Heat generation within the cratonic lithospheric mantle (CLM) is an important but poorly determined parameter for constructing cratonic geotherms. Direct measurement of heat producing element (HPE: K, U, and Th) concentrations in bulk-rock samples of cratonic mantle roots—provided as xenoliths in volcanic rocks such as kimberlites—is mostly compromised by infiltration of host melt into the xenoliths, resulting in over-estimates of heat production. Here we use in situ methods (laser ablation inductively coupled plasma mass spectrometry) on minerals from a variety of cratonic mantle peridotites to avoid host-magma contamination enabling new, more accurate determinations of heat production for a wide spectrum of model mantle lithologies. The most melt-depleted, least metasomatized peridotites indicate that heat generation in un-metasomatized depleted cratonic lithospheric mantle is negligible, at ∼0.00004 µW/m³, 10² to 10³ times less than models that use more enriched or metasomatized compositions. Refertilized cratonic peridotites, typical of many kimberlite hosted xenoliths, have more elevated, but still low heat generation, of 0.006 µW/m³. We propose that the heat generation of typical cratonic mantle peridotite lies between these two bounds, that is, between 0.00004 and 0.006 µW/m³. Both values produce lower estimates of lithospheric thickness, by ∼10 to up to 80 km, depending on model assumptions, than estimates using higher HPE concentrations measured on bulk-rock xenolith material.

中文翻译：

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克拉通地幔根部的热量产生——地幔捕虏体的新微量元素约束及其对克拉通地热的影响

克拉通岩石圈地幔 (CLM) 内的热量产生是构建克拉通地温的一个重要但不确定的参数。直接测量克拉通地幔根部大块岩石样品中的产热元素（HPE：K、U 和 Th）浓度（以金伯利岩等火山岩中的捕虏体形式提供）主要受到寄主熔体渗入捕虏体的影响，导致高估产热量。在这里，我们对来自各种克拉通地幔橄榄岩的矿物使用原位方法（激光烧蚀电感耦合等离子体质谱法），以避免宿主岩浆污染，从而能够对广泛的模型地幔岩性进行新的、更准确的产热测定。最融化的，³ , 10 ²到 10 ³比使用更丰富或交代成分的模型少。再肥克拉通橄榄岩是许多金伯利岩包体的典型特征，具有更高但仍然较低的发热，为 0.006 µW/m ³。我们认为典型克拉通地幔橄榄岩的产热介于这两个界限之间，即介于 0.00004 和 0.006 µW/m ^{3 之间}。根据模型假设，这两个值都产生了较低的岩石圈厚度估计值，大约 10 到 80 公里，而不是使用在大块岩石包体材料上测量的更高 HPE 浓度的估计值。