Thermobarometry and geochemistry of the mantle section beneath Morkoka pipe Central Yakutia Russia

The Morkoka pipe belonging to the territory of West Daldyn terrane but It has all the features which are characteristic to the Malo- Botuobinsky or Upper MunaThe lower part of mantle section is represented by the depleted lower part of mantle section with the high amount of sub  Ca garnets with the high amount like in Mir pipe and rather long lineal ilmenite trend from the LAB at 7.5 GPA to the Moho at 2 GPA which is also the common feature of most pipe from the Magan terrane an happens in the Upper Muna field  Though the Morkoka pipe itself is barren the nearest territories around contain similar indicator minerals which shot ha there is a group pf pipes and some of them may be diamondiferous. The TRE patterns show mainly S- type which is perspective for the prospecting of diamonds.  But the HFSE for the garnets reveal rather high Zr>Hf peaks which became higher with the HREE level, (Ta>Nb) and higher than La. The LILE and Ba are typically low  but Th U sometimes higher than Nb. The ilmenites reveal slightly concave patterns with the minima near Gd  or  reveal  opposite inclination  similar to garnets but with the elevated LREE part.  The HFSE are rather high an Ta-Nb are higher that Zr Hf Some samples with the high LREE also reveal elevated Th and U, indicating influence of the essentially carbonatitic melts.

It seems that the mantle beneath the Morkoka pipe wre originally depleted but regenerated but the H2O bearing melts possibly rather oxidized and this may be the reason of the rather low diamond grade.  The ilmenites were generated by the essentially carbonatitic protokimberlite melts which passed through the matrix where garnets prevail  Reaction of the maters with the different REE inclination produced concave REE  patterns

Grant RBRF 19- 05-00788