ChemCam results from the Shaler outcrop in Gale crater, Mars
ChemCam results from the Shaler outcrop in Gale crater, Mars
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DOI：
10.1016/j.icarus.2014.07.025
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发表时间：
2015-03-15
期刊：
影响因子：
3.2
通讯作者：
Vaniman, D.
中科院分区：
文献类型：
--
作者：
Anderson, Ryan;Bridges, J. C.;Vaniman, D.
在河流沉积露头“Shaler”进行的 ChemCam 活动对 28 个非土壤目标进行了观测，其中 26 个包括主动激光诱导击穿光谱 (LIBS)，所有这些都包括远程显微成像仪 (RMI) 图像。根据增益大小、纹理、颜色、抗侵蚀性和沉积结构，页岩露头可分为七相。 ChemCam 观测涵盖相 3 至相 7。对于所有目标，大多数颗粒都低于 RMI 分辨率的极限，但许多目标的部分可分辨颗粒比 0.5 毫米更粗。 Shaler 相在 LIBS 光谱和成分中从点到点显示出显着的分散性，但几个关键的成分趋势是明显的，最显着的是观察到的相的平均 K2O 含量。相 3 的 K2O 含量低于其他相，其成分与“蛇”（黄刀湾地层剖面中出现的碎屑岩脉）相似。相对于其他岩相，相 7 富含 1(20)，并显示出与 Yellowknife 湾附近浮岩的一些成分和结构相似性。其余相（4、5 和 6）的成分与 Sheepbed 和 Gillespie Lake 成员相似，尽管 Shaler 岩相的 K2O 和 FeOT 略有升高。Shaler 内的几个分析点表明存在长石，尽管这些点具有过量的 FeOT，表明存在 Fe 氧化物大多数 LIBS 分析的成分表明它们是辉石和长石的混合物，Shaler 长石成分比典型的辉石长石碱性更强，表明碱性玄武岩源区，特别是对于富含 K2O 的相 7。除了可能的氧化铁胶结物外，几乎没有证据表明 Shaler 存在化学蚀变，尽管硫酸钙矿脉与地层剖面中观察到的硫酸钙矿脉相当。沙勒的不同成分和推测的来源表明盖尔陨石坑边缘和周围的成分不均匀，以及间歇性的沉积期。
The ChemCam campaign at the fluvial sedimentary outcrop "Shaler" resulted in observations of 28 non-soil targets, 26 of which included active laser induced breakdown spectroscopy (LIBS), and all of which included Remote Micro-Imager (RMI) images. The Shaler outcrop can be divided into seven facies based on gain size, texture, color, resistance to erosion, and sedimentary structures. The ChemCam observations cover Facies 3 through 7. For all targets, the majority of the grains were below the limit of the RMI resolution, but many targets had a portion of resolvable grains coarser than similar to 0.5 mm. The Shaler facies show significant scatter in LIBS spectra and compositions from point to point, but several key compositional trends are apparent, most notably in the average K2O content of the observed facies. Facies 3 is lower in K2O than the other facies and is similar in composition to the "snake," a clastic dike that occurs lower in the Yellowknife Bay stratigraphic section. Facies 7 is enriched in 1(20 relative to the other fades and shows some compositional and textural similarities to float rocks near Yellowknife Bay. The remaining facies (4, 5, and 6) are similar in composition to the Sheepbed and Gillespie Lake members, although the Shaler fades have slightly elevated K2O and FeOT. Several analysis points within Shaler suggest the presence of feldspars, though these points have excess FeOT which suggests the presence of Fe oxide cement or inclusions. The majority of LIBS analyses have compositions which indicate that they are mixtures of pyroxene and feldspar. The Shaler feldspathic compositions are more alkaline than typical feldspars from shergottites, suggesting an alkaline basaltic source region, particularly for the K2O enriched Facies 7. Apart from possible iron-oxide cement, there is little evidence for chemical alteration at Shaler, although calcium-sulfate veins comparable to those observed lower in the stratigraphic section are present. The differing compositions, and inferred provenances at Shaler, suggest compositionally heterogeneous terrain in the Gale crater rim and surroundings, and intermittent periods of deposition. Published by Elsevier Inc.