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Biotite porphyroblast nucleation and growth: control by microfracture of pre-existing foliations in schists in the Robertson River Metamorphics, Australia

Published online by Cambridge University Press:  01 May 2009

B. K. Davis
B. K. Davis
Affiliation:
Department of Earth Sciences, James Cook University, Townsville, Queensland 4811, Australia
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Abstract

A macroscopic fold formed during the fourth deformation, D4, in the Robertson River Metamorphics, north Queensland, Australia. Growth of biotite, garnet, staurolite and andalusite porphyroblasts also occurred synchronous with D4. Only biotite porphyroblasts have formed preferred alignments across the fold, and they define two dominant orientations. The more common is parallel to D4 fold axes, which is also parallel to D1 D2 and D4 intersection lineations. The other varies up to 90° from this within the D4 axial plane. Mineral elongation lineations do not reflect the extension direction of the deformation in which they formed (D4), but are a function of pre-existing anisotropics in the rock parallel to intersection lin-eations. Porphyroblast growth is inferred to be a result of microfracturing along favourably oriented linear anisotropics formed by multiple intersection of foliations, as well as parting of the the S1, and S2 foliations.

Type
Articles
Information
Geological Magazine , Volume 133 , Issue 1 , January 1996 , pp. 91 - 102
Copyright
Copyright © Cambridge University Press 1996

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References

Bell, T. H., 1981. Foliation development: the contribution, geometry and significance of progressive bulk inhomogeneous shortening. Tectonophysics 75, 273–96.CrossRefGoogle Scholar
Bell, T. H., 1986. Foliation development and reactivation in metamorphic rocks: the reactivation of earlier foliations and decrenulation due to shifting patterns of deformation partitioning. Journal of Metamorphic Geology 4, 421–44.CrossRefGoogle Scholar
Bell, T. H., & Duncan, A. C., 1978. A rationalized and unified shorthand for lineations and fold axes in tectonites. Tectonophysics 47, T1–T5.CrossRefGoogle Scholar
Bell, T. H., & Hayward, N., 1991. Episodic metamorphic reactions during orogenesis: the control of deformation partitioning on reaction sites and reaction duration. Journal of Metamorphic Geology 9, 619–40.CrossRefGoogle Scholar
Bell, T. H., & Rubenach, M. J., 1983. Sequential porphyroblast growth and crenulation cleavage development during progressive deformation. Tectonophysics 92, 171–94.CrossRefGoogle Scholar
Bell, T. H., Rubenach, M. J., & Fleming, P. D., 1986. Porphyroblast nucleation, growth and dissolution in regional metamorphic rocks as a function of deformation partitioning during foliation development. Journal of Metamorphic Geology 4, 37–67.CrossRefGoogle Scholar
Black, L. P., Bell, T. H., Rubenach, M. J., & Withnall, I. W., 1978. Geochronology of discrete structural—metamorphic events in a multiply deformed Precambrian terrain. Tectonophysics 54, 103–37.CrossRefGoogle Scholar
Carmichael, D. M., 1967. On the mechanism of prograde metamorphic reactions in quartz-bearing pelitic rocks. Contributions to Mineralogy and Petrology 20, 244–67.CrossRefGoogle Scholar
Cox, S. F., & Etheridge, M. A., 1983. Crack-seal fibre growth mechanisms and their significance in the development of oriented layer silicate microstructures. Tectonophysics 82, 142–70.Google Scholar
Davis, B. K., 1993. Mechanism of emplacement of the Cannibal Creek Granite with special reference to timing and deformation history of the aureole. Tectonophysics 224, 337–62.CrossRefGoogle Scholar
Davis, B. K., 1995. Regional-scale foliation reactivation and reuse during formation of a macroscopic fold in the Robertson River Metamorphics, north Queensland, Australia. Tectonophysics 242, 293–311.CrossRefGoogle Scholar
Davis, B. K., & Forde, A., 1994. Regional slaty cleavage formation and fold axis rotation by re-use and reactivation of preexisting foliations: The Fiery Creek Slate Belt, North Queensland. Tectonophysics 230, 161–79.CrossRefGoogle Scholar
Gibson, R. L., 1992. Sequential, syndeformational porphyroblast growth during Hercynian low-pressure/high-temperature metamorphism in the Canigou massif, Pyrenees. Journal of Metamorphic Geology 10, 637–50.CrossRefGoogle Scholar
Hammond, R. L., 1987. The influence of deformation partitioning on dissolution and solution transfer in low-grade tectonic mélange. Journal of Metamorphic Geology 5, 195–211.CrossRefGoogle Scholar
Johnson, S. E., & Vernon, R. H., 1995. Stepping stones and pitfalls in the determination of an anticlockwise P—T—t deformation path: the low—P, high—T Cooma Complex, Australia. Journal of Metamorphic Geology 13, 165–83.CrossRefGoogle Scholar
Meneilly, A. W., 1982. Regional structure and syntectonic granite intrusion in the Dalradian of the Gweebarra Bay area, Donegal. Journal of the Geological Society, London 139, 633–65.CrossRefGoogle Scholar
Patrick, B. E., 1988. Synmetamorphic structural evolution of the Seward Peninsula blueschist terrane, Alaska. Journal of Structural Geology 10, 555–65.CrossRefGoogle Scholar
Phillips, E. R., & Key, R. M., 1992. Porphyroblast—fabric relationships: an example from the Appin Group in the Glen Roy area. Scottish Journal of Geology 28, 89–101.CrossRefGoogle Scholar
Reinhardt, J., & Rubenach, M. J., 1989. Temperature—time relationships across metamorphic zones: evidence from porphyroblast—matrix relationships in progressively deformed metapelites. Tectonophysics 158, 141–61.CrossRefGoogle Scholar
Ridley, J., 1986. Parallel stretching lineations and fold axes oblique to displacement direction — a model and observations. Journal of Structural Geology 8, 647–54.CrossRefGoogle Scholar
Tobisch, O. T., & Paterson, S. R., 1988. Analysis and interpretation of composite foliations in areas of progressive deformation. Journal of Structural Geology 10, 745–54.CrossRefGoogle Scholar
Watkinson, A. J., & Cobbold, P. R., 1981. Axial directions of folds in rocks with linear/planar fabrics. Journal of Structural Geology 3, 211–17.CrossRefGoogle Scholar
Weber, W., 1976. Gefugeuntersuchungen an transver-salgeschieferten Gesteinen aus dem ostlichen Rheineschen Schiefergebirge. Geologisches Jahrbuch 15, 3–98.Google Scholar
White, D. A., 1962. Georgetown 1:250,000 geological series explanatory notes. Canberra: Bureau of Mineral Resources, Geology and Geophysics.Google Scholar
Withnall, I. W., Bain, J. H. C., & Rubenach, M. J., 1980. The Precambrian geology of northeastern Queensland. In The Geology and Geophysics of Northeastern Australia (eds Henderson, R. A., and Stephenson, P. J.), pp. 109–28. Brisbane: Geological Society of Australia, (Queensland Division).Google Scholar