| 南秦岭碧口群岩石组合特征及其构造意义 |
| |
| 引用本文： | 裴先治.南秦岭碧口群岩石组合特征及其构造意义[J].地球科学与环境学报,1989(2). |
| |
| 作者姓名： | 裴先治 |
| |
| 作者单位： | 西安地质学院地勘系 |
| |
| 摘 要： | 碧口群是扬子板块西北缘中晚元古代古海沟—岛弧体系的重要组成部分。岩石组合、岩石化学及稀土元素特征研究表明,其下部为蛇绿岩组合,以大洋E型拉斑玄武岩为特征,代表古俯冲杂岩;上部为重力流沉积组合,以火山质碎屑浊积岩及陆源碎屑浊积岩为特征,类似于海沟型复理石组合,代表古海沟堆积。同时构造变形及变质作用特征表明,在蛇绿岩分布区发育有大型韧性剪切带和高压低温变质的蓝闪片岩。由此可见碧口群属于中晚元古代扬子板块西北缘的古海沟—俯冲地体。
|
| 关 键 词： | 碧口群 蛇绿岩 重力流沉积物 古海沟—俯冲地体 |
THE FEATURES AND THE TECTONIC SIGNIFICANCE OF ROCK ASSEMBLAGE IN THE BIKOU GROUP, SOUTHERN QINLING |
| |
| Pei Xianzhi.THE FEATURES AND THE TECTONIC SIGNIFICANCE OF ROCK ASSEMBLAGE IN THE BIKOU GROUP, SOUTHERN QINLING[J].Journal of Earth Sciences and Environment,1989(2). |
| |
| Authors: | Pei Xianzhi |
| |
| Institution: | Xi'an College of Geology |
| |
| Abstract: | The Bikou Group in the Southern Qinling is located on the jucture of Shaanxi, Gansu and Sichuan provinces.It is also an important component of the Middle-Late Proterozoic ancient trench (subduction)--island arc system in the Northwestern margin of the Yangtze plate.The Rb-Sr age of the metamorphic basic volcanic rocks is about 850-1300Ma.The study of the features of the rock assemblage, petrochemistry and REE demonstrates that the lower part of the Bikou Group is the ophiolite assemblage, the sequence of which from lower to upper is as follows. ( 1 ) metamorphic peridotites; ( 2 ) ultramafic-mafic com-plexes;( 3 ) diabase dikes; ( 4 ) basic volcanic rocks ( basic lavas and pillow lavas); (5) pelagic siliceous-pelitic rocks.The metamorphic peridotites in the ophiolite assemblage belong to the Alpine peridotites.The basic volcanic rocks are characterised by the oceanic E-type tholeiite, representing the remains of ancient oceanic crust and occurring in the paleo-subduction complex.The upper part of the Bikou Group is the pelagic facies gravity flow sediments, including the volcaniclastic turbidite association, the terrigenous clastic debris flow-grain flow sedimentary association, the terrigenous clastic turbidite association and pelagic facies pelite association.It is similar to the trench-type flysch association and represents the paleo-trench deposits. At the same time, the features of the structure deformation and metamorphism show that in the distributive region of the ophiolite the large-scale ductile shear belt and the high P/T metamorphic glaucophane-schist belt are developed.Thus it can be seen that the Bikou Group belong to Middle--Late Proterozoic paleotrench-subduction terain in the Northwestern margin of the Yangtze plate. |
| |
| Keywords: | Bikou Group gravity flow sediment paleo-trench-subduction terrain |
| 本文献已被 CNKI 等数据库收录！ |
|
