1 Sep In order to create a sustainable classification of igneous rocks which all geologists might use, an international body was set up by the IUGS: the. new terminology; we will try to stick to IUGS igneous rocks, but comprising ~50 % of IUGS names!) Igneous Rocks: A Classification and Glossary of Terms. 27 Aug Classification of igneous rocks can be based on their predominant grain The International Union of Geological Sciences (IUGS) classification.

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In the course of creating the classification, the Subcommission has established ten principles for its construction and for defining an appropriate nomenclature.

If the mineral mode cannot be determined as is often the case for volcanic rocks, then a chemical classification of total alkalis versus silica TAS is used.

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However, as we shall see is rather complex and best left to advanced students. An exact name can be given only if the mineralogical composition is known, which cannot be determined in the field. Please help improve this article by adding citations to reliable sources. This diagram does not determine whether a rock is gabbro, diorite, or anorthosite.

The IUGS systematics of igneous rocks | Journal of the Geological Society

This site uses cookies. Remember that porphyritic rocks have spent time in both worlds. There are other criteria used to decide that.

Journal of the Geological Society ; 5: The nomenclature for these classifications necessitates only rock names out of the c. Sign In or Create an Account. Carolus Linneaus proposed iyneous first classifcation for biological organisms in the 18th century.


Since this classification is being widely iugz, it bears discussion. Abstract In order to create a sustainable classification of igneous rocks which all geologists might use, an international body was set up by the IUGS: For our purposes, we will introduce and discuss a much simpler classification that will allow us to easily identify the more common igneous rocks.

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Articles with short description Articles needing additional references from September All articles needing additional references All articles with unsourced ivneous Articles with unsourced statements from February Classification system for igneous rocks.

Igneous petrology Igneous rocks. QAPF diagrams are not used to classify pyroclastic rocks or volcanic rocks if modal mineralogical composition is not determined, instead the TAS classification Total-Alkali-Silica is used.

Citing articles via Web Of Science The QAPF diagram has four minerals or mineral groups chosen as important cornerstones of the classification. These principles and their rationale have not previously been enunciated. VolumeNumber 5.

You could not be signed in. Subcommission on the Systematics of Igneous Rocks [1] fostered by Albert Streckeisen whence ckassification alternative name: Archive Current Issue Early Publication. Igneous rocks are classified on the basis of mineralogy, chemistry, and texture.

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This article needs additional citations for verification. The classification separates and individually classifies the pyroclastic, carbonatitic, melititic, lamprophyric and charnockitic rocks before entering the main QAPF classification for plutonic and volcanic rocks which is based on the modal mineral proportions of quartz Qalkali feldspar A and plagioclase P or of alkali feldspar Aplagioclase P and feldspathoids F.

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For instance, the classification of minerals is based on common anoins since minerals sharing common anions often have similar physical properties i. For example, aphanitic rocks are or volcanic origin while phaneritic rocks are plutonic. TAS is also classificatino if volcanic rock contains volcanic glass such as obsidian. By using this site, you agree to the Terms of Use and Privacy Policy.

The IUGS systematics of igneous rocks

Email alerts New issue alert. As noted in the sidebar to the left, this is largely a genetic classification based on the depth of origin of the rock volcanic at or near the surface, and plutonic at depth. Rock classifications also seek to reduce complexity. In order to create a sustainable classification of igneous rocks which all geologists might use, an international body was set up by the IUGS: QAPF diagrams are mostly used to classify plutonic rocks phaneritic rocksbut are also used to classify volcanic rocks if modal mineralogical compositions have been determined.