R7: Petrology, Mineralogy and Economic geology (Joint session with SRG)

[R7P-03] Chemical compositions of secondary olivine in mantle peridotites from the Hess Deep Rift

*Daisuke Gokan¹, Toshio Nozaka¹ (1. Okayama Univ.)

Keywords:Hess Deep Rift, mantle peridotite, alteration, secondary olivine, trace elements

We found secondary olivine in mantle peridotites from ODP Site 895, the Hess Deep Rift. The secondary olivine occurs as veins a few mm to hundreds mm wide, cutting primary olivine and coexisting with tremolite. Optimized microprobe analyses revealed that the secondary olivine has lower Fo, Ni, Ca and Al contents and higher Mn and Co contents than the primary olivine. These peculiar compositions may be the characteristics of olivine formed by amphibolite-facies alteration.