Cumulates

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Cumulative (from the Latin cumulare "to accumulate") is an igneous rock that was formed from a melt during the process of accumulation in magma chambers . It is characterized by a layered enrichment of one or more minerals. Cumulates are particularly common among mafic and ultramafic rocks.

Emergence

The inner structure of the basic mass of cumulative rock consists of a framework of crystals , the cumulus crystals , with plagioclase being the most common basic mass of this mixed crystal formation. Cumulus crystals grow largely freely in the melt of the accumulation and are therefore idiomorphic to hypidiomorphic . There are three types of cumulative structure:

  • Accumulate : consists of 93–100% cumulus crystal (ground mass), thus a monomineral rock
  • Mesocumulate : consists of 85–93% cumulus crystals with broad surfaces, small amounts of other minerals
  • Orthocumulate : consists of 75–85% cumulus crystals with narrow growth surfaces, the rest consists of minerals crystallized by the cumulus melt, such as olivines , pyroxenes , magnetites , orthoclases

literature

  • Martin Okrusch, Siegfried Matthes: Mineralogie: an introduction to special mineralogy, petrology and deposit science , Springer Berlin Heidelberg 8th edition, 2009

Web links