The role of hydrothermal cooling of the oceanic lithosphere for ocean floor bathymetry and heat flow
The role of hydrothermal cooling of the oceanic lithosphere for ocean floor bathymetry and heat flow
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DOI：
10.1002/2016jb013881
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发表时间：
2017-05
期刊：
影响因子：
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通讯作者：
H. Schmeling;G. Marquart;Viktor Nawa
中科院分区：
文献类型：
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作者：
H. Schmeling;G. Marquart;Viktor Nawa
研究了热液环流对大洋岩石圈冷却的影响。在一维岩石圈冷却模型中，我们利用一个标度律将水热对流包括在内，该标度律将瑞利数与努塞尔数联系起来。这一定律允许计算考虑额外热传输的有效导热系数。基于0.7-160 Ma的全球海底测深和地表热流数据集，我们基于下坡单纯形算法进行联合反演，以约束热液冷却的特征参数(除了经典的地幔温度、岩石圈厚度和岩石圈岩石的热膨胀系数)。水热冷却参数是控制热液穿透深度的裂隙长宽比、裂缝闭合和热液循环停止的特征胶结时间，以及当岩石圈顶部积累了足够的沉积盖层以防止热液流体逃往海洋时的封闭时间。最佳拟合参数集预测地幔温度在1350~1450℃之间，岩石圈厚度在70~90公里之间，并进一步表明：(1)如果考虑热液冷却效应，对数据的拟合度会大大提高；(2)水热冷却对于10 Ma的老岩石圈来说是重要的，并导致与1/平方根定律的显著偏离，指数接近1/3；(3)~1.5 Ma的老岩石圈完成了沉积封闭；(4)数据的拟合度明显提高了1.4倍，这可能是熔体凝固的影响。
We investigate the influence of hydrothermal circulation on cooling of oceanic lithosphere. We include hydrothermal convection in a 1‐D lithosphere cooling model by using a scaling law which relates the Rayleigh to the Nusselt number. This law allows calculating an effective thermal conductivity accounting for the extra heat transport. Based on a global data set for bathymetry and surface heat flow for ocean floor ages between 0.7 and 160 Ma, we perform a joint inversion based on a downhill simplex algorithm to constrain characteristic parameters for hydrothermal cooling (beside the classical parameter mantle temperature, thickness of the lithosphere, and thermal expansivity of lithosphere rocks). Hydrothermal cooling parameters are crack aspect ratio which controls the hydrothermal penetrations depth, characteristic cementation time at which cracks become closed and hydrothermal circulation ceases, and sealing time when enough sedimentary cover on top of the lithosphere has accumulated to prevent hydrothermal fluid escaping into the ocean. Best fitting parameter sets predict mantle temperatures between 1350 and 1450°C and lithosphere thickness between 70 and 90 km and further suggest that (1) the fit to the data is strongly improved if hydrothermal cooling effects are considered, (2) hydrothermal cooling is important for up to 10 Ma old lithosphere and leads to a significant deviation from the 1/square root—law with an exponent closer to 1/3, (3) sedimentary sealing is completed for ~1.5 Ma old lithosphere, and (4) fitting of the data is improved for an apparently 1.4 times higher value of thermal expansivity which may account for effects of melt solidification.