IUGS CLASSIFICATION OF IGNEOUS ROCKS PDF

Journal of the Geological Society ; 5 : — In the course of creating the classification, the Subcommission has established ten principles for its construction and for defining an appropriate nomenclature. The principles are: 1 use descriptive attributes; 2 use actual properties; 3 ensure suitability for all geologists; 4 use current terminology; 5 define boundaries of rock species; 6 keep it simple to apply; 7 follow natural relations; 8 use modal mineralogy; 9 if mode not feasible, use chemistry; 10 follow terminology of other IUGS advisory bodies. These principles and their rationale have not previously been enunciated. 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 Q , alkali feldspar A and plagioclase P or of alkali feldspar A , plagioclase P and feldspathoids F. 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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Journal of the Geological Society ; 5 : — In the course of creating the classification, the Subcommission has established ten principles for its construction and for defining an appropriate nomenclature. The principles are: 1 use descriptive attributes; 2 use actual properties; 3 ensure suitability for all geologists; 4 use current terminology; 5 define boundaries of rock species; 6 keep it simple to apply; 7 follow natural relations; 8 use modal mineralogy; 9 if mode not feasible, use chemistry; 10 follow terminology of other IUGS advisory bodies.

These principles and their rationale have not previously been enunciated. 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 Q , alkali feldspar A and plagioclase P or of alkali feldspar A , plagioclase P and feldspathoids F.

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. The nomenclature for these classifications necessitates only rock names out of the c. Shibboleth Sign In. OpenAthens Sign In. Institutional Sign In. Sign In or Create an Account. User Tools. Sign In. Advanced Search. Article Navigation.

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QAPF diagram

The classification of igneous rocks has been the subject of frequent debate and voluminous literature. Since this classification is being widely adopted, it bears discussion. However, as we shall see is rather complex and best left to advanced students. For our purposes, we will introduce and discuss a much simpler classification that will allow us to easily identify the more common igneous rocks. IUGS Classification. Carolus Linneaus proposed the first classifcation for biological organisms in the 18th century. This taxonomic classification was designed to simplify the complexity of nature by lumping together living species that shared common traits.

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A QAPF diagram is a double ternary diagram which is used to classify igneous rocks based on mineralogic composition. These are the mineral groups used for classification in QAPF diagram. Geologists worldwide accept the diagrams as a classification of igneous, especially plutonic rocks. QAPF diagrams are mostly used to classify plutonic rocks phaneritic rocks , but are also used to classify volcanic rocks if modal mineralogical compositions have been determined. 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. TAS is also used if volcanic rock contains volcanic glass such as obsidian.

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