On the thermal structure of the southern Tibetan crust
On the thermal structure of the southern Tibetan crust
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DOI：
10.1111/j.1365-246x.1985.tb01355.x
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发表时间：
1985-04
影响因子：
2.8
通讯作者：
C. Jaupart;J. Francheteau;X. Shen
中科院分区：
文献类型：
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作者：
C. Jaupart;J. Francheteau;X. Shen
本文对Francheteau等人最近在西藏南部进行的热流测量进行了定量分析。数据记录了54 ± 12 mW m-2的急剧热流异常。这里报告的现有沉积物年龄表明，由于沉积而产生的热效应可以忽略不计。在解释中必须考虑三个物理效应：西藏地壳复杂结构的热折射。瞬态热条件下的腐蚀和不稳定的横向传热。我们表明，热的折射可能是负责高达30%的热流变化。我们推导出一个新的公式的热流侵蚀校正，并表明，通常适用的校正可以是一个总高估热扰动地区。考虑到西藏南部地质特征的热折射可能的幅度，异常的幅度可能高达70 mW m-2。这种异常现象只可能是由于最近的浅层热源造成的。我们表明，在这种情况下，侵蚀的影响是小的（小于10%），无论侵蚀率是，因此不影响上述值显着。使用振幅和空间特征的异常，我们表明，源必须是年轻的100万年和浅于10公里。这与在同一地区进行的大地电磁测深的结果是一致的。该源可能是年轻的50万年，这将使它成为高原北部广泛观察到的地热活动的可能起源。这些结果证明，今天雅鲁藏布缝合带附近的西藏地壳融化过程非常活跃，距离印度-亚洲碰撞超过4500万年，距离印度岩石圈俯冲地点超过200公里。
Summary We present a quantitative analysis of the heat flow measurements recently made in southern Tibet by Francheteau et al. The data document a sharp heat flow anomaly of 54 ± 12 mW m-2. The sediment ages now available and reported here show that thermal effects due to sedimentation are negligible. Three physical effects must be taken into account in the interpretation: heat refraction across the complex structures of the Tibetan crust. erosion in transient thermal conditions and unsteady lateral heat transfer. We show that the refraction of heat may be responsible for up to 30 per cent of heat flow variations. We derive a new formula for the heat flow erosion correction and show that the correction which is usually applied can be a gross overestimate in thermally perturbed regions. Accounting for the possible magnitude of heat refraction across the geological features of southern Tibet, the amplitude of the anomaly could be as large as 70 mW m-2. The anomaly can only be due to a shallow and recent heat source. We show that in such a case erosion effects are small (less than 10 per cent), whatever the erosion rate is, and therefore do not affect the above values significantly. Using both the amplitude and the spatial characteristics of the anomaly, we show that the source must be younger than 1 Myr and shallower than 10 km. This is in good agreement with the results of magnetotelluric soundings carried out in the same area. The source could well be as young as 50 000 yr, which would make it a likely origin for the widespread geothermal activity observed further north on the Plateau. These results are evidence that melting processes are active today in the Tibetan crust near the Yalu-Zangbo suture zone, more than 45 Myr after the India-Asia collision and more than 200 km away from the site of underthrusting of the Indian lithosphere.