.mw-parser-output .hidden-begin{box-sizing:border-box;width:100%;padding:5px;border:none;font-size:95%}.mw-parser-output .hidden-title{font-weight:bold;line-height:1.6;text-align:left}.mw-parser-output .hidden-content{text-align:left}@media all and (max-width:500px){.mw-parser-output .hidden-begin{width:auto!important;clear:none!important;float:none!important))You can help expand this article with text translated from the corresponding article in Italian. (June 2022) Click [show] for important translation instructions. View a machine-translated version of the Italian article. Machine translation, like DeepL or Google Translate, is a useful starting point for translations, but translators must revise errors as necessary and confirm that the translation is accurate, rather than simply copy-pasting machine-translated text into the English Wikipedia. Consider adding a topic to this template: there are already 3,049 articles in the main category, and specifying|topic= will aid in categorization. Do not translate text that appears unreliable or low-quality. If possible, verify the text with references provided in the foreign-language article. You must provide copyright attribution in the edit summary accompanying your translation by providing an interlanguage link to the source of your translation. A model attribution edit summary is Content in this edit is translated from the existing Italian Wikipedia article at [[:it:Peperino]]; see its history for attribution. You should also add the template ((Translated|it|Peperino)) to the talk page. For more guidance, see Wikipedia:Translation.
Peperite at Puy de Crouel in Auvergne, France
Peperite from Cumbria, England. This example was formed during the Ordovician Period and it is of andesitic composition.

A peperite is a type of volcaniclastic rock consisting of sedimentary rock that contains fragments of younger igneous material and is formed when magma comes into contact with wet sediments.[1] The term was originally used to describe rocks from the Limagne region of France,[2] from the similarity in appearance of the granules of dark basalt in the light-coloured limestone to black pepper. Typically the igneous fragments are glassy and show chilled-margins to the sedimentary matrix, distinguishing them from clasts with a sedimentary origin.

Terminology

The term has been used to describe a wide variety of rocks that are interpreted to have formed by the interaction between magma and sediments. This usage has led to overlap with other terms such as hyaloclastite.[2] In the most recent edition of 'Igneous rocks' by Le Maître et al. [3] the definition is given as "A local term for a tuff or breccia, formed by the intrusion of magma into wet sediments. Usually consists of glassy fragments of igneous rock and some sedimentary rock", while White (2000) defines peperite as "a genetic term applied to a rock formed essentially in situ by disintegration of magma intruding and mingling with unconsolidated or poorly consolidated, typically wet sediments. The term also refers to similar mixtures generated by the same processes operating at the contacts of lavas and other hot volcaniclastic deposits with such sediments".[1]

Formation

When magma comes into contact with wet sediment several processes combine to produce the mixture of sedimentary and igneous clasts which is characteristic of a peperite. These processes are required to produce both the disintegration or fragmentation of magma to form juvenile clasts and the mingling of these clasts within the sediment.[1] Mechanisms proposed for the fragmentation of the magma include; fracturing due to the stresses associated with quenching, autobrecciation due to continuing flow in the cooling magma, pore-water steam explosions and magma-sediment density contrasts. The main mechanism suggested for mingling of the igneous clasts with the sediment is fluidisation, in the sense of particle support and transport by a fluid.[1]

Occurrence

Peperites are found world-wide in sediments with a significant water content at the time of formation associated with igneous rocks covering the compositional range from basalt to rhyolite.[1]

References

  1. ^ a b c d e Skilling, I.P., White, J.D.L/ & McPhie, J. 2002. Peperite: a review of magma-sediment mingling, Journal of Volcanology and Geothermal Research, 114, 1-17
  2. ^ a b de Goer de Herve, A. 2008. Chapter 5, Peperites from the Limagne Trench (Auvergne, French Massif Central), a distinctive feature of phreatomagmatic pyroclastics. History of semantic drift. In: Leyrit, H. & Montenat, C. (Eds.) Volcaniclastic rocks, from magmas to sediments, Taylor & Francis, 270pp.
  3. ^ Le Maître, R. W. et al. (Eds.) 2002. Igneous Rocks: A Classification and Glossary of Terms: Recommendations of the International Union of Geological Sciences Subcommission on the Systematics of Igneous Rocks
Categories