Thermal state and redox conditions of the Kaapvaal mantle: A study of xenoliths from the Finsch mine, South Africa

Lazarov, Marina; Woodland, Alan B.; Brey, Gerhard P.

doi:10.1016/j.lithos.2009.03.035

Cited by 90 publications

(60 citation statements)

References 45 publications

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“…We applied the recent calibration of the olivine-orthopyroxene-garnet oxybarometer of (Stagno et al 2013) to the extant database of cratonic garnet peridotite mantle samples that have the necessary compositional information, including measurements of the Fe 3+ /ΣFe of their garnets (Canil and O'Neill 1996;Creighton et al 2009Creighton et al , 2010Goncharov et al 2012;Lazarov et al 2009;Luth et al 1990;McCammon and Kopylova 2004;Woodland and Koch 2003;Woodland and Peltonen 1999;Yaxley et al 2012). We restricted our analysis to samples that had Fe 3+ /ΣFe measured by Mössbauer spectroscopy, the EPMA flank method (Höfer and Brey 2007) (Luth et al 1990) previous calibration (Gudmundsson and Wood 1995), the new oxybarometer tends to produce more oxidized values, and the differences tend to be larger at higher pressures, as previously noted by the authors of the new oxybarometer (Stagno et al 2013) (Fig.…”

Section: Revised Oxybarometrymentioning

confidence: 99%

“…5 for two samples from the Finsch mine (Lazarov et al 2009) and one from Premier (PHN 5267; Boyd and Mertzman 1987;Canil and O'Neill 1996). The Premier sample had measured Fe 3+ /ΣFe for garnet and Fig.…”

Section: Sensitivity Of Peridotite Fo 2 To Oxygen Addition or Subtracmentioning

confidence: 99%

“…The results of this calculation are plotted in Fig. 6 against the modal amount of garnet for a more extensive set of samples, mostly from the Finsch dataset of (Lazarov et al 2009). The key point is that for all these samples, less than 200 ppm O 2 is required to shift their redox state (relative log fO 2 ) from IW to EMOD.…”

Section: Sensitivity Of Peridotite Fo 2 To Oxygen Addition or Subtracmentioning

confidence: 99%

“…4. Data sources: Finsch F-15 and 695(Lazarov et al 2009), Premier (PHN 5267)(Boyd and Mertzman 1987;Canil and O'Neill 1996). Pressure-temperature conditions of calculation same as inFig.…”

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confidence: 99%

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The buffering capacity of lithospheric mantle: implications for diamond formation

Luth

Stachel

2014

Contrib Mineral Petrol

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50 ppm or less O 2 is required to shift a depleted mantle peridotite the observed four log units of fO 2 . Coupled with the observed distribution of samples at values of fO 2 intermediate between the most reduced (metal-saturated) and most oxidized (carbonate-saturated) possible values for diamond stability, these results demonstrate that peridotites are very poor sinks or sources of O 2 for possible redox reactions to form diamond. A corollary of the poor redox buffering capacity of cratonic peridotites is that they can be employed as faithful indicators of the redox state of the last metasomatic fluid that passed through them. We propose that diamond formation from CHO fluids is a predictable consequence either of isobaric cooling or of combined cooling and decompression of the fluid as it migrates upward in the lithosphere. This establishes a petrological basis for the observed close connection between subcalcic garnet and diamond: based on high solidus temperatures of harzburgite and dunite effectively precluding dilution of CHO fluids through incipient melts, such highly depleted cratonic peridotites are the preferred locus of diamond formation. Due to a rapid increase in solidus temperature with increasing CH 4 content of the fluid, diamond formation related to reduced CHO fluids may also occur in some cratonic lherzolites.

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Section: Revised Oxybarometrymentioning

confidence: 99%

Section: Sensitivity Of Peridotite Fo 2 To Oxygen Addition or Subtracmentioning

confidence: 99%

Section: Sensitivity Of Peridotite Fo 2 To Oxygen Addition or Subtracmentioning

confidence: 99%

“…4. Data sources: Finsch F-15 and 695(Lazarov et al 2009), Premier (PHN 5267)(Boyd and Mertzman 1987;Canil and O'Neill 1996). Pressure-temperature conditions of calculation same as inFig.…”

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confidence: 99%

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The buffering capacity of lithospheric mantle: implications for diamond formation

Luth

Stachel

2014

Contrib Mineral Petrol

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“…Based on a heat flow of 40-41 mW/m 2 , which is considered appropriate for the Kaapvaal craton (e.g., Lazarov et al, 2009), the calculated temperatures correspond to pressure ranges of 3.3-3.7 (∼110-120 km; olivine-spinel equilibrium) or 3.0-3.2 GPa (∼100-105 km; orthopyroxene-clinopyroxene solvus) for sample XM1/341; 3.1-3.4 GPa for XM1/345; and 3.0-3.3 GPa for XM1/362. Therefore, it appears that the three xenoliths were sampled from similar depths.…”

Section: Thermobarometrymentioning

confidence: 99%

LIMA U–Pb ages link lithospheric mantle metasomatism to Karoo magmatism beneath the Kimberley region, South Africa

Giuliani

Phillips

Maas

et al. 2014

Earth and Planetary Science Letters

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Erosion patterns and mantle sources of topographic change across the southern African Plateau derived from the shallow and deep records of kimberlites

Stanley

Flowers

Bell

2015

Geochem Geophys Geosyst

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Flow in the sublithospheric mantle is increasingly invoked as a mechanism to explain both modern and past surface topography, but the importance of this phenomenon and its influence at different localities are debated. Southern Africa is an elevated continental shield proposed to represent dynamically supported topography. However, this region is also characterized by a complex lithospheric architecture variably affected by Cretaceous heating, thinning, and metasomatic alteration. We used apatite (U-Th)/He thermochronometry on 15 Cretaceous kimberlites from an 600 km long transect across the Kaapvaal Craton, combined with information from xenoliths in these pipes, to determine the plateau interior erosion history. The goal was to determine the relationships with lithospheric modification patterns and thereby better isolate the sublithospheric contribution to elevation. The results document a wave of erosion from west to east across the craton from 120 to <60 Ma, initially focused along paleorivers and then retreating as a scarp across the landscape. This spatially variable erosion event was associated with limited modification of the Archean cratonic lithospheric mantle as recorded by mantle xenoliths and xenocrysts, implying that dynamic buoyancy sources may be required to explain the elevations. In contrast, off-craton to the southwest, a more pronounced regional erosion phase at 110-90 Ma was coincident with significant modification of the Proterozoic lithospheric mantle. This relationship suggests that lithospheric processes were more important contributors to erosion and topographic change off-craton than on-craton. Together, these results suggest that lithospheric architecture can have an important control on the surface expression of mantle dynamics.

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Thermal state and redox conditions of the Kaapvaal mantle: A study of xenoliths from the Finsch mine, South Africa

Cited by 90 publications

References 45 publications

The buffering capacity of lithospheric mantle: implications for diamond formation

The buffering capacity of lithospheric mantle: implications for diamond formation

LIMA U–Pb ages link lithospheric mantle metasomatism to Karoo magmatism beneath the Kimberley region, South Africa

Erosion patterns and mantle sources of topographic change across the southern African Plateau derived from the shallow and deep records of kimberlites

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