The Eastern Galicia Magnetic Anomaly is the best studied anomaly of the Central Iberian Arc. This is due to its location, on the Lugo‐Sanabria gneiss dome, and to the fact that its source rocks crop out in the Xistral Tectonic Window. Multiple studies of this anomaly have been carried out, but still, new results keep on shedding light on its understanding. This paper presents the first results on rock magnetic analyses, natural remanent magnetization, anisotropy of the magnetic susceptibility, X‐ray diffraction, and stable isotopes geochemistry carried out on the source rocks of this anomaly. Results suggest that magnetization responds to the increase in oxygen fugacity underwent by rocks affected by late Variscan (330‐300 Ma) extensional tectonics. Extensional detachments were the pathways that allowed the entrance of fluids that led to syntectonic crystallization of magnetite and hematite in metasediments and inhomogeneous S‐Type granitoids derived from their partial melting. Accordingly, magnetization is not linked to lithologies, but to extensional structures developed in the late Carboniferous/earliest Permian, during the Kiaman reverse superchron. Systematic reverse magnetic remanence exhibited by hematite‐bearing samples confirms the age of the magnetization and adds complexity to the interpretation of the anomaly. Understanding the EGMA contributes to the interpretation of other anomalies existing in the CIA, also located on thermal domes. The observed extension‐related magnetization probably affected most of the NW Iberian Massif, thus hindering the study of previous tectonics by paleomagnetic techniques. This work aims to provide new hints to interpret magnetic anomalies located in extensional tectonic contexts worldwide.

中文翻译：

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表征东部加利西亚磁异常的源头（西班牙西北部）：扩展在伊比利亚中部弧线磁化成因中的作用

东部加利西亚磁异常是伊比利亚中部弧线研究得最好的异常。这是由于其位于卢戈-萨纳布里亚片麻岩穹顶上的位置，以及其源岩在西斯特拉尔构造窗口中切出的事实。已经对该异常进行了多次研究，但仍然有新的结果使人们对它的理解更加清晰。本文介绍了在该异常源岩上进行的岩石磁性分析，自然剩余磁化强度，磁化率各向异性，X射线衍射以及稳定同位素地球化学的第一批结果。结果表明，磁化响应了受晚期瓦里斯坎（330-300 Ma）伸展构造影响的岩石所经历的氧逸度的增加。伸展性脱离是允许流体进入的通道，这些通道导致磁铁矿和赤铁矿在部分沉积和部分熔融的非均质S型花岗岩中的共晶结晶。因此，磁化强度与岩性无关，而与起亚曼反向超同步期间石炭纪/最早的二叠纪发育的伸展构造有关。赤铁矿样品表现出的系统性反向剩磁证实了磁化的年龄，并增加了异常解释的复杂性。了解EGMA有助于解释CIA中也存在于热穹顶上的其他异常。观察到的与伸展有关的磁化强度可能影响了西北伊比利亚大部分地块，因此阻碍了古地磁技术对先前构造的研究。这项工作旨在提供新的提示，以解释位于全球伸展构造背景下的磁异常。