Fast kimberlite ascent rates estimated from hydrogen diffusion profiles in xenolithic mantle olivines from southern Africa
AH Peslier, AB Woodland, JA Wolff - Geochimica et Cosmochimica Acta, 2008 - Elsevier
AH Peslier, AB Woodland, JA Wolff
Geochimica et Cosmochimica Acta, 2008•ElsevierFourier transform infrared spectrometry (FTIR) analyses of olivines from peridotite xenoliths
found in southern African kimberlites indicate 0 to 80ppm H2O concentrations. OH
absorbance profiles across olivine grains show homogeneous H contents from core to edge
for most samples. In one sample the olivines are H-free, while another has olivines
characterized by lower H contents at the grain edges compared to the cores, indicating H
loss during transport of the xenolith to the surface. Flat or near-flat H profiles place severe …
found in southern African kimberlites indicate 0 to 80ppm H2O concentrations. OH
absorbance profiles across olivine grains show homogeneous H contents from core to edge
for most samples. In one sample the olivines are H-free, while another has olivines
characterized by lower H contents at the grain edges compared to the cores, indicating H
loss during transport of the xenolith to the surface. Flat or near-flat H profiles place severe …
Fourier transform infrared spectrometry (FTIR) analyses of olivines from peridotite xenoliths found in southern African kimberlites indicate 0 to 80ppm H2O concentrations. OH absorbance profiles across olivine grains show homogeneous H contents from core to edge for most samples. In one sample the olivines are H-free, while another has olivines characterized by lower H contents at the grain edges compared to the cores, indicating H loss during transport of the xenolith to the surface. Flat or near-flat H profiles place severe constraints on the duration of H loss from olivine grains, with implications for kimberlite magma ascent rates. Diffusion equations were used to estimate times of H loss of about 4h for the sample with heterogeneous olivine H contents. Resulting kimberlite ascent rates are calculated to be 5–37ms−1 minimum, although these estimates are highly dependent on volatile contents and degassing behavior of the host kimberlite magma. Xenolithic olivines from alkali basalts generally have lower H contents and more pronounced H diffusion profiles than do those from kimberlites. This difference is likely caused by higher magma temperatures and lower ascent rates of alkali basalts compared to kimberlites.
Elsevier
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