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ⓘ Igneous petrology ..



Amygdules or amygdales form when the gas bubbles or vesicles in volcanic lava are infilled with a secondary mineral such as calcite, quartz, chlorite or one of the zeolites. Amygdules usually form after the rock has been emplaced, and are often associated with low-temperature alteration. Amygdules may often be concentrically zoned. Rocks containing amygdules can be described as amygdaloidal. The word is derived from the Latin word "amygdala" for almond tree and the Greek word "αμυγδαλή" for almond, reflecting the typical shape of an infilled vesicle. "Amygdule" is more common in US usage, ...



Anatexis refers to the partial melting of rocks. Traditionally, anatexis is used specifically to discuss the partial melting of crustal rocks, while the generic term "partial melting" refers to the partial melting of all rocks, in both the crust and mantle. Anatexis can occur in a variety of different settings, from zones of continental collision to mid-ocean ridges. It is believed that anatexis is the process largely responsible for the formation of migmatites. Furthermore, scientists have recently discovered that partial melting plays an increasingly important role in active crustal proc ...



Aphanite, or aphanitic as an adjective, is a name given to certain igneous rocks that are so fine-grained that their component mineral crystals are not detectable by the unaided eye. This geological texture results from rapid cooling in volcanic or hypabyssal environments. As a rule, the texture of these rocks is not the same as that of volcanic glass, with volcanic glass being non-crystalline, and having a glass-like appearance. Aphanites are commonly porphyritic, having large crystals embedded in the fine groundmass or matrix. The large inclusions are called phenocrysts. They consist ess ...



Boninite is a mafic extrusive rock high in both magnesium and silica, thought to be usually formed in fore-arc environments, typically during the early stages of subduction. The rock is named for its occurrence in the Izu-Bonin arc south of Japan. It is characterized by extreme depletion in incompatible trace elements that are not fluid mobile but variable enrichment in the fluid mobile elements. They are found almost exclusively in the fore-arc of primitive island arcs and in ophiolite complexes thought to represent former fore-arc settings or at least formed above a subduction zone. Boni ...



Borolanite is an historical petrological name for a pyroxene-melanite bearing nepheline syenite variety which contains nepheline-alkali feldspar pseudomorphs interpreted to be after leucite which occur as conspicuous white spots in the dark rock matrix. The rock occurs in the Borralan Igneous Complex or Loch Borralan Complex which is an alkalic igneous complex near Loch Borralan in northwest Scotland. The 1911 Britannica described borolanite as: one of the most remarkable rocks of the British Isles, found on the shores of Loch Borolan Loch Borralan in Sutherland, after which it has been na ...


Bowens reaction series

Within the field of geology, Bowens reaction series is the work of the petrologist Norman L. Bowen, who summarized, based on experiments and observations of natural rocks, the crystallization sequence of typical basaltic magma undergoing fractional crystallization. Bowens reaction series is able to explain why certain types of minerals tend to be found together while others are almost never associated with one another. He experimented in the early 1900s with powdered rock material that was heated until it melted and then allowed to cool to a target temperature whereupon he observed the typ ...


ⓘ Igneous petrology

  • Igneous petrology is the study of igneous rocks - those that are formed from magma. As a branch of geology, igneous petrology is closely related to volcanology
  • In igneous petrology a phenotype is an aphanitic igneous rock which is identified and classified according to the mineralogy of its phenocrysts, when
  • which they form. Petrology has three subdivisions: igneous metamorphic, and sedimentary petrology Igneous and metamorphic petrology are commonly taught
  • Experimental igneous petrology is the subset of experimental petrology concerned with quantifying the behavior of magmas and their associated igneous rocks at
  • or chemical change Migmatite  A mixture of metamorphic rock and igneous rock Petrology The branch of geology that studies the origin, composition, distribution
  • the Story of Igneous Petrology Princeton University Press. ISBN 0 - 691 - 10279 - 1. Best, Myron G. 1982 Igneous and Metamorphic Petrology San Francisco:
  • intrusions see Sierra Nevada batholith. Intrusions are one of the two ways igneous rock can form the other is extrusive rock, that is, a volcanic eruption
  • 2002 Igneous and Metamorphic Petrology Blackwell Publishing, 2nd ed. ISBN 1 - 4051 - 0588 - 7 Philpotts, Anthony R. 1990 Principles of Igneous and Metamorphic
  • The Stillwater igneous complex is a large layered mafic intrusion LMI located in southern Montana in Stillwater, Sweet Grass and Park Counties. The
  • Peralkaline rocks include those igneous rocks which have a deficiency of aluminium such that sodium and potassium are in excess of that needed for feldspar
  • Turner and Verhoogen, 1974, Igneous Petrology McGraw - Hill, pp. 603 620 Hyndman, Donald W., 1972, Igneous and Metamorphic Petrology McGraw - Hill, pp. 122 139
  • the Presidency College, Kolkata. He was known for his studies on igneous petrology and was an elected fellow of the Geological Survey of India, Indian
  • journal accepts high quality research papers in the fields of igneous and metamorphic petrology geochemistry and mineralogy. Topical coverage includes major
  • holocrystalline plutonic igneous rock. Its name is derived from the type locality in Essex County, Massachusetts, in the United States. Modern petrology identifies
  • In igneous petrology an intermediate composition refers to the chemical composition of a rock that has 52 - 63 wt SiO2 being an intermediate between felsic
  • ISBN 9788132215394. Winter, John DuNann 2001 An Introduction to Igneous and Metamorphic Petrology Upper Saddle River, New Jersey: Prentice - Hall. ISBN 0132403420
  • mineralogical changes within the igneous rocks and describing field relationships and textural evidence for magma differentiation. Petrology The branch of geology
  • the Moon is extremely reduced, all of its basalts are tholeiitic. Petrology Igneous differentiation Berndt, J., Koepke, J., and Holtz, F. 2004 An
  • In igneous petrology eutaxitic texture describes the layered or banded texture in some extrusive rock bodies. It is often caused by the compaction and
  • Compositions Journal of Petrology 47 12 2463 2489. Bibcode: 2006JPet...47.2463M. CiteSeerX doi: 10.1093 petrology egl051. Bergman, S. C

Enclave (geology)

In geology an enclave is an aggregate of minerals or rock observed inside another larger rock body. Usually it refers to such situations in plutonic rocks. Micro-granular enclaves in felsic plutons result from the introduction of mafic magma into the magma chamber an its subsequent cooling following incomplete mixing.



In geology, the term glomeroporphyritic refers to the grouping of phenocrysts, not necessarily of the same mineral, into distinct clusters within porphyritic igneous rocks.


Granite Mountain (Arkansas)

Granite Mountain is an igneous intrusion southeast of Little Rock, Arkansas. Despite being named after granite, the rock at Granite Mountain is actually syenite, a rock that is visually similar to granite, but contains much less quartz. The rock was formed in the Cretaceous period around 90 million years ago, after the lamproites at Prairie Creek and the later Magnet Cove complex, and before the formation of the Monroe Uplift and Jackson Dome.



Hornblendite is a plutonic rock consisting mainly of the amphibole hornblende. Hornblende-rich ultramafic rocks rare and when hornblende is the dominant mineral phase they are classified as hornblendites with qualifiers such as garnet hornblendite identifying a second abundant contained mineral. Metamorphic rocks consist mainly of amphiboles are called amphibolites.



Hyalopilitic is a textural term used in petrographic classification of volcanic rocks. Specifically, hyalopilitic refers to a volcanic rock groundmass, which is visible only under magnification with a petrographic microscope, that contains a mixture of very fine-grained mineral crystals either mixed with natural volcanic glass, or surrounded by thin bands of volcanic glass.



Kenyte is a variety of porphyritic phonolite or trachyte with rhomb shaped phenocrysts of anorthoclase with variable olivine and augite in a glassy matrix. It was originally described and named by J. W. Gregory in 1900 for the occurrence on Mount Kenya. Kenyte has also been reported from Mount Kilimanjaro and Mount Erebus in Antarctica. Kenyte has a glassy texture and may consist of vitreous glass, which contains large phenocrysts of feldspar anorthoclase.



Pneumatolysis is an obsolete geologic term for magma emitting gasses that alter surrounding rock or crystallize minerals. Pneumatolysis is now considered a type of hydrothermal interaction.

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