Skarn

Classification：Metamorphic Rock

A metasomatism metamorphic rock composed of calcium magnesium silicate minerals. It is mainly formed on the contact zone between carbonate and siliceous magma. A mineral rich in hydrothermal deposits.

Skarn, a metamorphic rock, is mainly composed of metamorphic rocks consisting of calcium rich or magnesium rich silicate minerals, usually formed by contact metasomatism. Mineral composition is mainly garnet, pyroxene and other silicate minerals. From fine to medium, coarse grains and unequal grains, stripes, patches, and massive structures. The important indicators of Skarn deposit are iron, copper, lead, zinc, tungsten, tin, beryllium, boron and so on. Double metasomatism plays a leading role. When the solution moves along the contact zone of carbonate rocks and aluminosilicate rocks, calcium diffuses into the direction of aluminosilicate rocks, and SiO2 and Al2O3 diffuse to the direction of carbonate rocks, thus the two rocks are metasomatism and form some reaction Skarn bands. Skarn is usually named after the main minerals, such as garnet Skarn and diopside Skarn.

Skarn definition:
Skarn, a metamorphic rock, is mainly composed of metamorphic rocks consisting of calcium rich or magnesium rich silicate minerals, usually formed by contact metasomatism. Mineral composition is mainly garnet, pyroxene and other silicate minerals. From fine to medium, coarse grains and unequal grains, stripes, patches, and massive structures. Color depends on mineral composition and particle size, often dark green, dark brown and light gray, and a large proportion.

Brief introduction:
A metamorphic rock formed by metasomatism, mainly on the contact zone of intermediate and acidic intrusions and carbonate rocks, on the basis of thermal contact metamorphism and under the influence of high temperature gasifying hydrothermal fluids. Igneous rocks (mainly neutral igneous rocks and acidic igneous rocks) and carbonates are mainly composed of carbonates.
Limestone or volcanic sedimentary system is a contact metasomatic metamorphic rock near the contact zone. Its name comes from silicon (old name silicon, for Si transliteration) and calcium (card for Ca transliteration).

Mineral composition:
The mineral composition is complex, mainly including pomegranite, diopside, wollastonite, epidote, tourmaline, enalite, chlorite, quartz and so on, and sometimes chalcopyrite, pyrite, galena, sphalerite and other minerals. It has different granular and granular structure. The grain is generally coarse and massive, and its color is deep. It often appears dark brown, dark green and so on, and its relative density is large.
Taxonomy of skarn:
According to the composition of the surrounding rock, it can be divided into the following several kinds:
Calcareous skarn: the formation of metasomatic limestone. The main minerals are garnet (calcite granlogite - calcite Series) and pyroxene (diopside - calcite - pyroxene Series), which sometimes contain mount Fu, wollastonite, Alinite, epidote, magnetite, carbonate minerals and quartz.
Magnesian skarn: magnesian skarn is formed by metasomatism dolomite or dolomitization limestone. The standard minerals include diopside, forsterite, spinel, mica, magnesite, serpentine, chive, amphibole, magnetite and dolomite.
Silicate skarn is formed by metasomatism of silicate rocks. Its composition is similar to that of calcareous Skarn. The most typical mineral is andalusite.

Related deposits:
Skarn has important practical significance. This rock is an important symbol for the search for the Skarn deposit. The minerals related to it are iron, copper, lead, zinc, tungsten, tin, beryllium, boron and so on. In the middle and lower reaches of Yangtze River, Daye iron and copper Skarn deposits are widely distributed in Tongling and other places.

Formation mechanism:
The former Soviet Union, 1945, 1947, Erren Ke 1948, 1955 is put forward based on the contact reaction of Skarn of this new theory. According to this theory, the formation of Skarn is due to the metasomatism of the carbonate rocks and aluminosilicate rocks under the action of the solution after the high temperature magmatic period by two kinds of disequilibrium medium. Spread the effect here (
Double metasomatism plays a leading role. When the solution moves along the contact zone of carbonate rocks and aluminosilicate rocks, calcium diffuses into the direction of aluminosilicate rocks, and SiO2 and Al2O3 diffuse to the direction of carbonate rocks, thus the two rocks are metasomatism and form some reaction Skarn bands. The other type is the contact percolation Skarn. It also occurs in the contact zone between carbonate rocks and aluminosilicate rocks, which is due to the single direction transportation of components. Skarn is usually near the intrusive body.
Carbonate or silicate rocks are formed by contact metasomatism, and there are other causes similar to Skarn mineral composition. The former Soviet scholars are called: (1) class Skarn, which are formed by metamorphic carbonate rocks such as limestone, calcareous tuff and similar rocks; (2) near Skarn.
A rock consisting of feldspar, quartz, alusite, or epidote, adjacent to the Skarn of the side of the intrusive body; (3) like Skarn, which is similar to the mineral composition of the Skarn and is not yet determined.
Rock; 4. Self reaction Skarn, a rock formed by calcium metasomatism from ultrabasic rocks and alkaline ultrabasic rocks. Skarn is usually named after the main minerals, such as garnet Skarn and diopside Skarn. Minerals related to calcareous Skarn include iron, cobalt, copper, platinum, tungsten, molybdenum, lead and zinc, gold, tin, scandium, niobium, rare earth and uranium, and the minerals associated with magnesium Skarn are boron, iron, zinc and gold mica.