irregular, wormy penetration by quartz in plagioclase feldspar; these wartlike, wormlike, or fingerlike bodies may develop during the late stages of crystallization of igneous rocks if the two minerals (quartz and feldspar) grow simultaneously in the presence of a volatile phase. Myrmekite also occurs after the rock crystallizes by replacement of the plagioclase during metasomatism or hydrothermal alteration. In rare cases the plagioclase may be almost completely obliterated by the quartz intergrowths. Although the origin is not always clear, it is evidently a late development in the rock. Felsic rocks (felsic and mafic rocks), such as granite, most commonly display this feature, especially if the plagioclase feldspar is adjacent to potash feldspar; rocks displaying this feature are said to have a myrmekitic texture.

* * *

Universalium. 2010.

Нужна курсовая?

Look at other dictionaries:

  • Myrmekite — describes a vermicular, or wormy, intergrowth of quartz in plagioclase. The intergrowths are microscopic in scale, typically with maximum dimensions less than 1 millimeter. The plagioclase is sodium rich, usually albite or oligoclase. These… …   Wikipedia

  • myrmekite — myr·me·kite …   English syllables

  • myrmekite — …   Useful english dictionary

  • Myrmekit — ist ein mikroskopisch dimensioniertes Wachstum von wurmförmigem Quarz im Plagioklas. Der Durchmesser der wurmartigen Quarzstängel oder Quarzröhren bewegt sich meist weit unter einem Millimeter. Diese Verwachsungsstruktur des Myrmekits mit… …   Deutsch Wikipedia

  • Rock microstructure — includes the texture of a rock and the small scale rock structures. The words texture and microstructure are interchangeable, with the latter preferred in modern geological literature. However, texture is still acceptable because it is a useful… …   Wikipedia

  • Lorence G. Collins — Der US amerikanische Petrologe Lorence G. Collins: «Zwei Pfade verzweigten sich im Wald...ich schlug den weniger begangenen ein...das war der Unterschied.» Aus Robert Frost: «The Road Less Taken (Der weniger begangene Weg)» Lorence Gene Larry… …   Deutsch Wikipedia

  • Radiohalo — Radiohalos are microscopic, spherical shells of discolouration in rocks, such as granite, or biotite caused by the inclusion of radioactive grains in the rock or by deposition of radioactive material in them. One widely accepted theory is that… …   Wikipedia

  • Micrographic texture — In petrology, micrographic texture is a fine grained intergrowth of quartz and alkali feldspar, interpreted as the last product of crystallization in some igneous rocks which contain high or moderately high percentages of silica. Micropegmatite… …   Wikipedia

  • Unité de Thiviers-Payzac — L unité de Thiviers Payzac, parfois aussi appelée nappe de Thiviers Payzac ou groupe du Bas Limousin, est une succession métasédimentaire du Bas Limousin, allant du Néoprotérozoïque terminal à l Ordovicien. Elle appartient au socle varisque du… …   Wikipédia en Français

  • Радиоореол — Радиоореол[1] (англ. Radiohalo), плеохроический ореол[2][3] (англ. pleochroic halos)  микроскопическая шаровидная оболочка с изменённой окраской, встречающаяся внутри минералов, таких как биотит, содержащихся в гранитах и других… …   Википедия

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”