Magmatic fabric acquisition mechanisms in a syenite: Results of a combined anisotropy of magnetic susceptibility and image analysis study

Launeau, Patrick; Cruden, A. R.

doi:10.1029/97jb02670

Cited by 145 publications

(117 citation statements)

References 61 publications

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“…a crystallization of titanomagnetite that is controlled by the silicate framework with interstitial magnetite grains crystallizing both along and perpendicular to the lineation of earlier crystallized minerals such as plagioclase (cf., Archanjo et al, 2002). Processes of drag and collisions between adjacent grains within a viscous flow could also result in the creation 20 of openings and closings normal to extensional direction (Launeau and Cruden, 1998). Thus the occurrence of elongated aggregates of titanomagnetite oriented perpendicular to the plagioclase alignment could generate the perpendicular orientation of the K 1 axis.…”

Section: Comparison Of the Ams Results Of The Different Rock Types Wimentioning

confidence: 99%

Paleocurrent direction measurements in a volcanic setting by means of anisotropy of magnetic susceptibility: A case study from the Lower Miocene Tepoztlán Formation (Transmexican Volcanic Belt, Central Mexico)

Lenhardt

Böhnel

Hinderer

et al. 2013

Sedimentary Geology

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Sources of ancient volcanic rocks are often unknown if they are either eroded and/or covered by younger deposits. This problem, as well as the provenance of reworked volcaniclastic, fluvial and mass-flow deposits, can be partially solved by the application of anisotropy of the magnetic susceptibility (AMS). For massive and poorly sorted volcaniclastic rocks in particular this may be the only way of finding reliable transport directions and therefore allowing for paleogeographic reconstructions. Here, we present a data set of 428 AMS measurements and 249 measurements of sedimentary paleocurrent indicators from the Miocene Tepoztlán Formation at the southern edge of the Transmexican Volcanic Belt (Central Mexico). The highest degree of reliability of AMS measurements is gained for data from lava samples and the lowest from mass flows. Sedimentary structures in sandstones and conglomerates such as trough cross-stratification, asymmetric ripple marks, and the shape of scours and channels could be used to calibrate the results from AMS data and to prove their reliability. AMS data on fluvial deposits point to a drainage system with a W-E flow direction, indicating an outflow of the river system into the ancient Gulf of Mexico.Keywords: Anisotropy of magnetic susceptibility; paleocurrent direction; volcaniclastic; Transmexican Volcanic Belt; Miocene; Mexico 3 In ancient volcanic settings, one challenge in the investigation of volcanic and volcaniclastic deposits is the determination of source vent locations, since former volcanic centers may be either eroded and/or covered by younger deposits. Furthermore, the determination of the provenance of fluvial and mass-flow deposits, arising from the volcanic ring plain itself (Manville et al., 2009, and references therein) or rivers in distal reaches, can also be problematic. In lava flows, both vesicle and crystal preferred orientations have been used extensively for this purpose (e.g., Waters, 1960;Smith and Rhodes, 1972;Walker, 1989;Cashman and Kauahikaua, 1997;Manga, 1998;Iezzi and Ventura, 2002). However, petrological structures such as foliation and lineation due to the movement of a lava flow are often difficult to observe and measure (Bascou et al., 2005). Massive pyroclastic rocks such as ignimbrites and block-and-ash flow deposits rarely show any measurable alignment or structure that can help determine flow direction. However, the magnetic fabric can be used to determine their paleocurrent direction, and the speed, precision, cheapness and range of applicability make it unique in this regard (Tarling and Hrouda, 1993).All materials, even if they do not acquire remanent magnetization, have a magnetic susceptibility (Liu et al., 2001), which is not always isotropic in the rock (Ising, 1942). This spatial susceptibility variation is defined as the anisotropy of magnetic susceptibility (AMS) and reflects the preferred orientation of magnetic minerals in the rock or sediments, i.e. its magnetic fabric (Hrouda, 1982;Tarling and Hrouda, 1993), which yields thr...

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Section: Comparison Of the Ams Results Of The Different Rock Types Wimentioning

confidence: 99%

Paleocurrent direction measurements in a volcanic setting by means of anisotropy of magnetic susceptibility: A case study from the Lower Miocene Tepoztlán Formation (Transmexican Volcanic Belt, Central Mexico)

Lenhardt

Böhnel

Hinderer

et al. 2013

Sedimentary Geology

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“…Também foram aplicados os métodos do tensor de inércia (Launeau & Cruden 1998) e dos Interceptos (Launeau et al 1990, Launeau & Robin 1996. Para os cálculos dos parâmetros de orientação e forma foram utilizados os programas Rf/Phi versão 1.0 (Mulchrone & Lisle 1999e Mulchrone & Meere 2001, baseado na técnica de Peach & Lisle (1979), RFPSHIM (Brandon 1996) fundamentado em Shimamoto & Ikeda (1976), Intercepts v. 2003(Launeau & Robin 2003a) e SPO v. 2003(Launeau e Robin 2003b.…”

Section: Sérgio Wilians De Oliveira Rodrigues and Frederico Meira Faleirosunclassified

“…Este método foi desenvolvido por Launeau & Cruden (1998) originalmente para quantificação de tramas de rochas magmáticas, tendo sido tipicamente aplicado para batólitos graníticos.…”

Section: Tensor De Inérciaunclassified

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Avaliação de métodos de quantificação da deformação finita por meio de simulações computacionais de deformação progressiva

Rodrigues

Faleiros

2007

RBG

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“…Archanjo et al, 2012;Bouchez, 1997;Cruden et al, 1999;Gleizes et al, 1998;Launeau and Cruden, 1998;López de Luchi et al, 2004;Petronis et al, 2012;Raposo et al, 2012;St Blanquat et al, 2001), lava flows (e.g. Cañón-Tapia and Coe, 2002;Cañón-Tapia, 2004;Loock et al, 2008), and dykes (e.g.…”

Section: Introductionmentioning

confidence: 99%

The relation between magnetite and silicate fabric in granitoids of the Adamello Batholith

et al. 2015

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Keywords:Rock fabrics in granites; X-ray micro-tomography; Anisotropy of magnetic susceptibility (AMS); 3D shape fabrics (SPO); Magnetic interactions AbstractThe link between the macroscopic silicate fabric and the magnetite-controlled AMS (anisotropy of magnetic susceptibility) fabric in ferromagnetic rocks was investigated through a comprehensive comparison between different fabric measurement techniques. Sample lithologies include tonalites and granodiorites from the Lago della Vacca Complex, Adamello Batholith, Italy. The datasets used to assess the link between subfabrics and the coherence between methods include: 1) macroscopic silicate fabric measured directly in the field; 2) macroscopic silicate fabric derived from image analysis (IA) of outcrop pictures and sample pictures; 3) shape-preferred orientations (SPO) of mafic silicates, 4) SPO of magnetite, and 5) calculated distribution of magnetite grains from computer-assisted highresolution X-ray tomography (X-ray CT) images; 6) fabrics derived from the AMS. Macroscopic mineral fabrics measured in the field agree with the IA results and with the SPO of mafic silicates obtained from the X-ray CT imaging. The X-ray CT results show that the SPO of the magnetite grains are consistent with the AMS data whereas the spatial distribution of the magnetite grains is less compatible with the AMS fabric. This implies that the AMS signal is mainly controlled by the shape of the magnetic carrier mineral rather than by the spatial arrangement of the magnetite grains. An exception is the presence of magnetite clusters. Furthermore, the SPO of mafic silicates and the SPO of the magnetite grains are consistent with the AMS data. Another finding of this study is that the magnetic susceptibility correlates linearly with the amount of magnetite in the samples. The coherent results obtained from a variety of methods reinforce the application of both AMS measurements and IA as robust tools to analyse fabrics in granitic intrusions.

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Magmatic fabric acquisition mechanisms in a syenite: Results of a combined anisotropy of magnetic susceptibility and image analysis study

Cited by 145 publications

References 61 publications

Paleocurrent direction measurements in a volcanic setting by means of anisotropy of magnetic susceptibility: A case study from the Lower Miocene Tepoztlán Formation (Transmexican Volcanic Belt, Central Mexico)

Paleocurrent direction measurements in a volcanic setting by means of anisotropy of magnetic susceptibility: A case study from the Lower Miocene Tepoztlán Formation (Transmexican Volcanic Belt, Central Mexico)

Avaliação de métodos de quantificação da deformação finita por meio de simulações computacionais de deformação progressiva

The relation between magnetite and silicate fabric in granitoids of the Adamello Batholith

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