Dacite is the volcanic equivalent of granodiorite. Group – volcanic. Colour – variable, but generally bluish-grey or pale grey. Texture – generally porphyritic.
What is a dacite rock?
dacite, volcanic rock that may be considered a quartz-bearing variety of andesite. Dacite is primarily associated with andesite and trachyte and forms lava flows, dikes, and sometimes massive intrusions in the centres of old volcanoes.
What is a dacite rock used for?
Dacite is sometimes used to produce crushed stone. It performs well as fill and as a loose aggregate in a wide variety of construction projects. It does not perform well as a concrete aggregate because its high silica content reacts with the cement.
What is the density of dacite?
2.8
Dacite. Andesite. (Volcanic arcs) Density >2.8. Low silica content (basic) = sodium feldspar + amphibole.
How does porphyry form in igneous rocks?
Porphyritic rocks are formed when a column of rising magma is cooled in two stages. In the first stage, the magma is cooled slowly deep in the crust, creating the large crystal grains, with a diameter of 2mm or more.
Is dacite plutonic or volcanic?
Main types of igneous rocks
| Weight % of SiO2 | Plutonic rock type | Volcanic rock equivalent |
|---|---|---|
| 45-53 | Gabbro | Basalt |
| 53-63 | Diorite | Andesite |
| 63-68 | Granodiorite | Dacite |
| 68-75 | Granite | Rhyolite |
What is the importance of dacite rock?
How fast does dacite magma flow?
Viscous dacite and rhyolite flows often form steep-sided mounds called lava domes over an erupting vent. Lava domes often grow by the extrusion of many individual flows >30 m (100 ft) thick over a period of several months or years. Such flows will overlap one another and typically move less than a few meters per hour.
