Metasomatism meaning metasomatism definition metasomatism exp. 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. Progressive metasomatism of serpentine in the sierra nevada of california gonool. 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. Geofluids 2010 10, 254269 abstract metamorphism and metasomatism both involve the reequilibration. In the powerpoint preferences dialog box, click general. This can be envisaged as the metamorphic rocks within the deep crust losing fluids and diss. 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. Replacement occurs when a mineralizing solution encounters minerals unstable in its presence.
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. Metasomatism article about metasomatism by the free. 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. Callegari, department of science, mineralogy and petrology, university of torino, italy 2. 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.
Mapping the distribution of fluids in the crust and. Hydrothermal solutions are naturally formed hot water solutions that are capable of dissolving and transporting substances and precipitating them to form new. When metamorphism is accompanied by a change in the chemistry of a rock, the rock is said to have been metasomatized best 1982. During metasomatism the rock remains in a solid state. Contact metamorphic rocks british geological survey.
Metamorphism, mineralogical and structural adjustments of solid rocks to physical and chemical conditions differing from those under which the rocks originally formed. 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. The structure is filled with ferromagnesian mineral that has been altered to chlorite and has a narrow rim. Regional metasomatic rocks at moderate and even shallow depths form the outer zones of metasomatic rock associations accompanying ore deposits nearore. The significant part of the monograph contains the characteristics of the main metasomatic. Metasomatism and metasomatic rocks indiana university. 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. 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.
The process by which the chemical composition of a rock is changed by. Changes produced by surface conditions such as compaction are usually excluded. 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. Save powerpoint presentations as pdf files office support. Anstnecr nodules of serpentine enclosed in mica schist close to a body of intrusive quartz diorite. 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.
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. Contact metamorphic rocks recommendations by the iugs subcommission on the systematics of metamorphic rocks. Trace element and isotopic ratios from least contaminated magmas. Origin, texture, and classification of metamorphic rocks. Fluid speciation in the cohs system at 1100oc and 0. Introduction 2 the stability and fate of subcontinental lithospheric mantle sclm is an important unresolved issue. In both kinds of ca metasomatism, the quartz vermicules tend to have constant thickness, but locally in. For complete, finegrained replacement, a large proportion of the replacement must be. 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.
Related to unequal partitioning of elements between solid phases and fluids. For a broad understanding of the response of a rock to changes in physicochemical conditions we therefore need to consider not only. During metasomatism the minerals that make up the original rock are partially or completely replaced by new minerals. The susceptibility of a rock to metasomatism depends partly on its mineralogical and structural characteristics and partly on the characteristics of the fluid i. Metasomatism and metasomatic rocksf british geological survey. Crystallization and breakdown of metasomatic phases in. Mapping the distribution of fluids in the crust and lithospheric mantle utilizing geophysical methods. Metasomatism and the chemical transformation of rock. The rim is microgranular and appears more felsic than the host rock. Metasomatism changes in the bulk composition of rocks in the solid stateoccurs to some degree in virtually all. The physicochemical processes of transport and reaction, acting in metasomatism, are described in relation to the available size of opening, from supercapillary to intralattice.
Metasomatic processes economic geology geoscienceworld. 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. 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. Metamorphic fluids and metasomatism is the property of its rightful owner. Metasomatism is the chemical alteration of a rock by hydrothermal and other fluids. By john paul hunt a dissertation in fulfilment of the requirements for the degree of msc in geology university of the witwatersrand 2005.
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. Powerpoint lectures, chapter 2 igneous classification 0. In the central portion of the photomicrograph there occurs a vesiclelike structure. Hagemann including metamorphogenic base and precious metal. Knill evidence from stable isotopes and other fluid tracers fiuid inclusions in metamorphosed and synmetamorphic b. This type of metamorphism is due to mechanical deformation, like when two bodies of rock slide past one another along a fault zone. Lecture 38 igneous geochemistry read white chapter 7 if you havent already today 1. Metasomatism and the chemical transformation of rock p. The north china craton ncc is one of the oldest archean cratons on the earth jahn et al. Physical and chemical processes that are implemented during the flow of magmas and or fluids within the upper mantle. In the igneous environment, metasomatism creates skarns, greisen, and may affect hornfels in the contact metamorphic aureole adjacent to an intrusive rock mass.
Metamorphosed and metamorphogenic ore deposits regional metamorphism and ore formation. Metasomatism definition of metasomatism by the free. Complete mineral transformations may occur, but the original rock texture may remain resulting in a pseudomorph. The data show that metasomatic features are controlled by. Powerpoint lectures, chapter 21 introduction to metamorphism 5. After holloway 1981 compositions and volumes of supercritical fluids in the earths crust. All structured data from the file and property namespaces is available under the creative commons cc0 license. It is postulated that such metasomatism in the upper mantle is a necessary precursor to continental alkaline volcanism.
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