Sprinkling
Einsprenglinge are macroscopically visible crystals that are embedded in the microcrystalline or glassy matrix of volcanic rock . The corresponding structure is called a porphyry structure .
Classification
If the sprinkles have crystallized out of the same melt as the base mass, they are also called phenocrystals (from Greek φαίνω phaíno , 'make visible') or phenocrists . In these cases, the basic mass consists largely of the same minerals as the injections. Since phenocrystals are the rule in rocks with a porphyry structure, the term phenocrystals is also used as a synonym for sprinkling . A typical example of phenocrysts are quartz - and feldspar crystals in a " quartz porphyry ".
If the intruders are foreign minerals that were swept away from the adjacent rock during the ascent of the magma , one speaks of xenocrystals (from Greek ξένος xénos , foreign, the stranger) or xenocrists . A typical example of xenocrystals are diamonds in kimberlites . When the magma rose, they were transported from their region of origin in the upper mantle to near the surface. Kimberlite vents are therefore important diamond deposits.
The term Antecristen (from Latin ante , “before”) has been coined for injections made from foreign minerals that came from another, previously not completely solidified magma and that entered the volcanic melt through magma mixing .
literature
- Martin Okrusch, Siegfried Matthes: Mineralogy: An introduction to special mineralogy, petrology and deposit science . 9th edition. Springer, Berlin and Heidelberg 2014, ISBN 978-3-642-34659-0 , pp. 190 , doi : 10.1007 / 978-3-642-34660-6 .
- Gregor Markl: Minerals and Rocks: Mineralogy - Petrology - Geochemistry . 3. Edition. Springer, Berlin and Heidelberg 2015, ISBN 978-3-662-44627-0 , pp. 17 , doi : 10.1007 / 978-3-662-44628-7 .
Individual evidence
- ^ Phenocrystal in the spectrum online lexicon of geosciences.