique du Globe, UMR 7516, Université de Strasbourg, 1 rue Blessig, Strasbourg, 67084, France; Center for Lithospheric Research, Czech Geological Survey, Klárov 3, Prague 1, 118 21, Czech Republic; CEA, DAM, DIF, Arpajon, 91297, France; Institut de Physique du Globe de Paris, CNRS, 1 rue Jussieu, Paris Cedex 05, 75238, France
推荐引用方式 GB/T 7714	Martelat J.-E.,Cardon H.,Lardeaux J.-M.,等. Geophysical evidences for large-scale mullion-type structures at the mantle–crust interface in southern Madagascar: implications for Neoproterozoic orogeny[J],2020,109(4).
APA	Martelat J.-E.,Cardon H.,Lardeaux J.-M.,Nicollet C.,Schulmann K.,&Pili E..(2020).Geophysical evidences for large-scale mullion-type structures at the mantle–crust interface in southern Madagascar: implications for Neoproterozoic orogeny.International Journal of Earth Sciences,109(4).
MLA	Martelat J.-E.,et al."Geophysical evidences for large-scale mullion-type structures at the mantle–crust interface in southern Madagascar: implications for Neoproterozoic orogeny".International Journal of Earth Sciences 109.4(2020).