甘肃北山预选区新场地段花岗岩类岩石特征研究

STUDY ON GRANITE CHARACTERISTICS OF XINCHANG SECTION OF CANDIDATE BEISHAN AREA,GANSU PROVINCE

我国高放废物地质处置库北山预选区,处置库候选围岩为花岗岩。新场地段是北山预选区中的一个有利地段,其围岩为花岗岩类岩石,主要包括二长花岗岩和花岗闪长岩,少量为石英闪长岩等。岩石中广泛产出角闪石、磁铁矿、榍石等多见于同熔型、I-型花岗岩类中的特征矿物;少部分花岗闪长岩中出现白云母、石榴子石等上地壳特征矿物。花岗岩类的常量化学成分,属高钾钙碱性系列花岗岩类,具同熔型或I-型花岗岩的特征。

Xinchang section is one of the candidate fields in Beishan area,Gansu Province—the preselected area for China′s high-level radioactive waste repository. The results show that the dominant rock characteriastics from Xinchang section are monolithic granite and granodiorite. The minor dominant rock is the quartz diorite. Mineral assemblage such as hornblende,magnetite,sphene,titanite,etc. show that the kinds of minerals mentioned above are of syntectic or I-typed granite. Some mineral assemblages of granodiorites such as muscovite,garnet,etc. are found during upper crust forming. The petrochemistry composition belongs to high potassium Ca-alkaline series, showing the special feature of syntectic or I-typed granite.