辽东后仙峪地区元古界超镁橄榄岩岩石学及其成因

超镁橄榄岩是作者在辽东大石桥后仙峪地区发现并命名的一种新类型岩石,是以镁橄榄石分子组成为标准而定义、阳离子过剩的一种岩石。由于阳离子过剩而形成独立的铁镁氧化物矿物,因此岩石的主要矿物为镁橄榄石、硅镁石、水镁石及磁铁矿。该超镁橄榄岩中矿物呈粒状、板状结构,具有角砾状火山喷发构造、类鬣刺状熔岩冷凝构造及团块状熔离构造。岩石具有分层现象,下部为镁橄榄岩,上部为磁铁矿硅镁石岩,其中含有镍黄铁矿,并构成海绵陨铁结构。岩石学研究表明这是一套富镁质超基性火山岩,相当于科马提岩,作为辽东硼矿的容矿岩石,它为镁硼酸盐矿床的形成提供了丰富的镁质来源。

Lithology and Genesis of the Paleozoic Ultra-Mafic Peridotite of the Houxianyu District in Eastern Liaoning

Ultra-mafic peridotite is a new type of rock found in the Houxianyu district,Dashiqiao,eastern Liaoning,and named by authors based on molecular components of forsterit,a rock containing excess cations.Cation surplus results in formation of independent Mg-Fe oxides such as forsterit,humite,and magnetite,in ultra-mafic peridotite which occurs as granular and tabular,with the structures of breccia volcanic erupitive,cooled spinifix pillow lava texture and massive liquation texture.The rock is of lamination with lower part being forsteit and upper part magnetitic humitite,with minor amount of pentlandite forming texture of iron-bearing sponge.Lithological study shows that it is a suit of Mg-rich basic volcanic rock,equivalent to kamatitie,which provides a great volume of magnesium for the deposition of Mg-rich borate deposit.