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

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 of both eclogitic and peridotitic paragenesis, which is demonstrated by olivine, sulfide, and Kfs inclusions. 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本研究首次证实，西伯利亚克拉通东北部砂矿金刚石中存在碳化铁（iron carbides）。研究发现，该类包裹体为多晶集合体，且碳化铁充填于金刚石内部裂隙中，由此直接佐证铁熔体首先被捕获。通过橄榄石、硫化物及钾长石（Kfs）包裹体的分析，证实榴辉岩相和橄榄岩相共生类型的金刚石中均存在碳化铁。在一颗含有橄榄石包裹体的金刚石样品中（镍含量为0.3 wt.%），检测到掺杂少量镍的碳化铁，表明该铁熔体与地幔橄榄岩未达到平衡状态。碳化铁的低镍含量，为俯冲地壳作为铁熔体的潜在来源提供了最有力的证据。含碳化铁包裹体的金刚石，其氮聚集状态相对较低（5%~35%），这与过渡带的高温环境并不相符。因此，我们有充分理由推断，本次研究的金刚石来源于岩石圈下部区域。综合各项分析因素，上升软流圈地幔与俯冲板片相互作用的模型更为合理。