What is the difference between basalt and diabase?

The term basalt is at times applied to shallow intrusive rocks with a composition typical of basalt, but rocks of this composition with a phaneritic (coarser) groundmass are more properly referred to as diabase (also called dolerite) or, when more coarse-grained (crystals over 2 mm across), as gabbro.

What are the characteristics of tholeiitic basalt?

Tholeiitic basalt is relatively rich in iron and poor in alkali metals and aluminium. Included in this category are most basalts of the ocean floor, most large oceanic islands, and continental flood basalts such as the Columbia River Plateau.

Where is basalt found?

Basalt is also an important rock type on other planetary bodies in the Solar System. For example, the bulk of the plains of Venus, which cover ∼80% of the surface, are basaltic; the lunar maria are plains of flood-basaltic lava flows; and basalt is a common rock on the surface of Mars .

What is the color of basalt?

Basalt is usually dark grey to black in colour, due to its high content of augite or other dark-coloured pyroxene minerals, but can exhibit a wide range of shading. Some basalts are quite light-coloured due to a high content of plagioclase, and these are sometimes described as leucobasalts.

What is the difference between basalt and diabase and gabbro?

Diabase and gabbro have the same general mineral composition as basalt, but they have a larger grain size. Basalt is identical to diabase and gabbro, but is very fine-grained. Basalt is from a melt that cooled very rapidly- in other words, on the surface of the earth or in the ocean. When basalt is broken, it leaves very sharp edges.

What is diabase?

What is Diabase? In the United States and Canada, the name diabase is used for a dark gray to black, fine-grained, intrusive igneous rock that has a composition similar to basalt and gabbro. The difference between basalt, diabase, and gabbro is in their grain size - which was determined by their cooling rates.

How big is a diabase rock?

It does not have the salt-and-pepper appearance of the specimen at the top of this page. This rock is approximately eight centimeters across. Diabase typically has a mineral composition that is dominated by the plagioclase feldspar known as labradorite (approximately 40% to 70% of the rock).

What is the difference between diabase and dolerite?

In the United Kingdom and a few other countries, diabase is known as dolerite. The two words are synonyms. Diabase: A specimen of diabase in which the plagioclase crystals are dark gray to black. It does not have the salt-and-pepper appearance of the specimen at the top of this page. This rock is approximately eight centimeters across.

Where can you find basalt?

The town of Basalt can be found in the U.S. state of Colorado. The rock variety is found every where lava is extruded. By definition Basalt is a fine-grained igneous rock that is usually black in color composed mainly of the minerals plagioclase and pyroxene. The ocean floor is comprised primarily of basalt.

What is basalt made of?

Basalt is the result of partial melting of meteoritic material (Earth is made of a huge mass of meteorites!), so it forms on other terrestrial planets (which also accumulated from meteorites) as well as Earth, making basalt the “mother liquor” of volcanoes on terrestrial planets.

What is basalt and why is it important?

Basalt makes up large parts of the ocean floor. It can form volcanic islands when it is erupted by volcanoes in ocean basins. The rock has also built huge plateaus on land. The dark plains on the Moon, known as maria, and, possibly, the volcanoes on Mars and Venus are made of basalt. Basalt has a strict chemical definition.

What are the three environments in which basalt is formed?

Basalt-Forming Environments. Most of the basalt found on Earth was produced in just three rock-forming environments: 1) oceanic divergent boundaries, 2) oceanic hotspots, and 3) mantle plumes and hotspots beneath continents. The images on this page feature some of these basalt-forming environments.

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