The environment of formation produces characteristic textures in igneous rocks which aid in their identification. These textures are: Phaneritic – This texture describes a rock with large, easily visible, interlocking crystals of several minerals.
What is porphyritic texture?
A porphyritic texture displays minerals in two distinct size populations: one or more minerals are consistently larger than the rest of the minerals in a rock. The rest of the smaller mineral grains are called the groundmass. Porphyritic textures are found in rocks with both coarse- and fine-grained groundmasses.
What is porphyritic texture and how is it interpreted?
Porphyritic texture is an igneous rock texture in which large crystals are set in a finer-grained or glassy groundmass. Porphyritic textures occur in coarse, medium and fine-grained igneous rocks. Usually the larger crystals, known as phenocrysts, formed earlier in the crystallisation sequence of the magma.
What’s the meaning of Phaneritic?
[ făn′ə-rĭt′ĭk ] Of or relating to an igneous rock in which the crystals are so coarse that individual minerals can be distinguished with the naked eye. Phaneritic rocks are intrusive rocks that cooled slowly enough to allow significant crystal growth.
What is the difference between porphyritic and pegmatitic textures?
Pegmatitic texture occurs during magma cooling when some minerals may grow so large that they become massive (the size ranges from a few centimetres to several metres). Porphyritic textures develop when conditions during cooling of a magma change relatively quickly.
What is a Phaneritic texture in igneous rocks?
PHANERITIC TEXTURE – Igneous rocks with large, visible crystals because the rock formed slowly in an underground magma chamber. PORPHYRITIC TEXTURE – an igneous rock in which PHENOCRYSTS (large crystals) are surrounded by a fine groundmass (very small crystals).
What does a porphyritic texture suggest about how an igneous rock formed?
This porphyritic texture indicates that the magma sat and cooled a bit below the Earth’s surface, thus giving time for the large crystals to grow, before erupting onto the surface and cooling very quickly. The large crystals are termed phenocrysts while the aphanitic rest of rock is called the groundmass.
What is the difference between Phaneritic and porphyritic rocks?
Phaneritic: any coarse-grained igneous rock, often intrusive, usually formed as a result of a longer cooling history (ex. granite, gabbro). Porphyritic: an igneous rock with one mineral (called the phenocryst) exhibiting a grain size larger than the remainder of the minerals (called the groundmass).
What does a porphyritic texture indicate about the cooling history of an igneous rock?
What does a porphyritic texture indicate about the cooling history of an igneous rock? It indicates that crystals were formed at depth (slow cooling) and then the magma moved to a shallow depth or erupted (fast cooling).
What is the difference between phaneritic and porphyritic rocks?
What is the difference between phaneritic and porphyritic?
Phaneritic: any coarse-grained igneous rock, often intrusive, usually formed as a result of a longer cooling history (ex. granite, gabbro). Porphyritic: an igneous rock with one mineral (called the phenocryst) exhibiting a grain size larger than the remainder of the minerals (called the groundmass).
What is porphyritic texture in geology?
Porphyritic Texture. Porphyritic texture is an igneous rock texture in which large crystals are set in a finer-grained or glassy groundmass. Porphyritic textures occur in coarse, medium and fine-grained igneous rocks. Usually the larger crystals, known as phenocrysts, formed earlier in the crystallisation sequence of the magma.
What is a phaneritic rock?
Phaneritic rocks are coarse-grained rocks which form below the Earth’s surface. The individual crystals are relatively even-sized and large enough for scientists to identify the different mineral grains that compose the rock. Granite rock with a phaneritic texture
What are the characteristics of aphanitic texture?
Aphanitic Texture. This includes the size and quality and interrelations of its grains and the fabric they form. Larger scale features, such as fractures and layering, are considered rock structures in comparison. There are nine main types of igneous rock textures: Phaneritic, vesicular, aphanitic, porphyritic, poikilitic, glassy, pyroclastic,…
