Degassing volcanic systems, expressed by fumaroles, thermal anomalies, and hydrothermal alteration and deposition at the surface provide insights into the underlying structural architecture and the magmatic system. While the fumarole sites are easily identified and investigated, areas of diffuse degassing and associated hydrothermal alteration are barely explored. Here we investigate high-resolution optical and thermal infrared (TIR) data, acquired by unoccupied aircraft systems (UAS) at the La Fossa cone (Vulcano Island) in November 2018. The data provides insights into the structural complexity of degassing sites and associated processes at the surface. Applying the Structure from Motion (SfM) approach, we generate a photomosaic database with a 0.05 m and 0.7 m pixel resolution for the optical and infrared datasets, respectively. A Principal Component Analysis (PCA) was applied to the optical data to detect, define and extract areas of hydrothermal alteration and sulfuric deposition on a pixel base, with a feature detection threshold of up to 25 cm². By comparing optical data, PCA results and the IR data, we found a broad alteration zone dominated by diffuse degassing surrounding the main fumaroles, which with ~ 60,000 m² is ten times larger than the area covered by fumaroles and yellowish sulfuric deposits. Spectral and thermal characteristics of this alteration zone suggest a segmentation into at least 13 distinct subregions. Hydrothermal alteration and deposition were analyzed considering their pixel density and spectral signature (RGB) and show the highest pixel density in the center of the fumarole field, accompanied by a systematic color shift. The same region is characterized by a systematic change in azimuths of thermal lineaments and sulfuric clusters from the dominating trend NW-SE by ~90 degrees to NE-SW. We conjecture this to be controlled by a permeability contrast due to a subsurface structure or crater intersection, facilitating a more direct gas ascent in the center of the fumarole field. We provide a precise and complete database for the state and extent of the La Fossa fumarole field, which can be used for comparative monitoring of spatio-temporal changes within the hydrothermal system at the surface.

由喷气孔，热异常以及地表热液蚀变和沉积所表示的火山系统脱气，为洞悉潜在的构造和岩浆系统提供了见识。尽管可以轻松地识别和研究富马酚的位置，但几乎没有探索过扩散脱气和相关热液蚀变的区域。在这里，我们研究了高分辨率的光学和热红外（TIR）数据，该数据是由2018年11月在La Fossa锥体（武尔卡诺岛）的空客飞机系统（UAS）获取的。该数据提供了对脱气场所和相关过程的结构复杂性的见解在表面。应用“运动结构”（SfM）方法，我们为光学和红外数据集分别生成了像素分辨率为0.05 m和0.7 m的光镶嵌数据库。²。通过比较光学数据，PCA结果和IR数据，我们发现了一个宽的蚀变带，主要是围绕着主要的喷气孔的弥散脱气，大约有60,000 m ²比富马油和淡黄色硫矿床覆盖的面积大十倍。该蚀变带的光谱和热学特征表明至少要分成13个不同的子区域。分析了水热蚀变和沉积，考虑到它们的像素密度和光谱特征（RGB），并显示了在喷气孔中心的最高像素密度，并伴随着系统的色移。同一地区的特征是，热系和含硫团簇的方位角发生了系统性变化，从主要趋势NW-SE到NE-SW约90度变化。我们推测这是由于地下结构或火山口相交所引起的渗透率差异所控制，从而促进了在富马ole气田中心更直接的天然气上升。