| 中朝陆台北侧褶皱带(中段)蛇绿岩的地球化学特征 |
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| 引用本文： | 田昌烈,曹从周,杨芳林.中朝陆台北侧褶皱带(中段)蛇绿岩的地球化学特征[J].地球学报,1989,11(1):107-129. |
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| 作者姓名： | 田昌烈 曹从周 杨芳林 |
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| 作者单位： | 中国地质科学院沈阳地质矿产研究所;中国地质科学院沈阳地质矿产研究所;中国地质科学院沈阳地质矿产研究所 |
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| 摘 要： | 中朝陆台北侧褶皱带(中段)中,出露有两条蛇绿岩带:一条是温都尔庙加里东期蛇绿岩带(简称南带);一条是索伦山-贺根山华力西期蛇绿岩带(简称北带)。两条岩带具有不同的时空格局和明显的地球化学差异。通过对两条蛇绿岩带地球化学研究,讨论了蛇绿岩形成的古构造环境。南带蛇绿岩可能是在岛弧边缘附近海盆地扩张脊中形成的;北带蛇绿岩可能是在大洋中脊形成的,它标志着中朝板块和西伯利亚板块之间的碰撞带位置。
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GEOCHEMICAL FEATURES OF OPHIOLITE IN THE FOLD BELT ON THE NORTH SIDE OF THE SINO-KOREAN PLATFORM |
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| TIAN Chang-lie,CAO Cong-zhou and YANG Fang-lin.GEOCHEMICAL FEATURES OF OPHIOLITE IN THE FOLD BELT ON THE NORTH SIDE OF THE SINO-KOREAN PLATFORM[J].Acta Geoscientia Sinica,1989,11(1):107-129. |
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| Authors: | TIAN Chang-lie CAO Cong-zhou and YANG Fang-lin |
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| Institution: | Shenyang Institute of Geology and Mineral Resources, CAGS;Shenyang Institute of Geology and Mineral Resources, CAGS;Shenyang Institute of Geology and Mineral Resources, CAGS |
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| Abstract: | In the fold belt along the north side of the Sino-Korean Platform there occur two ophiolite zones: the Caledonian Ondor Sum ophiolite zone (called the south zone for short) and the early Variscan Solon Mts.-Hegen Mts, ophiolite zone (called the north zone for short).The Ondor Sum ophiolite is the oldest remains of the ancient Mongolian ocean plate subducting by different stages towards the south (towards the continent) and of the Sino-Korean plate accreting towards the north. Thus it is formed by a series of tectonic slabs that were obducted southwards in the early part of the Early Paleozoic.From below upwards, the original ophiolite sequence consists of metam-orphic peridotite, harzburgite and bunite ultramaficmafic cumulative complex (including pyroxenite and gabbro), basic lavas with pillow structure and radiolarian siliceous rocks.The north ophiolite zone, extending in a nearly E-W direction, is composed of ophiolites in the Solon Mts, Bumbat, the Hegen Mts., Wusinihei and Meilaotetula, whose age is early Late Paleozoic.The original ophiolite sequence is in ascending order: (1) metamorphic peridotite composed of Iherzolite, harzburgite and dunite (strongly depleted upper mantle); (2) ultramafic-mafic cumulative complex which is composed of dunite, feldspathic dunite and chromite in the lower part, stratified tro-ctolite and gabbro in the middle part, and massive grabbre at the top; and (3) sheeted dike swarms and metamorphic basic lavas.Through studies of the content of general elements,as well as the abundances of trace and rare earth elements, the authors have obtained the following recognitions: (1) In the south zone the metamorphic peridotite is composed of weakly depleted mantle substances; while in the north zone metamorphic peridotite is composed of weakly depleted Iherzolite and strongly depleted harzburgite and dunite. This indicates that the south and north zones are greatly different in the degree of partial melting of the mantle substances. (2) In the ophiolite of the south and north zones there are two suites of basic lavas which are different in age and composition. In the north zone, the metamorphic basic lavas belong to deep-sea tholeiite, characterized by LREE depletion and a low abundance of big-ion elements; while in the south zone, the composition of the basic lavas is near that of slightly alkaline tholeiite, and the lavas are characterized by LREE enrichment and a high abundance of big-ion elements and might be formed in the spreading ridge near the margin of the island arc. (3) During the formation of the Solon Mts. -Hegan Mts. ophiolites, the Xilinhot area at its southern side and the Dong Ujimqin Banner at the northern side respectively belonged to the margins of the south and the north old lands. The chemical characteristics of the volcanic rocks are similar to those of the island-arc lavas, and are greatly different from those of the Hengens Mts. ophiolite. This feature proves that the ophiolite in the north zone not only represents the oceanic crustal fragments of the anciedt Mongolian ocean, but also marks the position of the suture line between the Sino-Korean and Sibrian plates. |
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