张八岭群火山岩地球化学特征及其构造学意义

安徽滁州张八岭地区的张八岭群分为2组。一是下部北将军组,以千枚岩和片岩为主;二是上部西冷岩组,主要为一套变质火山岩系。张八岭岩群的细碧-石英角斑岩系主要发育于西冷岩组中,具多旋回特点。细碧-石英角斑岩系以石英角斑岩为主,细碧岩次之,角斑岩类稀少。该岩系的火山岩富碱、富钠,具双峰值特征,其主量元素、微量元素和稀土元素地球化学特征表明,它形成于非造山张性环境,为裂陷槽,是与晚元古代罗迪尼亚(Rodinia)超大陆裂解有关的岩浆作用的产物。

Geochemical characteristics of volcanic rocks and its tectonic implications in Zhangbaling group

Zhangbaling group was divided into two formations, one was the underlied Beijiangjun formation, which was mainly made of phyllite and schist, the other was overlaid Xilengyan formation, made of metamorphic volcanic rocks.The spilite-quartz keratophyre sequence in Zhangbaling group was developed in Xilengyan formation and was possessed of multicyclic characteristics. The spilite quartz keratophyre sequence was mainly consisted of quartz keratophyre, secondly spilite and rarely keratophyre. The volcanic rocks of this sequence were characteristic of rich alkaline and sodium and double peak value. The geochemical properties of the major, minor and trace elements of the sequence showed that the sequence formed in an environment of anorogenic extension, was an aulacogen and was a result of magmatism related to the splitting of Rodinia supercontinent in Late Proterozoic era.