| 南海IODP 349航次基底玄武岩中碳酸盐岩脉的岩石学特征* |
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| 引用本文： | 许佳锐,陈毅凤,王宝云.南海IODP 349航次基底玄武岩中碳酸盐岩脉的岩石学特征*[J].热带海洋学报,2018,37(6):63-73. |
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| 作者姓名： | 许佳锐 陈毅凤 王宝云 |
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| 作者单位： | 1. 中国科学院边缘海与大洋地质重点实验室(广州地球化学研究所), 广东 广州 5106402. 中国科学院大学, 北京1000493. 同位素地球化学国家重点实验室, 中国科学院广州地球化学研究所, 广东 广州 510640; |
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| 基金项目： | 国家自然科学基金(91428102, 41876064);IODP中国349和367航次资助 |
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| 摘 要： | 国际大洋发现计划(International Ocean Discovery Program, IODP)349航次在南海东部次海盆和西南次海盆残留扩张脊附近的U1431和U1433站位首次钻取基底玄武岩, 通过对16块基底玄武岩内的碳酸盐岩脉薄片镜下观察以及激光拉曼光谱分析, 揭示碳酸盐矿物为方解石和文石, 为典型的洋壳低温热液蚀变次生矿物。U1431站位碳酸盐岩脉为独立的方解石脉、文石脉交替出现; 而U1433站位则存在方解石脉、文石脉和方解石-文石共生脉三种情况。此外, U1431站位在基底~42.1m处出现了平行的方解石脉和文石脉, 揭示U1431存在不同来源热液的多期活动, 即可能存在多次或多阶段不同的热液注入。U1431和U1433站位的碳酸岩脉中, 文石的矿物集合体形状基本一致, 呈块状、纤维状和放射纤维状; 而方解石存在差异, U1431的方解石以斑块状、块状、粒状和纤维状出现, 而U1433的方解石仅出现块状。U1431站位的碳酸盐岩脉的丰度明显高于U1433站位。这些均揭示U1431站位的低温热液活动强, 而U1433站位则相对弱。两个站位的热液活动不同很可能是由于区域地质环境的差异造成——U1431附近的巨大海山为其提供了热液补给, 而U1433远离热液的补给/渗漏点。
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| 关 键 词： | 基底碳酸盐岩脉 激光拉曼光谱 方解石和文石 低温热液 南海 IODP349航次 |
| 收稿时间： | 2018-01-09 |
Petrography of carbonate veins in basement basalts from the South China Sea Exp. 349 |
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| Jiarui XU,Yifeng CHEN,Baoyun WANG.Petrography of carbonate veins in basement basalts from the South China Sea Exp. 349[J].Journal of Tropical Oceanography,2018,37(6):63-73. |
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| Authors: | Jiarui XU Yifeng CHEN Baoyun WANG |
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| Institution: | 1. CAS Key Laboratory of Ocean and Marginal Sea Geology, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China2. University of Chinese Academy of Sciences, Beijing 1000493. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences Guangzhou 510640, China |
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| Abstract: | The basaltic basement in the South China Sea was cored for the first time during International Ocean Discovery Program (IODP) Exp 349. The basalt was collected from Sites U1431 and U1433 close to the fossil spreading ridge in East and Southwest Sub-basins, respectively. Carbonate veins (n=16) within the basalt were investigated under microscope and by the laser Raman spectra. At Site U1431, the carbonate veins consisted of calcite veins or aragonite veins, while at Site U1433 the carbonate veins are composed of either calcite veins, or aragonite veins, and calcite-aragonite mixed veins. Meanwhile, the calcite veins and aragonites alternated, and at ~42.1 m below basement, two calcite veins and one aragonite vein occurred parallel, likely indicating that multiple hydrothermal fluids of different sources have circulated there. At both sites, the textures of aragonite are generally the same-blocky, fibrous, and radiating fibers. However, it is not the case for calcite. At Site U1431, the calcite is clotted blocky, blocky, granule, and fibrous, while at Site U1433 the calcite only occur as blocks. The abundance of carbonate veins at Site U1431 is much higher than that at Site U1433. These suggest that the low-temperature hydrothermal circulation at Site U1431 is stronger than that at Site U1433. Different local geology and environment mostly lead to the differences in hydrothermal activity at these two sites: Site U1431 is close to a giant seamount that serves as a recharge site, while Site U1433 is far away from any recharge or discharge site. |
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| Keywords: | carbonate veins Laser Raman spectra calcite aragonite low temperature hydrothermal fluid flow South China Sea IODP Exp349 |
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