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Globally elevated titanium, tantalum, and niobium (TITAN) in ocean island basalts with high 3 He/ 4 He

2008; Wiley; Volume: 9; Issue: 4 Linguagem: Inglês

10.1029/2007gc001876

1525-2027

Matthew G. Jackson, Stanley R. Hart, A. E. Saal, Nobumichi Shimizu, Mark D. Kurz, J. Blusztajn, A. C. Skovgaard,

High-pressure geophysics and materials

We report evidence for a global Ti, Ta, and Nb (TITAN) enriched reservoir sampled by ocean island basalts (OIBs) with high 3 He/ 4 He ratios, an isotopic signature associated with the deep mantle. Excesses of Ti (and to a lesser degree Nb and Ta) correlate remarkably well with 3 He/ 4 He in a data set of global OIBs, demonstrating that a major element signature is associated with the high 3 He/ 4 He mantle. Additionally, we find that OIBs with high 3 He/ 4 He ratios have moderately radiogenic 187 Os/ 188 Os (>0.135). The TITAN enrichment and radiogenic 187 Os/ 188 Os in high 3 He/ 4 He OIBs indicate that they are melts of a mantle domain that hosts a nonprimitive (nonchondritic) component. The observation of TITAN enrichment in the high 3 He/ 4 He mantle may be important in balancing the Earth's budget for the TITAN elements. Understanding the origin of the TITAN enrichment is important for constraining the evolution of the enigmatic high 3 He/ 4 He mantle domain.