Lower mantle geotherms, flux, and power from incorporating new experimental and theoretical constraints on heat transport properties in an inverse model
Lower mantle geotherms, flux, and power from incorporating new experimental and theoretical constraints on heat transport properties in an inverse model
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DOI：
10.5194/ejm-34-149-2022
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发表时间：
2022-02
影响因子：
2.1
通讯作者：
A. Hofmeister
中科院分区：
文献类型：
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作者：
A. Hofmeister
抽象的。在不假定地球矿物学的情况下，设计了一种反转方法来探测地球的热状态。这限制了下地幔(Lm)的热导率(κ)，方法是将体积模量(B)和压力(P)与深度(Z)的地震学模型结合起来，得到新的结果∂ln(κ)/∂P∼7.33/BT)和κ上可用的长度超过毫米的高温(T)数据。考虑大样本可以解释最近揭示的热传输性质对长度尺度的依赖关系。将变量分离应用于地震学∂B/∂P随深度的变化随T而变化，得到的Lm DT/Dz取决于∂2B/∂P2和∂B/∂T，它们在密相之间变化不大。与Lm不同，地震∂B/∂P在核上方200公里处是不连续的，与模型有关的∼，我们的结果是通过这个微小的层(D‘’)外推的。对于高(氧化物)和低(硅酸盐)κ的情况，通量和功率由DT/DZ计算。地热计算与κ无关，因此与矿物学无关，但需要指定某一深度的参考温度：考虑的范围很大。深度熔融的限制被用来确定我们的地热、通量和功率曲线中哪一条最能代表地球内部。除了含有极小的∂2B/∂P2的氧化物成分外，LM加热核心，使其熔化。深层加热是由于日均1000公里和月平均重心波动产生的周期性应力所致。
Abstract. An inverse method is devised to probe Earth's thermal state without assuming its mineralogy. This constrains thermal conductivity (κ) in the lower mantle (LM) by combining seismologic models of bulk modulus (B) and pressure (P) vs. depth (z) with a new result, ∂ln(κ) / ∂P ∼ 7.33/BT, and available high temperature (T) data on κ for lengths exceeding millimeters. Considering large samples accounts for the recently revealed dependence of heat transport properties on length scale. Applying separation of variables to seismologic ∂B/∂P vs. depth isolates changes with T. The resulting LM dT / dz depends on ∂2B/∂P2 and ∂B/∂T, which vary little among dense phases. Because seismic ∂B/∂P is discontinuous and model dependent ∼ 200 km above the core, unlike the LM, our results are extrapolated through this tiny layer (D′′). Flux and power are calculated from dT / dz for cases of high (oxide) and low (silicate) κ. Geotherm calculations are independent of κ, and thus of LM mineralogy, but require specifying a reference temperature at some depth: a wide range is considered. Limitations on deep melting are used to ascertain which of our geotherm, flux, and power curves best represent Earth's interior. Except for an oxide composition with miniscule ∂2B/∂P2, the LM heats the core, causing it to melt. Deep heating is attributed to cyclical stresses from > 1000 km daily and monthly fluctuations of the barycenter inside the LM.