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 ?
The mafic cumulate include olivine gabbro, norite, gabbro-norite, and hornblende gabbro.
These plutonic rocks range in composition from gabbro to monzogranite and, collectively, cover an area of approximately 80 [km.
Other anomalies in the Mt Venn area locate along the margins of the gabbro complex with no obvious source of the anomaly detected on the surface or are covered by colluvium and alluvium.
In both oceanic crust and ophiolites, the gabbro layer is underlain by the mantle, which extends thousands of kilometers down to Earth's core.
Though far from the Moho, the bottom of the hole lies within reach of the gabbro layer that forms the bottom 4 kilometers of the ocean crust.
He added, "Such gearless panamax vessels with higher cargo carrying capacity will be to the benefit of our local customers, who can now carry more gabbro in each shipment.
To increase capacity for the FIFA World Cup 2022 and the Qatar National Vision 2030, the Qatar Primary Materials Company (QPMC) initiated the expansion of the Gabbro Berth Terminal at Mesaieed, making it the largest bulk terminal in the Middle East and one of the largest aggregate unloading terminals in the world.
This zone is characterised by a quartzite band heavily mineralized with pyrrhotite, pyrite and chalcopyrite within anorthositic gabbro, and returned anomalous silver values up to 12.
A statement issued by State Holding, a Qatar-based company focused on investment efforts on the industrial and real estate sectors in the Mena region and Europe, said that after the Qatari government lifted the 150,000 tonne limit on importing construction material, Fujairah (the UAE) has become the number one exporter of gabbro to the local market.
Under this agreement, QPMC will provide Ashghal with 41 million tonnes of limestone and 51 million tonnes of gabbro aggregates in order to continue and complete its building and constructions programmes and projects in Qatar.
Oman is aiming at a ten-fold increase in its export of gabbro to Qatar in the next couple of years, Oman Chamber of Commerce and Industry (OCCI) Member Mohammed bin Butti Niyadi said on Sunday.
1), comprises gabbro, pyroxenite, and relatively homogeneous harzburgites (mantle tectonite?