How does a QAPF diagram work?
The QAPF diagram utilizes four minerals, or mineral groups, to classify igneous rocks. These minerals are quartz (Q), Alkali feldspars (A), plagioclase feldspars (P), and feldspathoids (F). F and Q cannot form in plutonic rocks simultaneously due to the difference in their respective silica contents.
What is a plutonic igneous rock?
Intrusive, or plutonic, igneous rock forms when magma is trapped deep inside the Earth. Intrusive rocks have a coarse grained texture. Extrusive Igneous Rocks: Extrusive, or volcanic, igneous rock is produced when magma exits and cools above (or very near) the Earth’s surface.
Which is a characteristic of a plutonic igneous rock?
Plutonic rocks form when magma cools within the Earth’s crust. The rate of cooling of the magma is slow, allowing large crystals to grow. Plutonic rocks are characteristically coarse-grained.
What is the composition of diorite?
Diorite
| Type | Igneous Rock |
|---|---|
| Chemical Composition | Intermediate |
| Color | Approximately half dark, half white minerals |
| Mineral Composition | Sodium – Calcium Plagioclase, Quartz, Hornblende, Biotite |
| Miscellaneous | Salt and Pepper Appearance |
What is the composition of Lamprophyre?
Petrography. The Hour lamprophyres are melanocratic, holocrystalline rocks with porphyritic textures, containing phenocrysts of euhedral–subhedral pyroxene, brown amphibole and olivine. The matrix consists of subhedral–anhedral pyroxene, brown amphibole, K-feldspar, and carbonate.
What are the examples of plutonic igneous rock?
Plutonic Igneous Rocks. Intrusive igneous rocks, formed by the slow solidification of magma deep below the surface and characterized by large crystals. Named after Pluto, the Roman god of the underworld. Examples include granite, gabbro and peridotite.
What is plutonic rock in geography?
Plutonic rocks are igneous rocks that solidified from a melt at great depth. Magma rises, bringing minerals and precious metals such as gold, silver, molybdenum, and lead with it, forcing its way into older rocks. The rock is later exposed by erosion. A large body of this type of rock is called a pluton.
What are four types of plutonic structures?
Plutonic structures include huge solidified magma chambers called batholiths, laccoliths, stocks, bysmaliths, and lopoliths, while smaller hypabyssal structures include diapirs, dikes and dikelets, ring dykes, sills, volcanic necks and plugs, and cone sheets.
What is a QAPF diagram in geology?
Streckeisen diagram A QAPF diagram is a double ternary diagram which is used to classify igneous rocks based on mineralogic composition. The acronym QAPF stands for ” Quartz, Alkali feldspar, Plagioclase, Feldspathoid (Foid)”. These are the mineral groups used for classification in QAPF diagram.
How do you classify pyroclastic rocks using a QAPF diagram?
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).
What is TAS diagram of igneous rocks?
TAS diagram. The classification of igneous rocks is largely based on two diagrams: QAPF diagram for plutonic rocks (formed in the crust) and TAS diagram for volcanic rocks.
What is the classification of igneous rocks?
The classification of igneous rocks is largely based on two diagrams: QAPF diagram for plutonic rocks (formed in the crust) and TAS diagram for volcanic rocks. I made the schemes using the coordinates provided in the following book: Le Maitre, R. W. (2005).