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We present new partition coefficients for various trace elements including Cl between olivine, pyroxenes, amphibole and coexisting chlorine-bearing aqueous fluid in a series of high-pressure experiments at 2 GPa between 900 and 1,300°C in natural and synthetic systems. Diamond aggregates were added to the experimental capsule set-up in order to separate the fluid from the solid residue and enable in situ analysis of the quenched solute by LA-ICP-MS. The chlorine and fluorine contents in mantle minerals were measured by electron microprobe, and the nature of OH defects was investigated by infrared spectroscopy. Furthermore, a fluorine-rich olivine from one selected sample was investigated by TEM. Results reveal average Cl concentrations in olivine and pyroxenes around 20 ppm and up to 900 ppm F in olivine, making olivine an important repository of halogens in the mantle. Chlorine is always incompatible with Cl partition coefficients [D.sup.olivine/fluid.sub.Cl] varying between [10.sup.-5] and [10.sup.-3], whereas [D.sup.orthopyroxene/fluid.sub.Cl] and [D.sup.clinopyroxene/fluid.sub.Cl] are ~[10.sup.-4] and [D.sup.amphibole/fluid.sub.Cl] is ~5 x [10.sup.-3]. Furthermore, partitioning results for incompatible trace element show that compatibilities of trace elements are generally ordered as [D.sup.amph/fluid] ≅ [D.sup.cpx/fluid] > [D.sup.opx/fluid] > [D.sup.ol/fluid] but that [D.sup.mineral/fluid] for Li and P is very similar for all observed silicate phases. Infrared spectra of olivine synthesized in a F-free Tibearing system show absorption bands at 3,525 and ~ 3,570 [cm.sup.-1]. In F ± Ti[O.sub.2]-bearing systems, additional absorption bands appear at ~ 3,535, ~ 3,595, 3,640 and 3,670 [cm.sup.-1]. Absorption bands at ~ 3,530 and ~3,570 [cm.sup.-1], previously assigned to humite-like point defects, profit from low synthesis temperatures and the presence of F. The presence of planar defects could not be proved by TEM investigations, but dislocations in the olivine lattice were observed and are suggested to be an important site for halogen incorporation in olivine. Keywords Halogens * Trace element partitioning * Mantle * Defects * TEM, Introduction Mantle minerals such as olivine, ortho- and clinopyroxene can host up to several hundreds ppm water (Rauch and Keppler 2002; Hirschmann et al. 2005; Stalder et al. 2005, 2008; [...]

Modal metasomatism in the Kaapvaal craton lithosphere is well documented in upper mantle xenoliths sampled by both group I (mainly late Cretaceous) and group II (mainly early Cretaceous to late Jurassic) kimberlites in the Kimberley area. The metasomatic style is characterized by introduction of K, H and large ion lithophile/high field strength (LIL/HFS) elements into the lithospheric mantle leading to the crystallization of hydrous potassic phases such as phlogopite and/or K-amphibole. Textures indicate that the hydrous phases either replace pre-existing assemblages in peridotites, forming the metasomatized peridotite suite (phlogopite-K-richterite-peridotites: PKPs) or crystallize from K-rich melts, forming the mica-amphibole-rutile-ilmenite-diopside (MARID) suite of xenoliths. These K-rich assemblages become potential low melting source components for alkaline incompatible trace element enriched magmas. The timing of metasomatism and its temporal and possible genetic relation to kimberlite magmatism is poorly constrained because of the rarity of phases in the metasomatic assemblages suitable for precise dating. Here we present precise sensitive high resolution ion microprobe (SHRIMP) U-Pb formation ages of 88 [+ or -] 2 (1[sigma] = 1 standard deviation) and 82 [+ or -] 3 Ma data for zircons from a K-richterite-phlogopite-bearing metasomatized peridotite (PKP) and a MARID xenolith respectively, sampled by a group I kimberlite. Both average PKP and MARID zircon ages are indistinguishable from emplacement ages of group I kimberlites in the Kimberley area dated at 83 [+ or -] 4 (2[sigma]) and 84 [+ or -] 0.9 Ma. One exceptionally old age spot of 102 [+ or -] 5 Ma from a PKP zircon provides evidence for modal metasomatism predating group I kimberlite emplacement by several millions of years with minor resetting of the U-Pb isotopic system of most analyzed PKP zircons to a group I emplacement age. Detailed textural and mineral chemical analysis, including high energy X-ray mapping and analysis of fluid inclusion daughter crystals, indicates a complex reaction history for both PKPs and MARIDs. U-Pb zircon ages from this study combined with literature data and experimentally derived models for MARID formation are used to suggest that MARID-formation is concurrent and genetically related to both group I and II kimberlite magmatism in the Kimberley area. MARID and PKP zircon ages are also consistent with the idea first proposed by Dawson and Smith (Geochim Cosmochim Acta 41: 309-323, 1977) that metasomatized peridotites may form from interaction of hydrous fluids expelled by solidifying MARID-type melts with peridotitic wall rocks.

Research on quartz crystals found in Mole Granite, Australia reveal information regarding post-entrapment changes regarding fluid inclusions. The authors find that these modifications can be attributed to deformation processes, and are more common in phenocrysts and vein quartz than free-standing crystals quartz.