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 ?
Qatar should store various varieties of gabbro in big quantities for the smooth execution of these projects, he said, adding that Oman is well prepared to meet Qatar's growing need for it.
3d) of the Blue Mountain Granodiorite have clear intrusive relationships relative to both the early gabbro and the late monzogranite of the Landry Brook pluton.
It seemed to us that the entire gabbro layer in the Oman ophiolite crust, from uppermost mantle to the surface, could have formed when melt material periodically collected in relatively small pools that subsequently crystallized into solid "melt lenses.
According to the agreement, QPMC will supply Ashghal with 91 million tonnes of gabbro and limestone for the next five years, making it one of QPMC's biggest customers and forming a catalyst for infrastructural development in Qatar.
The SDWZS intrusion is comprised of three lithologies: 1) gabbroic rocks, 2) ultramafic rocks that include hornblendite and feldspathic hornblendite and 3) gossan which include sulphide-bearing hornblendite, less commonly gabbro and tectonized equivalents.
This complex is dominated by a layered cumulate sequence, that grades from troctolite through olivine gabbro to gabbro (Fig.
On the walls of Atlantis Bank, as we named the feature, we sampled gabbro and peridotite, proof that drilling here should be productive.
Although the recent drilling effort fell short of its goal -- the gabbro deposits -- several signs indicate that this long-sought layer may lie within a few hundred meters of the bottom of the hole, says Dick.
The company has announced the commencement of the sale of the gabbro material located at the company's stockpiles and storage areas in Mesaieed and Lusail, to contractors from the public and private from 20 August, 2015.
The delegation was in the country to assess how it could expand imports of gabbro for construction ahead of the 2022 FIFA World Cup, and to discuss with QPMC's capacity to stock raw materials such as gabbro.
1 million tonnes of PGE-Cu deposit is associated with the Eastern Border Gabbro unit of the Coldwell Complex
The three shallow exploratory holes drilled to date have tested only the near surface parts of Target 1, which is a large VTEM indicated sulphide body located near the southern end of the 12 kilometre long gabbro intrusion.