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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Hydrothermal heat flux through aged oceanic crust: where does the heat escape?
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Hydrothermal heat flux through aged oceanic crust: where does the heat escape?

机译：通过老化的洋壳的热液热通量：热量在哪里逸出？

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Recent publications suggest that most of the fluid flow in the upper oceanic crust is channelized through small volumes of rock and vented into the ocean. This implies that at flanks of generally thinly sedimented mid-ocean ridges, focused discharge at the seafloor should be concentrated most likely at outcrops, high-angle normal faults or seamounts. These vents should be associated with a significant heat flow signature. However, only few observations worldwide support this assumption up to now. On our quest for focused fluid exchange between young oceanic crust and the ocean we surveyed a 720 km long and 40-90 km wide off-axis portion of seafloor intersecting the East Pacific Rise near 14°14'S. A wealth of geophysical methods including high-resolution swath mapping bathymetry, single channel seismics, sediment echo sounding, magnetics and heat flow determinations were used. Heat flow data in the tectonic corridor cover crustal ages of 0.3-9.3 Ma. With respect to the conductive plate cooling model the data show the well-known pattern of low values close to th ridge, associated with vigorous hydrothermal circulation of cold seawater through the young upper crust, and a fast recovery to almost lithospheric conductive cooling values at a surprisingly young crustal age of 9.3 Ma. Although the sediment cover is fairly thin, measurements with 3.6 m violin bow type heat probe were possible almost everywhere within the investigated area. A detailed survey between two large seamounts at 4.5 Ma revealed localized extremely high values of up to 617 mW/m~2 (275% of the expected heat flow) at the foot of the seamount. This is interpreted as a clear indication of focused discharge of hydrothermal fluid. If we, however, relate heat flow normalized by the expected conductive heat loss to the character of igneous basement, heat flow is highest in areas with an almost flat and sedimented basement, and lowest within ～10-20 km of seamounts and other rough basement relief. We therefore hypothesize that the large number of seamounts covering the ocean floors governs a major amount of convective heat loss of aging oceanic lithosphere.
机译：最近的出版物表明，大洋上地壳中的大部分流体流通过少量的岩石被引导并排入海洋。这意味着在大体上沉积较薄的中海脊的侧面，海底的集中排放应最可能集中在露头，大角度正断层或海山处。这些通风孔应与明显的热流特征相关联。但是，到目前为止，全世界只有很少的观察支持这种假设。为了寻求年轻的洋壳与海洋之间的流体交换，我们调查了720 km长和40-90 km宽的海底离轴部分，与14°14'S附近的东太平洋上升相交。使用了大量的地球物理方法，包括高分辨率测绘测绘测深法，单通道地震，沉积物回波测深，磁学和热流测定。构造走廊的热流数据覆盖了0.3-9.3 Ma的地壳年龄。关于导电板冷却模型，数据显示出众所周知的低值模式，靠近脊部，与冷海水通过年轻上地壳的剧烈水热循环有关，并且在一定温度下可快速恢复至近岩石圈的导电冷却值。地壳年龄为9.3 Ma，令人惊讶。尽管沉积物覆盖层很薄，但在研究区域内几乎所有地方都可以使用3.6 m小提琴弓型热探针进行测量。在4.5 Ma处的两个大型海山之间进行的详细调查显示，海山脚下的局部极高值高达617 mW / m〜2（预期热流量的275％）。这被解释为热液集中排放的明确指示。但是，如果我们将通过预期的传导性热损失归一化的热流与火成岩基底的特性联系起来，那么在基底几乎平坦且沉积的区域，热流最高，而在海山和其他粗糙基底的约10-20 km之内，热流最低。救济。因此，我们假设，覆盖海床的大量海山控制了衰老的海洋岩石圈的大量对流热损失。

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