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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Geology and tectonics of the southwestern boundary of the unstable sector of Mt. Etna (Italy)
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Geology and tectonics of the southwestern boundary of the unstable sector of Mt. Etna (Italy)

机译：山不稳定区西南边界的地质与构造。埃特纳火山（意大利）

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The Etna volcano is known to be unstable and gradually moving downslope toward east and south. The study of the local geology and structure of these unstable flanks and of their boundaries is important to understand the evolution of the flank instability and the stress field driving the spreading of the edifice. In this paper we present the geological evolution of the lower south-western sector of Mount Etna base on a detailed field survey at 1:10,000 scale. This area located at the boundary of the unstable south-eastern flank of the volcano is affected by the active Ragalna Fault and by distinctive eruptive fissures (Monte Calvario formation, 18-15 ka). The Monte Calvario formation is made of viscous lavas often associated to breccia and autoclastic lava facies fed by a set of eruptive fissures NE-SW oriented. Their emplacement occurred immediately before the Ellitico caldera collapse, marking a previously poorly constrained shift in the feeding system of the volcano. The orientation of these eruptive fissures and lineaments, and the geometry of the sedimentary substratum modeled from subsurface data, indicate that the area was dominated by a local stress field consistent with the lateral spreading of Mount Etna since at least from the final Ellirtico phase (about 18 ka) with a nearly constant mean displacement rate. These data give new insights into the geology and structure of the flank instability at Etna. The main geologic hazard of the studied area is not related to the opening of a new eruptive fissures, but it is posed by the presence into II Calvario quarry of fluoro-edenite, an asbestiform mineral that caused an high mortality rate for respiratory system cancer in Biancavilla town. In fact the Monte Calvario formation groups other eruptive fissures with similar volcanological and geochemical characteristics, where hydrothermal alteration occurred with the likely formation of health-threatening minerals.
机译：埃特纳火山（Etna）火山是不稳定的，并逐渐向东和南下倾斜。这些不稳定侧面的局部地质和结构及其边界的研究对于了解侧面不稳定性的演变以及驱动建筑物扩展的应力场非常重要。在本文中，我们以1：10,000比例的详细实地调查为基础，介绍了埃特纳火山西南下部的地质演化。该区域位于火山不稳定东南翼的边界，受活跃的拉格纳断裂和独特的喷发裂隙（蒙特卡尔瓦里奥组，18-15 ka）影响。 Monte Calvario地层是由粘性熔岩构成的，这些熔岩通常与角砾岩和自碎熔岩相有关，这些熔岩相是由一组NE-SW定向的喷发性裂缝提供的。他们的进驻发生在Ellitico破火山口倒塌之前，这标志着火山的进料系统此前受限制的移位。这些喷发裂缝和构造的方向以及根据地下数据建模的沉积基底的几何形状表明，该区域由局部应力场控制，该应力场至少从埃利特里科期末开始就与埃特纳火山的侧向扩展相一致（大约18 ka），平均位移率几乎恒定。这些数据为埃特纳火山侧翼不稳定的地质和结构提供了新的见解。研究区域的主要地质灾害与新的火山爆发的发生无关，但它是由氟钙辉石（一种石棉状矿物）存在于卡尔瓦里奥二世采石场造成的，氟石辉石导致了呼吸系统癌症的高死亡率。比安卡维拉镇。实际上，蒙特卡尔瓦里奥地层将其他火山喷发裂缝与火山岩和地球化学特征相似，其中发生了热液蚀变，可能形成威胁健康的矿物。

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