Abstract Geophysical methods of analysis were applied, in order to investigate the deep structure and the geothermal potential of the Methana Volcano (NE Peloponnesus, Greece). The study is based on a re-evaluation and reinterpretation of legacy magnetotelluric (MT) data with modern analysis methods, as well as 3-D inversion of aeromagnetic data constrained by in situ measurements of magnetic susceptibility. Magmatic systems are located in regions of active tectonic processes that often play a controlling role. The MT method is effective in delineating low resistivity functional elements of volcanic systems, such as magma chambers, vents, thermal fluid reservoirs and thermal fluid circulation conduits, the latter two of which are typically associated with active faults. The aeromagnetic data can assist in mapping the configuration, hence emplacement modes of volcanic rocks at depth. Accordingly, the joint interpretation of these lines of evidence, together with structural and geochemical information, is expected to allow insight into the influence of contemporary tectonics on the inception and evolution of the volcano. The contemporary stress field is mainly extensional, NNE-SSW oriented and overall homogeneous; in the area of Methana it allows for the formation of WNW-ESE north-easterly dipping normal faults, W-E faults consistent with the synthetic (dextral) R-shear direction of Riedel's shear theory and NW-SE faults consistent with the antithetic (sinistral) R′-shear direction; all such features have been mapped on Methana Peninsula. The magnetotelluric data imaged a significant geothermal reservoir developing around an intersection of the three active fault zones (normal, R and R′) at depths of 1–1.5 km below the centre of the peninsula, as well as elongate epiphenomenal conductivity anomalies associated with the circulation of thermal fluids along all three fault zones. The 3-D magnetic susceptibility model strongly suggests that the intrusion and emplacement of magmas were guided by the same active fault zones, with particular reference to the R and R′ shears whose influence is imprinted on the configuration of volcanic rocks at depth. The joint interpretation of all lines of evidence indicates that magmatism and volcanism at Methana are almost completely controlled by tectonic activity in a manner analogous to the situation of the large Santorini Volcanic Complex. It also indicates that the reservoir is replenished through the weak permeable zone created by the intersection of the R and R′ shears, which is very probably collocated with the main vent of intrusive magmatic activity and may connect with a shallow magma chamber at depths greater than 4.5 km. The apparently common origin and similarities/differences in the circulation paths of thermal fluids may amply explain both the individual characteristics and similarities/differences in the chemical composition of thermal spring discharges, which have been reported by hitherto geochemical investigations.

中文翻译：

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Methana 火山——希腊地热资源及其与区域构造的关系

摘要 应用地球物理分析方法来研究 Methana 火山（希腊伯罗奔尼撒半岛东北部）的深层结构和地热潜力。该研究基于使用现代分析方法重新评估和重新解释传统大地电磁 (MT) 数据，以及受原位磁化率测量限制的航磁数据的 3-D 反演。岩浆系统位于经常起控制作用的活动构造过程区域。MT 方法在描绘火山系统的低电阻率功能要素方面是有效的，例如岩浆房、喷口、热流体储层和热流体循环管道，后两者通常与活动断层有关。航磁数据可以帮助映射配置，因此火山岩在深处的侵位模式。因此，对这些证据线的联合解释，连同结构和地球化学信息，有望让人们深入了解当代构造对火山的形成和演化的影响。当代应力场以张性为主，NNE-SSW 取向，整体均质；在 Methana 地区，它允许形成 WNW-ESE 向东北倾斜的正断层，WE 断层与 Riedel 剪切理论的合成（右向）R 剪切方向一致，而 NW-SE 断层与对立（左旋）一致R′-剪切方向；所有这些特征都已绘制在 Methana 半岛上。大地电磁数据对在半岛中心以下 1-1.5 公里深度的三个活动断层带（正常断层带（正常断层带、R 断层带和 R'）的交叉点周围发育的一个重要地热储层进行了成像，以及与沿所有三个断层带的热流体循环。3-D 磁化率模型强烈表明岩浆的侵入和侵位是由相同的活动断层带引导的，特别是参考 R 和 R' 剪切，它们对深部火山岩的构造有影响。对所有证据的联合解释表明，Methana 的岩浆活动和火山活动几乎完全受构造活动的控制，其方式类似于大型圣托里尼火山复合体的情况。这也表明储层通过 R 和 R' 剪切带相交形成的弱渗透带进行补给，该带很可能与侵入岩浆活动的主喷口并置，并可能与深度大于4.5 公里。热流体循环路径的明显共同起源和相似/差异可以充分解释迄今为止地球化学调查报告的温泉排放化学成分的个体特征和相似/差异。它很可能与侵入岩浆活动的主喷口并置，并可能与深度大于 4.5 公里的浅岩浆房相连。热流体循环路径的明显共同起源和相似/差异可以充分解释迄今为止地球化学调查报告的温泉排放化学成分的个体特征和相似/差异。它很可能与侵入岩浆活动的主喷口并置，并可能与深度大于 4.5 公里的浅岩浆房相连。热流体循环路径的明显共同起源和相似/差异可以充分解释迄今为止地球化学调查报告的温泉排放化学成分的个体特征和相似/差异。