gabbro


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gabbro:

see basaltbasalt
, fine-grained rock of volcanic origin, dark gray, dark green, brown, reddish, or black in color. Basalt is an igneous rock, i.e., one that has congealed from a molten state.
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Gabbro

 

magmatic rock of basal composition, containing approximately equal parts of basal plagioclase (labradorite, bytownite) and colored minerals (pyroxenes, less frequently amphibole and olivine) and mineral ores in small quantities. Strictly, gabbro consists of plagioclase and monoclinic pyroxene. Varieties of gabbro include norites of plagioclase and rhombic pyroxenes and troctolites of plagioclase and olivine. If the gabbro contains olivine together with pyroxene, the rock is called olivine gabbro. Gabbros rich in plagioclase (85-90 percent) are called plagioclasites. Among these are labradorites, whose plagioclases often possess a beautiful bluish or greenish play of colors. The chemical composition of gabbro is approximately 45-50 percent silica and up to 20 percent oxides of iron and magnesium. The color is black or dark green, sometimes mottled. Typical gabbros that have hardened at great depths are characterized by approximately identically-sized crystals of the light and dark minerals that constitute it; gabbro in small masses usually has an ophitic structure. (The plagioclase is in the form of well-formed crystals, and the dark minerals fill the interstices between the plagioclases.) The forms and spatial distributions of the gabbro are large laccoliths, lopoliths, dikes, and stocks. Dimensions of the formations reach enormous magnitudes. (For example, the Duluth massif in Canada covers an area up to 5,000 sq km.) In the USSR there are large massifs of gabbro in the Urals, the Ukraine, the Kola Peninsula, the Transcaucasus, and other regions; outside the USSR there are gabbro masses in the Republic of South Africa, France, Scotland (Great Britain), and other countries. When gabbro disintegrates, ferrous clays, ochers, and, less frequently, low-quality kaolins are formed. Gabbros sometimes contain masses of ore minerals and in such cases may be used as ores of copper, nickel, and titanium. Gabbros are often used as building or facing stone of great strength, for exterior and interior facing, predominantly in the form of polished slabs (for example, the columns of the Lenin Library in Moscow), and for manufacturing gravel and road-paving stone.

gabbro

[′gab·rō]
(petrology)
A group of dark-colored, intrusive igneous rocks with granular texture, composed largely of basic plagioclase and clinopyroxene.

gabbro

Igneous rock similar to diorite, predominantly composed of ferromagnetic minerals with crystals visible to the eye; has the same mineral composition as basalt.
References in periodicals archive ?
Prospecting activities along the prospective gabbro contact is limited to grab sampling (much of the contact is covered) and there has been no previous drilling.
The water released in the metamorphism of basalt, gabbro and blueschist to eclogite moves towards the surface due to positive buoyancy and causes partial melting of the peridotite of the overlying mantle wedge by lowering the temperature required for melting (Figure 8).
Both mafic (gabbro, scapolite metagabbro, and amphibolite) and granitoid protolith are transformed to albitite along veining, where the central vein consists of nearly pure albite (Figures 3(a)-3(b)).
Schistose amphibolite and metagabbro are represented by fine-grained, equigranular rocks of granonematoblastic, nematoblastic, relict gabbro, poikilitic texture.
According to Principle 7, any gabbro quarry operating during, or before, 1912 is a possible source for the Titanic headstones, whereas any quarry that opened after 1912 is not possible.
The material quarried consists of a high quality fresh gabbro, which is crushed, screened and graded on-site.
The former Late Late Show host co-owns the firm with his wife Kathleen and their pay - [euro]58,052 including pension payments of [euro]1,052 - was quite modest compared to Gabbro's overall performance.
"We lowered down the drill string and spun it into massive gabbro and drilled 500 meters in two weeks--the most successful hard-rock hole ever drilled.
Eight samples were selected for the present study: four from the Talavera gabbro and four from the La Solanilla gabbro (Fig.
This expansion will give Oryx Industries a total production of eight million tonnes of quarry products per annum, about eight per cent of Fujairah's total gabbro production in 2015.
Stevin Rock, which has been operating in Ras Al Khaimah since 1975, produces and sells more than 46m tonnes of high-grade Limestone, Gabbro rock, concrete and asphalt aggregates for the construction industry.
Glaciers and tugs of the earth and water pushed this piece of gabbro rock so far and no farther, and then Herndon applied his tools and took it, again, so far and no farther.