TY - JOUR

T1 - Diamond-rich placer deposits from iron-saturated mantle beneath the northeastern margin of the Siberian Craton

AU - Shatsky, Vladislav S.

AU - Ragozin, Alexey L.

AU - Logvinova, Alla M.

AU - Wirth, Richard

AU - Kalinina, Viktoria V.

AU - Sobolev, Nikolay V.

PY - 2020/7

Y1 - 2020/7

N2 - We demonstrate for the first time the presence of iron carbides in placer diamonds from the northeastern region of the Siberian craton. It was found that the inclusions are polycrystalline aggregates, and iron carbides filling the fissures in the diamonds, thus providing clear evidence that the iron melts were captured first. Iron carbides were identified in diamonds containing mineral inclusions of eclogitic (Kfs, sulfide) and peridotitc (olivine) paragenesis. Iron carbides with minor amounts of admixed nickel were detected in a diamond sample containing an olivine inclusion (0.3 wt% Ni), indicating that the iron melt was not in equilibrium with the mantle peridotite.The low nickel contents of the iron carbides provide the best evidence that the subducted crust is a likely source of the iron melt. Diamonds containing carbide inclusions are characterised by a relatively low nitrogen aggregation state (5–35%), which is not consistent with the high temperature of the transition zone. Therefore, we have reason to assume that the studied diamonds are from the lower regions of the lithosphere. Considering all factors, the model for the interaction of the ascending asthenospheric mantle with the subducting slab seems to be more realistic.

AB - We demonstrate for the first time the presence of iron carbides in placer diamonds from the northeastern region of the Siberian craton. It was found that the inclusions are polycrystalline aggregates, and iron carbides filling the fissures in the diamonds, thus providing clear evidence that the iron melts were captured first. Iron carbides were identified in diamonds containing mineral inclusions of eclogitic (Kfs, sulfide) and peridotitc (olivine) paragenesis. Iron carbides with minor amounts of admixed nickel were detected in a diamond sample containing an olivine inclusion (0.3 wt% Ni), indicating that the iron melt was not in equilibrium with the mantle peridotite.The low nickel contents of the iron carbides provide the best evidence that the subducted crust is a likely source of the iron melt. Diamonds containing carbide inclusions are characterised by a relatively low nitrogen aggregation state (5–35%), which is not consistent with the high temperature of the transition zone. Therefore, we have reason to assume that the studied diamonds are from the lower regions of the lithosphere. Considering all factors, the model for the interaction of the ascending asthenospheric mantle with the subducting slab seems to be more realistic.

KW - Diamond

KW - Iron carbide inclusions

KW - Mantle

KW - Siberian craton

KW - Subducted crust

KW - MATO-GROSSO

KW - JUINA AREA

KW - HIGH-PRESSURE

KW - OXYGEN FUGACITY

KW - CARBON

KW - ION-BEAM FIB

KW - EARTHS MANTLE

KW - PHASE-COMPOSITION

KW - NITROGEN

KW - FE-C SYSTEM

UR - http://www.scopus.com/inward/record.url?scp=85082923447&partnerID=8YFLogxK

U2 - 10.1016/j.lithos.2020.105514

DO - 10.1016/j.lithos.2020.105514

M3 - Article

AN - SCOPUS:85082923447

VL - 364-365

JO - Lithos

JF - Lithos

SN - 0024-4937

M1 - 105514

ER -