Zum Problem der Bruchbildung, Schieferung und Faltung

Hoeppener, Rolf

doi:10.1007/bf01802011

Cited by 81 publications

(10 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Synthetic shear on crenulation cleavages is commonly assumed (e.g. Hoeppener, 1956;Williams, 1976), but displacements arising from such shearing are commonly difficult to distinguish from micro-displacements due to volume loss associated with strain-induced dissolution (Hobbs et al, 1976, pp. 231-252;Gray & Durney, 1979).…”

Section: Fold Development and Inferred Shear Sensesmentioning

confidence: 99%

Microstructural analysis of the classical spiral garnet porphyroblasts of south‐east Vermont: evidence for non‐rotation

Hayward

1992

Journal Metamorphic Geology

View full text Add to dashboard Cite

New data strongly suggest that the classical spiral garnet porphyroblasts of south-east Vermont, USA, generally did not rotate, relative to geographical coordinates, throughout several stages of non-coaxial ductile deformation. The continuity of inclusion trails (S,) in these porphyroblasts is commonly disrupted by planar to weakly arcuate discontinuities, consisting of truncations and differentiation zones where quartz-graphite S, bend sharply into more graphitic S,. Discontinuous, tight microfold hinges with relatively straight axial planes are also present. These microstructures form part of a complete morphological gradation between near-orthogonally arranged, discontinuous inclusion segments and smoothly curving, continuous S, spirals. Some 2700 pitch measurements of well-developed inclusion discontinuities and discontinuous microfold axial planes were taken from several hundred vertically orientated thin sections of various strike, from specimens collected at 28 different locations around the Chester and Athens domes. The results indicate that the discontinuities have predominantly subvertical and subhorizontal orientations, irrespective of variations in the external foliation attitude, macrostructural geometry and apparent porphyroblast-matrix rotation angles. Combined with evidence for textural zoning, this supports the recent hypothesis that porphyroblasts grow incrementally during successive cycles of subvertical and subhorizontal crenulation cleavage development. Less common inclined discontinuities are interpreted as resulting from deflection of anastomosing matrix foliations around obliquely orientated crystal faces prior to inclusion. Most of the idioblastic garnet porphyroblasts have a preferred crystallographic orientation. Dimensionally elongate idioblasts also have a preferred shape orientation, with long axes orientated normal to the mica folia, within which epitaxial nucleation occurred.Truncations and differentiation zones result from the formation of differentiated crenulation cleavage seams against porphyroblast margins, in association with progressive and selective strain-induced dissolution of matrix minerals and locally also the porphyroblast margin. Non-rotation of porphyroblasts, relative to geographical coordinates, suggests that deformation at the microscale is heterogeneous and discontinuous in the presence of undeformed, relatively large and rigid heterogeneities, which cause the progressive shearing (rotational) component of deformation to partition around them. The spiral garnet porphyroblasts therefore preserve the most complete record of the complex, polyphase tectonic and metamorphic history experienced in this area, most of which was destroyed in the matrix by progressive foliation rotation and reactivation, together with recrystallization.

show abstract

Section: Fold Development and Inferred Shear Sensesmentioning

confidence: 99%

Microstructural analysis of the classical spiral garnet porphyroblasts of south‐east Vermont: evidence for non‐rotation

Hayward

1992

Journal Metamorphic Geology

View full text Add to dashboard Cite

show abstract

“…Zun/iehst bildet sieh h/iufig diejenige Sehar st/irker aus, die etwa senkreeht auf der Ebene maximaler Tangentialversehiebung der Deformation M steht (Abb. 14) und die wir als antithetische Sehar bezeichnen (R. HOEPPENER 1956, nach H. CLOOS 1986. Bei erheblichen Deformationsbetrtigen kann sp~iter die synthetisehe Schar das lJbergewicht erlangen.…”

Section: Abb 2 Bodmmer Deformationstiseh Mit Sehahpultunclassified

Zur physikalischen Tektonik Bruchbildung bei verschiedenen affinen Deformationen im Experiment

1969

View full text Add to dashboard Cite

Mit 14 Abbildungen ZusammenfassungIn einem tJberbliek fiber s~mtliehe affinen Deformationen wird der Bereieh der Deformationen herausgestelh, die no& nieht im Experiment auf die Zusammenh~inge zwisehen Bruchbildung und Art der Deformation untersueht sin& Eine Apparatur, mit der die vorhandenen Lfieken in unserer experimentellen Erfahmng teilweise geschlossen werden k6nnen, wird besehrieben. Die Ergebnisse erster Versuchsreihen werden dargelegt. AbstractA review of all homogeneous deformations shows that part of deformations which has, so far, not been studied in relation to fracturing and kind of deformation. An apparatus is described which enables the gaps in our experimental experience to be closed. The resul~s of the first series of experiments are shown.

show abstract

“…They have been noted in various parts of the world and in rocks of different ages, for instance the Devonian Hunsruckschiefer of West Germany (Hoeppener, 1956;Roy, 1978); the Late Precambrian Ballachulish Slates, West Scotland (Voll, 1960); and the Cambrian Mettawee Slate of West Vermont, U.S.A. (Maltman, A. J., 1971, unpubl. thesis, Urbana, Illinois).…”

Section: Introductionmentioning

confidence: 99%

Chlorite-mica stacks in low-strain rocks from central Wales

1982

View full text Add to dashboard Cite

Weakly deformed, low grade, Lower Palaeozoic metasediments from central Wales contain abundant stack-like intergrowths of chlorite and white mica that closely resemble stacks described from the Devonian Hunsruckschiefer of West Germany; the Ordovician Martinsburg Slate, New Jersey, U.S.A.; and elsewhere. Several theories have been proposed to explain the origin of such stacks, including a detrital origin; strain-controlled growth of chlorite on a detrital mica nucleus; and strain-controlled intergrowth during metamorphism. None of these satisfactorily explains the central Wales stacks. A detrital origin is precluded by the presence of many stacks with shapes too delicate to have survived transportation, and a lack of hydrodynamic equivalence between the stacks and the clastic host grains. Features inconsistent with strain-controlled growth are constant alignment parallel to bedding but non-systematic orientation with respect to tectonic cleavage, their common occurrence in undeformed rocks, and petrographic evidence that they precede the tectonic cleavage. It is proposed that the stacks formed during diagenesis and low-grade metamorphism, and before the onset of deformation, through mimetic growth on a primary bedding fabric composed of clay minerals.

show abstract

Zum Problem der Bruchbildung, Schieferung und Faltung

Cited by 81 publications

References 26 publications

Microstructural analysis of the classical spiral garnet porphyroblasts of south‐east Vermont: evidence for non‐rotation

Microstructural analysis of the classical spiral garnet porphyroblasts of south‐east Vermont: evidence for non‐rotation

Zur physikalischen Tektonik Bruchbildung bei verschiedenen affinen Deformationen im Experiment

Chlorite-mica stacks in low-strain rocks from central Wales

Contact Info

Product

Resources

About