A specific example is the Skaergaard intrusion in Greenland. The igneous complex is mostly granitic in composition, but this piece is a tonalite, possibly a cumulate of some sort. Embayed crystal of quartz in a dacite porphyry. This example, from the marginal border series of the intrusion, has augite enclosing plagioclase and olivine. Poikilitic texturein which one large crystal encloses many smaller crystals. The sulfide minerals generally form an interstitial matrix to a silicate cumulate. This sample of rhyolite also has strong flow alignment of the microlites. Cumulate Adcumulate Orthocumulate.
rocks are igneous rocks formed by the accumulation of crystals from a magma either by settling or floating. Cumulate rocks are igneous rocks formed by the accumulation of crystals from a magma either by settling or floating.
Cumulate rocks are named according to their texture; cumulate texture is. He recommends that the classification of cumulate textures should be These are cumulates in which the intercumulus liquid crystallized in a. Wager, L.
Cumulate textures SpringerLink
R. and W. A.
Deer,Geological investigations of East Greenland, Part III.
Most grains are about the same size. One way to infer the composition of the magma that created the cumulate rocks is to measure groundmass chemistry, but that chemistry is problematic or impossible to sample.
The dark blobs that make up the sieve appearance are melt inclusions that formed during rapid, probably skeletal crystal growth. Sparks,The role of compositional convection in the formation of adcumulate rocks, Lithos 17, — Perthite exsolution texture, with irregular albite exsolution lamellae in microcline host crystals.
The pillow margin quenched to glass, enclosing euhedral phenocrysts. Categories : Plutonic rocks Igneous petrology.
a. Crystals. Textural Terms in Igneous Petrology.
Video: Cumulate texture definition geology Igneous Rocks Intro and Textures
Adcumulate - Cumulus crystals continue to grow and displace the intercumulus liquid. Example: Opx adcumulate texture. Petrology course, igneous textures, Union College Geology Department. Mesocumulate texture, in which liquid trapped between cumulate crystals was able to.
The radial growth causes them to characteristally have an extinction cross, typically with the N-S and E-W directions being at or close to extinction.
They have textures or mineralogy different than the surrounding material, and so are generally easy to spot.
Please help to improve this article by introducing more precise citations. Skeletal plagioclase phenocrysts in basalt, along with some of olivine, in a microcrystalline matrix. Dissolution is faster along crystal defects, which can give such crystals odd shapes.