Magic lunark mantle
#MAGIC LUNARK MANTLE PLUS#
We report in situ ultrasonic velocity measurements on a series of partially molten samples, composed of mixtures of olivine plus 0.1 to 4.0 volume % of basalt, under conditions relevant to the LVZ. The two scenarios imply drastically distinct physical and geochemical states, leading to fundamentally different conclusions on the dynamics of plate tectonics. The LVZ has been proposed to originate from either partial melting or a change in the rheological properties of solid mantle minerals. It coincides in depth with the asthenosphere, a mantle region of lowered viscosity that may be essential to enabling plate motions. The low-velocity zone (LVZ) is a persistent seismic feature in a broad range of geological contexts. The slope of the weaker δ 56Fe-Mg# trend defined by the combined set of all mantle peridotites from this study is more consistent withĮxperimental evidence supports mantle partial melting in the asthenosphere.Ĭhantel, Julien Manthilake, Geeth Andrault, Denis Novella, Davide Yu, Tony Wang, Yanbin Either disequilibrium melting increased the modelled α mantle-melt for these particular sites or the difference between average peridotite and basalt may be reduced by partial re-equilibration between the isotopically heavy basalts and the isotopically light depleted lithospheric mantle during melt ascent. significantly higher than the observed difference between averages for all the peridotites and the basalts in this study (corresponding to Δ56Fe mantle-basalt ≈ 0.1‰). This modelled value implies Fe isotope fractionation between residual mantle and mantle-derived melts corresponding to Δ56Fe mantle-basalt ≈ 0.2-0.3‰, i.e. These three sites display a particularly good correlation and define an isotope fractionation factor of ln α mantle-melt ≈ 0.3‰.
![magic lunark mantle magic lunark mantle](https://i.pinimg.com/originals/f0/c6/83/f0c683322257438c5321cc76bf569c4d.png)
In contrast to most other peridotites investigated in this study, spinel lherzolites and harzburgites from three localities (Horoman, Kamchatka and Lherz) are virtually unaffected by metasomatism. The slope of depletion trends (δ 56Fe versus Mg#) of the peridotites was used to model Fe isotope fractionation during partial melting, resulting in α mantle-melt ≈ 1.0001-1.0003 or ln α mantle-melt ≈ 0.1-0.3‰. Taken together, these findings imply that Fe isotopes fractionate during partial melting, with heavy isotopes preferentially entering the melt. Furthermore, the peridotites display a negative correlation of δ 56Fe with Mg# indicating a link between δ 56Fe and degrees of melt extraction.
![magic lunark mantle magic lunark mantle](https://spielraum.co.at/Images/Einzelkarten/Magic/PLS/PLS-065-Keldon_Mantle.png)
The peridotites yield an average δ 56Fe = 0.01‰ and are significantly lighter than the basalts (average δ 56Fe = 0.11‰).
![magic lunark mantle magic lunark mantle](https://i.ebayimg.com/images/g/R2kAAOSwmTxfLFRd/s-l300.jpg)
High precision Fe isotope measurements have been performed on various mantle peridotites (fertile lherzolites, harzburgites, metasomatised Fe-enriched peridotites) and volcanic rocks (mainly oceanic basalts) from different localities and tectonic settings. Partial melting and melt percolation in the mantle: The message from Fe isotopes