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A scanning electron microscope study of post-depositional changes in the northeast Niğde ignimbrites, South Central Anatolia, Turkey

Published online by Cambridge University Press:  05 July 2018

S. Yurtmen  and
G. Rowbotham
S. Yurtmen
Affiliation:
Çukurova Üniversitesi, Mühendislik-Mimarlik Fakültesi, Jeoloji Mühendisligi Bölümü, 01330, Balcali, Adana, Turkey
G. Rowbotham
Affiliation:
Department of Earth Sciences, University of Keele, Keele, Staffordshire, ST5 5BG, UK
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Abstract

The ignimbrites of the northeast Niğde area, which are subdivided into the Lower, Middle and Upper ignimbrites on the basis of their compositional and stratigraphical characteristics, display textural variations from the base to the top. A large proportion of these ignimbrites have been altered and recrystallized by the processes of compaction, welding and devitrification, and as a result of volatile movement. The alteration and recrystallization processes include four stages: hydration, glassy and spherulitic stages accompanied by vapour-phase crystallisation. In the early phases of devitrification, detailed shard shapes are easily recognisable with the scanning electron microscope, but as alteration proceeds clarity of detail disappears because compaction results in collapse of the structure of the rock. Spherulitic and vapour-phase crystallisation usually involves the growth of alkali feldspar and cristobalite. These later stages are more common in the Upper Ignimbrite than the Middle and Lower ignimbrites.

Keywords

ignimbriteNiğdecompactionweldingdevitrificationhydrationglassyspheruliticvapour-phase
Type
Research Article
Information
Mineralogical Magazine , Volume 63 , Issue 1 , February 1999 , pp. 131 - 141
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1999

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References

Bates, R.L. and Jackson, J.A. (eds.) (1980) Glossary of geology. Amer. Geol. Inst., Falls Church, Virginia, USA pp. 1–175.Google Scholar
Branney, M.J. and Kokelaar, P. (1992) A reappraisal of ignimbrite emplacement: progressive aggradation and changes from particulate to non-particulate flow during emplacement of high-grade ignimbrite. Bull. Volcanol., 54, 504–20.CrossRefGoogle Scholar
Carr, R.G. (1981) A scanning electron microscope study of post depositional changes in the Matahina ignimbrite. North Island, New Zealand. N.Z. J. Geol. Geophys., 24, 429–39.Google Scholar
Cas, R.A.F. and Wright, J.V. (1987) Volcanic Successions. Unwin-Hyman, 578 pp.CrossRefGoogle Scholar
Chapin, C.E. and Lowell, G.R. (1979) Primary and secondary flow structures in ash-flow tuffs of the Gribbles Run paleovalley, central Colorado. Geol. Soc. Amer. Spec. Pap., 180, 137–54.Google Scholar
Elston, W.E. and Smith, E.I. (1970) Determination of flow direction of rhyolite ash-flow tuffs from fluidal textures. Geol. Soc. Amer. Bull., 81, 3393–406.CrossRefGoogle Scholar
Ewart, A. (1965) Mineralogy and petrology of the Whakamuru Ignimbrite in the Maraetai area of the Taupo volcanic zone, New Zealand. N.Z. J. Geol. Geophys., 8, 611–77.CrossRefGoogle Scholar
Lirer, L., Pescatore, T., Booth, B. and Walker, G.P.L. (1973) Two Plinian pumice-fall deposits from Somma Vesuvius, Italy. Geol. Soc. Amer. Bull., 84, 759–72.2.0.CO;2>CrossRefGoogle Scholar
Ross, G.S. and Smith, R.L. (1961) Ash-flow tuffs, their origin, geological relations and identification. U.S. Geol. Surv. Prof. Pap., 366.Google Scholar
Schminke, H.U. (1974) Volcanological aspects of peralkaline silicic welded ash-flow tuffs. Bull. Volcanol., 38, 594–636.CrossRefGoogle Scholar
Sheridan, M.F. (1970) Fumarolic mounds and ridges of the Bishop Tuff, California. Geol. Soc. Amer. Bull., 81, 851–68.CrossRefGoogle Scholar
Smith, R.L. (1960b) Zones and zonal variations in welded ash flows. U.S. Geol. Surv. Prof. Pap., 345–F, 149–59.Google Scholar
Sparks, R.S.J. (1976) Grain size variations in ignim-brites and implications for the transport of pyroclastic flows. Sedimentology, 23, 147–88.CrossRefGoogle Scholar
Sparks, R.S.J. and Walker, G.P.L. (1973) The ground surge deposit: a third type of pyroclastic rock. Nature, Phys. Sci., 241, 62–4.CrossRefGoogle Scholar
Sparks, R.S.J., Wilson, L. and Hulme, G. (1978) Theoretical modelling of the generation, movement and emplacement of pyroclastic flows by column collapse. J. Geophys. Res., 83, 1727–39.CrossRefGoogle Scholar
Yurtmen, S. (1993) Petrological and geochemical studies of pre-Cretaceous metamorphic and Pliocene volcanic rocks in the area Northeast of Niğde, Turkey. PhD thesis, Univ. Keele, UK (unpublished).Google Scholar