桂北四堡群中科马提岩系及其成因类型

桂北四堡群中许多镁铁质—超镁铁质岩体,实际上是火山岩或次火山岩。有的还具有科马提岩岩流的结构分层,其堆积带上部橄榄石和辉石晶体间隙中充填有基质物质。这些基质中发育了典型的橄榄石鬣刺结构。科马提岩与其伴生玄武岩属具成因联系的同一演化系列。在微量元素及REE特征上,区内科马提岩具有较好的Ⅱ类科马提岩属性,它们系亏损地幔经较小程度部分熔融产生。

THE KOMATIITIC SERIES AND IT'S GENETIC TYPE OF SIBAO GROUP IN NORTHERN GUANGXI

Many of the mafic - ultramafic rock bodies in Sibao Group occurring in northern Guangxi are actualy vol-canics or subvolcanics. Some of them developed layering of structural fractionation as komatiitic flows. There is matrix material existing among the olivine and augite crystals in the upper part of the cumulate zone and typical spinifex texture of olivine found in the matrix. The komatiites and the associated basslts belong to the same evolution series with genetic relationship regarding to their trace elements and REE features. The komatiites in this region show perfect characteristics of group I komatiites produced through certain degree of partial melting from depleted mantle.