Incompatible element

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

Mantle sources beneath the Cameroon Volcanic Line: geochemistry and geochronology of the Bamoun plateau mafic rocks

Abstract: The age and origin of the volcanism along the Cameroon Volcanic Line (CVL) are still a matter of debate. We present major and trace element compositions as well as Sr–Nd–Pb–Hf isotopic results for mafic rocks from the Bamoun area, in the central part of the Cameroon Volcanic Line, as well as for two samples from recent eruptions of Mt. Cameroon. Lava flows are mostly basalts and hawaiites with transitional affinity. Some samples are among the oldest rocks of the CVL, with ages older than 51 My while some rocks are very young, around 0.05 My. All the samples are enriched in incompatible elements, indicating that melts were formed in a garnet-bearing mantle source. Different mantle sources participated to the formation of the Bamoun lavas. One source is isotopically similar to the main volcanic rocks of the CVL and probably represents an important part of the subcontinental lithospheric mantle. The second source is enriched in incompatible elements and shows a marked positive Eu anomaly, probably related to the participation of pyroxenites in the partial melting processes. The third mantle source is similar to the source of the Mt. Cameroon. This mantle source was known previously only in the Mt. Cameroon lavas, and we report its occurrence for the first time in old lavas and in other location along the CVL.

Mechanism for the extrusion of KREEP.

Abstract: The evolution of the final residue of the magma ocean from the time it entered the anorthositic crust until it was extruded is modeled. The magma density first increased as anorthite and orthopyroxene crystallized, but once ilmenite precipitation began the density dropped. The KREEPy magma collected beneath the thinnest parts of the anorthitic crust, and intruded the crust when the density dropped below that of the adjacent crustal materials. The nearly constant degree of incompatible element fractionation moon-wide was maintained because the rapid drop in density during ilmenite crystallization occurred after about the same degree of crystallization at all locations. The high viscosity of the final residue of the magma ocean and its low density contrast with the crust initially resulted in very slow migration through the crust.

Continental alkali basalts as mixtures of kimberlite and depleted mantle: Evidence from Kilbourne Hole Maar, New Mexico

Abstract: A depleted-mantle nodule from Kilbourne Hole, New Mexico, has been analyzed in detail to test a recent model for the formation of alkali basalts by two-component mixing of depleted mantle and enriched (kimberlite) mantle. The bulkrock chemistry of the nodule can be reconstructed from its constituent phases, except for calcium, sodium and several incompatible elements. It is found that acid-leachates derived from the surfaces of the minerals contain the "missing" complement of these elements. Furthermore, major element compositions indicate that each leachate may be a mixture of nodule mineral plus kimberlite. It is suggested that the host alkali basalt lava could have formed by the same mixing process, as the lava and enclosed nodule are in approximate Nd isotopic equilibrium, and calculated mineral/melt partition coefficients for the rare earth elements (REE) between nodule minerals and host lava match those determined experimentally.