volcanic rock assemblages

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• Rock microstructure — includes the texture of a rock and the small scale rock structures. The words texture and microstructure are interchangeable, with the latter preferred in modern geological literature. However, texture is still acceptable because it is a useful… …   Wikipedia

• 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

• igneous rock — Any of various crystalline or glassy, noncrystalline rocks formed by the cooling and solidification of molten earth material (magma). Igneous rocks comprise one of the three principal classes of rocks, the others being metamorphic and sedimentary …   Universalium

• metamorphic rock — Any of a class of rocks that result from the alteration of preexisting rocks in response to changing geological conditions, including variations in temperature, pressure, and mechanical stress. The preexisting rocks may be igneous, sedimentary,… …   Universalium

• Ultramafic rock — Ultramafic (also referred to as ultrabasic) rocks are igneous and meta igneous rocks with very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are composed of usually greater than 90% mafic minerals (dark… …   Wikipedia

• alteration mineral assemblages — GLOSSARY OF VOLCANIC TERMS Mineral assemblages found in rocks that result from chemical reactions between the original rock and an agent of alteration (for example, hot volcanic vapors or hydrothermal fluids) …   Glossary of volcanic terms

• Mount Meager — The Mount Meager volcanic complex rising above the Pemberton Valley. Summits left to right are Capricorn Mountain, Mount Meager proper and Plinth Peak …   Wikipedia

• dating — I In geology and archaeology, the process of determining an object s or event s place within a chronological scheme. Scientists may use either relative dating, in which items are sequenced on the basis of stratigraphic clues (see stratigraphy) or …   Universalium

• 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

• Volcanogenic massive sulfide ore deposit — Volcanogentic massive sulfide ore deposit at Kidd Mine, Timmins, Ontario, Canada, formed 2.4 billion years ago on an ancient seafloor. Volcanogenic massive sulfide ore deposits (VMS ) are a type of metal sulfide ore deposit, mainly Cu Zn Pb which …   Wikipedia

• Earth Sciences — ▪ 2009 Introduction Geology and Geochemistry       The theme of the 33rd International Geological Congress, which was held in Norway in August 2008, was “Earth System Science: Foundation for Sustainable Development.” It was attended by nearly… …   Universalium