Spinel-peridotite xenoliths from Kapfenstein (Graz Basin, Eastern Austria): A geochemical and petrological study

1996 ◽  
Vol 57 (1-2) ◽  
pp. 23-50 ◽  
Author(s):  
O. Vasellil ◽  
H. Downes ◽  
M. F. Thirlwall ◽  
R. Vannucci ◽  
N. Coradossi
Keyword(s):  
Spinel Peridotite ◽  
Peridotite Xenoliths ◽  
Eastern Austria

Proterozoic lithosphere in Marie Byrd Land, West Antarctica: Re–Os systematics of spinel peridotite xenoliths

2003 ◽  
Vol 196 (1-4) ◽  
pp. 131-145 ◽  
Author(s):  
Monica R. Handler ◽  
Richard J. Wysoczanski ◽  
John A. Gamble
Keyword(s):  
Spinel Peridotite ◽  
West Antarctica ◽  
Peridotite Xenoliths

Minor elements in olivine from spinel lherzolite xenoliths: implications for thermobarometry

1997 ◽  
Vol 61 (405) ◽  
pp. 257-269 ◽  
Author(s):  
Suzanne Y. O'Reilly ◽  
D. Chen ◽  
W. L. Griffin ◽  
C. G. Ryan
Keyword(s):  
Trace Element ◽  
Garnet Peridotite ◽  
Spinel Peridotite ◽  
Spinel Lherzolite ◽  
Proton Microprobe ◽  
Minor Elements ◽  
Spinel Lherzolites ◽  
Peridotite Xenoliths ◽  
Trace Element Contents ◽  
Element Contents

AbstractThe proton microprobe has been used to determine contents of Ca, Ti, Ni, Mn and Zn in the olivine of 54 spinel lherzolite xenoliths from Australian and Chinese basalts. These data are compared with proton-probe data for Ni, Mn and Zn in the olivine of 180 garnet peridotite xenoliths from African and Siberian kimberlites. Fe, Mn, Ni and Zn contents are well-correlated; because the spinel lherzolite olivines have higher mean Fe contents than garnet peridotite olivines (average Fo89.6vs. Fo90–92) they also have lower Ni and higher Mn contents. Zn and Fe are well-correlated in garnet peridotite olivine, but in spinel peridotites this relationship is perturbed by partitioning of Zn into spinel. None of these elements shows significant correlation with temperature. Consistent differences in trace-element contents of olivines in the two suites is interpreted as reflecting the greater degree of depletion of Archean garnet peridotites as compared to Phanerozoic spinel lherzolites. Ca and Ti contents of spinel-peridotite olivine are well correlated with one another, and with temperature as determined by several types of geothermometer. However, Ca contents are poorly correlated with pressure as determined by the Ca-in-olivine barometer of Köhler and Brey (1990). This reflects the strong T-dependence of this barometer: the uncertainty in pressure (calculated by this method) which is produced by the ±50°C uncertainty expected of any geothermometer is ca ± 8 kbar, corresponding to the entire width of the spinel-lherzolite field at 900–1200°C.

Trace-element and isotopic characteristics of spinel peridotite xenoliths from Saudi Arabia

1995 ◽  
Vol 123 (1-4) ◽  
pp. 53-65 ◽  
Author(s):  
J. Blusztajn ◽  
S.R. Hart ◽  
N. Shimizu ◽  
A.V. McGuire
Keyword(s):  
Saudi Arabia ◽  
Trace Element ◽  
Spinel Peridotite ◽  
Peridotite Xenoliths

Seismic anisotropy of the lithospheric mantle beneath Marie Byrd Land, West Antarctica: Constraints from peridotite xenoliths

2020 ◽  
Author(s):  
Seth Kruckenberg ◽  
Vasileios Chatzaras
Keyword(s):  
Lithospheric Mantle ◽  
Seismic Anisotropy ◽  
P Wave ◽  
Spinel Peridotite ◽  
Seismic Structure ◽  
West Antarctica ◽  
The West ◽  
West Antarctic ◽  
Peridotite Xenoliths ◽  
Static Conditions

<p>Constraining the seismic structure of the West Antarctic mantle is important for understanding its viscosity structure, and thus for accurately predicting the evolution of the West Antarctic Ice Sheet.  Seismic anisotropy, which is the dependence of seismic velocities on the propagation and polarization direction of seismic waves, is a valuable tool for understanding mantle deformation and flow.  We provide petrological and microstructural data from a suite of 44 spinel peridotite xenoliths entrained in Cenozoic (1.4 Ma) basalts of 7 volcanic centers located in Marie Byrd Land, West Antarctica.  Equilibration temperatures obtained from three different calibrations of the two-pyroxene geothermometer and the olivine-spinel Fe-Mg exchange geothermometer range from 780°C to 1200°C, calculated at a pressure of 1500 MPa.  This range of temperatures corresponds to extraction depths between 39 and 72 km, constraining the source of the xenoliths within the lithospheric mantle above the low velocity zone modelled by seismic studies.</p><p>The Marie Byrd Land xenoliths are fertile with average clinopyroxene mode that ranges between 15 and 24%.  Based on their modal composition, xenoliths are predominantly classified as lherzolites (n=30), with lesser occurrences of harzburgite (n=4), wehrlite (n=3), dunite (n=3), olivine websterite (n=1), websterite (n=1), and clinopyroxenite (n=2).  Petrological data suggest that the xenoliths have been affected by various degrees of partial melting as well as by reaction with silicate melts or fluids.  For example, clinopyroxenes in the more fertile lherzolites and wehrlites show a constant TiO<sub>2</sub> concentration at 0.65 wt% and 0.8 wt% over a range of olivine Mg# values, while TiO<sub>2</sub> decreases rapidly with increasing Mg#, down to 0.01 wt% in the more refractory harzburgites and dunites.  The observed trend is interpreted to indicate a refertilization process.  Microstructures also indicate multiple episodes of reactive melt percolation under either static conditions or during the late stages of deformation.  Pyroxenes may enclose rounded olivine grains in crystallographic continuity with neighbouring grains, cross-cut the subgrain boundaries of olivine grains, or show an interstitial habit, either forming cuspate-shaped grains in olivine triple junctions or films along olivine-olivine grain boundaries.  Olivine shows a range of crystallographic preferred orientation (CPO) patterns, including the A-type, axial-[010], axial-[100], and B-type.  Pyroxenes have weaker but not random CPOs with [001] axes having similar orientation to olivine [100] axes in the majority of the xenoliths.  Calculated P and S waves anisotropy is variable (2–12%) and increases with olivine fraction but decreases with both increasing ortho- or clinopyroxene content.  P-wave anisotropy is correlated with the strength of olivine CPO expressed with the M-index and increases with increasing strength of the orthopyroxene CPO, but seems to be less correlated with the strength of the clinopyroxene CPO.</p>

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