现代海底热液活动的分布、成因及热液柱研究

IOCAS-IR > 海洋环流与波动重点实验室

	现代海底热液活动的分布、成因及热液柱研究
	栾锡武
学位类型	博士
	1999
学位授予单位	中国科学院海洋研究所
学位授予地点	中国科学院海洋研究所
学位专业	海洋地质
关键词	现代海底热液活动分布热源与通道等间距分布自脉动热液柱热通量
摘要	在研究了全球四百多个现代海底热液活动区的水深、地形、构造特征后，给出了现代海底热液活动在空间、水深、地形地貌、构造方面的分布特征，及热液活动分布和扩张速率的关系，热液活动地区的热流、地震等方面的特征。现代海底热液活动的成因问题至今仍是一个不十分清楚的问题，况且热液活动区的地理位置不同，构造背景不同，成因机制也有很大差异。但已经知道要形成热液活动必须具备三个基本条件，即：热源、水源和热液通道。本文重点讨论了岩浆热源和热液通道这两个方面，并在此基础上给出了三个不同的热液模型。首先讨论了大洋扩张脊轴地壳岩浆房的存在。在快速、中速扩张的大洋中脊之下，有明显的轴地壳岩浆房存在，这些区域也是现代海底热液活动最为活跃的地方。在慢速扩张的大洋中脊之下，地震实验的结果没有发现地壳岩浆房的存在，但地震和重力工作却在现在已知的热液活动区之下发现了和轴地壳岩浆房相关的低速带和低密度区。接下来文章讨论了轴地壳岩浆房的形态、深度和轴地壳岩浆房过程。建立了一套流体力学模型对岩浆流体在浮力的作用下的向上迁移，在重力作用下的侧向迁移及迁移引起的围岩的破裂进行了讨论。计算出了岩浆流体在地壳中向上迁移的形态。理论计算结合实测数据，讨论了海底裂隙的类型、出现的位置及方向。讨论了现代海底热液活动区中热液喷口的丰度和海底地形、海底裂隙的宽度、海底裂隙的丰度之间的关系。提出三种现代海底热液活动模型。模型－针对沿扩张脊裂隙中的热液流体从隔离层中汲取化学元素并隔层加热后，由于热膨胀，通常靠近下面的热液流体密度小，靠近上面的热液流体密度大，从而造成密度梯度。这是一种重力不稳定的现象，所以冷流体趋于下沉，而热流体趋于上升。这个动力学过程遵循质量守恒，能量守恒和动量守恒定律。本文从这些定律约束的基本方程出发，在合理简化的基础上，给出了问题的解析解并讨论了解的周期性。提出现代海底热液活动区沿扩张脊是等间距分布的。模型二是一个火山口模型，从热液流体在不同温压下的特性出发，提出热液喷发的自脉动特性。模型三对应岩浆流体溢流出海底的情况，提出薄层的熔岩流冷却、破裂可以形成短时的热液活动。热液流体喷出海底后形成热液柱。本文从理论上讨论了热液柱的形态，旋转和自保持特点。最后从七个方面估算了现代海底热液活动输向海洋的热通量，将各种方法得到的数据进行了比较，并对结果进行了讨论。
其他摘要	Alike volcanic activity, hydrothermal activity is one form of heat releasing of the Earth from its core to its surface, and the founding of the hydrothermal activity opened another window for us to study the Earth. Based on the study of more than 440 hydrothermal fields, the thesis gives the brief characters of hydrothermal fields on the space distribution and depth distribution, topography, morphology, heatflow, plume anomaly, earthquake and biology. The thesis also gives the brief introduction of the method of hydrothermal activity exploration. The forming mechanism of the hydrothermal activity is not quit clear, further more, different site, different tectonic setting, the forming mechanism of the hydrothermal activity is also different. But based on the basic character of the hydrothermal activity, we know that its forming needs three basic conditions, that are heat source, fluid source, and the fluid channel. The thesis emphasized the discuss of the heat source and the fluid channel, and then gives three forming models of hydrothermal activity. The existed of the shallow crust axis magma chamber (AMC) is discussed, and point that the AMCs clearly exist under the area of fast to middle fast spreading ridges, and that areas usually have intense hydrothermal activity. There are no AMCs detected by seismic work under the slow spreading ridges, but there are area of low velocity zone (LVZ) and low density that relate to the AMC. The shape、depth and the process of the AMC are also discussed. Established a fluid dynamics method to describe the buoyancy-driven vertical migration and the gravity driven lateral migration of magma fluid and its resulting propagation of magma fluid-filled cracks. The genetic Algorithms is used to calculate the shape of the magma fluid during its vertical migration in the shallow crust. Based on the result of calculation and field measurement, the relationship between hydrothermal vents abundance and the fissure density、average width is discussed. And found that high abundance of vent corresponds to the relatively low abundance of fissure and big average width. Three model of hydrothermal forming are given in this thesis. A new concept of buffer layer is established, that layer separate the high temperature magma fluid and the cool down flow sea water, and point that the hydrothermal field in ridge axial valley is distributed with equal distances. Due to special character of the hydrothermal fluid under high pressure and high temperature, the thesis carefully studied the flow of the hydrothermal fluid and point that the hydrothermal field in volcanic crater is selfpulsating. Seven method are used to calculate the heatflux from the hydrothermal activity system to the ocean, and found that different method gives different results, the results and the reason why they are different are discussed in the thesis, the possibly causes may be there are more hydrothermal fields are not detected until now.
页数	138
语种	中文
文献类型	学位论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/269
专题	海洋环流与波动重点实验室
推荐引用方式 GB/T 7714	栾锡武. 现代海底热液活动的分布、成因及热液柱研究[D]. 中国科学院海洋研究所. 中国科学院海洋研究所,1999.

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