| 海南岛石炭纪双峰式火山岩及其板块构造背景 |
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| 引用本文： | 夏邦栋,施光宇.海南岛石炭纪双峰式火山岩及其板块构造背景[J].岩石学报,1991,7(1):54-62. |
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| 作者姓名： | 夏邦栋 施光宇 |
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| 作者单位： | 南京大学地球科学系，南京大学地球科学系，南京大学地球科学系，南京大学地球科学系，上海师范大学地理系 南京 210008，南京 210008，南京 210008，南京 210008，上海 200234 |
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| 基金项目： | 国家自然科学基金,编号为地85081 |
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| 摘 要： | 海南岛西部的石炭纪火山岩为一套大洋拉斑玄武岩-流纹斑岩的双峰式火山岩。玄武岩中的不相容元素和稀土元素的丰度和比值,以及稀土分配模式与大陆裂谷的拉斑玄武岩的地球化学特征一致,说明海南岛晚古生代裂谷作用的存在。玄武质岩浆来源于地幔深部,演化程度较低,受下地壳物质混染。流纹质岩浆不是玄武岩浆结晶分异产物,而是受裂谷区高热流影响,由陆壳部分熔融形成。
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| 关 键 词： | 海南岛 双峰式火山岩 石炭纪 大陆裂谷 |
THE CARBONIFEROUS BIMODAL VOLCANIC ROCKS IN HAINAN ISLAND AND THEIR PLATE TECTONIC SETTING |
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| Xia Bangdong Yu Jinhai Fang Zhong Wang Ciyin.THE CARBONIFEROUS BIMODAL VOLCANIC ROCKS IN HAINAN ISLAND AND THEIR PLATE TECTONIC SETTING[J].Acta Petrologica Sinica,1991,7(1):54-62. |
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| Authors: | Xia Bangdong Yu Jinhai Fang Zhong Wang Ciyin |
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| Abstract: | Carboniferous metamorphosed volcanic rocks extend discontinuously about 80 km in E-W direction in the western part of Hainan Island, China, Their original rocks are oceanic tholeiites and rhyoporphyrites, respectively. They can be referred to bimodal volcanic rocks according to their geological, petrographic and petrochemical features. Basalts are mainly located in the we stern part of this volcanic rock belt, and acidic rocks in the eastern part. These volcanic rocks are generally interbedded with metasandstones, metasiltstones, metapelites and so on. Comparing with ocean floor basalts and MORBs all over the world, the Carboniferous basalts from Hainan Island have higher MgO and FeO,and lower SiO_2,Al_2O_3,CaO and Na_2O contents. Calculated results indicate that the host magma contains more orthopyroxene and less plagioclase, and underwent only low grade evolution. A AFM diagram shows the formation of these basalts is relative to the early stage of the whole evolution process of tholeiitic magma.These basalts have higher incompatible trace element and REE abundances. Their average ratios of La/Yb, Rb/Sr,K/Rb are greatly identical with those of tholeiites formed in continental rifts,given by K.C, Condie (1976). All of facts suggest that a rifting was created in Hainan Island during the late Palaeozoic, and the degree of its development can be compared with that of the present Afar rift.Magnesium basalts and ultrabasic and intermediate-basle volcanic rocks from Hainan Island construct a consistent tholeiitie evolution series, which suggest that their original magma is magnesial picritie one. During fractional crystallization, the original magma must have assimilated the lower crustal materials, subsequently, it rose and erupted with great speed according to the initial ~(87)Sr/~(86)Sr ratio (0.7063) and K)2O and MgO contents. |
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| Keywords: | Hainan Island Bimodal volcanic rocks Carboniferous period Continental rift |
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