Calc-alkaline and calc-alkalic are equivalent terms applied to groups of igneous rocks that commonly occur together and that have compositions related by the characteristic chemical trends specified below. Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock Understanding the genesis of these rocks is important, because they make up a major part of the crust of the continents.
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Calc-alkaline series
The diverse rock types in the calc-alkaline series include volcanic types such as basalt, andesite, dacite, rhyolite, and also their coarser-grained intrusive equivalents (gabbro, diorite, granodiorite, and granite). Basalt (bəˈsɔːlt ˈbeisɔːlt ˈbæsɔːlt is a common Extrusive Volcanic rock. For the extinct cephalopod genus see Andesites. Andesite (ˈændəsaɪt is an igneous, Volcanic rock, of intermediate Dacite ( deɪsaɪt) is an igneous, volcanic rock with a high iron content This page is about a volcanic rock For the ghost town see Rhyolite Nevada, and for the satellite system see Rhyolite/Aquacade. Gabbro (ˈɡæbrəʊ is a dark coarse-grained intrusive Igneous rock chemically equivalent to Basalt. Diorite (ˈdaɪəraɪt is a grey to dark grey intermediate intrusive Igneous rock composed principally of Plagioclase Feldspar (typically Granodiorite (ˌgrænəˈdaɪəraɪt/ /ˌgreɪn- is an intrusive Igneous rock similar to Granite, but contains more Plagioclase than Potassium feldspar Granite (ˈɡrænɪt is a common and widely occurring type of intrusive, Felsic, igneous rock. They do not include silica-undersaturated, alkalic, or peralkaline rocks. Normative mineralogy is a geochemical calculation of the whole rock geochemistry of a rock sample which estimates the idealised mineralogy of a rock according to the principles
Geochemical characterization
Characteristic chemical trends relate compositions of rocks as arranged in a series from basalt to rhyolite (intrusive equivalents from gabbro to granite). Basalt (bəˈsɔːlt ˈbeisɔːlt ˈbæsɔːlt is a common Extrusive Volcanic rock. This page is about a volcanic rock For the ghost town see Rhyolite Nevada, and for the satellite system see Rhyolite/Aquacade. Gabbro (ˈɡæbrəʊ is a dark coarse-grained intrusive Igneous rock chemically equivalent to Basalt. Granite (ˈɡrænɪt is a common and widely occurring type of intrusive, Felsic, igneous rock. Analyses document that the chemical constituent silica (SiO2) in compositions of rocks in this series typically ranges from almost 50 weight percent (basalt and gabbro) to over 70 percent (rhyolite and granite). Peacock named the series in 1931 as part of a proposal to distinguish rock series based on concentrations of other chemical constituents plotted against silica: his proposal is rarely applied rigorously today, but his scheme still provides insight. Barker (1983, page 89) has explained Peacock's scheme as follows: "On a variation diagram in which weight percentages of other oxide components are plotted against silica, CaO generally declines with increasing SiO2 and is eventually exceeded by the sum of Na2O and K2O . . . The silica content at which CaO equals (Na2O + K2O) is estimated by interpolation and is defined as the alkali-lime index . . . Rock suites in which the total of alkali oxides exceed that of CaO at a silica content less than 51 wt % are called alkalic . . . Those with an alkali-lime index between 56 and 61 are calcalkalic . . . "
Yet other criteria have been used to separate rocks of the calc-alkaline and tholeiitic series. Tholeiitic basalt is an Igneous rock, a type of Basalt. Like all basalt the rock type is dominated by Clinopyroxene plus Plagioclase, with minor For the calc-alkaline rock series, iron decreases as silica increases. Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 The Chemical compound silicon dioxide, also known as silica or silox (from the Latin " Silex " is an Oxide In contrast, for the tholeiitic series, iron increases as silica increases, silica-rich rocks are less common, and potassium concentrations at similar silica values are lower.
Calc-alkaline magmas are typically hydrous, and also typically are more oxidized, with higher oxygen fugacities. Hydrate is a term used in Inorganic chemistry and Organic chemistry to indicate that a substance contains Water. In geology a redox buffer is an assemblage of minerals or compounds that constrains oxygen Fugacity as a function of temperature
Geologic context
Calc-alkaline rocks typically are found above subduction zones, commonly in volcanic arcs, and particularly on those arcs on continental crust. A volcanic arc is a chain of volcanic islands or Mountains formed by Plate tectonics as an oceanic Tectonic plate subducts under The continental crust is the layer of granitic, Sedimentary, and Metamorphic rocks which form the Continents and the areas of shallow seabed
Petrologic origin
Rocks in the series are thought to be genetically related by fractional crystallization and to be at least partly derived from magmas of basalt or andesite composition formed in the Earth's mantle. Fractional crystallization is one of the most important geochemical and physical processes operating within the Earth's crust and mantle. Basalt (bəˈsɔːlt ˈbeisɔːlt ˈbæsɔːlt is a common Extrusive Volcanic rock. For the extinct cephalopod genus see Andesites. Andesite (ˈændəsaɪt is an igneous, Volcanic rock, of intermediate The mantle is a part of an Astronomical object. The interior of the Earth, similar to the other Terrestrial planets, is Chemically divided Trends in composition can be explained by a variety of processes. Many explanations focus on water content and oxidation states of the magmas. In geology a redox buffer is an assemblage of minerals or compounds that constrains oxygen Fugacity as a function of temperature Magma (Plurals magmas and magmata) is molten rock that sometimes forms beneath the surface of the Earth (or any other Terrestrial planet Proposed mechanisms of formation begin with partial melting of subducted material and of mantle peridotite altered by water and melts derived from subducted material. In Geology, a subduction zone is an area on Earth where two tectonic plates meet and move towards one another with one sliding underneath the other Mechanisms by which the calc-alkaline magmas then evolve may include fractional crystallization, assimilation of continental crust, and mixing with partial melts of continental crust. The continental crust is the layer of granitic, Sedimentary, and Metamorphic rocks which form the Continents and the areas of shallow seabed
References
- Daniel S. Barker, Igneous Rocks, Prentice Hall, Inc. Englewood Cliffs, NJ, 417 pages (1983)
See also
Tholeiitic basalt is an Igneous rock, a type of Basalt. Like all basalt the rock type is dominated by Clinopyroxene plus Plagioclase, with minor For the extinct cephalopod genus see Andesites. Andesite (ˈændəsaɪt is an igneous, Volcanic rock, of intermediate Basalt (bəˈsɔːlt ˈbeisɔːlt ˈbæsɔːlt is a common Extrusive Volcanic rock. Granite (ˈɡrænɪt is a common and widely occurring type of intrusive, Felsic, igneous rock. Igneous differentiation is an umbrella term for the various processes by which Magmas undergo bulk chemical change during the Partial melting process coolingDapyx Software network: MP3 Explorer | Ebook Manager | Zenithic