Melt percolation and reaction atop a plume: evidence from the poikiloblastic peridotite xenoliths from Boree (Massif Central, France)

Article Abstract:

A study was conducted on poikiloblastic peridotite xenoliths from Boree, France using electron and microprobe, thermal ionization mass spectrometry and laser fluorination techniques. Results suggest that poikiloblastic harzburgite xenoliths (P-type) was formed through melt percolation-reactions in a lherzolite precursor (G-type) during lithospheric erosion by an uprising plume. Numerical simulation results further indicate that the petrogenesis of P-type and G-type xenoliths occurred within a percolation-reaction column at the boundary of lithosphere and plume.

France, Natural history, Rocks, Igneous, Xenoliths, Percolation, Percolation (Hydrology)

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Syndeformational recrystallization - dynamic or compositionally induced?

Article Abstract:

The chemical composition of porphyroclasts and recrystallized grains of plagioclase, clinopyroxene and hornblende were studied in samples from a high grade shear zone of the Ivrea Zone, Italy, to estimate the relative importance of driving potentials. Findings showed that the release of compositional Delta-G is essential if the driving potentials are expected to have a significance in terms of affecting a physical process. The only way to change the chemical composition is by ionic exchange through a migrating boundary.

Analysis

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Origin of the recrystallization front in the Ronda peridotite by km-scale pervasive porous melt flow

Article Abstract:

Kilometer-scale pervasive porous flow occurs in the refractory portion of the spinel tectonites and the coarse-granular domain of the Ronda peridotite. Porous melt flowing in the upper mantle significantly affects partial mantle melt compositions. The origin of the recrystallization front is accomplished mainly by melting/dissolution. Processes associated with coarse-granular peridotites and fine- and layered granular facies show complex overprinting relationship in both time and space.

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