乳山海阳所地区超镁铁岩的主要特征

MAJOR CHARACTERISTICS OF ULTRAMAFIC ROCKS IN THE HAIYANGSUO AREA

摘要:

乳山海阳所地区超镁铁岩多以包体状赋存于新元古代片麻状二长花岗岩中，成群出现、分段集中；主要岩石类型有蛇纹石化橄辉岩、辉橄岩、透闪石化单斜辉石岩、角闪石岩和少量斜长角闪岩（变辉长岩），偶见纯橄岩；化学成分上贫镁、铝，富铁、钙，m／f比值为0．92～5．44；稀土总量为9．44×10－6～88．56×10－6，∑LREE／∑HREE=215～5．93；所含微量元素与上地幔丰度比较，其中相容元素Ni，Co均亏损，不相容元素Rb，Cs，Ta，Th，Hf则均富集。从超基性岩到基性岩的微量元素变化特点可以看出，形成超镁铁岩的构造环境曾由活动陆缘向火山岛弧发生过迁移。海阳所地区超镁铁岩的宏观特征和化学成分特点与蛇绿岩中超镁铁岩差异较大，属非蛇绿岩型的超镁铁岩，为胶南造山带形成初期的深成侵入岩。

Abstract:

A set of ultramafic rocks with an outcropping area of 4. 5km2 spread in Haiyangsuoarea,Rushan city of Shandong Province. They occur largely as inclusions in Neoproterozoicslightly gneissic adamellite. The individual inclusions vary in size from 1m2 for small ones to1. 7km2 for the largest one. They are elongated and as lens in shape. The direction of longaxes ranges between 60°~80°. The magnetic survey and drilling data have shown that theultramafic rocks are all rootless blocks. Serpentinized olivine pyrox...