Composition of Secondary Melt Inclusions in Magnesiochromite of a Mantle Lherzolite Xenolith from the V. Grib Kimberlite Pipe (East European Craton) as an Indicator of Low H2O Content of the Kimberlite Melt

IF 0.7 4区地球科学 Q4 GEOSCIENCES, MULTIDISCIPLINARY Doklady Earth Sciences Pub Date : 2024-06-20 DOI:10.1134/s1028334x24602505

A. A. Tarasov, A. V. Golovin, E. V. Agasheva, N. P. Pokhilenko

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Abstract

This paper describes secondary crystallized melt inclusions trapped in magnesiochromite of lherzolite xenolith from the V. Grib kimberlite pipe (Arkhangelsk diamondiferous province). It is shown that the inclusions are microportions of melt related to magmatism, which was further formed this pipe. Daughter minerals assemblage of inclusions in magnesiochromite contain Na‒K‒Ca-, Na‒Mg-, Ca‒Mg-, Mg-, and Ca-bearing carbonates; Na–Mg carbonates with additional PO\(_{4}^{{3 - }}\), Cl^–, and SO\(_{4}^{{2 - }}\) anions; chlorides; sulfate; phosphate; and silicate. The mineral assemblage of daughter phases, the amount of carbonates (77 vol %) and silicates (tetraferriphlogopite) (15 vol %) and Ca : Na : K ratios within the inclusions indicate that this melt was an alkali-enriched carbonate liquid with a low content of SiO₂ (≤6 wt %) and H₂O (≤0.6 wt %). As is known, serpentine in kimberlites is a major H₂O-bearing mineral, but the problem of water sources during serpentinization of kimberlites and an actual H₂O content in kimberlite melts is a controversial issue. The absence of serpentine and the low H₂O content (≤0.6 wt %) of the studied melt inclusions in comparison with those of kimberlites of the V. Grib kimberlite pipe (10‒14 wt %) indicate the key role of external fluids during serpentinization of these kimberlites.

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来自 V. Grib 金伯利岩管（东欧克拉通）的地幔蛭石异长岩中镁铬酸盐二次熔融包裹体的成分作为金伯利岩熔体低 H2O 含量的指标

摘要本文描述了捕获于 V. Grib 金伯利岩管（阿尔汉格尔斯克金刚石矿区）菱锰矿异质岩中的二次结晶熔体包裹体。研究表明，这些包裹体是与岩浆活动有关的熔融物的微小部分，这些熔融物进一步形成了这一管道。镁铬铁矿包裹体中的子矿物集合体包含Na-K-Ca-、Na-Mg-、Ca-Mg-、Mg-和含Ca的碳酸盐；Na-Mg碳酸盐与额外的PO\(_{4}^{3 - }}\), Cl-和SO\(_{4}^{2 - }}\) 阴离子；氯化物；硫酸盐；磷酸盐和硅酸盐。子相的矿物组合、碳酸盐（77 wt %）和硅酸盐（四铁闪长岩）（15 wt %）的含量以及包裹体中 Ca : Na : K 的比率表明，这种熔体是一种富含碱的碳酸盐液体，其中 SiO2（≤6 wt %）和 H2O（≤0.6 wt %）的含量较低。众所周知，金伯利岩中的蛇纹石是一种主要的含 H2O 矿物，但金伯利岩蛇纹石化过程中的水源问题以及金伯利岩熔体中 H2O 的实际含量是一个有争议的问题。与 V. Grib 金伯利岩管的金伯利岩（10-14 wt %）相比，所研究的熔体包裹体中没有蛇纹石，且 H2O 含量较低（≤0.6 wt %），这表明外部流体在这些金伯利岩的蛇纹石化过程中起着关键作用。

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来源期刊

Doklady Earth Sciences 地学-地球科学综合

CiteScore

1.40

自引率

22.20%

发文量

138

审稿时长

3-6 weeks

期刊介绍： Doklady Earth Sciences is a journal that publishes new research in Earth science of great significance. Initially the journal was a forum of the Russian Academy of Science and published only best contributions from Russia. Now the journal welcomes submissions from any country in the English or Russian language. Every manuscript must be recommended by Russian or foreign members of the Russian Academy of Sciences.