Alkali feldspar megacryst growth: Geochemical modelling

Słaby, Ewa; Galbarczyk-Gąsiorowska, Luiza; Seltmann, Reimar; Müller, Axel

doi:10.1007/s00710-006-0135-7

Cited by 50 publications

(30 citation statements)

References 57 publications

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“…Detailed studies of Karkonosze crystal geochemistry provide various lines of evidence for this view (Słaby et al 2007a(Słaby et al , b, 2008a. Any interpretation of detected element variability within the crystals requires certainty that the variability is a primary feature inherited from the igneous system.…”

Section: Discussionmentioning

confidence: 99%

“…Some of the zones appear to have crystallized in a homogenous magmatic environment having clear geochemical affinities with the end-member magmas in the Karkonosze pluton (Słaby et al 2007b), whereas others crystallized in heterogeneous domains of hybridized magma. Geochemical modeling of megacryst growth revealed that zones that can be related to almost pure mafic end-member magma are rare and their width extremely narrow (Słaby et al 2007a). Those zones that crystallized in coherent felsic or variably hybridized magma are common.…”

Section: Basic Principlesmentioning

confidence: 99%

“…The compatible elements Ba, Sr, and Rb were selected for this study of feldspar growth. In terms of these elements, mixing occurred between mafic lamprophyric magma enriched in barium and strontium and impoverished in rubidium, and felsic magma with the opposite characteristics (Słaby and Götze 2004;Słaby et al 2007a, Słaby and. In whole rocks, barium is positively correlated with strontium but negatively with rubidium.…”

Section: Feldspar Heterogeneitymentioning

confidence: 99%

“…The microscale can be clearly recognized in mineral compositions and growth morphologies (Gagnevin et al 2005;Ginibre et al 2004;Pietranik and Koepke 2009;Słaby and Götze 2004;Słaby et al 2007aSłaby et al , b, 2008aTepley et al 2000;Waight et al 2000). Induced by mixing, crystal growth progresses in an environment where the dispersion of magmas proceeds by chaotic stretching and folding (Liu 1994b;Perugini and Poli 2004;Perugini et al 2002;Perugini et al 2003).…”

Section: Introductionmentioning

confidence: 99%

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Chaotic three-dimensional distribution of Ba, Rb, and Sr in feldspar megacrysts grown in an open magmatic system

Słaby

Śmigielski

Śmigielski³

et al. 2011

Contrib Mineral Petrol

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As has been demonstrated in recent years, the heterogeneities of coeval magmas can be more successfully revealed by zoned megacrysts rather than by analysis of the whole rocks hosting them. Here, the geochemical heterogeneities of feldspar megacrysts from the Karkonosze granite, Poland, are investigated by LA-ICP-MS. The crystals are the product of migration and growth in regions of poorly mixed magmas. 3D-modeling of the Ba, Sr, and Rb distributions emphasizes the importance of micro-domain growth morphologies. Two models of element behavior-a relative concentration model and a composition gradient model-provide a potentially effective tool for tracking the mixing process on a microscale. Measured concentrations of elements of different mobilities do not agree with what might be expected from the mixing of two end-member magmas. If mixing was the only process occurring, linear correlations between the concentrations of any two elements should be observed; this, however, is not the case. For combinations of any two of the three elements, modeling reveals differing non-linear correlations between concentrations. The megacryst heterogeneities provide an insight into how mixing magmas are chaotically advected to growing crystals and the degree of inter-magma element exchange between the magmas.

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Section: Discussionmentioning

confidence: 99%

Section: Basic Principlesmentioning

confidence: 99%

Section: Feldspar Heterogeneitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Chaotic three-dimensional distribution of Ba, Rb, and Sr in feldspar megacrysts grown in an open magmatic system

Słaby

Śmigielski

Śmigielski³

et al. 2011

Contrib Mineral Petrol

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“…Alkali feldspar is frequently used to give insight into complex magmatic and metamorphic processes (e.g., Vernon 1986Vernon , 2004Knesel et al 1999;Perini et al 2003;Ginibre et al 2004Ginibre et al , 2007Zellmer and Clavero 2006;Słaby et al 2007aSłaby et al , b, 2008Ishii et al 2007;Menegon et al 2008;Vernon and Paterson 2008). The composition of a megacryst, in recording many local events during magma evolution, can be expected to give detailed information about changes in its environment throughout the duration of its growth.…”

Section: Introductionmentioning

confidence: 99%

Protomylonite evolution potentially revealed by the 3D depiction and fractal analysis of chemical data from a feldspar

Słaby

Domonik

Śmigielski

et al. 2014

Contrib Mineral Petrol

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An alkali feldspar megacryst from a protomylonite has been studied using laser ablation-ICP-mass spectrometry combined with cathodoluminescence imaging, Raman spectroscopy, and electron probe microanalysis. The aim was to determine the original (magmatic) geochemical pattern of the crystal and the changes introduced by protomylonitization. Digital concentration-distribution models, derivative gradient models, and fractal statistics, e.g., Hurstexponent values are used in a novel way to reveal subtle changes in the trace-element composition of the feldspar. Formation of the crystal is reflected in a slightly chaotic trace-element (Ba, Sr, and Rb) distribution pattern that is more or less characterized by continuous development from a fairly homogeneous environment. Derivative gradient models demonstrate a microdomain pattern. Fractal statistics show that element behavior was changeable, with Ba and Sr always more persistent (continuing) and Rb always less persistent, with the latter showing a tendency to migrate. The variations in the Hurst exponent are, however, too large to be explained by magmatic differentiation alone. The observed element behavior may be explained by structural changes revealed by Raman spectroscopy and CL. In high-strain domains, T-O-T modes become stronger for Si-O-Al than Al-O-Al linkages. Increasing amounts of Al-O--Al defects are demonstrated by cathodoluminescence. Both may result from small-distance diffusion creep, making the crystal geochemical pattern slightly patchy. In turn, the marginal part of the megacryst has a mosaic of randomly orientated, newly crystallized K-feldspars. The re-growth is confirmed by trace-element distribution patterns and fractal statistics which identify an abrupt change in the transformation environment. The novel set of tools used in this study reveals a complicated history of megacryst formation and transformation that otherwise would be difficult to unravel and decipher.Communicated by J. Hoefs. Electronic supplementary materialThe online version of this article

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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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Alkali feldspar megacryst growth: Geochemical modelling

Cited by 50 publications

References 57 publications

Chaotic three-dimensional distribution of Ba, Rb, and Sr in feldspar megacrysts grown in an open magmatic system

Chaotic three-dimensional distribution of Ba, Rb, and Sr in feldspar megacrysts grown in an open magmatic system

Protomylonite evolution potentially revealed by the 3D depiction and fractal analysis of chemical data from a feldspar

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

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