Internal structure of basalt flows: insights from magnetic and crystallographic fabrics of the La Palisse volcanics, French Massif Central

Boiron, Tiphaine; Bascou, Jérôme; Camps, Pierre; Ferré, E. C.; Maurice, Claire; Guy, Bernard; Gerbe, Marie-Christine; Launeau, Patrick

doi:10.1093/gji/ggs115

Cited by 23 publications

(16 citation statements)

References 60 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The anisotropy of magnetic susceptibility (AMS) is a widely used method to reveal the petrofabric of magma intrusions and lava flows, because it may provide valuable information on the flow dynamics (e.g. Cañón-Tapia, 2004;Hastie et al, 2011;Zhang et al, 2011;Boiron et al, 2013;Moreira et al, 2014;Hrouda et al, 2015). To better interpret the AMS and avoid difficulties related, for example, to the AMS-axes permutation producing inverse susceptibility fabrics due to the presence of single-domain magnetite grains, Bascou et al (2005) and more recently Boiron et al (2013) showed the importance of comparing the AMS with the shape and crystallographic preferred orientations (SPO and CPO).…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Evidence of sheared sills related to flank destabilization in a basaltic volcano

et al. 2016

Self Cite

View full text Add to dashboard Cite

International audiencePiton des Neiges basaltic volcano (La Réunion) has been deeply dissected by erosion, exposing large volumes of debris avalanche deposits. To shed light on the factors that led to volcano flank destabilizations, we studied the structure, the crystallographic and magnetic fabrics of the substratum of a debris avalanche unit. This substratum is a complex of N50 seaward-dipping sills that has been exposed by the avalanche. Structural observations show that the sill plane in contact with the avalanche is one of the latest intrusions in the sill complex. In this uppermost sill, the anisotropy of magnetic susceptibility (AMS) is correlated to the crystallographic preferred orientation of magmatic silicate minerals, allowing us to use AMS as a proxy to infer the magmatic flow. The AMS fabric across the intrusion is strongly asymmetric, which reveals that the contact sill was emplaced with a normal shear displacement of its hanging wall. The shear displacement and the magma flow in the intrusion are both directed toward the NNE, i.e. toward the sea, which is also the direction of the slope and of the debris avalanche runout. Because all the sills in the intrusion complex have a similar dip and dip direction, it is likely that several of them also underwent a cointrusive slip toward the NNE. We conclude that this cointrusive normal slip, repeated over many intrusions of the sill complex, increased the flank instability of the volcano. This incre-mental instability may have ended up into the observed debris avalanche deposit. At Piton de la Fournaise, the active volcano of La Réunion, sill intrusion and cointrusive flank displacement have been inferred from geophys-ical studies for the April 2007 eruption. By providing direct evidence of sheared sills, our study substantiates the idea that repeated sill intrusions may eventually trigger flank destabilizations in basaltic volcanoes

show abstract

Section: Methodsmentioning

confidence: 99%

“…Pole figures were calculated using the average crystallographic orientation for each grain (i.e. one data point per grain, as in Boiron et al (2013)). Results are presented on equal area, lower hemisphere projections in the specimen reference frame.…”

Section: Methodsmentioning

confidence: 99%

Evidence of sheared sills related to flank destabilization in a basaltic volcano

et al. 2016

Self Cite

View full text Add to dashboard Cite

show abstract

“…Compared to other texture-determining techniques, electron backscatter diffraction (EBSD) has the advantage that the preferred orientation of various minerals and grain sizes can be determined in a polyphase aggregate (Prior et al, 1999). EBSD has therefore been used in recent magnetic fabric studies to determine which minerals carry the magnetic anisotropy (Bascou et al, 2002;Boiron et al, 2013). successfully modelled the paramagnetic anisotropy in mafic rocks based on EBSD data and single crystal properties.…”

Section: Introductionmentioning

confidence: 99%

Magnetic fabrics in the Bjerkreim Sokndal Layered Intrusion, Rogaland, southern Norway: Mineral sources and geological significance

et al. 2016

View full text Add to dashboard Cite

Magnetic anisotropy can provide important information about mineral fabrics, and thus magmatic processes, particularly when it is known how multiple mineral species contribute to the anisotropy. It may also affect the direction of induced or remanent magnetization, with important consequences for paleomagnetic studies or the interpretation of magnetic anomalies. Here, we aim at describing the magnetic fabrics in the Bjerkreim Sokndal Layered Intrusion and identifying their carriers.Anisotropies of magnetic susceptibility and remanence were measured on samples covering different geographic locations and stratigraphic units within the Bjerkreim Sokndal Layered Intrusion. The intrusion is characterized by magmatic layering and has a synform structure, with strong foliation on the limbs. Detailed comparison between magnetic and mineral fabric shows that they are not necessarily coaxial, but the minimum susceptibility, and minimum anhysteretic remanence are generally normal to the foliation or the magmatic layering. The minimum susceptibility and anhysteretic remanence are associated with pyroxene (100) axes, and the maximum susceptibility and anhysteretic remanence are sub-parallel to the pyroxene [001] axes in layers MCU IVc and MCU IVe for which electron backscatter data are available. However, the paramagnetic anisotropy of pyroxene is too weak to explain the observed anisotropy. We propose that the magnetic anisotropy of magnetite-free specimens is carried by hemo-ilmenite exsolutions within pyroxene, in addition to pyroxene itself. When present, multi-domain magnetite dominates both the anisotropy of magnetic susceptibility and anhysteretic remanence, due to shape-preferred orientation and distribution anisotropy. The orientation of the magnetic fabric appears independent of carrier, due to their common deformation history, but the degree of anisotropy is stronger for magnetite-bearing specimens. The results of this study will facilitate future structural interpretations and may be used to correct for magnetization deflection.

show abstract

“…При этом более половины изученных пластовых магматических тел имеют обращённый тип магнитной текстуры, когда максимальная ось K 1 направлена перпендикулярно плоскости покрова или силла. Такой тип AMS может быть первичным и отражать преобладающее вертикальное движение расплава, однако чаще он вторичный и обусловлен присутствием однодоменных ферримагнитных зёрен, образовавшихся в результате окисления или распада нестабильных низкожелезистых титаномагнетитов [13]. Эксперименты показывают, что первичная ориентировка эллипсоида AMS может быть восстановлена после температурного воздействия или размаг-ничивания переменным магнитным полем [13,14].…”

unclassified

Design features of the Franz Josef Land volcanic provinces (Arctic Ocean): estimation of lava direction by anisotropy of magnetic susceptibility

Abashev

Vernikovsky

Верниковский³

et al. 2019

Доклады Академии наук

View full text Add to dashboard Cite

The paper presents the first results of studying the anisotropy of magnetic susceptibility in the basalts from Hooker Island, associated with the direction of the melt movement, the location of the eruption centers and the morphology of magmatic bodies. The established features of the primary magnetic fabrics correspond to the trap mechanism of formation of the volcanic province of the Franz Josef Land Archipelago and are a reflection of the simultaneous action of numerous small eruption centers. Previously obtained conclusions about the long, during the Early Jurassic - Early Cretaceous, multi-stage history of magmatism are not confirmed.

show abstract

Internal structure of basalt flows: insights from magnetic and crystallographic fabrics of the La Palisse volcanics, French Massif Central

Cited by 23 publications

References 60 publications

Evidence of sheared sills related to flank destabilization in a basaltic volcano

Evidence of sheared sills related to flank destabilization in a basaltic volcano

Magnetic fabrics in the Bjerkreim Sokndal Layered Intrusion, Rogaland, southern Norway: Mineral sources and geological significance

Design features of the Franz Josef Land volcanic provinces (Arctic Ocean): estimation of lava direction by anisotropy of magnetic susceptibility

Contact Info

Product

Resources

About