Ultramafic lamprophyres (UMLs) are mantle rocks that provide important information about the composition of specific carbonate–silicate alkaline melts in the mantle as well as the processes contributing to their origin. Minerals of the spinel group typically occur in UMLs and have a unique “genetic memory.” Investigations of the spinel minerals from the UMLs of the Chadobets complex show the physicochemical and thermodynamic features of the alkaline rocks’ crystallization. The spinels of these UMLs have four stages of crystallization. The first spinel xenocrysts were found only in damtjernite pipes, formed from mantle peridotite, and were captured during the rising of the primary melt to the surface. The next stages of the spinel composition evolution are related to the high-chromium spinel crystallization, which changed to a high-alumina composition. The composition then changed to magnesian ulvöspinel–magnetites with strong decreases in the Al and Cr amounts caused by the release of carbon dioxide, rapid temperature changes, and crystallization of the main primary groundmass minerals such as phlogopite and carbonates. Melt inclusion analyses showed the predominance of aluminosilicate (phlogopite, clinopyroxene, and/or albite) and carbonate (calcite and dolomite) daughter phases in the inclusions that are consistent with the chemical evolution of the Cr-spinel trend. The further evolution of the spinels from magnesian ulvöspinel–magnetite to Ti-magnetite is accompanied by the formation of atoll structures caused by resorption of the spinel minerals.

中文翻译：

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Chadobets情结（俄罗斯西伯利亚克拉通）的超镁铁质煌斑岩的尖晶石组成变化

超镁铁煌斑岩（UMLs）是地幔岩石，可提供有关地幔中特定碳酸盐-硅酸盐碱性熔体的组成及其成因的重要信息。尖晶石族的矿物质通常存在于UML中，并具有独特的“遗传记忆”。对Chadobets复合物的UML中的尖晶石矿物的研究表明，碱性岩石的结晶具有物理化学和热力学特征。这些UML的尖晶石具有四个结晶阶段。最初的尖晶石异晶体仅在由地幔橄榄岩形成的damtjernite管道中发现，并在初级熔体上升至表面时被捕获。尖晶石成分演变的下一阶段与高铬尖晶石结晶有关，变成了高氧化铝成分。然后，该成分变为镁质ulvöspinel-磁铁矿，其中的铝和铬含量显着下降，这是由于二氧化碳的释放，快速的温度变化以及主要的主要地基矿物（如金云母和碳酸盐）的结晶引起的。熔体夹杂物分析显示，夹杂物中铝硅酸盐（金云母，斜向辉石和/或钠长石）和碳酸盐（方解石和白云石）子相占优势，这与Cr-尖晶石趋势的化学演化相一致。尖晶石从镁的ulvöspinel-磁铁矿到Ti-磁铁矿的进一步发展伴随着由尖晶石矿物的吸收引起的环礁结构的形成。然后，该成分变为镁质ulvöspinel-磁铁矿，其中的铝和铬含量显着下降，这是由于二氧化碳的释放，快速的温度变化以及主要的主要地基矿物（如金云母和碳酸盐）的结晶引起的。熔体夹杂物分析显示，夹杂物中铝硅酸盐（金云母，斜向辉石和/或钠长石）和碳酸盐（方解石和白云石）子相占优势，这与Cr-尖晶石趋势的化学演化相一致。尖晶石从镁的ulvöspinel-磁铁矿到Ti-磁铁矿的进一步发展伴随着由尖晶石矿物的吸收引起的环礁结构的形成。然后，该成分变为镁质ulvöspinel-磁铁矿，其中的铝和铬含量显着下降，这是由于二氧化碳的释放，快速的温度变化以及主要的主要地基矿物（如金云母和碳酸盐）的结晶引起的。熔体夹杂物分析显示，夹杂物中铝硅酸盐（金云母，斜向辉石和/或钠长石）和碳酸盐（方解石和白云石）子相占优势，这与Cr-尖晶石趋势的化学演化相一致。尖晶石从镁的ulvöspinel-磁铁矿到Ti-磁铁矿的进一步发展伴随着由尖晶石矿物的吸收引起的环礁结构的形成。以及主要的主要地基矿物如金云母和碳酸盐的结晶。熔体夹杂物分析显示，夹杂物中铝硅酸盐（金云母，斜向辉石和/或钠长石）和碳酸盐（方解石和白云石）子相占优势，这与Cr-尖晶石趋势的化学演化相一致。尖晶石从镁的ulvöspinel-磁铁矿到Ti-磁铁矿的进一步发展伴随着由尖晶石矿物的吸收引起的环礁结构的形成。以及主要的主要地基矿物如金云母和碳酸盐的结晶。熔体夹杂物分析显示，夹杂物中铝硅酸盐（金云母，斜向辉石和/或钠长石）和碳酸盐（方解石和白云石）子相占优势，这与Cr-尖晶石趋势的化学演化相一致。尖晶石从镁的ulvöspinel-磁铁矿到Ti-磁铁矿的进一步发展伴随着由尖晶石矿物的吸收引起的环礁结构的形成。