桂北中元古代的科马提岩

MIDDLE PROTEROZOIC KOMATIITE IN NORTHERN GUANGXI

桂北四堡群的科马提岩,自下而上分为堆晶带、鬣剌带和冷凝带。它们分别由辉石质科马提岩、具鬣刺结构的玄武质科马提岩和淬碎熔岩组成。与国外太古代绿岩带科马提岩对比,岩石化学成分、分带性、特有的鬣刺结构及区域变质特征、含矿性等方面亟相似。但我国华南元古代科马提岩也有自己的特点,产于元古代古大陆边缘,化学成分为超镁铁—镁铁质,且以镁铁质为主。

Komatiite in the Sibao Group of northern Guangxi may be divided in ascending order into the cumulus zone, spinifex zone and chilled zone. They are represented by pyroxenic komatiire, basaltic komatiite with spinifex texture and vitric lavas,respectively. The komatiite in this area is very similar to those in Archean greenstone belts abroad with respect ot the petrochemical composition, zoning, special spinifex texture, characteristics of regional metamorphism and ore potentiality.But the Proterozoic komatiite in South China has its own characteristics. It occurs on the margins of the Proterozoic paleocontinent and is of ultramafic-mafic composition but mainly of mafio composition.