Between 1992 and the mid 2010s, strong uplift has been observed centred on Uturuncu volcano in Bolivia. More recently it was shown that a smaller-amplitude moat of subsidence surrounds the uplift. We propose that this “sombrero” pattern can be the signature of elastic-plate deformation due to a buoyant fluid stored beneath it. We take the base of the “plate” to be the brittle ductile transition which, in this region, is shallow when compared with the crustal thickness. First, we show experimentally that this type of storage can produce the observed deformation pattern. Secondly, we adapt a plate deformation model and use it to invert the surface deformation published by Henderson and Pritchard (2017). A total of 1681 inversions was performed to span the wide range of physical-parameter values. We found that our model can find a source that reproduces the vertical deformation well for a large range of parameters. The viable sources mostly correspond to a thin plate (≈5 km) or a magma with high buoyancy (possibly suggesting the presence of a volatile phase in the storage zone). Interestingly, the petrologically-determined magma storage depth before the last eruption of Uturuncu (≈4±2 km) is approximately the same as the plate thickness deduced. The radial displacement is less correctly reproduced than the vertical. The, at most, 15.6 m magma layer needed to reproduce the total observed uplift since 1992 is smaller than the typical thickness for seismic detection, which can explain why it was not detected. Storage of buoyant silicic magma at a shallow brittle-ductile transition in hot continental crust may be applicable to other large silicic systems.

在1992年至2010年代中期，观察到强烈的隆升集中在玻利维亚的Uturuncu火山上。最近的研究表明，隆起周围有一个较小幅度的下沉护城河。我们建议这种“宽边帽”模式可以作为弹性板变形的标志，这是由于在其下方存储有浮力的流体。我们以“板块”的底部为脆性的韧性过渡层，与地壳厚度相比，在该区域内是较浅的。首先，我们通过实验证明这种类型的存储可以产生观察到的变形模式。其次，我们调整板变形模型并将其用于反转Henderson和Pritchard（2017）发表的表面变形。总共进行了1681次反演，以覆盖广泛的物理参数值。我们发现，我们的模型可以找到一个可在很大范围的参数下很好地再现垂直变形的源。活源主要对应于薄板（≈5km）或具有高浮力的岩浆（可能表明在存储区中存在挥发性相）。有趣的是，在最后一次喷发乌图伦库之前（约4±2 km），由岩石学确定的岩浆储藏深度与推算的板厚大致相同。径向位移比垂直位移更不正确。自1992年以来，最多可重现15.6 m的岩浆层，以重现观测到的总隆起，该厚度小于地震探测的典型厚度，这可以解释为什么未探测到该岩浆。