Heat flow measured over the Juan de Fuca Ridge: Evidence for widespread hydrothermal circulation in a highly heat transportive crust
Heat flow measured over the Juan de Fuca Ridge: Evidence for widespread hydrothermal circulation in a highly heat transportive crust
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在胡安德富卡海脊上测量的热流：高传热地壳中广泛热液循环的证据
DOI：
10.1029/jb082i030p04845
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发表时间：
1977
影响因子：
--
通讯作者：
C. Lister
中科院分区：
文献类型：
--
作者：
E. Davis;C. Lister
在以北方胡安·德富卡海脊和Sovanco断裂带交叉点为中心的100平方公里地震反射剖面网格上进行了104次热流测量。剖面间距约为10 km，热流站位于每个轨道线交叉点。断裂带以南的地壳是年轻的（0- 180万年），沉积物覆盖是不完整的，平均而言，与任何合理的岩石圈形成模型所预测的相比，热流量非常低。站与站之间的热流变异性很高，且与当地地形或结构无关，并且变异性的性质和大小无法通过热流折射或快速沉积的热效应来解释。这些观察结果表明，开放的地下水循环在有效渗透的基岩重新分配的热量，并导致高度局部化的散射导电测量。总热流的很大一部分直接通入海洋。在探险者海脊侧翼，断裂带以北，地壳较老（3.3-6.6百万年）。并完全沉淀。热流值的局部变异性仍然很大，但可以探测到热流与沉积厚度之间的关系。平均而言，热流随着沉积物厚度的减少而增加，虽然这种变化是在适当的意义上，但所观察到的热流变化的幅度不能用简单的传导机制来解释，例如冷沉积物的沉积。观测到的热流与沉积厚度之间的关系可以用高传热地壳中广泛的热液循环来解释。发现沉积物底部的水温在100° C和200°C之间。在胡安·德富卡海脊沉积物充填的轴向谷中也观察到热流与沉积物厚度之间的类似关系，估计那里的基底温度在100° C至300°C之间。胡安·德富卡海脊侧翼的基底温度估计平均要低得多，在25° C至200°C之间。这可能是地下水通过地下室露头通风的结果。在探索者海脊的侧翼，开放环流被厚而连续的沉积物覆盖层所阻止，该地区的热流平均值（5.7 HFU，其中1 HFU = 1 μcal cm−2 s−1）应该是该年龄地壳总传导热通量的可靠估计（450万年）。平均）。这与来自太平洋的其他可靠数据点一起，支持热流对热流年龄（HFU）的简单依赖性= 12.0/年龄1/2（百万年）。
1补充附录1和2可在缩微胶片上提供整篇文章。美国地球物理联合会，1909 K街，西北，华盛顿，华盛顿特区，20006年。文件J77-005; $1.00。付款必须随订单一起进行。
One hundred four heat flow measurements were made on a 100-km-square grid of seismic reflection profiles centered over the intersection of the northern Juan de Fuca ridge and the Sovanco fracture zone. Profile spacing was roughly 10 km, and heat flow stations were located at each track line intersection. South of the fracture zone the crust is young (0–1.8 m.y.), sediment cover is incomplete, and on average, heat flow is very low in comparison with that predicted by any reasonable model for lithosphere creation. Station to station heat flow variability is high and uncorrelated with local topography or structure, and the nature and magnitude of variability cannot be accounted for by the thermal effects of either heat flow refraction or rapid sedimentation. These observations suggest that open groundwater circulation in effectively permeable basement rocks redistributes the heat and causes highly localized scatter in conductive measurements. A large portion of the total heat flow is ventilated directly to the sea. On the Explorer ridge flank, north of the fracture zone, the crust is older (3.3–6.6 m.y.) and fully sedimented. Large local variability in heat flow values still exists, but a relationship between heat flow and sediment thickness can be detected. On average, heat flow increases with decreasing sediment thickness, and although the variation is in the proper sense, the magnitude of the observed heat flow variation cannot be explained by simple conductive mechanisms, such as deposition of cold sediments. The observed relationship between heat flow and sediment thickness can be accounted for by widespread hydrothermal circulation in a highly heat transportive crust. Water temperatures at the base of the sediments are found to range between about 100° and 200°C. A similar relationship between heat flow and sediment thickness is observed for the sediment-filled axial valley on the Juan de Fuca ridge, and basement temperatures estimated there range between about 100° and 300°C. Basement temperatures estimated over the Juan de Fuca ridge flanks are on the average much lower and range between ≪25° and 200°C. This is probably a result of groundwater ventilation through basement outcrops there. On the Explorer ridge flank, open circulation is prevented by the thick and continuous sediment cover, and the heat flow average over the area (5.7 HFU, where 1 HFU = 1 μcal cm−2 s−1) should be a reliable estimate of the total conductive heat flux for this age crust (4.5 m.y. on average). This, with other reliable data points from the Pacific, supports a simple dependence of heat flow upon age of heat flow (HFU) = 12.0/age1/2 (m.y.).
1 Supplementary Appendices 1 and 2 are available with entire article on microfiche. Order from American Geophysical Union, 1909 K Street, N.W., Washington, D.C. 20006. Document J77-005; $1.00. Payment must accompany order.