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Incompatible element

About: Incompatible element is a research topic. Over the lifetime, 2420 publications have been published within this topic receiving 154052 citations.


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Journal ArticleDOI
TL;DR: A wide range of Cenozoic basaltic compositions, including primary or primitive basanites, alkali olivine basalts, OLSs, oLSs and evolved hawaftes and mugearites, are represented in the Dubbo volcanic province, central New South Wales, Australia as discussed by the authors.

49 citations

Journal ArticleDOI
TL;DR: In this article, the authors analyzed 2-cm-thick slabs of a drill core through the UG-2 chromitite layer for platinum-group elements and found that the ratios between the different platinum-groups change progressively.
Abstract: Samples representing consecutive 2-cm-thick slabs of a drill core through the UG-2 chromitite layer were analyzed for platinum-group elements. The results, when plotted against height, reveal an interesting pattern, with sequences that follow exponential curves of the type Y = ZX k , where Y equals the concentration of the element in samples taken at a distance X from the base of the layer, and Z is a constant. The data fit the curves with correlation coefficients of better than 0.90, and levels of significance less than 0.1 percent, which shows that the fit cannot be due to chance but that a process following or approximating an exponential equation must have been involved. The most probable such process is fractionation according to the Rayleigh law. It is postulated that these sequences that follow the Rayleigh law formed by bottom crystallization when the magma was in motion. Calculations indicate that the elements supplied to the site of crystallization were withdrawn from a surprisingly small thickness of magma and that their supply was not limited by diffusion.Between the sequences that follow the Rayleigh law are sequences that probably crystallized from stagnant magma, so that the supply of elements to the site of crystallization was diffusion controlled. In these sequences the ratios between the different platinum-group elements change progressively.It is argued that these results reveal that the platinum-group minerals crystallized very early in UG-2 layer-type deposits and show a pattern of element behavior conforming closely with that of a classical compatible element which has a very large bulk distribution coefficient. Therefore, the well-known processes of enrichment applicable to such elements during processes of melting and crystallization could have been operative.This one example is not sufficient to disclaim the possibility that platinum-group elements can also behave like incompatible elements under different conditions, as is assumed by many authors in this field.

49 citations

Journal ArticleDOI
TL;DR: The Shuksan schist comprises a structurally coherent, metabasaltic member of the Easton Formation, the uppermost allochthon (Shuksan thrust plate) in the thrust system of the western North Cascades of Washington State as discussed by the authors.
Abstract: The Shuksan schist comprises a structurally coherent, metabasaltic member of the Easton Formation, the uppermost allochthon (Shuksan thrust plate) in the thrust system of the western North Cascades of Washington State. Late Jurassic metamorphism at moderately high P/T produced interlayering of actinolite-bearing greenschist assemblages with blue amphibole-bearing rocks. Major and trace element analyses of twelve greenschist and blueschist samples have been used to establish similarities between the basaltic protolith and moderately to strongly fractionated Type I MORB, to distinguish the effects of seafloor alteration superimposed on the primary igneous chemistry, and to evaluate the origin and nature of the chemical controls which produced the two mineral assemblages. The twelve analyzed samples exhibit moderate to strong LREE depletion, and characteristically low concentrations of other non-labile trace elements such as Nb, Th and Hf. The highly to moderately incompatible elements Ti, P, Nb, Zr, Hf, Y, Sc, and the REE vary by factors of 1.5 to 3.5 within the suite in a systematic pattern, increasing smoothly with increasing total iron. The relative enrichments of these elements are inversely proportional to bulk partition coefficients estimated for fractionation of basaltic magmas. The magnitude of the negative europium anomaly increases with overall incompatible element enrichment. These variations are consistent with the production of a wide spectrum of compositions by different degrees of low pressure fractionation of similar Type I MORB parent magmas. The concentrations of Sr, Rb, Na, and K vary irregularly and do not correlate with the non-labile trace elements. K and Rb are substantially elevated over typical MORB values in most samples and exhibit a consistently lower ratio (K/Rb=400 vs 1000) than fresh MORB. Concentrations of these four elements are believed to have been modified by low temperature seafloor alteration (pre-metamorphic) characterized by the formation of K-rich celadonitic clays, palagonite and minor potassium feldspar. The critical chemical variables that control the occurrence of actinolite and blue amphibole in the Shuksan schists are total iron, Fe2O3-content and Na/Ca (all high in blueschists). The chemical features were largely established by magmatic processes and inherited from the igneous parent rocks; the chemically more evolved samples are blueschists. The Fe2O3-content and Na/Ca, however, may be modified during alteration, rendering initial bulk compositions near the chemical boundary susceptible to changes which may shift rock compositions from one compatibility field to the other. Heterogeneous alteration of pillow lavas and other fragmental deposits, followed by intense flattening during metamorphism, provides a mechanism for generating blueschists and greenschists interlayered on the cm scale.

49 citations

Journal ArticleDOI
TL;DR: Apatite from the Umvimeela Dyke, an unlayered dike that parallels the Great Dyke over much of its length, contains less Cl than is seen in the Ultramafic Sequence cumulates of the great dyke.
Abstract: Apatite from the Great Dyke of Zimbabwe is relatively rich in the hydroxy-fluorapatite end-members. The mole fraction of fluorapatite increases from approximately 40% in cumulates of the Ultramafic Sequence to over 60% in a sample near the top of the exposed Mafic Sequence. The chlorapatite component decreases from a typical high of 10–20 mole% in the Ultramafic Sequence to about 1% in the uppermost part of the Mafic sequence. However, within-sample variation may be as great as the entire stratigraphic variation. Halogen contents of marginal samples generally are similar to axial samples, but tend not to have as high Cl concentration and tend to OH-enrichment. Biotite compositions approach hydroxyl end-member compositions, and apatite-biotite OH-F exchange geothermometers give an average closure temperature of 564° C. Apatite from the Umvimeela Dyke, an unlayered dike that parallels the Great Dyke over much of its length, contains less Cl than is seen in the Ultramafic Sequence cumulates of the Great Dyke. While the overall stratigraphic trend is characterized by a decrease in the Cl/F ratio with stratigraphic height, within the P1 unit at the top of the Ultramafic Sequence there is a positive correlation between Cl and other incompatible elements such as Na and Ce. The apparent contradiction between the general stratigraphic trend of decreasing Cl/F ratio with fractionation and the apparent increase in Cl and other incompatible elements seen in the P1 unit can be explained by assuming that the Great Dyke magma chamber was degassing near its top, where confining pressure was lowest and Cl was preferentially lost to a separating volatile-rich fluid. As cumulates formed on the floor, they entrapped liquid that was increasingly depleted in Cl at the higher stratigraphic levels. However, at any given stratigraphic interval, either local fluid enrichment or the eventual crystallization of halogen-bearing minerals that incorporate the smaller F ion in preference to the larger Cl ion led to a local increase in the Cl/F ratio.

48 citations

Journal ArticleDOI
TL;DR: In this article, the mixing phenomenon involving a variety of mantle source components is used to test the mixing hypothesis, a combined use of Nd isotopes and hygromagmaphmaphile elemental ratios is proven very powerful.

48 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20237
202216
202157
202056
201960
201851