| Reference Type | Journal (article/letter/editorial) |
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| Title | The nature and origin of orbicular rocks from near Deshai, Swat Kohistan, Pakistan |
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| Journal | Mineralogical Magazine | ISSN | 0026-461X |
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| Authors | Symes, R. F. | Author |
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| Bevan, J. C. | Author |
| Qasim Jan, M. | Author |
| Year | 1987 (December) | Volume | 51 |
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| Issue | 363 |
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| Publisher | Mineralogical Society |
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| Download URL | https://rruff.info/doclib/MinMag/Volume_51/51-363-635.pdf+ |
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| DOI | doi:10.1180/minmag.1987.051.363.02Search in ResearchGate |
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| Generate Citation Formats |
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| Mindat Ref. ID | 1436 | Long-form Identifier | mindat:1:5:1436:0 |
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| GUID | 0 |
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| Full Reference | Symes, R. F., Bevan, J. C., Qasim Jan, M. (1987) The nature and origin of orbicular rocks from near Deshai, Swat Kohistan, Pakistan. Mineralogical Magazine, 51 (363) 635-647 doi:10.1180/minmag.1987.051.363.02 |
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| Plain Text | Symes, R. F., Bevan, J. C., Qasim Jan, M. (1987) The nature and origin of orbicular rocks from near Deshai, Swat Kohistan, Pakistan. Mineralogical Magazine, 51 (363) 635-647 doi:10.1180/minmag.1987.051.363.02 |
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| In | (1987, December) Mineralogical Magazine Vol. 51 (363) Mineralogical Society |
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| Abstract/Notes | AbstractOrbicular dioritic-noritic rocks from an area of mixed metemorphic and igneous rocks in Swat Kohistan, northern Pakistan, have been examined petrographically and chemically in order to determine the nature and origin of the orbicular texture. Using textural and compositional sequences it has been possible to relate the apparently different orbs to one another, and obtain a sequence of orb formation. The majority of the orbs comprise a series of distinct layers (shells) surrounding a central zone (core). Plagioclase, clinopyroxene, orthopyroxene and hornblende form the bulk of the shells. The cores have been extensively recrystallized. The development of a ‘comb-layered’ texture in some orbs and in associated layered rocks is comparable to that commonly described from other occurrences. A dual igneous/metasomatic crystallization history is invoked to explain the features of the orbs in this locality, the oscillatory zoning of the orbicular structure being caused by the alteration of primary minerals, such as pyroxene to amphibole, due to fluctuations in the pH2O of the magma. |
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