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Gabbro is known in the construction industry by the trade name of black granite. [31] However, gabbro is hard and difficult to work, which limits its use. [32] The term "indigo gabbro" is used as a common name for a mineralogically complex rock type often found in mottled tones of black and lilac-grey.
By contrast, more mafic rocks, such as tonalite, gabbro and diorite, have 1 to 5 ppm uranium, and limestones and sedimentary rocks usually have equally low amounts. Many large granite plutons are sources for palaeochannel -hosted or roll front uranium ore deposits , where the uranium washes into the sediments from the granite uplands and ...
Examples of phaneritic igneous rocks are gabbro, diorite, and granite. Porphyritic textures develop when conditions during the cooling of magma change relatively quickly. The earlier formed minerals will have formed slowly and remain as large crystals, whereas, sudden cooling causes the rapid crystallization of the remainder of the melt into a ...
The cumulate rock is a plagioclase-pyroxene cumulate (a gabbro) and the melt is now more felsic and aluminous in composition (trending towards andesite compositions). In the above example, the plagioclase and pyroxene need not be pure end-member compositions (anorthite-enstatite), and thus the effect of depletion of elements can be complex.
In the construction industry, black rocks that share the hardness and strength of granitic rocks are known as black granite. In geological terms, black granite might be gabbro , diabase , basalt , diorite , norite , or anorthosite .
The Lilesville Granite was then intruded by the Pee Dee Gabbro, which can be confirmed by the presence of granite xenoliths in the gabbro. [1] During the Triassic, a system of normal faults including the Jonesboro fault cut through the area [ 7 ] and a period of sedimentation followed [ 8 ] and deposition of clastic rocks such as conglomerates ...
Mafic rocks have a relatively low silica content and are composed mostly of pyroxenes, olivines and calcic plagioclase. These rocks (basalt, gabbro) are usually dark coloured, and have a higher density than felsic rocks. Ultramafic rock is very low in silica, with more than 90% of mafic minerals (komatiite, dunite).
The rock formations created by the rift included gabbro and granite intrusive rocks and basalt lavas. [4] In the Lake Superior region, the upwelling of this molten rock may have been the result of a hotspot which produced a triple junction. [2] The hotspot domed the rocks of the Lake Superior area.