Some remarks on fabric overprints and constrictional AMS fabrics in igneous rocks

Schulmann, Karel; Ježek, Josef

doi:10.1007/s00531-011-0681-z

Cited by 25 publications

(15 citation statements)

References 45 publications

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“…In these cases, the AMS can be interpreted in terms of mineral-(phyllosilicate) preferred orientation; the principal AMS axis (k1) is then directly correlated to the magmatic lineation and the minimum axis (k3) can be considered as the pole of the magmatic foliation. However, recent studies suggest that during the emplacement (magmatic conditions) some deformation phases may overprint each other contributing to the finite strain ellipsoid and, thus, the study of AMS alone does not necessarily unravel the complete deformational history of the granite (Schulmann & Ježek, 2012). In addition, the correspondence between deformation axes from felspar and biotite is not always univocal (Kratinová et al, 2010;Román-Berdiel, Pueyo-Morer, & Casas-Sainz, 1995).…”

Section: Methodsmentioning

confidence: 99%

Anisotropy of magnetic susceptibility of the Pyrenean granites

et al. 2017

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In this paper, we report on a compilation of more than 2200 sites (more than 10,000 individual measurements) where anisotropy of magnetic susceptibility (AMS) was studied in granites from the Variscan Pyrenees. The standardization and homogenization of this information has allowed us to produce three Main Maps that synthesize all the information related with the AMS of the Pyrenean granites. We also describe the problems found during the construction of the database (variable geo-positioning, different published information, etc.). The information derived from 21 granite bodies, the database, and the synthesis maps (magnetic susceptibility, Km, and the orientation of the magnetic foliation, plane perpendicular to k3, and of the magnetic lineation, k1) allow us to see for the first time a complete image of this important kinematic and petrographic indicator. ARTICLE HISTORY

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Section: Methodsmentioning

confidence: 99%

Anisotropy of magnetic susceptibility of the Pyrenean granites

et al. 2017

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“…Hence, the younger granites of the plutonic complex (Jizera, Harrachov, and Krkonoše) record the ~ NNE‐SSW shortening of this crustal block, replaced by vertical shortening perhaps owing to collapse of the pluton roof, and the ~ WNW‐ESE stretching (Figure a). The superposition of flat onto steep foliations about a common stretching direction, best exemplified by the prolate AMS ellipsoids in the Jizera granite (Figure b), is not only in agreement with the results of numerical modeling [ Kratinová et al ., ; Schulmann and Ježek , ] but also seems to be a general feature of syntectonic plutons emplaced in a strike‐slip setting [e.g., Bouchez et al ., ; Archanjo et al ., ; Greiling and Verma , ]. Local, channelized flow of the phenocryst‐poor residual magmas (as recorded by mafic schlieren) then occured within this already highly crystallized but still actively deforming magma chamber.…”

Section: Discussionmentioning

confidence: 97%

Multistage magma emplacement and progressive strain accumulation in the shallow‐level Krkonoše‐Jizera plutonic complex, Bohemian Massif

et al. 2013

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[1] Field relationships combined with new U-Pb zircon geochronology suggest that the shallow-level Krkonoše-Jizera plutonic complex, northern Bohemian Massif, was assembled successively from bottom to top, starting with emplacement of the separately evolved S-type Tanvald granite (317.3 ± 2.1 Ma), followed by at least two voluminous batches of the I-type porphyritic Liberec (319.5 ± 2.3 Ma) and Jizera (320.1 ± 3.0 Ma and 319.3 ± 3.7 Ma) granites. The intrusive sequence was completed by uppermost, minor intrusions of the equigranular Harrachov (315.0 ± 2.7 Ma) and Krkonoše granites. The I-type granites exhibit an unusually complex pattern of superposed feldspar phenocryst and magnetic fabrics as revealed from the anisotropy of magnetic susceptibility (AMS). The outer Liberec granite preserves margin-parallel foliations and lineations, interpreted to record emplacement-related strain captured by cooling from the pluton floor and walls. In contrast, the inner Jizera, Harrachov, and Krkonoše granites were overprinted by synmagmatic strain resulting from dextral movements along regional strike-slip faults cutting the opposite ends of the plutonic complex. Late-stage felsic dikes in the Liberec and Jizera granites reorient from horizontal to vertical (lineation-perpendicular) attitude in response to changing the least principal stress direction, whereas mafic schlieren do not do so, representing only randomly oriented small-scale thermal-mechanical instabilities in the phenocryst framework. In general, this case example challenges the common approach of inferring pluton-wide magma flow from interpolated foliation, lineation, and schlieren patterns. More likely, magmatic fabrics in large plutons record complex temporal succession of superposed strains resulting from diverse processes at multiple scales.

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“…In contrast, the submagmatic marginal fine‐grained granodiorite is marked by a T parameter that is shifted to mostly oblate shapes and exhibits a narrow and truncated histogram distribution. This distribution is attributed to magma flow in the submagmatic state (Ježek et al, ) or to transposition of an earlier magmatic fabric in magmatic state (Kratinová et al, ; Kratinová, Ježek, et al, ; Schulmann & Ježek, ).…”

Section: Discussionmentioning

confidence: 99%

Crystal Mush Flow in Small Concentrically Expanded Pluton (Castle Crags Pluton; Klamath Mountains, CA, USA)

Machek

Závada

Roxerová

et al. 2019

Geochem Geophys Geosyst

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Understanding of the processes of magmatic fabric formation in crystal‐rich magmas and their reflection in rock magnetic properties are important for understanding pluton formation and intrusion mechanisms. On the example of small concentrically zoned Castle Crags pluton in the Klamath Mountains (CA, USA) we provide reconstruction of the flow/deformation mechanisms of the crystal‐rich magma and pluton growth based on detailed structural mapping and microstructural analysis employing the anisotropy of magnetic susceptibility, microstructural analysis, and crystallographic preferred orientation. Our study reveal microstructural evidence for progressive development of magmatic textures in the pluton core transitioning to submagmatic and eventually subsolidus fabric at the pluton periphery, that is interpreted in terms of the flow/deformation of the crystal mush. The documented magmatic textures are linked to anisotropy of magnetic susceptibility parameters and orientation. The recorded anomalous degree of anisotropy of magnetic susceptibility found in the pluton is attributed to tiling and plastic deformation of magnetite grains by the surrounding phenocrysts. The concentric structure of the pluton resulted from horizontal compaction and margin parallel stretching of the dense crystal mush around the vertically intruding trondhjemite magma in the pluton core. The Castle Crags pluton is interpreted as a concentrically expanded pluton, which grew at least by two increments of granodiorite and trondhjemite magma emplacement.

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Some remarks on fabric overprints and constrictional AMS fabrics in igneous rocks

Cited by 25 publications

References 45 publications

Anisotropy of magnetic susceptibility of the Pyrenean granites

Anisotropy of magnetic susceptibility of the Pyrenean granites

Multistage magma emplacement and progressive strain accumulation in the shallow‐level Krkonoše‐Jizera plutonic complex, Bohemian Massif

Crystal Mush Flow in Small Concentrically Expanded Pluton (Castle Crags Pluton; Klamath Mountains, CA, USA)

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