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| 2. |
- Kruhl, Jörn H., et al.
(författare)
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The equilibration of high-angle grain boundaries in dynamically recrystallized quartz: The effect of crystallography and temperature
- 2002
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Ingår i: Journal of Structural Geology. - 0191-8141. ; 24, s. 1125-1137
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Tidskriftsartikel (refereegranskat)abstract
- Dynamically recrystallized and sutured quartz grains from metamorphic rocks with different strain intensities and temperature conditions ranging from ca. 350°C to ca. 700°C have been studied. Universal-stage measurements on quartz-quartz high-angle grain boundaries show that they are never curved but always consist of straight segments which preferentially occupy specific crystallographic orientations in relation to both neighboring crystals. With increasing temperature the segments preferentially concentrate in a decreasing number of orientations, mainly near the rhombohedral {101̄1} planes. The crystallographic data and the observations on grain boundary geometries suggest that: (i) grain boundary orientations are strongly crystallographically controlled, (ii) this control is the main factor on the textural equilibration of quartz-quartz grain boundaries in metamorphic rocks, and (iii) grain boundaries from dynamically recrystallized quartz should be regarded as annealed and equilibrated fabrics that are stable against subsequent annealing as long as the material is not redeformed. © 2002 Elsevier Science Ltd. All rights reserved.
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| 3. |
- Peternell, Mark, 1974, et al.
(författare)
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Automation of pattern recognition and fractal-geometry-based pattern quantification, exemplified by mineral-phase distribution patterns in igneous rocks
- 2009
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Ingår i: Computers & Geosciences. - : Elsevier BV. - 0098-3004. ; 35, s. 1415-1426
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Tidskriftsartikel (refereegranskat)abstract
- This study analyses the possibility of accurate quantification of automatically digitized mineral-phase distribution patterns in igneous rocks. Based on their colour contrast, different minerals were manually and automatically digitized on micro to macro scales. Depending on the digitized mineral phase, the accuracy of the automated digitizing procedure varies. Quantification of mineral distribution patterns was performed by box-counting. The results do not depend greatly on the pattern's pixel density and are similar to each other, even if automatic recording is performed at reduced precision in comparison to manual recording. Consequently, box-counting measurement of automatically recorded mineral distribution patterns (i) leads to fast and accurate pattern quantification, (ii) allows analysis of various phase distribution patterns from micro to macro scales, and (iii) forms an excellent basis for receiving information on pattern-forming processes, which is not available otherwise. © 2009 Elsevier Ltd. All rights reserved.
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| 4. |
- Peternell, Mark, 1974, et al.
(författare)
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Combined quantification of anisotropy and inhomogeneity of magmatic rock fabrics - An outcrop scale analysis recorded in high resolution
- 2011
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Ingår i: Journal of Structural Geology. - : Elsevier BV. - 0191-8141. ; 33, s. 609-623
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Tidskriftsartikel (refereegranskat)abstract
- Magmatic mineral distribution patterns in a syntectonic syenite pluton have been recorded at high resolution over several square metres on quarried faces. The anisotropy and inhomogeneity of K-feldspar and mafic mineral distribution patterns have been quantified using two methods originally based on fractal geometry. (1) Map-counting, based on box-counting, illustrates an inhomogeneity on the decimetre to metre scale and highlights diffuse structures that can be related to mafic schlieren or felsic dykes that are not visible on the rock surface. (2) We have developed a mapping of rock fabric anisotropy (MORFA) method that leads to the detection of further magmatic structures that are not visible in the field. With MORFA a magmatic lineation and its variation over large areas is determined, as well as fabrics on the decimetre to 1 m scales, which possibly represent flow or fracture structures in the crystallising magma. © 2011 Elsevier Ltd.
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| 6. |
- Peternell, Mark, 1974, et al.
(författare)
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Macro and microstructures as indicators of the development of syntectonic granitoids and host rocks in the Camboriú region, Santa Catarina, Brazil
- 2010
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Ingår i: Journal of South American Earth Sciences. - : Elsevier BV. - 0895-9811. ; 29, s. 738-750
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Tidskriftsartikel (refereegranskat)abstract
- In the northeastern Dom Feliciano Belt, Santa Catarina/Brazil, Paleoproterozoic rocks (mainly the Camboriú Complex) and Neoproterozoic granitoids - with the older Itapema Granite and the younger Corre-mar, Rio Pequeno and Serra dos Macacos granites - experienced a deformation history from magmatic to greenschist facies temperatures, under different rheological conditions. The concordance of flat amphibolite facies structures of the Camboriú Complex and magmatic and subsolidus structures in the Itapema Granite indicate the late-tectonic character of the latter. Based on tectonic features, the Corre-mar Granite is interpreted as older than the Rio Pequeno Granite and as related to transcurrent tectonics of the Southern Brazilian Shear Belt.In all granites, microstructures point to widespread magmatic alignment, followed by weak subsolidus and, locally, amphibolite to greenschist facies deformation. Magmatic foliations are progressively weaker in the younger granites. Synmagmatic shear zones in the Rio Pequeno Granite are possibly concentrated at the intrusive contact. The weak solid-state deformation at late-magmatic conditions argues for magmatism within a low-strain zone, which is compatible with the location of the area relative to the Major Gercino and Itajaí shear zones. The amphibolite to greenschist facies deformation structures are attributed to continuous deformation within the same low-strain zone during decreasing temperatures. © 2009 Elsevier Ltd.
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