A Cr isotopic study of the Bon Accord NiO body in the Barberton greenstone belt, South Africa

作者：Tredoux Marian^*; Roelofse Frederick; Shukolyukov Alexander

来源：Chemical Geology, 2014, 390: 182-190.

DOI：10.1016/j.chemgeo.2014.10.017

• Cr isotopes
• Archaean
• Barberton greenstone belt
• Ni-rich rock
• Core formation
• Deep mantle

An unusual oxide body, enriched in Ni and the platinum-group elements, was found in the north-western part of the Barberton greenstone belt, South Africa, in the 1920s. With mineralogy and geochemistry which are extremely anomalous, and do not conform to that of any other Ni-rich crustal rocks, it has been interpreted as either an Archaean paleo-meteorite or of terrestrial deep-mantle origin. Cr isotopic ratios were used to evaluate the merits of these two possibilities. Isotopic analyses returned values for epsilon(53) of 0.00 epsilon units, within a 2 s error, relative to a terrestrial standard. We interpret this information, together with trace element data from the surrounding peridotites, as pointing to a terrestrial origin for the body, and conclude that the current dataset is not inconsistent with a deep-mantle origin, as a remnant of core formation, with subsequent transport to and emplacement in the lithosphere by a mantle plume.

• 出版日期2014-12-18