Incompatible element

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

Can Kimberlites be generated from an ordinary mantle

Abstract: Kimberlites are characterized by a high concentration of incompatible elements, including light rare earths. However, Nd isotopic evidence indicates that their source regions do not have a long history of enrichment. If kimberlites can be generated from non-enriched mantle sources by simple partial melting processes, this implies that crystal–liquid partition coefficients for some trace elements are lower for kimberlitic liquids than for basalts or andesites. From a comparison of clinopyroxene megacrysts (regarded as equilibrated with kimberlite at depth) with existing kimberlite data we argue here that low crystal–liquid partition coefficients for the rare earths are plausible.

Trace element geochemistry of high alumina basalt - Andesite - Dacite - Rhyodacite lavas of the Main Volcanic Series of Santorini Volcano, Greece

Abstract: Trace element systematics throughout the cal-calkaline high alumina basalt — basaltic andesite — andesite — dacite — rhyodacite lavas and dyke rocks of the Main Volcanic Series of Santorini volcano, Greece are consistent with the crystal fractionation of observed phenocryst phases from a parental basaltic magma as the dominant mechanism involved in generating the range of magmatic compositions. Marked inflection points in several variation trends correspond to changes in phenocryst mineralogy and divide the Main Series into two distinct crystallisation intervals — an early basalt to andesite stage characterised by calcic plagioclase+augite+olivine separation and a later andesite to rhyodacite stage generated by plagioclase augite+hypersthene+magnetite+apatite crystallisation. Percent solidification values derived from ratios of highly incompatible trace elements agree with previous values derived from major element data using addition-subtraction diagrams and indicate that basaltic andesites represent 47–69%; andesites 70–76%; dacites ca. 80% and rhyodacite ca. 84% crystallisation of the initial basalt magma. Least squares major element mixing calculations also confirm that crystal fractionation of the least fractionated basalts could generate derivative Main Series lavas, though the details of the least squares solutions differ significantly from those derived from highly incompatible element and addition-subtraction techniques. Main Series basalts may result from partial melting of the mantle asthenosphere wedge followed by limited olivine+pyroxene+Cr-spinel crystallisation on ascent through the sub-Aegean mantle and may fractionate to more evolved compositions at pressures close to the base of the Aegean crust. Residual andesitic to rhyodacite magmas may stagnate within the upper regions of the sialic Aegean crust and form relatively high level magma chambers beneath the southern volcanic centres of Santorini. The eruption of large volumes of basic lavas and silicic pyroclastics from Santorini may have a volcanological rather than petrological explanation.

Degree of melting and source composition of Cenozoic basalts in southwest Japan: Evidence for mantle upwelling by flux melting

Abstract: Based on a study of Cenozoic basalts in southwest Japan where mantle upwelling is considered to have occurred, the degree of melting for primary magmas and weight fractions of residual phases are quantitatively estimated using mass balances for major and compatible components among magma, residual phases and source. Assemblage and composition of the residual phases are obtained from melting experiments of primary magmas, and various source compositions were assumed. The calculation shows an increase of degree of melting toward the upwelling center from approximately 4 to 20%. This is consistent with a change in the residue from a spinel Iherzolite to a harzburgite, which was determined by melting experiments. We also obtain constraints on the source composition. Peridotite with more than 3.0 wt % Al2O3 and 2.0 wt % CaO and a high Al2O3/CaO ratio of approximately 1.5 is suitable as a source. Incompatible element concentrations of the source for Cenozoic basalts in southwest Japan are calculated assuming a batch melting model. At the center of upwelling, the source is anomalously enriched in incompatible elements (up to 200 times compared with primitive mantle model) excepting Nb, while that of upwelling margin has primitive or slightly enriched concentrations. These variations can be explained by addition of fluid (flux melting) and subsequent upwelling of enriched material from the deep mantle (e.g., lower-upper mantle boundary or core-mantle boundary). The flux melting model also explains the low potential temperature of approximately 1300 °C of the upwelling mantle. Cenozoic volcanism in southwest Japan may have been caused with a plume with abundant volatile and incompatible components rather than a plume of anomalously high temperature (e.g., Hawaii).