Phreatomagmatic explosive origin of Hrad Vallis, Mars
Phreatomagmatic explosive origin of Hrad Vallis, Mars
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火星赫拉德山谷的热岩浆爆炸起源
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
P. Mouginis
中科院分区：
文献类型：
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作者：
L. Wilson;P. Mouginis
[1]赫拉德谷（英语：Hrad Vallis）是一个深约370米，长约800公里的凹陷，位于火星极乐平原，北纬34°，西经218°。一个独特的存款，存在于Hrad Vallis源区的两侧，沿凹陷走向的最大宽度为沿着70 km，下部单元延伸到凹陷两侧近100 km处，上部单元延伸到约50 km处。维京海盗号和火星轨道器照相机（MOC）的图像显示了叶状存款边界，流变变形，以及存款内直径270-580米的许多陨石坑。该存款与宽约30 km、高约100-150 m的宽阔地形隆起相吻合，该隆起沿沿着走向沿着河谷两侧延伸至少100 km。我们建议，这些功能形成时，一个堤防下的山谷的轴产生了浅的窗台，这反过来又是部分负责的上升地形。隆起的其余部分由一个泥浆状的喷出物存款组成，这些喷出物来自一次大规模的蒸汽岩浆爆炸，这是由于岩床的中心部分与地壳上部几百米处的富冰岩层之间在燃料-冷却剂型相互作用中发生了剧烈的机械和热混合。观测到的喷出物的范围和厚度以及赫拉德凹陷的深度意味着爆炸蒸汽压力高达360 MPa，喷出物的速度为400 m s-1，并且在原始表面以下350-400 m的深度侵入了至少150 m厚的岩床。
[1] Hrad Vallis is a ∼370 m deep, ∼800 km long depression located at 34°N, 218°W, in Elysium Planitia, Mars. A distinctive deposit, present on both sides of the source area of Hrad Vallis, has a maximum width of ∼70 km along the strike of the depression, a lower unit extends for nearly 100 km away from the depression on either side, and an upper unit extends for ∼50 km. Viking and Mars Orbiter Camera (MOC) images show lobate deposit boundaries, rheomorphic deformation, and numerous craters 270–580 m in diameter within the deposit. The deposit coincides with a broad topographic rise ∼30 km wide and ∼100–150 m high extending along the sides of the valley for at least 100 km along strike. We propose that these features formed when a dike underlying the axis of the valley generated a shallow sill, which in turn is partly responsible for the rise topography. The remainder of the rise consists of a mud-like deposit of ejecta from a large-scale phreatomagmatic explosion due to violent mechanical and thermal mixing between the central part of the sill and ice-rich rock layers in the upper few hundred meters of the crust in a fuel-coolant-type interaction. The observed range and thickness of ejecta and the depth of the Hrad depression imply explosion steam pressures up to 360 MPa, ejecta speeds of ∼400 m s−1, and a sill at least 150 m thick intruded at a depth of ∼350–400 m below the original surface.