Heat transfer through the sediments of the Mounds Hydrothermal Area, Galapagos Spreading Center at 86°W
Heat transfer through the sediments of the Mounds Hydrothermal Area, Galapagos Spreading Center at 86°W
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通过 Mounds 热液区沉积物的热传递，加拉帕戈斯传播中心，西经 86°
DOI：
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发表时间：
1983
期刊：
影响因子：
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通讯作者：
R. V. Herzen
中科院分区：
文献类型：
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作者：
K. Becker;R. V. Herzen
在86°W的加拉帕戈斯扩散中心，通过DSDP Leg 70站点506-509的12个孔中每30±10m沉积物中约10m间隔的温度测量和11个8-12 m长的活塞芯上多达5个热敏电阻的温度测量，揭示了加拉帕戈斯扩散中心丘区的传热过程。325个探针值显示，每个岩心的热导率随深度的增加呈显著的线性增加。大约一半的温度-热阻曲线是非线性的，适合于稳态垂直孔隙水平流模型。结果表明，总热流高且多变，局部热液流量约为10 ~ 8 m/s，与个别土丘有关。在丘陵以南约5 km的低热流带中，补给速率相似，而在丘陵高热流带周围的中热流带（0.17 ~ 0.42 W/m2）补给速率较慢。建议在距离放电丘约100米的范围内，可能存在缓慢夹带式补给。同时也表明，北邻土丘地壳块的主要断层有强烈的局部放电。在扩展轴以北约95公里处，在DSDP 510站点，114米沉积物覆盖的温度为2.7米。地壳呈线性，这与该层的水力阻力足以封闭基底水和底水之间的自由热液交换的建议一致。结合Karato和Becker（本期）的热流数据和物性数据，认为在地形较为光滑的基底内，≈50 m的沉积物可能是封闭热液环流的阈值厚度。我们认为，当沉积物的厚度接近这个阈值时，丘的形成可能与热液通过沉积物的强迫局部化有关。
Heat transfer processes at the mounds area of the Galapagos Spreading Center at 86°W are revealed by temperatures measured at ≈ 10-m intervals in the 30±10m sediment at each of 12 holes at DSDP Leg 70 Sites 506–509 and by temperatures of up to five thermistors on eleven 8–12 m long piston cores. The 325 needle-probe values show a significant linear increase of thermal conductivity with depth in each core. About half of the temperature-thermal resistance profiles are nonlinear and are fit to a steady state, vertical pore water advection model. Results indicate high and variable total heat flow and localized hydrothermal discharge at ≈ 10−8 m/s, associated with individual mounds. Recharge is indicated at similar rates in the low heat flow belt ≈ 5 km south of the mounds and is suggested at slower rates in the intermediate heat flow (0.17–0.42 W/m2) belt surrounding the mounds heat flow high. Possible slow entrained recharge within ≈ 100 m of discharging mounds is suggested. Also suggested is strong local discharge along the major fault bounding the mounds crustal block to the north. About 95 km north of the spreading axis, at DSDP Site 510, temperatures in the 114-m sediment cover on 2.7-m.y. crust are linear, consistent with the suggestion that the hydraulic resistance of this layer is sufficient to seal off free hydrothermal exchange between basement and bottom water. The combination of heat flow data and the physical properties data of Karato and Becker (this issue) suggests that ≈ 50 m of sediment may be a threshold thickness for sealing of hydrothermal circulation within basement, where the topography is smooth. We suggest that the formation of mounds may be associated with the forced localization of hydrothermal discharge through the sediment, as its thickness approaches this threshold value.