Evidence for a mantle component shown by rare gases, C and N isotopes in polycrystalline diamonds from Orapa (Botswana) [rapid communication]

Details Evidence for a mantle component shown by rare gases, C and N isotopes in polycrystalline diamonds from Orapa (Botswana) [rapid communication] Evidence for a mantle component shown by rare gases, C and N isotopes in polycrystalline diamonds from Orapa (Botswana) [rapid communication]

Dec 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005e%26psl.240..559g&link_type=abstract

Earth and Planetary Science Letters, Volume 240, Issue 3-4, p. 559-572.

Computer Science

8

Scientific paper

In an attempt to constrain the origin of polycrystalline diamond, combined analyses of rare gases and carbon and nitrogen isotopes were performed on six such diamonds from Orapa (Botswana). Helium shows radiogenic isotopic ratios of R/Ra = 0.14 1.29, while the neon ratios (21Ne/22Ne of up to 0.0534) reflect a component from mantle, nucleogenic and atmospheric sources. 40Ar/36Ar ratios of between 477 and 6056 are consistent with this interpretation. The (129Xe/130Xe) isotopic ratios range between 6.54 and 6.91 and the lower values indicate an atmospheric component. The He, Ne, Ar and Xe isotopic compositions and the Xe isotopic pattern are clear evidence for a mantle component rather than a crustal one in the source of the polycrystalline diamonds from Orapa. The δ13C and δ15N isotopic values of - 1.04 to - 9.79‰ and + 4.5 to + 15.5‰ respectively, lie within the range of values obtained from the monocrystalline diamonds at that mine. Additionally, this work reveals that polycrystalline diamonds may not be the most appropriate samples to study if the aim is to consider the compositional evolution of rare gases through time. Our data shows that after crystallization, the polycrystalline diamonds undergo both gas loss (that is more significant for the lighter rare gases such as He and Ne) and secondary processes (such as radiogenic, nucleogenic and fissiogenic, as well as atmospheric contamination). Finally, if polycrystalline diamonds sampled an old mantle (1 3.2 Ga), the determined Xe isotopic signatures, which are similar to present MORB mantle no fissiogenic Xe from fission of 238U being detectable imply either that Xe isotopic ratios have not evolved within the convective mantle since diamond crystallization, or that these diamonds are actually much younger.

Affiliated with

Also associated with

No associations

Rating

Evidence for a mantle component shown by rare gases, C and N isotopes in polycrystalline diamonds from Orapa (Botswana) [rapid communication] does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Evidence for a mantle component shown by rare gases, C and N isotopes in polycrystalline diamonds from Orapa (Botswana) [rapid communication], we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Evidence for a mantle component shown by rare gases, C and N isotopes in polycrystalline diamonds from Orapa (Botswana) [rapid communication] will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1430253