俄罗斯贝加尔裂谷带中呼兰霍博克火山岩岩石学及地球化学研究

Petrology and geochemistry of Hulanhoboke volcano in Baikal rift,Russia.

位于贝加尔裂谷带通京盆地中的呼兰霍博克火山火山锥由火山弹、火山灰等火山碎屑岩和基性熔岩（橄榄玄武岩）组成。橄榄玄武岩中橄榄石可分为具有较高Mg^#值的捕虏晶和Mg^#值相对较低的斑晶。部分斜长石斑晶具有核-幔一边结构，且幔部发生减压分解，一些单斜辉石晶体（俘虏晶）边部发生了减压分解。根据岩石的化学成分，该玄武岩属于橄榄粗玄岩系列，轻稀土强烈富集，重稀土相对亏损，轻重稀土之间分异较大，具有与OIB相似的微量元素和同位素地球化学特征。岩石学和元素地球化学研究表明，该橄榄玄武岩的源区和岩浆的形成可能与地幔柱活动有关；岩浆演化经历了压力骤减的过程，在岩浆快速上升过程中，深部形成的矿物（可能是地幔矿物的俘虏晶）减压分解。快速上升的岩浆几乎未受大陆地壳的混染，仅捕获了少量流纹质熔体。

The volcanic cone of Hulanhoboke Volcano in Tongjing basin, Baikal rift region, consists of volcanic debris such as volcanic bombs, volcanic ashes and marie lava. Olivine xenocrysts characterize with higher Mg^# relative to olivine phenoerysts in basalt. Some plagioclase phenocrysts have inverse zone and core-mantle-rim textures, and the mantle of plagioclase phenocrysts shows decompressing decomposition texture. One kind clinopyroxene rim shows decomposition texture. Based on chemical composition, this basalt belongs to shoshonite series; the light rare earth elements are strongly enriched and differentiate from the heavy rare earth elements obviously. Their geochemical characteristics of trace elements and isotopic compositions are similar to OIB. Petrologic and geochemical research indicates that the source of olivine basalt and the fraction of magma may relate to mantle plume. The magma eruption was rather fast, which led the formation of observed decomposition texture in plagioclase and clinopyroxene xenocrysts. The magma was rarely contaminated by continental crustal m,terial. The studied magma captured a little shallow wall-rock which occurs as rhyolitic inclusion.