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Topics related to "mafic rock"

igneous rock
igneous rock One of three major classes of rock produced by the cooling and solidifying of molten magma. All igneous rocks are crystalline and most resist erosion. Extrusive, or volcanic, igneous rocks, such as basalt, form by the rapid cooling of molten material at the surface. Intrusive, or hyper... Read more
petrology
petrology branch of geology specifically concerned with the origin, composition, structure, and properties of rocks , primarily igneous and metamorphic, and secondarily sedimentary. It includes petrography, the systematic description and classification of rocks using microscopic examination of roc... Read more
Sela
Sela or Selah [Heb.,=rock], in the Bible, unidentified town, S of the Dead Sea. Amaziah captured it and renamed it Joktheel. Some identify Sela with Petra . Sela in the first chapter of Judges seems to be another rock. ... Read more
rock
rock aggregation of solid matter composed of one or more of the minerals forming the earth's crust. The scientific study of rocks is called petrology. Rocks are commonly divided, according to their origin, into three major classes—igneous, sedimentary, and metamorphic. Igneous Rocks ... Read more
Cephas
Cephas , in the Gospels, Jesus' name for St. Peter. It is a transliteration of the Aramaic word for rock, and identical in meaning with "Peter" in Greek. ... Read more
metamorphic rock
metamorphic rock An aggregate of minerals formed by the recrystallization of pre-existing rocks in response to a change of pressure, temperature, or volatile content. Metamorphic rocks can generally be divided into four types: (a) regional metamorphic rocks, formed in response to changes leading to ... Read more
schist
schist , metamorphic rock having a foliated, or plated, structure called schistosity in which the component flaky minerals are visible to the naked eye. Schists are distinguished from the other foliated rocks, slates and gneisses, by the size of their mineral crystals; these are larger than those ... Read more
sedimentary rock
sedimentary rock Type of rock formed by deposition of sediment derived from pre-existing rocks, which may have been sedimentary, igneous or metamorphic. Most sediment accumulates on the bed of the sea, having been dumped there by rivers, or having accumulated as dead sea creatures fall to the seafl... Read more
joint
joint in geology, fracture in rocks along which no appreciable movement has occurred (see fault ). Nearly vertical, or sheet, joints that result from shrinkage during cooling are commonly found in igneous rocks. Similar joints occur in thick beds of sandstone and gneiss, with the sheets resembling... Read more
rock crawler
rock crawler name applied to the slender, wingless insects of the family Grylloblattidae in the order Orthoptera. They have long antennae and range in length from 1/2 to 1 in. (15-30 mm). Rock crawlers occur at altitudes of 1,500 to 6,500 ft (450-2,000 m), where they live in caves, under rock... Read more

Encyclopedia entries related to "mafic rock"

cleavage and other tectonic foliations in rocks
Book article from: The Oxford Companion to the Earth ...enable the viewer to see through rock specimens, and in outcrops...parallel surfaces or zones in a rock. This broad definition encompasses...original grain arrangement or rock fabric changes by developing...banding such as alternating mafic and felsic layers in a gneiss...pressure-solution ... Read more
igneous rock classification
Book article from: The Oxford Companion to the Earth ...continuum of rock compositions. The proliferation of igneous rock names that were based upon the names of the localities at...Geological Sciences (IUGS) has a glossary of more than 1500 rock terms, from ‘A-type granite’ and ‘abessedite...classification is based upon the silica (SiO 2 ... Read more
seismic properties of rocks
Book article from: The Oxford Companion to the Earth ...velocity of a particular rock. Figure 1, which is a compilation...is slower than gabbro (mafic), which is slower than peridotite...anisotropy in individual rock units, which is sometimes...as micro-cracks in the rock close, reducing their porosity... Read more
iron–nickel deposits
Book article from: The Oxford Companion to the Earth ...ores related to laterites and those associated with mafic and ultramafic rock types in a wide range of tectonic settings. Each type...potassium, sodium, and calcium are leached from the rock into the underlying water-table, where they may subsequently... Read more
Bowen, Norman Levi
Book article from: The Oxford Companion to the Earth ...under another Canadian, A. L. Daly. His classical studies of rock-forming minerals began with the investigation of the relationships...feldspars and then those of the iron–magnesium silicates (mafic minerals) found in igneous rocks. He soon discovered the so... Read more
chromites
Book article from: The Oxford Companion to the Earth chromites Chromite (FeCr 2 O 4 ) is the only ore mineral of chromium (Cr) and is found, usually in small amounts, in mafic and ultramafic rocks (igneous rocks containing a large proportion of olivine and pyroxene). Chromite deposits are of two main... Read more
supergene and residual deposits
Book article from: The Oxford Companion to the Earth ...deposits form when intense weathering removes much of a rock's components and concentrates a few of them to very high...from the dissolution of the carbonate component of the host rock by organic acids that were generated by decaying vegetation...generated by the intense weathering of iron-rich rocks such as ... Read more
lithosphere
Book article from: The Oxford Companion to the Earth ...the uppermost part of the upper mantle (Fig. 1). Whereas the base of the crust is essentially a compositional boundary between mafic and ultramafic rocks, characterized by a rapid increase in seismic P-wave velocity to more than 8 km s −1 (the Mohorovicic... Read more
granulite and the granulite facies
Book article from: The Oxford Companion to the Earth ...unable to migrate without freezing. In some instances, there is clear evidence for the accompanying emplacement of mantle-derived mafic magmas, providing a source for the anomalous heating. Bruce W. D. Yardley Bibliography Harley, S. L. (1998) On the occurrence... Read more

Dictionary entries related to "mafic rock"

mafic
Book article from: A Dictionary of Earth Sciences mafic Applied to any igneous rock which has a high proportion of pyroxene and olivine , such that its colour index is between 50 and 90 (i.e. it is dark coloured). Read more
colour index
Book article from: A Dictionary of Earth Sciences colour index The total volume percent of mafic (coloured) silicate minerals in an igneous rock. The mafic minerals would include the olivine group...for classifying igneous rocks. If a rock has 60% modal mafic minerals it has a colour index of 60... Read more
basanite
Book article from: A Dictionary of Earth Sciences basanite An extrusive , mafic igneous rock consisting of a feldspathoid mineral ( nepheline , analcite , or leucite ), olivine , plagioclase feldspar , pyroxene , and minor... Read more
leucitite
Book article from: A Dictionary of Earth Sciences ...extrusive , undersaturated (see SILICA SATURATION ), mafic igneous rock consisting of essential leucite and augite , with accessory...apatite . When olivine or nepheline are also present, the rock is termed an olivineleucitite or a nepheline-leucitite... Read more
lamprophyre
Book article from: A Dictionary of Earth Sciences ...A dark-coloured, strongly porphyritic , intrusive igneous rock, containing abundant euhedral phenocrysts of biotite and/or...olivine , diopside , apatite , or opaque oxides, set in a mafic , felsic , or glassy groundmass . There are no felsic phenocrysts present in this rock type. The lamprophyres are ... Read more
schlieren
Book article from: A Dictionary of Earth Sciences ...of streaked-out, linear, planar, or discoidal aggregates of mafic minerals more densely concentrated than in the host rock, with which they have diffused boundaries. Some schlieren may represent partly remobilized, mafic-rich xenoliths , streaked out by the flow of the enclosing... Read more
melanosome
Book article from: A Dictionary of Earth Sciences melanosome Dark-coloured bands rich in mafic and aluminous minerals, e.g. biotite , sillimanite , and garnet...removal of the quartz and feldspar components of the original rock along non-penetrative cleavage planes developed as a result...stresses imposed during the regional metamorphic event. The mafic ... Read more
melteigite
Book article from: A Dictionary of Earth Sciences melteigite An undersaturated, intrusive igneous rock containing essential nepheline and alkali pyroxene ( aegirine...displaying a colour index of 70–90. With decreasing mafic mineral content and increasing nepheline content melteigites pass into ijolites and then into urtites . All three rock types ... Read more
granofels
Book article from: A Dictionary of Earth Sciences granofels A little-used name for a massive granoblastic metamorphic rock , consisting of equant grains of quartz and feldspar , hence lacking a foliation . Minor mafic minerals consist of pyroxene and garnet . The anhydrous mineral assemblages... Read more
peridotite model
Book article from: A Dictionary of Earth Sciences ...compressional and S-wave velocities and gravity data. The probable composition is peridotite , eclogite , or an intermediate between the two. Xenoliths in kimberlites , and mafic volcanic rocks found at the surface, also suggest this composition. Read more

Related newspaper, magazine, and trade journal articles from HighBeam Research

Igneous rock associations in Canada 3. Large Igneous Provinces (LIPs) in Canada and adjacent regions: 3 Ga to Present.(Series)
Magazine article from: Geoscience Canada; 9/1/2004; ; 700+ words ; ...punctuated by numerous periods during which large volumes of mafic magma were emplaced. Such magmas not generated by a 'normal...regional uplift, and ore deposits. However, given that many mafic units in Canada remain poorly characterized, a concerted geochronology... Read more
Igneous rock associations 8. Arc magmatism II: geochemical and isotopic characteristics.(Series)
Magazine article from: Geoscience Canada; 3/1/2007; ; 700+ words ; ...andesitic) rocks. Experiments suggest that calc-alkalic mafic magmas are formed by melting of a hydrated mantle...variety of ways, including the fractionation of a more mafic parent, mixing between mafic and felsic magmas (a process supported, in many... Read more
Igneous Rock Associations 7. Arc magmatism I: relationship between subduction and magma genesis.(SERIES)
Magazine article from: Geoscience Canada; 12/1/2006; ; 700+ words ; ...for the partial melting in the mantle wedge, which produces mafic magma, and in the crust, produces felsic magma. Arc magmatism...a steep geothermal gradient and underplating of the crust by mafic magma may transfer sufficient heat to induce anatexis. During... Read more
Pillow basalt.(Word to the Wise)(Editorial)
Magazine article from: Rocks & Minerals; 7/1/2005; ; 690 words ; Basalt is a fine-grained igneous rock that is primarily composed of the iron- and magnesium-rich...calcium-rich plagioclase feldspar. It forms from the rapid cooling of mafic (Si[O.sub.2] concentration between 48 and 52 wt. %) magma...pillows serve the same purpose as ripple marks in sedimentary rock. This ... Read more
Gold in the Canadian shield.
Magazine article from: Rocks & Minerals; 3/1/2006; ; 700+ words ; ...Shield ) is composed of ancient rock formations and is the most...resulting in fractures from which mafic lava oozed out under the water and onto the granitic rock patches. Much of the Shield...today. Through many cycles, mafic lavas and volcanic ejecta were...low-relief, fresh, hard, impervious ... Read more
PREHNITE.(crystal mineral)
Magazine article from: Rocks & Minerals; 5/1/1999; ; 700+ words ; Brandberg, Namibia Mafic lava flows have long supplied wonderful...hydrothermal mineral in veins and cavities in mafic igneous rocks. It is also found in granite...from cavities within diabase, or trap-rock, flows of Triassic age (Fenner 1910; Lewis...specimens have also been collected at trap-rock ... Read more
MINERALS OF THE Pea Ridge Mine, Washington County, Missouri.
Magazine article from: Rocks & Minerals; 3/1/1998; ; 700+ words ; ...zone, and (4) the silicified zone. Other rock types include a volcaniclastic rock as exotic fragments in the deposit, rare-earth-ele...bearing breccia pipes, granitic dikes, and mafic dikes. The spatial relationship of the rock types is shown on the geologic map of...skarn alteration of the ... Read more
Greenstone.(Word to the Wise)
Magazine article from: Rocks & Minerals; 11/1/2008; ; 700+ words ; ...minerals, even as minor constituents in a rock, can impart a distinct green color, especially...fine-grained, altered, or metamorphosed mafic igneous rock (e.g., basalt, gabbro, or diabase) that...also comprise, to varying degrees, large rock sequences of Precambrian age (Archaean... Read more
The microminerals of Valley Quarry: Gettysburg, Adams County, Pennsylvania.(Through the 'Scope)
Magazine article from: Rocks & Minerals; 5/1/2006; ; 700+ words ; ...Taylor and Royer 1981). Rock types include sandstone...intruded by Jurassic-aged mafic intrusion sheets and dikes...body of mafic intrusive rock, known as the Gettysburg...direction. The intrusive rock in the area of Valley quarry... Read more
Gold, base metals, diamonds have junior miners hopping; Fertile ground for a cluster of exploration projects.(FORT FRANCES / RAINY RIVER)
Magazine article from: Northern Ontario Business; 10/1/2008; ; 700+ words ; ...junior had been exploring a mafic-intrusive body called the North Rock Prospect looking for copper...that geologists call an ultra-mafic fragmental. The rocks discovered...soft, black-coloured, altered rock that has been often been used... Read more