ABSTRACT We modelled thermo-rheological perturbations, related to the emplacement of a magmatic body in the upper crust. This approach was considered relevant for the areas characterized by elevated surface heat flow and chiefly for the geothermal fields. The numerical conductive thermal model applied to the Larderello geothermal area in Tuscany, allowed to constrain size, depth and timing of emplacement of the pluton. We inferred that the emplacement of a magmatic body, at a minimum depth of 3 km, having a horizontal extension of 14 km and a maximum thickness of 8 km, can reasonably reproduce the observed regional surface heat flow anomaly of the Larderello area, when 300 (± 100) kyr are elapsed from the magma emplacement. Even assuming an incremental growth, the first magma injection should not be older than 1 ± 0.3 Ma. Results of the thermal model were used to set up a rheological model and to simulate the drifting of the brittle-ductile transition during the cooling of the pluton. A comparison with the K-horizon profile, a prominent seismic reflector in the Larderello area, was then performed. It was found that the K-horizon approximately corresponds with the pluton roof and with the current location of the brittle-ductile transition.

中文翻译：

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与上地壳中花岗岩侵位相关的区域热流变场：对 Larderello 地区的影响（意大利托斯卡纳）

摘要 我们模拟了与岩浆体在上地壳的侵位有关的热流变扰动。这种方法被认为适用于以地表热流升高为特征的区域，主要是地热田。应用于托斯卡纳 Larderello 地热区的数值传导热模型允许限制岩体入位的大小、深度和时间。我们推断，一个岩浆体侵位最小深度3 km，水平延伸14 km，最大厚度8 km，可以合理再现观测到的Larderello地区区域地表热流异常，当300 (± 100) kyr 从岩浆侵位开始。即使假设增量增长，第一次岩浆注入不应超过 1 ± 0.3 Ma。热模型的结果用于建立流变模型并模拟岩体冷却过程中脆-韧转变的漂移。然后与 Larderello 地区突出的地震反射体 K 地平线剖面进行了比较。发现 K 层与岩体顶板和脆性-韧性转变的当前位置大致对应。