Magmatic ocean-continent transitions

Type Article
Date 2019-06
Language English
Author(s) Guan HuixinORCID1, 2, Geoffroy Laurent1, 2, Gernigon Laurent3, Chauvet Francois1, 2, Grigne Cecile1, 2, Werner Philippe4
Affiliation(s) 1 : Univ Bretagne Occidentale, F-29238 Brest, France.
2 : CNRS, UMR 6538, Lab Domains Ocean, F-29280 Plouzane, France.
3 : Geol Survey Norway NGU, Trondheim, Norway.
4 : Univ Strasbourg, F-67089 Strasbourg, France.
Source Marine And Petroleum Geology (0264-8172) (Elsevier Sci Ltd), 2019-06 , Vol. 104 , P. 438-450
DOI 10.1016/j.marpetgeo.2019.04.003
WOS© Times Cited 13
Keyword(s) Volcanic passive margins, SDRs, Polyphased lithospheric, Extension
Abstract

Continental extension may, or may not, be coeval with significant mantle melting, leading to the formation of distinct types of passive margins (respectively magma-poor or volcanic), with distinct crustal structures. Especially in inter-cratonic mobile areas, magmatic breakup and development of volcanic passive margins (VPMs) may postdate the early development of a non-magmatic continental rift system. The time-span between the amagmatic and the magmatic systems may be relatively short or, conversely, long (tens of millions years). Such evolution is often associated with a significant apparent asymmetry in the wideness of conjugate VPMs. In this paper, we attempt to re-interpret the structure of three paired VPMs which developed close to, but separately from, a previous amagmatic aborted rift system. Due to opposite dips in major crustal detachment faults accommodating extension from sedimentary to volcanic stages, those composite margins tend to individualize a fault-dissected continental block (here designed as L-Block) along one of the conjugate margins. In addition to the amount and distribution of amagmatic extension, the time-span between amagmatic and magmatic extension exerts a major structural and rheological control on the final structure of the ocean-continent transitions, The finite margin geometry may be erroneously interpreted as resulting from a continuous process from hyper extension to the final magmatic breakup. However, the early syn-sedimentary extension appears, in many cases, to be low-rate or episodic. Consequently, the VPM final breakup of the lithosphere may shift away from the original amagmatic stretched area to the rifted margin.

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