Hydrothermal activity recorded in post Noachian‐aged impact craters on Mars
Hydrothermal activity recorded in post Noachian‐aged impact craters on Mars
复制标题
火星后诺亚时代撞击坑记录的热液活动
DOI：
10.1002/2015je004989
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
B. Ehlmann
中科院分区：
文献类型：
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作者：
S. Turner;J. Bridges;S. Grebby;B. Ehlmann
此前曾使用 CRISM 报道过火星上古代诺亚时代和西方时代的陨石坑存在热液系统，但亚马逊时代的撞击坑中却没有报道过。然而，nakhlite 陨石确实提供了亚马逊热液活动的证据。本研究使用亚马逊地形图内 144 个直径≥7 公里的撞击坑和 14 个较小的撞击坑（直径 3-7 公里）的 CRISM 数据来寻找可能因撞击引起的热液蚀变而形成的矿物，或显示古代蚀变地壳的挖掘。在 3-7 公里的撞击坑中没有发现任何证据表明存在水合矿物。在三个复杂的撞击坑中发现了水合矿物，这些撞击坑位于北纬 52.42°、东经 39.86° 的伊斯美尼乌斯·拉克斯四边形、北纬 8.93°、东经 141.28° 的极乐世界以及先前研究的斯托克斯陨石坑内。这三个陨石坑的直径分别为20公里、62公里和51公里。水合矿物露头的位置及其相关形态表明，这三个撞击坑中的两个——未命名的伊斯梅尼乌斯·拉库斯撞击坑和斯托克斯撞击坑——可能存在撞击诱发的热液系统，因为它们的中央隆起处含有蚀变组合，而这些蚀变组合在喷射物中并不明显。在 Ismenius Lacus 陨石坑中央隆起和边缘的冲积扇内发现了绿泥石和铁蛇纹石，而斯托克斯陨石坑则含有大量铁/镁/铝页硅酸盐。然而，不能排除挖掘起源。我们的工作表明，撞击引起的热液作用在亚马逊地区很少见，并且/或撞击引起的热液蚀变对于 CRISM 的检测来说不够普遍或空间广泛。
Hydrothermal systems have previously been reported in ancient Noachian and Hesperian‐aged craters on Mars using CRISM but not in Amazonian‐aged impact craters. However, the nakhlite meteorites do provide evidence of Amazonian hydrothermal activity. This study uses CRISM data of 144 impact craters of ≥7 km diameter and 14 smaller craters (3–7 km diameter) within terrain mapped as Amazonian to search for minerals that may have formed as a result of impact‐induced hydrothermal alteration or show excavation of ancient altered crust. No evidence indicating the presence of hydrated minerals was found in the 3–7 km impact craters. Hydrated minerals were identified in three complex impact craters, located at 52.42°N, 39.86°E in the Ismenius Lacus quadrangle, at 8.93°N, 141.28°E in Elysium, and within the previously studied Stokes crater. These three craters have diameters 20 km, 62 km, and 51 km. The locations of the hydrated mineral outcrops and their associated morphology indicate that two of these three impact craters—the unnamed Ismenius Lacus Crater and Stokes Crater—possibly hosted impact‐induced hydrothermal systems, as they contain alteration assemblages on their central uplifts that are not apparent in their ejecta. Chlorite and Fe serpentine are identified within alluvial fans in the central uplift and rim of the Ismenius Lacus crater, whereas Stokes crater contains a host of Fe/Mg/Al phyllosilicates. However, excavation origin cannot be precluded. Our work suggests that impact‐induced hydrothermalism was rare in the Amazonian and/or that impact‐induced hydrothermal alteration was not sufficiently pervasive or spatially widespread for detection by CRISM.