Temperature and oxygen state of kimberlite magma from the North China Craton and their implication for diamond survival

Zhu, Ren-Zhi; Ni, Pei; Wang, Guoguang; Ding, Jun‐Ying; Kang, Ning

doi:10.1007/s00126-021-01057-0

Cited by 10 publications

(4 citation statements)

References 72 publications

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“…This assumption has been shown to be valid theoretically (Marini et al., 2011) and experimentally for silicate melts (Fiege et al., 2015) as well as in natural komatiite systems (Caruso et al., 2017) if S degassing occurs under strongly oxidising conditions (i.e., log ( f O 2 ) ≥ QFM+2). However, the oxidation state of kimberlite magmas during ascent and related fluid exsolution, that is, before late‐stage oxidation (see Section 6.1), might be relatively reduced (log ( f O 2 ) ∼ QFM‐3 to QFM+2 based on olivine‐spinel equilibrium: Fedortchouk & Canil, 2004; Zhu et al., 2021). This suggests that sulfur would likely be lost as H 2 S rather than SO 2 in exsolved fluids, a process which decreases δ 34 S in the residual melt (Marini et al., 2011).…”

Section: Discussionmentioning

confidence: 99%

Sulfur Isotope Constraints on the Petrogenesis of the Kimberley Kimberlites

Giuliani

Magalhães

Soltys

et al. 2021

Geochem Geophys Geosyst

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hence providing insights into the composition of the upper convective mantle beneath continents. This definition does not consider Group II kimberlites or orangeites, which have been recently recognised to be carbonate-rich olivine lamproites (Mitchell, 2020;Pearson et al., 2019) and are sourced in metasomatized portions of the sub-continental lithospheric mantle (Becker & le Roex, 2006;Pearson et al., 2019). Recently, the sources of kimberlite melts have come under increased scrutiny. Woodhead et al. (2019) showed that, at least until around 200 Ma, kimberlites appear to have formed from a relatively homogeneous source with Nd-Hf isotope compositions close to the chondritic uniform reservoir (CHUR) model of Earth's primitive mantle. Giuliani et al. (2021) further argued that this source is equivalent to the PREvalent MAntle (PRE-MA) component that is widely observed in ocean island and continental basalts. However, kimberlites emplaced since 200 Ma in several large kimberlite provinces (Brazil, western Canada, southern Africa) display initial 143 Nd/ 144 Nd and 176 Hf/ 177 Hf ratios that reach significantly lower (i.e., sub-chondritic) values compared to those that have been observed to date in older kimberlites. As discussed by Woodhead et al. ( 2019), the steep Nd or Hf isotope versus time trend shown by Mesozoic (∼180-70 Ma) kimberlites in southern

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Section: Discussionmentioning

confidence: 99%

Sulfur Isotope Constraints on the Petrogenesis of the Kimberley Kimberlites

Giuliani

Magalhães

Soltys

et al. 2021

Geochem Geophys Geosyst

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“…In this regard, it is noteworthy that kimberlites with very high-Mg# olivine from Lac de Gras, Canada (core mean Mg# = 89.4-92.1; n = 26) and Siberia (89.8-91.8; n = 6) plus lamproites from the West Kaapvaal craton, South Africa, generally show substantially higher proportions of (unresorbed) octahedral diamonds compared to Cretaceous southern African kimberlites with lower Mg# (85.3-91.3; n = 12) in olivine 18,41 . However, in kimberlites from Wafangdian and Mengyn (China), lower diamond grades correlate with higher relative abundances of octahedral diamonds 44 . A more detailed assessment of the potential relationship between diamond rounding, diamond resorption features, and olivine composition would be required to better understand the full effect of kimberlite-related metasomatism on the quality and therefore value of diamonds, which is another fundamental factor controlling the economics of diamondbearing kimberlite.…”

Section: Diamond Resorption By Kimberlite Melts In the Lithospheric M...mentioning

confidence: 97%

Diamond preservation in the lithospheric mantle recorded by olivine in kimberlites

Giuliani,

Phillips,

Pearson

et al. 2024

International Kimberlite Conference Extended Abstracts: 2024

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“…From south to north, the Mengyin kimberlites are separated into the Changma, Xiyu and Poli belts (Yin et al, 2005;Yang et al, 2009). According to Zhu et al (2022), nearly all kimberlites found in Mengyin areas have porphyritic textures with olivine as macrocrysts that have been serpentinized or replaced by carbonates (Fig. 1).…”

Section: Geological Backgrounds and Samplesmentioning

confidence: 99%

In situ single-crystal X-ray diffraction of olivine inclusion in diamond from Shandong, China: implications for the depth of diamond formation

Wang

Nestola

et al. 2023

Eur. J. Mineral.

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Abstract. We have investigated a suite of natural diamonds from the kimberlite pipe of the Changma Kimberlite Belt, Mengyin County, Shandong Province, China, with the aim of constraining pressures and temperatures of formation. Here we report the non-destructive investigation of an olivine inclusion still entrapped within a lithospheric diamond by single-crystal X-ray diffraction. We were able to refine anisotropically its crystal structure to R1= 1.42 % using ionized scattering curves; this allows estimation of the composition of the olivine as Mg1.82Fe0.18SiO4. This composition corresponds to a calculated unit-cell volume equal to V= 292.70 Å3 at room temperature and pressure. We have validated the above-calculated composition and unit-cell volume by releasing the inclusion from the diamond host, resulting in a consistent composition calculated using non-destructive methods of Mg1.84Fe0.16SiO4 and V= 292.80 ± 0.07 Å3. Considering that the unit-cell volume of the olivine still inside its diamond host is V= 289.7 ± 0.2 Å3, we calculated a residual pressure Pinc= 1.4 ± 0.1 GPa with respect to the released crystal and Pinc= 1.3 ± 0.2 GPa with respect to the volume calculated from the “composition” indirectly retrieved by the structure refinement under ambient conditions. The two values of Pinc overlap within experimental uncertainty. We performed Fourier transform infrared (FTIR) analysis on the diamond host in order to calculate its mantle residence temperature, Tres, which resulted in a value of 1189 ∘C (for an assumed diamond age of 3 Ga) and 1218 ∘C (for an age of 1 Ga), with an average Tres equal to 1204 ± 15 ∘C. Using the most up-to-date pressure–volume–temperature equations of state for olivine and diamond, the residual pressure Pinc= 1.4 ± 0.1 GPa and average residence temperature of the diamond host Tres= 1204 ∘C, we retrieved a pressure of entrapment Ptrap= 6.3 ± 0.4 GPa. Using the non-destructive approach and relative Pinc = 1.3 GPa, we obtained a perfectly overlapping Ptrap= 6.2 GPa, within experimental uncertainty. This entrapment pressure corresponds to depths of about 190 ± 12 km. These results demonstrate that for high-quality crystal structure data measured on inclusions still trapped within diamond hosts, even a non-destructive approach can be used to calculate the depth of formation of diamond–olivine pairs. In terms of geological implications, the results from this work show that Changma diamonds formed under a conductive geotherm lying between 35 and 40 mW m−2, at a depth of about 190 km. This value lies within the recently reported upper limit of the average depth of formation of worldwide lithospheric diamonds, which is 175 ± 15 km and is in agreement with P–T data obtained in the literature from kimberlite xenoliths.

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Temperature and oxygen state of kimberlite magma from the North China Craton and their implication for diamond survival

Cited by 10 publications

References 72 publications

Sulfur Isotope Constraints on the Petrogenesis of the Kimberley Kimberlites

Sulfur Isotope Constraints on the Petrogenesis of the Kimberley Kimberlites

Diamond preservation in the lithospheric mantle recorded by olivine in kimberlites

In situ single-crystal X-ray diffraction of olivine inclusion in diamond from Shandong, China: implications for the depth of diamond formation

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