Hydrothermal processes at mid-ocean ridges: Results from scale analysis and single-pass models
Hydrothermal processes at mid-ocean ridges: Results from scale analysis and single-pass models
复制标题
大洋中脊的热液过程：尺度分析和单程模型的结果
DOI：
10.1029/148gm09
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
L. Germanovich
中科院分区：
文献类型：
--
作者：
R. Lowell;L. Germanovich
海洋脊顶的热液过程涉及热供给动力学和地壳渗透率演化之间的复杂相互作用，这给热液建模者带来了广泛的挑战。其中包括：(1)热量供给与热液换热之间的详细关系；(2)控制热液喷口稳定性和长期演化的机制，包括集中流动和扩散流动的关系；(3)与岩浆和构造事件相关的时间变异性；(4)沸腾、相分离和喷口氯度演化；地球化学和生物过程控制喷口场特征和演化。在这里，我们在尺度分析和单通道模型的背景下解决了一些这样的问题。尺度分析表明，均匀系统中羽流传热与观测到的黑烟流不一致。单通道模型表明，黑烟炉喷发需要在岩浆房上方有一个不超过几十米厚的导电边界层和一个渗透性在10 -13和10 -11 m2之间的排出带。长期的喷口稳定性要求保持薄的导电边界，可能是通过岩浆补充和裂缝扩展的某种组合，以及广泛的补给带来防止硬石膏堵塞。如果岩脉局部增加了两个数量级的渗透率，并提供了相当一部分的事件羽流热量，则事件羽流可能是由岩脉位置驱动的。
Hydrothermal processes at ocean ridge crests involve a complex interplay between the dynamics of heat supply and the evolution of crustal permeability that results in a broad spectrum of issues to challenge hydrothermal modelers. Among these are: (1) the detailed relationships between heat supply and hydrothermal heat transfer, (2) the mechanisms controlling vent stability and long-term evolution of hydrothermal vents, including the relationship between focused and diffuse flow, (3) temporal variability related to magmatic and tectonic events, (4) boiling, phase separation and the evolution of vent chlorinity, and (5) the linkages among heat transfer, fluid flow, geochemical and biological processes in controlling character and evolution of vent fields. Here we address a number of these issues in the context of scale analysis and single-pass models. Scale analysis shows that plume heat transfer in a homogeneous system with an imposed heat flux from below does not correspond to observed black smoker flow. Single-pass models show that black smoker venting requires a conductive boundary layer no more than a few tens of meter thick above a magma chamber and a discharge zone with permeability between 10 -13 and 10 -11 m 2 . Long-term vent stability requires that the thin conductive boundary be maintained, probably by some combination of magma replenishment and crack propagation, and a broad recharge zone to prevent clogging by anhydrite. Event plumes may be driven by dike emplacement provided the dike locally increases the permeability by two orders of magnitude and provides a significant fraction of event plume heat.