Dunite nodules (Foss) and megacrysts of olivine (Fos3 s4 ) and clinopyroxene (FS13W043En44) are present as rare inclusions in the rhyodacite (~ 66wt %SiO z ) of Kauaopuu Ridge, Oahu, Hawaii. The rhyodacite is interbedded with caldera-filling tholeiitic lavas of the Waianae volcano. Results: (I) Dunite nodules (::;; I cm) consist of xenomorphic-granular olivine and minor chrome spinel and clinop...

The Trinity peridotite (northern CA) contains numerous lithologic sequences consisting of dunite to harzburgite to spinel lherzolite to plagioclase lherzolite. Previous workers have documented geochemical gradients in these sequences consistent with melt-rock reaction processes occurring around dunites, interpreted to reflect conduits for melt ascent. We have undertaken a study of Li isotope co...

[1] Dunites in the mantle section of the Oman ophiolite represent conduits for chemically isolated melt transport through the shallow mantle beneath oceanic spreading centers. These dunite melt conduits exhibit a scale-invariant power law relationship between width and cumulative abundance, as measured over 4 orders of magnitude. We use this size/frequency distribution to assess several hypothe...

Recent numerical simulations of reactive dissolution along a solubility gradient in a viscously deformable and vertically upwelling column predict that the combined effect of orthopyroxene (opx) dissolution and compaction causes melts to segregate within individual dunite channels [1]. The simulations indicate that the physical and chemical nature of the melt source and overlying peridotite det...

Tabular dunites in the Josephine peridotite of southwestern Oregon represent conduits for melt extraction from the upper mantle. The amount of melt trapped within these channels during cooling and exhumation of the peridotite massif was calculated using a mass-balance approach. These calculations suggest that no more than 0·1^0·2 vol. % melt could have been trapped within these dunites after cr...

The ultramafic portions of the Proterozoic ophiolite, Eastern Desert, Egypt, contain significant chromitite concentrations that are mainly located in the central and southern parts of the Eastern Desert as small and irregular bodies within a fully serpentinized dunite and harzburgite. Chromitite spinel exhibits a wide range of composition from high Cr to high Al varieties. The Cr# of chromian s...

The podiform chromitite deposits of the Ordovician Sorkhband ultramafic complex, southwestern Makran, are the largest chromitite deposits in Iran. The Sorkhband ultramafic complex comprises of a northern part of dunite, podiform chromitite, olivine clinopyroxenite, wehrlite and olivine websterite and a southern part of foliated diopsidic harzburgite with subordinate dunite, olivine clinopyroxen...

0019-1035/$ see front matter 2010 Elsevier Inc. A doi:10.1016/j.icarus.2010.10.022 ⇑ Corresponding author at: Department of Space Institute, 1050 Walnut St., Suite 300, Boulder, CO 8030 546 9687. E-mail address: [email protected] (A.C. Barr). The volume of melt produced in hypervelocity planetary impacts and the size and shape of the melted region are key to understanding the impact historie...

In the Appalachian Mountains of Vermont, USA, variably serpentinized ultramafic rocks mark Ordovician Taconic orogenic suture zone. These provide evidence for several alteration events that occurred during orogenesis. The largest these bodies occurs as a partially meta-dunite located in East Dover, Vermont. Whole-rock X-ray fluorescence spectroscopy and electron microprobe data on samples are i...