enow.com Web Search

Search results

  1. Results from the WOW.Com Content Network
  2. Color index (geology) - Wikipedia

    en.wikipedia.org/wiki/Color_index_(geology)

    According to the Encyclopædia Britannica, color indices, 0–50 are felsic, 50–90 are mafic, and 90–100 are ultramafic. [6] An online geology textbook provides an example of the use of another classification scheme, in which color indices 0–15 are felsic, 15–45 are intermediate, 45–85 are mafic, and 85–100 are ultramafic. [9]

  3. Intermediate composition - Wikipedia

    en.wikipedia.org/wiki/Intermediate_composition

    In igneous petrology, an intermediate composition refers to the chemical composition of a rock that has 51.5–63 wt% SiO 2 being an intermediate between felsic and mafic compositions. Typical intermediate rocks include andesite and trachyandesite among volcanic rocks and diorite and granodiorite among plutonic rocks

  4. Phonolite - Wikipedia

    en.wikipedia.org/wiki/Phonolite

    Total alkali vs. silica classification scheme (TAS), as proposed in Le Maitre's 2002 Igneous Rocks – A classification and glossary of terms [3]: 237 Phonolite is a fine-grained equivalent of nepheline syenite. They are products of partial melting, are silica-undersaturated, and have feldspathoids in their normative mineralogy.

  5. Bowen's reaction series - Wikipedia

    en.wikipedia.org/wiki/Bowen's_reaction_series

    The series is divided into two branches, the continuous (felsic minerals: feldspars) and the discontinuous (mafic minerals).The minerals at the top of the illustration (given aside) are first to crystallize and so the temperature gradient can be read to be from high to low with the high-temperature minerals being on the top and the low-temperature ones on the bottom.

  6. Felsic - Wikipedia

    en.wikipedia.org/wiki/Felsic

    Felsic magmas and lavas have lower temperatures of melting and solidification than mafic magmas and lavas. Felsic rocks are usually light in color and have specific gravities less than 3. The most common felsic rock is granite. Common felsic minerals include quartz, muscovite, orthoclase, and the sodium-rich plagioclase feldspars (albite-rich).

  7. Mafic - Wikipedia

    en.wikipedia.org/wiki/Mafic

    The mafic rocks also typically have a higher density than felsic rocks. The term roughly corresponds to the older basic rock class. [9] Mafic lava, before cooling, has a low viscosity, in comparison with felsic lava, due to the lower silica content in mafic magma. Water and other volatiles can more easily and gradually escape from mafic lava.

  8. Diorite - Wikipedia

    en.wikipedia.org/wiki/Diorite

    Diorite is an intrusive igneous rock composed principally of the silicate minerals plagioclase feldspar (typically andesine), biotite, hornblende, and sometimes pyroxene.The chemical composition of diorite is intermediate, between that of mafic gabbro and felsic granite.

  9. Calc-alkaline magma series - Wikipedia

    en.wikipedia.org/wiki/Calc-alkaline_magma_series

    The calc-alkaline magma series is one of two main subdivisions of the subalkaline magma series, the other subalkaline magma series being the tholeiitic series. A magma series is a series of compositions that describes the evolution of a mafic magma, which is high in magnesium and iron and produces basalt or gabbro, as it fractionally crystallizes to become a felsic magma, which is low in ...