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Petroleum Geochemical Survey
Published in Muhammad Abdul Quddus, Petroleum Science and Technology, 2021
‘Crystallization’ is the physical process of the separation and purification of dissolved solids from solution. The dissolved solids are separated, from a given solution, during the crystallization process according to their melting points in almost pure crystalline form. Fractional crystallization is the separation or solidification of minerals in solution or molten state according to the order of their melting points. From hot magma, as it cools, the first to crystallize is the highest-melting-point mineral, followed by progressively lower-melting-point minerals, along with the drop in temperature.
Igneous Petrology and the Nature of Magmas
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Fractional crystallization, the opposite of fractional melting, occurs when a magma partially crystallizes and the remaining magma becomes segregated from the crystals. In these circumstances, the new evolved magma will have a different composition from its parental magma. The evolved magma, which is more felsic than its parent was, may move upwards, leaving the high-temperature (mafic) minerals behind. Fractional crystallization, like fractional melting, has been a key process contributing to differentiation of Earth.
Platinum-group element mineralization in the British Tertiary Volcanic Province
Published in Adam Piestrzyński, Mineral Deposits at the Beginning of the 21st Century, 2001
Of all the PGM occurrences identified, the ELS on Rum hosts by far the most diverse and abundant assemblage. Total PGE concentrations locally exceed 2 ppm in individual chromitite layers (Power et al. 2000a). For comparison the WLS is notably poorer in PGE indicating that substantial PGE fractionation occurred in the ELS. The abundance of PGE seems to correlate with the presence of cumulus plagioclase suggesting that an evolved magma played a significant role in the mineralization process. Also, there is a general correlation with the boundaries between the megacyclic units. The stratigraphic control of the PGE in the ELS on Rum indicates that the mineralization occurred during the magmatic stage of the crystallization of the complex. Differences between the occurrences can be attributed directly to magma mixing at different stages during fractional crystallization. This is also reflected in the stratigraphic variation of chrome spinel compositions as shown by Power et al. (2000b). A similar control may exist in the WLS as well as on Mull and Skye, but further work needs to be done in these places to establish the link to the stratigraphy.
Using amphibolite chemistry to assist structural and stratigraphic interpretation at Broken Hill, Australia
Published in Australian Journal of Earth Sciences, 2021
Also referred to as differentiation, fractional crystallisation refers to the gradual solidification process during cooling of sills or other layered intrusions wherein the crystals that grow from a magma at any instant have compositions that are different from the magma itself, so that removal of these crystals (by process such as gravity settling, for example) imposes a permanent change on the composition of the magma remaining in the sill. This process forces a compositional profile on the sill. Elements that prefer to concentrate in early formed minerals such as olivine, pyroxene and chromite show concentrations in the mafic crystal-rich base and then show upward depletion in the sill. Elements that are preferentially concentrated in the melt (incompatible elements) build up in concentration higher in the sill.