Tuffite

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Tuffite is a tuff containing both pyroclastic and detrital materials, but predominantly pyroclasts (Glossary of Geology).

According to IUGS definition tuffite contains 75% to 25% volcanic (epiclastic) material.[1]

There are several classifications that define tuffite. The classification present in the IUGS recommendation are based on the definition established by Schmid (1981).[2] Shvetsov defined tuffites as rocks containing 50-90% of the volcanic fragments.[3] Tuffite should therefore contain more than half of volcanic material. If rock contains more than 75% to 90% of pyroclastic material it is referred to as tuff. Some other, mostly older sources state that tuffite may contain 10-50% volcanic material.[4]

The adjective tuffitic is used for sediments containing less than 25% volcanic fragments.

A tuffite consists of angular and/or rounded fragments of effusive rocks and their minerals, also may contain volcanic ash, pumice and clay minerals. Nonvolcanic material may consist of terrigenous, chemical precipitates or organogenic components. Quartz or mica and an admixture of carbonates, siliceous rock fragments or organic remains may be common.

References[edit]

  1. ^ Le Maitre (Editor), 2002, Igneous rocks A Classification and Glossary of Terms Recommendations of the International Union of Geological Sciences Subcommission on the Systematics of Igneous Rocks. Cambridge University Press, Cambridge, p. 9
  2. ^ Schmid, R., 1981, Descriptive nomenclature and classification of pyroclstic deposits and fragments: Recommendations of the IUGS Subcommission on the Systematics of Igneous Rocks. Geology. The Geological Society of America. Boulder, 9, pp. 41–43
  3. ^ Vozárová, A., 2009, Petrohraphy of sedimentary rocks. Comenius University Press, Bratislava, Bratislava, 173 pp. (in Slovak)
  4. ^ Petránek, Jan (2007). "On-line geological encyclopedia". Pyroklastické horniny. geology.cz. Retrieved 2012-07-21.  (in Czech)