Fortey, N. J., Michie, U. McL. (1978) Aegirine of possible authigenic origin in Middle Devonian sediments in Caithness, Scotland. Mineralogical Magazine, 42 (324) 439-442 doi:10.1180/minmag.1978.042.324.05
Reference Type | Journal (article/letter/editorial) | ||
---|---|---|---|
Title | Aegirine of possible authigenic origin in Middle Devonian sediments in Caithness, Scotland | ||
Journal | Mineralogical Magazine | ISSN | 0026-461X |
Authors | Fortey, N. J. | Author | |
Michie, U. McL. | Author | ||
Year | 1978 (December) | Volume | 42 |
Page(s) | 439-442 | Issue | 324 |
Publisher | Mineralogical Society | ||
Download URL | https://rruff.info/doclib/MinMag/Volume_42/42-324-439.pdf+ | ||
DOI | doi:10.1180/minmag.1978.042.324.05Search in ResearchGate | ||
Mindat Ref. ID | 2957 | Long-form Identifier | mindat:1:5:2957:9 |
GUID | ae5c1abe-5ca8-489b-bb49-019433daa47c | ||
Full Reference | Fortey, N. J., Michie, U. McL. (1978) Aegirine of possible authigenic origin in Middle Devonian sediments in Caithness, Scotland. Mineralogical Magazine, 42 (324) 439-442 doi:10.1180/minmag.1978.042.324.05 | ||
Plain Text | Fortey, N. J., Michie, U. McL. (1978) Aegirine of possible authigenic origin in Middle Devonian sediments in Caithness, Scotland. Mineralogical Magazine, 42 (324) 439-442 doi:10.1180/minmag.1978.042.324.05 | ||
In | (1978, December) Mineralogical Magazine Vol. 42 (324) Mineralogical Society | ||
Abstract/Notes | SummaryAn occurrence of aegirine in Middle Devonian lacustrine beds in Caithness is described. The mineral occurs as euhedral to subhedral prismatic crystals within a finely laminated siltstone. Microprobe analyses reveal a remarkably ‘pure’ composition consisting almost entirely of Na, Fe3+, Si, and O. X-ray diffractometry yielded the unit cell data: a 9·657 Å, b 8·800 Å, c 5·296 Å, and β 107·37°. Comparison with other natural aegirine compositions shows marked differences from those of igneous or metamorphic origin but a close similarity to a unique occurrence of authigenic aegirine in the lacustrine Green River Formation of Wyoming, U.S.A. Consideration of the nature of the Caithness occurrence, and comparison of the Devonian Orcadian basin with the Eocene Green River basin indicate similar geological environments. It is suggested that the mineral formed in hypersaline conditions in which sodium may have been derived from contemporaneous alkaline volcanism within the Orcadian basin. |
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