When metamorphism is accompanied by a change in the chemistry of a rock, the rock is said to have been metasomatized best 1982. Replacement occurs when a mineralizing solution encounters minerals unstable in its presence. Metasomatism article about metasomatism by the free. Progressive metasomatism of serpentine in the sierra nevada of california gonool. Powerpoint lectures, chapter 2 igneous classification 0. The process by which the chemical composition of a rock is changed by. Heat is generated by the friction of sliding along the zone, and the rocks tend to crushed and pulverized due to the sliding. Anstnecr nodules of serpentine enclosed in mica schist close to a body of intrusive quartz diorite. The physicochemical processes of transport and reaction, acting in metasomatism, are described in relation to the available size of opening, from supercapillary to intralattice. Metasomatism is the chemical alteration of a rock by hydrothermal and other fluids.
Callegari, department of science, mineralogy and petrology, university of torino, italy 2. Lecture 38 igneous geochemistry read white chapter 7 if you havent already today 1. Hydrothermal solutions are naturally formed hot water solutions that are capable of dissolving and transporting substances and precipitating them to form new. Metasomatism and the chemical transformation of rock. Metasomatism definition of metasomatism by the free. Origin, texture, and classification of metamorphic rocks. Ultramafic metasomatism ideal mineral zonation due to metasomatism in metasomatism definition is metamorphism that involves changes in the chemical composition as well as in the texture of rock. In the context of mantle metasomatism, enriched refers to the addition of trace elements such as sr, ba, zr, and rareearth elements ree which can. In the central portion of the photomicrograph there occurs a vesiclelike structure. Powerpoint lectures, chapter 21 introduction to metamorphism 5. Introduction 2 the stability and fate of subcontinental lithospheric mantle sclm is an important unresolved issue. The north china craton ncc is one of the oldest archean cratons on the earth jahn et al. In the powerpoint preferences dialog box, click general.
Metasomatism meaning metasomatism definition metasomatism exp. Mapping the distribution of fluids in the crust and lithospheric mantle utilizing geophysical methods. In the context of mantle metasomatism, enriched refers to the addition of trace elements such as sr, ba, zr, and rareearth elements ree which can be highly mobile in the mantle rockfluid systems. In the metamorphic environment, metasomatism is created by mass transfer from a volume of metamorphic rock at higher stress and temperature into a zone with lower stress and temperature, with metamorphic hydrothermal solutions acting as a solvent. Physical and chemical processes that are implemented during the flow of magmas and or fluids within the upper mantle. Crystallization and breakdown of metasomatic phases in. Files are available under licenses specified on their description page. Contact metamorphic rocks british geological survey. Hagemann including metamorphogenic base and precious metal.
During metasomatism the rock remains in a solid state. In both kinds of ca metasomatism, the quartz vermicules tend to have constant thickness, but locally in. Metasomatism may be driven by a tectonic event and so be associated with a change in p, t conditions, but as will be shown from the following examples, fluid. Ii origin, texture, and classification of metamorphic rocks teklewold ayalew encyclopedia of life support systems eolss some metamorphic rocks, particularly those buried to depths of several kilometers, contain numerous veins rich in quartz and feldspar. Alkali metasomatism, skarns, greisens, tourmalinites, rodingites, blackwall alteration and listvenites. During metasomatism the minerals that make up the original rock are partially or completely replaced by new minerals. Follow these instructions to set the print quality of the pdf. Geofluids 2010 10, 254269 abstract metamorphism and metasomatism both involve the reequilibration. This type of metamorphism is due to mechanical deformation, like when two bodies of rock slide past one another along a fault zone. Metasomatism and metasomatic rocksf british geological survey. Metasomatism and the chemical transformation of rock p. The relation of metasomatism to ore deposits is discussed, and the new concept of formation of oreconcentrating dense salt melts and related light metasomatic fluids is proposed. For complete, finegrained replacement, a large proportion of the replacement must be.
N2 concepcion del oro, the second largest copper producing district of mexico, contains sulfide and iron oxide minerals disseminated in skarn matrix surrounding a granodiorite stock. All structured data from the file and property namespaces is available under the creative commons cc0 license. Metasomatism changes in the bulk composition of rocks in the solid stateoccurs to some degree in virtually all. Metasomatism and metasomatic rocks indiana university. Metamorphic rocks and processes metamorphism comes from the greek words meta change morphe form metamorphic rocks form by solidstate no melting transformation of preexisting rock by processes that take place beneath earths surface. The susceptibility of a rock to metasomatism depends partly on its mineralogical and structural characteristics and partly on the characteristics of the fluid i. The process by which the chemical composition of a rock is changed through the introduction or extraction of chemicals dissolved in fluids that migrate through the rocks pores. Fluid speciation in the cohs system at 1100oc and 0. Therefore, it is appropriate to compare myrmekite formed by ca metasomatism of kfeldspar in granitic rocks with myrmekite formed by ca metasomatism of plagioclase in anorthosite.
Regional metasomatic rocks at moderate and even shallow depths form the outer zones of metasomatic rock associations accompanying ore deposits nearore. This can be envisaged as the metamorphic rocks within the deep crust losing fluids and diss. Changes produced by surface conditions such as compaction are usually excluded. The structure is filled with ferromagnesian mineral that has been altered to chlorite and has a narrow rim. Referring to the ultimate demise of metasomatism as a largescale process, they go on to say. Metasomatic replacement is the method whereby wood petrifies silica replaces the wood fibres, one mineral forms a pseudomorph of another, or an ore body takes the place of an equal volume of rock. After holloway 1981 compositions and volumes of supercritical fluids in the earths crust.
The magmatists won the argument with the experimental work of tuttle and bowen 1958 and for many years metasomatism was neglected recent developments in chemical, isotopic. If so, share your ppt presentation slides online with. Spot light on using the rare earth elements ree to constrain mantle sources and conditions of petrogenesis gg325 l38, f20 modeling igneous petrogenesis however, other concurrent processes can obscure the. Metasomatism the replacement of certain minerals by others with substantial change in the chemical composition of the rock, occurring under the influence of. Under print quality paper pdf, set the desired quality to an option of your choice. Metamorphism, mineralogical and structural adjustments of solid rocks to physical and chemical conditions differing from those under which the rocks originally formed.
In the metamorphic environment, metasomatism is created by mass transfer from a volume of metamorphic rock at higher stress and temperature into a zone with lower stress and temperature, with metamorphic hydrothermal solutions. Metasomatism involves the changes in rock composition that occur when material in solution is added to the rock, or material is taken away, as the result of fluids flowing through a rock. In the igneous environment, metasomatism creates skarns, greisen, and may affect hornfels in the contact metamorphic aureole adjacent to an intrusive rock mass. It is postulated that such metasomatism in the upper mantle is a necessary precursor to continental alkaline volcanism. The rim is microgranular and appears more felsic than the host rock. Contact metasomatism contact metasomatism is a process of formation of new mineral by reaction between the contact rock and the escaping high temperature gaseous emanation with other important materials from the magma chamber. The data show that metasomatic features are controlled by. The significant part of the monograph contains the characteristics of the main metasomatic. Metamorphic fluids and metasomatism is the property of its rightful owner. Knill evidence from stable isotopes and other fluid tracers fiuid inclusions in metamorphosed and synmetamorphic b. Save powerpoint presentations as pdf files office support. Process of mineralogical and structural textural changes of rocks in the solid state in response to physical and chemical conditions which differ from those under which they originated. Heatliberating events, such as igneous intrusions emplaced into cool crustal rocks, will result not only in loss of heat to the surrounding environment, but also in the transport of volatile components, which are responsible for metasomatic processes.
Trace element and isotopic ratios from least contaminated magmas. Contact metamorphic rocks recommendations by the iugs subcommission on the systematics of metamorphic rocks. Metamorphosed and metamorphogenic ore deposits regional metamorphism and ore formation. Mapping the distribution of fluids in the crust and.
295 314 416 1077 353 96 1348 838 85 799 1484 1577 247 769 1250 1623 887 615 338 255 1537 892 1242 1170 878 1229 123 155 1307 1098 1449 342 1147 582 553 697 440 344 1408 905