Sr, Nd and Pb isotope and minor element geochemistry of lamproites and kimberlites

Details Sr, Nd and Pb isotope and minor element geochemistry of lamproites and kimberlites Sr, Nd and Pb isotope and minor element geochemistry of lamproites and kimberlites

Dec 1985

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1985e%26psl..76...57f&link_type=abstract

Earth and Planetary Science Letters, Volume 76, Issue 1-2, p. 57-70.

Computer Science

79

Scientific paper

All samples studied here exhibit low ɛNd (lamproites; Western Australia = -10 to -19.2 and Smoky Butte = -21.6 to -25.9: Group II kimberlites: Finsch Mine = -5.8 to -7.4) and (87Sr/86Sr)i > Bulk Earth. They are all LREE enriched (up to 1000 × chondrite) and have high trace element contents (i.e. Rb, Rb, Ba, Th, K, Ta, Sr, P, Hf, Zr and Ti). Smoky Butte and Finsch rocks plot below the Pb-ore growth curve (206Pb/204Pb) = 16.02-16.64 and 17.74-17.99, and 207Pb/204Pb = 15.19-15.28 and 15.48-15.57, respectively) consistent with two-stage evolutions whereas the Western Australia rocks exhibit high 207Pb/204Pb (15.71-15.75) with unradiogenic 206Pb/204Pb (17.23-17.57) indicative of a more complex three-stage evolution. These lamproites and Group II kimberlites were at least predominantly derived from source regions which had had low Sm/Nd, but variable U/Pb and Rb/Sr for between 1 and 2.5 Ga. Such source regions are inferred to exist within the subcontinental mantle lithosphere.
Different styles of trace element enrichment are recognised which with time develop different isotope-isotope trends. High Rb/Sr, Rb/Ba and K/Ti ratios observed in Group II kimberlites and metasomatised peridotites are probably related to the migration of H2O-rich fluids within the upper mantle, while the lamproites have features consistent with the introduction of small volume silicate melts to their source regions, i.e. high Ti/K, Ta/Yb and low Rb/Ba. At Smoky Butte Rb/Sr was also low, but the Western Australia rocks have high Rb/Sr because they are relatively less enriched in Sr. Hence high Rb/Sr ratios (and with time high 87Sr/86Sr) are developed in mantle source with both high and low Rb/Ba.
Inferred μ for the last stage of evolution of their source regions is < 7.5 for all the rocks studied and there is a striking positive correlation between ɛNd and 206Rb/204Pb, which indicates that low Sm/Nd and U/Pb ratios coexist (over long periods of time) within the subcontinental mantle lithosphere.

Affiliated with

Also associated with

No associations

Rating

Sr, Nd and Pb isotope and minor element geochemistry of lamproites and kimberlites 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 Sr, Nd and Pb isotope and minor element geochemistry of lamproites and kimberlites, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Sr, Nd and Pb isotope and minor element geochemistry of lamproites and kimberlites will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1161314