Oxidation of Archean upper mantle caused by crustal recycling

Gao, Lei; Liu, Shuwen; Cawood, Peter A.; Hu, Fangyang; Wang, J.; Sun, Guangyi; Hu, Yalu

doi:10.1038/s41467-022-30886-4

Cited by 20 publications

(31 citation statements)

References 56 publications

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“…Projection of the thermometric estimates for diamond Oli-CHR1 on this geotherm (Fig. 3) yields formation conditions of P ∼ 5.7(0.4) GPa and T ∼ 1015(50) • C that are within the largely unperturbed depth interval (Liu et al, 2022). These results are fairly consistent with thermodynamic modelling in multicomponent, natural peridotitic systems (Ziberna et al, 2013), which predicts that in very depleted (highly refractory) harzburgite with bulk Cr# = 0.32 and along a 35 mW m −2 geotherm, spinel is stable up to 5.5 GPa and 1000 • C, where it reaches a Cr# spinel of ca.…”

Section: Thermobarometric Analysis Of the Inclusion Pair And Thermal ...mentioning

confidence: 92%

“…However, assuming negligible vertical movement of the diamond in the rigid cratonic lithosphere, an approximate estimate of the entrapment pressure can be obtained by projecting thermometric estimates for the inclusion pair onto the local xenolith geotherm (Korolev et al, 2018;Nimis et al, 2020). Studies of mantle xenoliths from the Udachnaya kimberlite (Ionov et al, 2010;Goncharov et al, 2012;Yaxley et al, 2012;Doucet et al, 2013;Miller et al, 2016;Liu et al, 2022) indicate a deep lithospheric root (∼ 230 km) but show a relatively large range of geothermal gradients, spanning between the 35 and 40 mW m −2 model conductive geotherms of Hasterok and Chapman (2011) (see Fig. 3).…”

Section: Thermobarometric Analysis Of the Inclusion Pair And Thermal ...mentioning

confidence: 99%

“…35 mW m −2 conductive geotherm. Liu et al (2022) showed that heating and deformation in the deep lithospheric portion were variable, not strictly concurrent, and likely controlled by local small-scale processes. Pokhilenko et al (1991Pokhilenko et al ( , 1993 proposed that megacrystalline peridotite xenoliths constituted the principal host rocks of Siberian diamonds and, by extension, that the formation and storage of diamonds occurred under cold conditions consistent with a 35 mW m −2 conductive geotherm.…”

Section: Thermobarometric Analysis Of the Inclusion Pair And Thermal ...mentioning

confidence: 99%

“…3), consistent with the establishment of a cold geothermal gradient over the whole Udachnaya lithosphere at the time of diamond formation. Considering the ages of diamonds at Udachnaya (3.5-3.1, ∼ 2 and ∼ 1.8 Ga; Richardson and Harris, 1997;Pearson et al, 1999a, b;Wiggers de Vries et al, 2013), these cold conditions persisted for billions of years in some portions of the Udachnaya lithosphere, particularly in the 140-190 km depth interval (Liu et al, 2022). Based on these lines of evidence, our diamond Oli-CHR1 also most likely formed and equilibrated under conditions close to a 35 mW m −2 geotherm.…”

Section: Thermobarometric Analysis Of the Inclusion Pair And Thermal ...mentioning

confidence: 99%

“…Thermo-/oxybarometric analysis of the inclusion pair determined the P -T -f O 2 conditions at the time of its entrapment in the host diamond, and from this result, the physical conditions under which the crystallization of Oli-CHR1 diamond occurred could be inferred, and additionally information about the redox state of this portion of the Siberian craton at the time of diamond formation could be provided. Our knowledge of the redox and thermal state of the mantle under Udachnaya largely relies on data obtained from mantle xenoliths in the kimberlite (Ionov et al, 2010;Goncharov et al, 2012;Yaxley et al, 2012;Doucet et al, 2013;Miller et al, 2016;Liu et al, 2022). These data are supposed to constrain the physicalchemical conditions of the cratonic mantle at the time of kimberlite eruption (360 ± 7 Ma; Kinny et al, 1997) but do not generally probe the redox state of the Siberian craton at an early stage of its geological history.…”

Section: Introductionmentioning

confidence: 99%

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Relatively oxidized conditions for diamond formation at Udachnaya (Siberia)

et al. 2022

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Abstract. Thanks to the physical strength of diamonds and their relatively unreactive chemical nature, their mineral inclusions may remain exceptionally preserved from alteration processes and chemical exchanges with surrounding minerals, fluids and/or melts following diamond formation. Cr-bearing spinels are relatively common inclusions found in peridotitic diamonds and important oxybarometers providing information about the oxygen fugacity (fO2) of their source mantle rocks. Here, we investigated a magnesiochromite–olivine touching pair in a diamond from the Udachnaya kimberlite (Siberia) by in situ single-crystal X-ray diffraction and energy-domain synchrotron Mössbauer spectroscopy, aiming to constrain the physical–chemical conditions of diamond formation and to explore the redox state of this portion of the Siberian craton when the diamond was formed. The P–T–fO2 entrapment conditions of the inclusion pair, determined by thermo- and oxybarometric analyses, are ∼ 5.7(0.4) GPa and ∼ 1015(50) ∘C (although entrapment at higher T and re-equilibration during subsequent mantle storage are also possible) and fO2 near the enstatite–magnesite–olivine–diamond (EMOD) buffer. The determined fO2 is similar to, or slightly more oxidized than, those of xenoliths from Udachnaya, but whilst the xenoliths last equilibrated with the surrounding mantle just prior to their entrainment in the kimberlite at ∼ 360 Ma, the last equilibration of the inclusion pair is much older, occurring at 3.5–3.1, ∼ 2 or ∼ 1.8 Ga before final encapsulation in its host diamond. Hence, the similarity between xenoliths and inclusion fO2 values indicates that the modern redox state of this portion of the Siberian lithosphere was likely attained relatively early after its formation and may have persisted for billions of years after diamond formation, at least at the local scale. Moreover, the oxygen fugacity determination for the inclusion pair provides direct evidence of diamond formation near the EMOD buffer and is consistent with recent models suggesting relatively oxidized, water-rich CHO fluids as the most likely parents for lithospheric diamonds.

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Section: Thermobarometric Analysis Of the Inclusion Pair And Thermal ...mentioning

confidence: 92%