The Ishtar Terra highlands on Venus consist of Lakshmi Planum, an Australia-sized crustal plateau with an average elevation of ~4 km that is comparable to that of the Tibetan Plateau, surrounded by elongated mountain belts with elevations of around 10 km, taller than the Himalayas. The region is floored by thick crust that is comparable to that of cratons on Earth. On Earth, plateaus and mountain belts result from the collision of tectonic plates. However, the origin of Ishtar Terra remains enigmatic because Venus lacks Earth-like plate tectonics. Here we use three-dimensional thermo-chemo-mechanical computational simulations of Venus-like mantle convection to show how magmatism and tectonics emerge from mantle dynamics. The simulations show that a lithosphere weakened as a result of high initial hydration or high surface temperatures enhances convective thinning and decompression melting, favouring the emplacement of a thick magmatic crust on top of a deep residual depleted mantle. The stiffer residual root deflects mantle flow outwards, leading to the formation of fold belts around the buoyant lithosphere that are consequently uplifted into a plateau and preserved from further deformation. The modelled topography, crustal thicknesses and gravity is consistent with observational constraints of Ishtar Terra. Our findings suggest that plateau formation on Venus may operate similarly to craton formation on the hot early Earth, before the onset of plate tectonics.

金星上的伊什塔尔高原由拉克希米高原组成，这是一个澳大利亚大小的地壳高原，平均海拔约为 4 公里，与青藏高原相当，周围环绕着海拔约 10 公里的细长山脉带，比地球还要高。喜马拉雅山。该地区的地壳很厚，可与地球上的克拉通相媲美。在地球上，高原和山地带是由构造板块碰撞形成的。然而，伊什塔尔泰拉的起源仍然是个谜，因为金星缺乏类似地球的板块构造。在这里，我们使用类金星地幔对流的三维热化学机械计算模拟来展示岩浆作用和构造如何从地幔动力学中产生。模拟表明，由于高初始水合作用或高表面温度而削弱的岩石圈增强了对流减薄和减压熔融，有利于在深部残留的贫化地幔顶部形成厚的岩浆壳。较坚硬的残余根部使地幔流向外偏转，导致在浮力岩石圈周围形成褶皱带，从而将其抬升到高原并防止进一步变形。模拟的地形、地壳厚度和重力与伊什塔尔泰拉的观测限制一致。我们的研究结果表明，在板块构造开始之前，金星上的高原形成可能与炎热的早期地球上的克拉通形成类似。