layered belts

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• Ultramafic to mafic layered intrusions — are found in typically ancient cratons and are rare but worldwide in distribution. The intrusive complexes exhibit evidence of fractional crystallization and crystal segregation by settling or floating of minerals from a melt. Ideally the… …   Wikipedia

• Precambrian time — Interval of geologic time from с 3. 8 billion years ago, the age of the oldest known rocks, to 544 million years ago, the beginning of the Cambrian Period. This interval represents more than 80% of the geologic record and thus provides important… …   Universalium

• Ophiolite — Ordovician ophiolite in Gros Morne National Park, Newfoundland. An ophiolite (  / …   Wikipedia

• geology — /jee ol euh jee/, n., pl. geologies. 1. the science that deals with the dynamics and physical history of the earth, the rocks of which it is composed, and the physical, chemical, and biological changes that the earth has undergone or is… …   Universalium

• Peridotite — A peridotite is a dense, coarse grained igneous rock, consisting mostly of the minerals olivine and pyroxene. Peridotite is ultramafic and ultrabasic, as the rock contains less than 45% silica. It is high in magnesium, reflecting the high… …   Wikipedia

• Africa — /af ri keuh/, n. 1. a continent S of Europe and between the Atlantic and Indian oceans. 551,000,000; ab. 11,700,000 sq. mi. (30,303,000 sq. km). adj. 2. African. * * * I Second largest continent on Earth. It is bounded by the Mediterranean Sea,… …   Universalium

• Australia — /aw strayl yeuh/, n. 1. a continent SE of Asia, between the Indian and the Pacific oceans. 18,438,824; 2,948,366 sq. mi. (7,636,270 sq. km). 2. Commonwealth of, a member of the Commonwealth of Nations, consisting of the federated states and… …   Universalium

• Fashions — ▪ 2009       The faltering global economy determined the direction of fashion during 2008. Initially, the euro s significant appreciation against the dollar proved a boon to style conscious travelers who, visiting the U.S. from abroad as the year …   Universalium

• plate tectonics — plate tectonic, adj. Geol. a theory of global tectonics in which the lithosphere is divided into a number of crustal plates, each of which moves on the plastic asthenosphere more or less independently to collide with, slide under, or move past… …   Universalium

• sedimentary rock — Rock formed at or near the Earth s surface by the accumulation and lithification of fragments of preexisting rocks or by precipitation from solution at normal surface temperatures. Sedimentary rocks can be formed only where sediments are… …   Universalium

• Superior craton — in the west. The western margin extends from northern Minnesota through eastern Manitoba to northwestern Ontario.The formation of the Superior craton is best explained within the context of 2.72 2.68 Ga accretion of small continental plates and… …   Wikipedia