刘家坪杂岩体的岩石特征及时代

LITHOLOGIC FEATURES AND TIME OF THE LIUJIAPING COMPLEX ROCK BODIES IN SHAANXI PROVINCE

刘家坪杂岩体出露于扬子准地台西北边缘。该区扬子期岩浆活动,早期为刘家坪组海底喷发的中～酸性火山岩系,晚期先后侵入有角闪辉长岩—石英闪长岩—斜长花岗岩—辉绿岩脉。岩浆岩具有幔源岩浆及造山带地区火山岩的特征。据震旦系覆于刘家坪杂岩体之上,其底部砂砾岩的砾石中有杂岩体成分,以及杂岩体侵入于同位素年龄值为6.43亿年的刘家坪组之中,认为刘家坪杂岩体时代为前震旦纪。

The Liujiaping complex occurs on the northwest margin of the Yangzi paraplatform.Magma activities in the researched area can be divided into two stages:the early stage is the eruptive intermediate—acidity volcanic rocks from submarine and the later stage is the intrusive amphibole gabbro —quartz diorite-plagio granite-diabase veins.The magmatite is characterized by the mantle-derived magma and the volcanic rocks occurring in orogenic belt.The Sinian System overlying on the Liujiaping complex bodies,the gravels in gravelly rocks at the bottom containing complex components and the complex body intrusive into the Liujiaping Formation(its isotopic age is 643 Ma)have proved that the time of the Liujiaping complex body would be the later Yangzi Stage of the early Sinian Period.