Abstract

Similar to the other areas of the Late Cenozoic volcanic province of Central Asia, the Udokan volcanic plateau (UVP) was formed in the time span between the Middle Miocene and the Pleistocene. Its rocks are highly alkaline and vary from alkaline picrobasalts and basanites to alkaline trachytes. The compositional variations of the rocks were controlled by two differentiation trends, which corresponded to different generation conditions of the parental magmas. The rocks with low SiO₂ contents (<45 wt %) were formed by melts of low degrees of melting, whose melts were derived under elevated pressures and temperatures. The formation of the rocks with 45–61 wt % SiO₂ was associated with the differentiation of basalt melts, which were derived at shallower depths and at lower temperatures. The geochemical characteristics of the UVP basaltoids make them similar to OIB-type basalts. They are also close in Sr, Nd, and Pb isotopic composition, corresponding to the parameters of the moderately depleted mantle, which is close to the composition of oceanic basalt sources corresponding to the mantle of deep mantle plumes. The corresponding mantle component is present in the sources of other volcanic regions of the Late Cenozoic intraplate volcanic province in Central Asia, which indicates that the material of a lower mantle plume was involved in the formation of these regions.

中文翻译：

---

中亚晚新生代乌多坎火山高原的结晶参数、熔体成因和岩浆来源

摘要

与中亚晚新生代火山省的其他地区类似，乌多坎火山高原（UVP）形成于中中新世和更新世之间的时间跨度。它的岩石呈强碱性，从碱性五氯玄武岩和玄武岩到碱性粗面岩不等。岩石的成分变化受两种分异趋势的控制，这两种分异趋势对应于母岩浆的不同生成条件。_{SiO 2}含量低（<45 wt%）的岩石是由低熔化度的熔体形成的，其熔体是在升高的压力和温度下产生的。_{含 45-61 wt% SiO 2}的岩石的形成与玄武岩熔体的分化有关，玄武岩熔体是在较浅的深度和较低的温度下产生的。UVP类玄武岩的地球化学特征使其与OIB类玄武岩相似。它们的Sr、Nd和Pb同位素组成也很接近，对应于中度亏损地幔的参数，这接近于深部地幔柱地幔对应的大洋玄武岩来源的组成。相应的地幔成分存在于中亚晚新生代板内火山区其他火山区的物源中，表明这些区域的形成涉及下地幔柱物质。