赞皇杂岩中白虎庄片麻岩成因及时代研究

Study on the Genesis and Age about Baihuzhuang Gneiss of ZanHuang Complex

赞皇杂岩中的白虎庄片麻岩位于邢台县西,主要由角山黑云斜长片麻岩及黑云斜长片麻岩组成。岩石具有高硅、高铝、富钠、贫钾及低K2O/Na2O比值的特点,Mg#指数为33.37～45.63。该片麻岩具有中等-强烈程度的稀土元素分异,具有轻微的铕负异常。其富集Rb、Ba等大离子亲石元素,亏损Nb、等高场强元素。属于高铝的TTG,推断其成因与俯冲洋壳熔融有关。LA-ICP-MS锆石U-Pb定年结果表明,白虎庄片麻岩形成于2 545.5±7.9 Ma,属新太古代中晚期产物。

Baihuzhuang gneiss of ZanHuang complex is located in the west of Xingtai county, mainly consists of hornblende black mica plagioclase gneiss and black mica plagioclase gneiss. The gneiss are characterized by high silicon, aluminum and sodium, poor potassium and low ratio of K2O/Na2 O, and the Mg# index was 33.37 to 45.63. It has medium-strong rare earth element differentiation and slight europium negative anomaly. For the gneiss belongs to high aluminum’s TTG that enrich lithophile elements Rb and loss high field strength element Nb, Ta, the article speculate it formed by subduction and melting of oceanic crust. LA-ICP-MS zircon U-Pb age data indicate that the rocks formed within the range of 2545.5±7.9 Ma, consequently, their formation age is restricted at middle and late Neoarchean.