Basalts And Granites
If instead they form by melting preexisting crustal rocks they represent a.
Basalts and granites. The saturation surface in the basalt shows a strong temperature dependence from 1400 to 1200 c. The difference between granites and basalts is in silica content and their rates of cooling. If the melt extrudes onto the surface this can lead to extensive basalt flows that form what are called flood basalts where hundreds of square kilometers of basaltic lava can be produced. All rocks of igneous origin consist of magma or molten earth that finds its way up to.
Granites that form the thick framework of the all continental crusts and also of those defined as anomalous oceanic crusts were mainly extracted in the archean from the upper mantle and later reworked metamorphism anatexis in later. Plutonic rock formed in the earth. Igneous rocks are formed by the crystallisation of a magma. Intrusive slowly cooled inside the crust.
Granite makes up the cores of continents and much of the bulk of major. Since the rate of cooling and solidification of magmas inside the earth. It most commonly forms as an extrusive rock such as a lava flow but can also form in small intrusive bodies such as an igneous dike or a thin sill it has a composition similar to gabbro the difference between basalt and gabbro is that basalt is a fine grained rock while. Below 1200 the saturation surface turns down sharply and becomes nearly temperature independent.
A basalt is about 53 sio2 whereas granite is 73. Basalt extrusive igneous volcanic rock that is low in silica content dark in color and comparatively rich in iron and magnesium. Basalts may be broadly classified on a chemical and petrographic basis into two main groups. Basalt is a dark colored fine grained igneous rock composed mainly of plagioclase and pyroxene minerals.
Granite is an intrusive igneous rock with a felsic composition. The tholeiitic and the alkali basalts. The saturation surface for zircon in late stage lunar basalts and granites has been determined over the temperature range1400 1070 c. Earth contains three kinds of rocks namely igneous rocks sedimentary rocks and metamorphic rocks basalt and granite are two types of igneous rocks.
Learn more about basalt in this article. If i type granites are descended from basalts then their formation represents net growth of the continents and net removal from the mantle of elements that are highly concentrated in the crust such as the heat producing radioactive isotopes 40 k and 238 u.