Magmatic breakup as an explanation for magnetic anomalies at magma-poor rifted margins

Abstract

International audienc

Crustal structure and evolution of the Pyrenean-Cantabrian belt: A review and new interpretations from recent concepts and data

“…15). Other authors even question the validity of the magnetic anomalies in the Atlantic for plate reconstructions (Bronner et al, 2011;Nirrengarten et al, 2017). From an onshore geological perspective, conclusive kinematic evidence for the direction of basin opening during the Albian-Cenomanian in the Pyrenees is lacking.…”

“…oceanic magnetic anomalies, rotation poles). In addition to the uncertainties in the early Cretaceous history arising from the diverse interpretation of the J-anomalies in the North Atlantic (chrons M0 to M4; Sibuet , 2004;Bronner et al, 2011;Nirrengarten et al, 2017), the reconstructed separation between the Iberian and Eurasian plates in the late Cretaceous, previous to the widely accepted onset of the Pyrenean orogeny at ~84 Ma, range from 200 km in the east of the Pyrenees and 100 km in the west (Roest and Srivastava, 1991) to 180 km or 150-140 km in the central Pyrenees (Olivet, 1996;Barnett-Moore et al, 2016). To this discrepancy we can affix the purported separation of 400 km consumed by scissor-like convergence since the early Cretaceous envisaged by Sibuet et al (2004) and Vissers and Meijer (2011), discussed above.…”

“…The envisaged north-dipping normal faults of the margin, however, contrast with the basement-involved south-dipping thrust system that is proposed in present-day sections of the continental slope (e.g. (Bronner et al, 2011;Nirrengarten et al, 2017). Whatever the significance of these anomalies, a mid-late Early Cretaceous onset of spreading based on the width of the Bay of Biscay oceanic domain was postulated decades ago (Williams, 1975;Montadert et al, 1979).…”

Magnetic signature of large exhumed mantle domains of the Southwest Indian Ridge – results from a deep-tow geophysical survey over 0 to 11 Ma old seafloor

“…Therefore, in view of the low magnetization of the young (< 11 Ma) serpentinized rock at the SWIR, it is unlikely that strong magnetic anomalies could be related solely to serpentinization; this would be even truer at > 100 Ma old OCTs. Instead, it supports the hypotheses that (1) intrusive or extrusive material is required (Bronner et al, 2011;Russell and Whitmarsh, 2003) to account for a significant magnetic signal in the exhumed mantle domains of OCTs and that (2) the interpretation of this signal as resulting from seafloor spreading is precluded in the absence of a homogeneous and well-established upper oceanic crust. Consequently, the kinematic reconstructions of magma-poor passive margins using weak anomalies identified over exhumed mantle domains need to be treated with caution.…”

“…The aim is to better understand the complexity of the marine magnetic anomalies observed above the serpentinized mantle rocks exhumed at mid-oceanic ridges . Finally we discuss the implications of our findings for the understanding of exhumed mantle domains at OCTs of magma-poor rifted margins and the origin and significance of broad zones of chaotic magnetic patterns are discussed (Russell and Whitmarsh, 2003;Sibuet et al, 2007;Bronner et al, 2011;Tucholke and Sibuet, 2012;Bronner et al, 2012).…”