Stratigraphy of the Caloris basin, Mercury: Implications for volcanic history and basin impact melt
Stratigraphy of the Caloris basin, Mercury: Implications for volcanic history and basin impact melt
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DOI：
10.1016/j.icarus.2014.11.003
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发表时间：
2015-04-01
期刊：
影响因子：
3.2
通讯作者：
Watters, Thomas R.
中科院分区：
文献类型：
--
作者：
Ernst, Carolyn M.;Denevi, Brett W.;Watters, Thomas R.
卡洛里斯盆地是水星最年轻的大型撞击盆地，由火山平原填满，这些平原在光谱上与周围的物质截然不同。后平原的撞击坑分布在盆地内部，大小不一的陨石坑分布在盆地内部，他们挖掘的物质的光谱使人们能够估计火山填充物的厚度，并揭示地下表面的性质。内陆火山平原的厚度始终至少为2.5公里，有些地方达到3.5公里，向盆地边缘的填充物较薄。在长波长地形或方位角下，没有观察到填充厚度的系统变化。平原厚度与盆地内大水平尺度上的海拔变化之间缺乏相关性，这表明平原的侵位肯定早于影响盆地的长波地形变化的大部分，如果不是全部的话。在加洛里斯内陆平原上，没有直径大于10公里的凹陷或明确掩埋的(幽灵)陨石坑。这种幽灵陨石坑的存在表明，下列情景中的一种或多种必须成立：平原足够厚，足以掩埋在卡洛里斯撞击事件和平原侵位之间形成的所有陨石坑的证据；平原是在盆地形成后不久侵位的；或者盆地内部复杂的构造变形掩盖了埋藏的陨石坑所定位的褶皱脊环。穿透地表火山平原的每一次撞击都会暴露出这种低反射材料(LRM)，这为探索近地表地层学提供了一种手段。如果LRM的所有产状都来自同一层，则地下LRM矿床至少有7.5-8.5公里厚，其顶部可能曾经构成卡洛里斯盆地的底部。卡洛里斯形成的撞击将产生一层3-15公里厚的撞击熔体；这样的一层可以解释LRM的整个厚度。这种物质可能来自下地壳和上地幔的组合。(C)2014 Elsevier Inc.保留所有权利。
Caloris basin, Mercury's youngest large impact basin, is filled by volcanic plains that are spectrally distinct from surrounding material. Post-plains impact craters of a variety of sizes populate the basin interior, and the spectra of the material they have excavated enable the thickness of the volcanic fill to be estimated and reveal the nature of the subsurface. The thickness of the interior volcanic plains is consistently at least 2.5 km, reaching 3.5 km in places, with thinner fill toward the edge of the basin. No systematic variations in fill thickness are observed with long-wavelength topography or azimuth. The lack of correlation between plains thickness and variations in elevation at large horizontal scales within the basin indicates that plains emplacement must have predated most, if not all, of the changes in long-wavelength topography that affected the basin. There are no embayed or unambiguously buried (ghost) craters with diameters greater than 10 km in the Caloris interior plains. The absence of such ghost craters indicates that one or more of the following scenarios must hold: the plains are sufficiently thick to have buried all evidence of craters that formed between the Caloris impact event and the emplacement of the plains; the plains were emplaced soon after basin formation; or the complex tectonic deformation of the basin interior has disguised wrinkle-ridge rings localized by buried craters. That low-reflectance material (LRM) was exposed by every impact that penetrated through the surface volcanic plains provides a means to explore near-surface stratigraphy. If all occurrences of LRM are derived from a single layer, the subsurface LRM deposit is at least 7.5-8.5 km thick and its top likely once made up the Caloris basin floor. The Caloris-forming impact would have generated a layer of impact melt 3-15 km thick; such a layer could account for the entire thickness of LRM. This material would have been derived from a combination of lower crust and upper mantle. (C) 2014 Elsevier Inc. All rights reserved.