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Andesite is characterized by a porphyritic texture, and it is an extrusive igneous rock. As it was ejected at the surface, the magma from which it formed finished cooling very quickly, resulting in the formation of fine-grained groundmass. This occurred after the magma had cooled slowly for some time deep below the surface, resulting in the formation of huge crystals.
Is there both intrusive and extrusive porphyritic?
The igneous rock known as porphyry is characterized by the presence of bigger crystals known as phenocrysts within a groundmass of finer grains. In accordance with this understanding, true porphyry is considered to be an intrusive rock. It is possible for extrusive (lava) rock to have a porphyritic texture; nevertheless, the correct word for this type of rock is porphyritic rock, not porphyry3.
Is the porphyritic process invasive?
This rock is an example of an intrusive porphyritic formation… Using the petrographic microscope, a porphyritic volcanic sand grain can be detected. [Citation needed] The little needle-like crystals that surround the larger grain in the middle belong to a completely different size class than the larger grain that is in the center.
Which kind of igneous rocks are considered to be porphyritic?
Explanation: A porphyritic texture is one that is distinguished by the presence of big crystals (phenocrysts) embedded within a groundmass of coarser grain size. Hence, porphyritic rocks are quite common and include andesite, granite, and even some basalts.
What processes lead to the formation of porphyritic rocks?
When magma that has been gradually crystallizing and cooling beneath the surface of the Earth’s crust is suddenly erupted at the surface, it causes the remaining magma that has not yet crystallized to rapidly cool. This results in the formation of a porphyritic texture. The majority of volcanic rocks have this particular texture… Several types of volcanic rocks have this particular texture.
Porphyritic
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What processes lead to the formation of porphyritic andesite?
Andesite material with a porphyritic texture: This rock is an example of an extrusive igneous intrusion. As it was ejected at the surface, the magma from which it formed finished cooling very quickly, resulting in the formation of fine-grained groundmass. This occurred after the magma had cooled slowly for some time deep below the surface, resulting in the formation of huge crystals.
What can we deduce about the formation process of an igneous rock from the presence of a porphyritic texture?
What does the presence of a porphyritic texture in an igneous rock tell us about its previous stages of cooling? It suggests that crystals were created at a great depth, during a process known as gradual cooling, and that the magma subsequently migrated to a shallow depth or erupted.
Is basalt classified as a porphyritic rock?
The minerals plagioclase feldspar and pyroxene make up the majority of basalt’s composition. There are a few different types of textures that can be found in basalt, including glassy, massive, porphyritic, vesicular, and scoriaceous. The mineral known as porphyrite, also known as porphyritic basalt, can be identified by its prominent crystals, which are typically plagioclase and can be either white or tan in color.
Is andesite classified as a porphyritic rock?
Andesite is most commonly used to refer to fine-grained rocks, which are typically porphyritic in nature. These rocks roughly correspond to the intrusive igneous rock diorite in terms of their composition, and they are made up primarily of andesine, which is a plagioclase feldspar, and one or more ferromagnesian minerals, such as pyroxene or biotite.
Is gabbro classified as a porphyritic rock?
The texture of gabbro is typically equigranular, although it can occasionally exhibit a porphyritic quality as well. This is particularly the case when plagioclase oikocrysts have developed earlier than the groundmass minerals.
Which rocks are considered intrusive?
Igneous intrusive rock, also known as plutonic rock, is a type of rock that is generated when lava is driven into older rocks at greater depths inside the crust of the Earth. This magma then slowly solidifies below the surface of the Earth, however it may be revealed at a later time due to erosion. A wide diversity of rock types can be produced by igneous intrusions.
What kind of rock is considered to be an intrusive type?
Large crystals are formed as a result of the slow cooling that takes place below the surface of the Earth, which allows for the crystallization of intrusive igneous rocks. Diabase, diorite, gabbro, granite, pegmatite, and peridotite are all kinds of rocks that fall within the category of intrusive igneous rocks… The igneous rock known as dacite is typically white in color and has fine grains. It is formed by extrusion.
Which is it: Aphanitic’s intrusiveness or its extrusiveness?
Hence, intrusive igneous rocks have coarse-grained textures known as phaneritic, and extrusive igneous rocks have fine-grained textures known as aphanitic. Visible crystals are present in phaneritic textures.
What kind of granite is called porphyritic?
Igneous rocks with a phaneritic texture can be coarsely crystalline, as is the case with granites. Crystals in porphyritic granites can range in size from very large to very minute, although even the smallest crystals are still of a respectable size. Phenocrysts are the names given to the large crystals that can be found in porphyritic rocks. K-feldspar phenocrysts are a common mineral found in porphyritic granites.
Where may one find rocks with a porphyritic texture?
Granite-porphyry is the name given to the type of rock that exists when the ground mass is made up of tiny crystals of feldspar and quartz. Both are made of granite, and both may be found in the elvan dikes that run through the tin area in Cornwall. At the Porcupine gold camp in Ontario, quartz-porphyry can be found quite frequently.
Why is andesite composed of porphyritic crystals?
Andesite is typically porphyritic, meaning that it has bigger crystals of plagioclase, known as phenocrysts, that developed before to the extrusion that brought the magma to the surface, and these larger crystals are embedded in a matrix that has finer grains. Phenocrysts of either pyroxene or hornblende can also be found quite frequently.
Andesite belongs to the category of igneous rocks known as.
Andesite is a granular rock that can be classified as either igneous or volcanic in origin. Although the crystals are too small to be seen without the aid of a magnifying glass, the rock has a dark gray color and is composed of an equal amount of light and dark minerals. There are times when andesite could have some bigger crystals within it.
What is it that distinguishes andesite from other rocks?
Andesite is a type of dark, fine-grained, brown or greyish intermediate volcanic rock that is frequently found in lava. It can also have a grayish appearance. Andesite may contain trace amounts of the minerals biotite, pyroxene, or amphibole in its make-up.
What kind of rock is referred to as basalt?
The brittle, dark rock known as basalt originates from volcanoes. In the crust of the Earth, basalt is by far the most prevalent form of rock. Depending on the conditions under which it is produced, basalt can either be brittle and crumbly or solid and huge (see Figure 1).
Is phaneritization present in basalt?
Basalt, andesite, and rhyolite are all types of volcanic rocks that fall within the aphanitic category… The igneous rocks gabbro, diorite, and granite are all examples of the phaneritic subgroup. The formation of porphyritic textures occurs when the conditions that prevail during the cooling of a magma undergo rapid shifts.
How would you describe the basalt’s consistency?
The quick cooling of volcanic magma results in basalts almost usually having an aphanitic, or fine-grained, mineral texture.
What does the presence of a porphyritic texture in an igneous rock tell us about its previous stages of cooling?
Its porphyritic texture is evidence that the magma sat and cooled a little bit below the surface of the Earth. This allowed the huge crystals to develop before the lava erupted onto the surface and immediately cooled. The huge crystals are known as phenocrysts, whereas the rest of the rock, which is aphanitic, is referred to as the groundmass.
What does the presence of a porphyritic texture in an igneous rock tell us about the conditions in which it cooled?
What does the presence of a porphyritic texture in an igneous rock tell us about its evolutionary path? The history of the rock’s cooling occurred in two stages: first, the rock cooled at a greater depth, producing larger crystals; then, magma carried the rock to the surface, where the residual liquid cooled more quickly, producing smaller crystals.
What characteristics set porphyritic texture apart from other types of igneous rock?
The more substantial crystals will be carried away by the lava. After that, the lava will rapidly cool, and when it does, the larger crystals will be surrounded by much smaller crystals. A porphyry is a type of igneous rock that is characterized by having a porphyritic texture (see Figure 7.14) and contains crystals that range in size from very small to very large.