Where does porphyritic basalt come from?
Porphyritic Basalt
| Type | Igneous Rock |
|---|---|
| Texture | Porphyritic |
| Origin | Extrusive/Volcanic |
| Chemical Composition | Mafic |
| Color | Dark Gray to Black |
Where are porphyritic rocks found?
When the ground mass is composed of small crystals of feldspar and quartz, the rock is called granite-porphyry. Both are of the composition of granite, and both are found in the elvan dikes of the tin district in Cornwall. Quartz- porphyry is common in the Porcupine gold camp, Ontario.
Where are basalts most commonly found?
Basalt is the most common composition of lava rocks that cool from magma, liquid rock that rises from the deep Earth at volcanoes. Today basalt is forming at many active rifts, including Iceland, the East African Rift Valley, the Red Sea and the Rio Grande Valley of New Mexico and Colorado.
Which rock can have porphyritic texture?
igneous rocks
Porphyritic texture is a very common texture in igneous rocks in which larger crystals (phenocrysts) are embedded in a fine-grained groundmass. Porphyry is an igneous rock that contains larger crystals (phenocrysts) in a fine-grained groundmass. K-feldspar phenocrysts in this sample.
How do you identify porphyritic rocks?
Porphyritic intrusive rocks have a matrix with individual crystals easily distinguished with the eye, but one group of crystals appearing clearly much bigger than the rest, as in a porphyritic granite. The term comes from from the Ancient Greek πορφύρα (porphyra), meaning “purple”.
What minerals are in porphyritic rocks?
Porphyry (/ˈpɔːrfəri/ POR-fə-ree) is a textural term for an igneous rock consisting of coarse-grained crystals such as feldspar or quartz dispersed in a fine-grained silicate rich, generally aphanitic matrix or groundmass.
Where is basalt found in the Philippines?
Normal (N)-MORB-like basalts were found at DSDP Sites 290 and 447 near the Central Basin Fault to the SW of Site 1201D, and enriched (E)-MORB-like basalts were found at DSDP Site 291 in the southern West Philippine Basin. OIB-like basalts were found at DSDP Sites 292, 294 and 446 (Fig. 1).
Where is basalt found in America?
Much of the Klamath Mountains of northern California and southern Oregon is broken-up pieces of 150 to 450 million year old seafloor crust (the 150 million year old Josephine Ophiolite is a good example), while most of eastern Washington and Oregon (the Columbia River Basalt), and northeastern California (the Modoc …
What is an example of porphyritic texture?
Examples of porphyritic rocks are: andesite porphyry and rhyolite porphyry. Glassy or vitreous textures occur during some volcanic eruptions when the lava is quenched so rapidly that crystallization cannot occur. The result is a natural amorphous glass with few or no crystals. Examples include obsidian and pumice.
Where is kimberlite rock found?
Generally speaking, kimberlites are found only in cratons, the oldest surviving areas of continental crust, which form the nuclei of continental landmasses and have remained virtually unchanged since their formation eons ago.
Is porphyritic basalt volcanic or plutonic?
Igneous Rocks
| Atlas of Igneous Rocks | ||
|---|---|---|
| Rock Name / Image | Texture | Occurance |
| Basalt: Olivine Basalt Porphyry | Porphyritic | Volcanic |
| Bostonite (Trachyte Porphyry) | Porphyritic | Volcanic |
| Carbonatite: Siderite Carbonatite | Phaneritic | Plutonic |