Parameters controlling the density of welded ignimbrites—A case study on the Incesu Ignimbrite, Cappadocia, Central Anatolia

• Published in: Chemie der Erde 2009-01, Vol.69 (4), p.341-357
• Main Authors: Lepetit, P., Viereck-Goette, L., Schumacher, R., Mues-Schumacher, U., Abratis, M.
• Format: Article
• Language: English
• Subjects: Cappadocia; Content of phenocrysts and xenoliths; Density; Ignimbrite; Incesu Ignimbrite
• ISSN: 0009-2819; 1611-5864
• DOI: 10.1016/j.chemer.2009.05.004

Maximum density of the vitrophyre zone of a welded ignimbrite is commonly taken as a direct measure for the degree of welding and thus indirectly for the reconstruction of the paleo-thickness and emplacement temperature of welded ignimbrites [Cas, R.A.F., Wright, J.V., 1987. Volcanic Successions. Chapman and Hall, London; Riehle, J.R., Miller, T.F., Bailey, R.A., 1995. Cooling, degassing and compaction of rhyolitic ash flow tuffs: a computational model. Bull. Volcanol. 57, 319–336]. Variations in primary lithology with respect to phenocrysts and lithic fragments, however, remain unconsidered. Due to the complex formation processes of ignimbrites, a broad variation in primary lithologies is possible, expressed in the established classification of tuffs after Schmid [1981. Descriptive nomenclature and classification of pyroclastic deposits and fragments; recommendations of the IUGS Subcommission on the systematics of igneous rocks. In: Zankl, H., Michot, P., Schwab, K. (Eds) Alfred-Wegener-Symposium I and II. Geol. Rundsch. 70, 794–799]. Nevertheless, the effect of primary lithology on the vitrophyre density may be neglected at low crystal- and lithic-contents: The results of this study on the Incesu Ignimbrite, Central Anatolia, reveal the negligibility of crystals and lithics as their content is only as high as 11 vol% in the vitrophyre zone of the Incesu Ignimbrite. Thus, the uncorrected bulk rock density of the vitrophyre zone of an ignimbrite may serve as a measure of its paleo-thickness at the point sampled. This correlation may then be used to identify the source of an ignimbrite if it is partly eroded.