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The mafic rocks also typically have a higher density than felsic rocks. The term roughly corresponds to the older basic rock class. [9] Mafic lava, before cooling, has a low viscosity, in comparison with felsic lava, due to the lower silica content in mafic magma. Water and other volatiles can more easily and gradually escape from mafic lava.
Gabbro (/ ˈɡæbroʊ / GAB-roh) is a phaneritic (coarse-grained and magnesium- and iron-rich), mafic intrusive igneous rock formed from the slow cooling magma into a holocrystalline mass deep beneath the Earth 's surface. Slow-cooling, coarse-grained gabbro is chemically equivalent to rapid-cooling, fine-grained basalt.
The magmas that produce ultrapotassic rocks are produced by a variety of mechanisms and from a variety of sources, but generally occur in a heterogenous, anomalous, phlogopite-bearing upper mantle. [2] The following conditions are favorable for the formation of ultrapotassic magmas. [3] partial melting at a great depth; low degrees of partial ...
Dike (geology) A magmatic dike (vertical) cross-cutting horizontal layers of sedimentary rock, in Makhtesh Ramon, Israel. In geology, a dike or dyke is a sheet of rock that is formed in a fracture of a pre-existing rock body. Dikes can be either magmatic or sedimentary in origin. Magmatic dikes form when magma flows into a crack then solidifies ...
Magmatism. Geological map showing the Gangdese batholith, which is a product of magmatic activity about 100 million years ago. Magmatism is the emplacement of magma within and at the surface of the outer layers of a terrestrial planet, which solidifies as igneous rocks. It does so through magmatic activity or igneous activity, the production ...
QAPF diagram for the classification of plutonic rocks Devils Tower, United States, an igneous intrusion exposed when the surrounding softer rock eroded away. Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form intrusions, such as batholiths, dikes, sills, laccoliths, and volcanic necks.
Model of the crystallization of a subsurface magma chamber. The Skaergaard intrusion was formed 56 million years ago during the opening of the North Atlantic Ocean. [1] The intrusion was emplaced beneath the preexisting rock in the region, including plateau basalt and gneiss. [1][2] The intrusion has a general oval shape, which is atypical in ...
Magma mixing occurs when magmas of a different composition intrude a larger magma body. In some cases, the melts are immiscible and stay separated to form pillow like collections of denser mafic magmas on the bottom of less dense dense felsic magma chambers. The mafic pillow basalts will demonstrate a felsic matrix, suggesting magma mingling ...