【作者】 黄俊；

【导师】 肖龙； Philip Russel Christensen；

【作者基本信息】 中国地质大学 ， 行星地质与比较行星学， 2013， 博士

【摘要】 火星在人类太阳系探测活动中具有独特的地位,可以通过对其进行较为快速和系统的探测来回答许多重要的行星科学问题。火星探测的主要科学目标是认识行星的地质演化,了解构造和气候的相互作用,以及揭示适合生命生存的环境。国际上已经进行了41次火星探测任务：从1965年开始的飞越探测,到随后四十多年的环绕探测,着陆器探测以及表面巡游车探测。这些系统的探测任务为我们揭示了这颗红色星球的许多重要特征,包括全球的地形,地质构造和火山作用,表面矿物和元素成分,近地表水的分布,固有的剩磁磁场,重力场和地壳结构,以及大气成分和其随时间变化的状态。我国对火星地质和比较行星学的研究起步晚、基础薄弱。但是,随着我国综合国力的不断增强,国家已经制定了中长期的深空探测计划,将不断打造“中华牌”的深空探测工程。嫦娥探月工程、空间站工程,以及规划中的自主火星及其它太阳系天体的探测,都将在未来5-10年陆续展开。行星科学学科建设也在不断得到重视。因此,利用现有探测数据,进行火星的表面的形貌学、年代学、矿物学和火山学研究,不仅是重要的国际前沿课题,同时也将为我国的火星探测提供必要的知识支撑,符合国家战略要求,并具有重要的科学意义。太阳系类地行星都经历了类似的形成和早期演化过程(30亿年以前),但后期的地质演化过程差异明显,导致了四个类地行星的表面形貌、成分和内部结构存在巨大的差异。例如,地球地质构造活动频繁,表面平均年龄约为1亿年,导致了保存的早期(早于25亿年的太古宙和冥古宙)火山岩浆记录极少。而火星表面分布有大量的火山形迹(火山群和熔岩平原),是太阳系类地行星中火山活动特征最为明显和保存早期火山形迹特征最完好的行星。这些古老火山形迹的形貌、成分和后期改造特征,是揭示火星早期热演化和后期地质过程的最好的研究对象,也是研究太阳系行星火山作用和比较行星火山学最为理想的天体,对于了解和认识地球早期的火山岩浆活动,研究地球与近地星体的异同和相互关系,开展比较行星学研究具有重要意义。因此,对于火星表面古老火山作用的研究具有极其重要的意义。本论文首先简要介绍了火星表面的火山作用形迹,总结了研究进展,并提出了尚未解决的问题；然后展示了新开发的利用热红外多光谱数据对于火星表面成分的半定量分析的方法；详细阐述了对新发现的火星南部高原古老火山的形貌学和年代学的研究,揭示了它们在火星热演化历史上的重要意义；报告了在萨梅斯亚(Thaumasia)平原新发现的岩墙,并对叙利亚-萨梅斯亚地块(STB:Syria-Thaumasia Block)中的熔岩平原的表面成分和热物理性质进行了研究,探讨了萨西斯高原的隆升以及水手大峡谷的形成对于该区熔岩平原形成机制的影响。本论文的基本内容包括以下几个方面：1.热红外多光谱数据对于火星表面成分的半定量分析的方法研究。在过去的几十年里面,人们利用红外光谱仪器研究火星表面的成分和物理性质。利用TES(Thermal Emission Spectrometer)获得的数据,前人建立了多个火星全球的定量化数据(包括反照率,矿物成分和热惯量)。随着新的热红外(如THEMIS, Thermal Emission Imaging System)和可见光/近红外(如OMEGA, Observatoire pour la Mineralogie, l’Eau, les Glaces et l’Activite和CRISM, Compact Reconnaissance Imaging Spectrometer for Mars)科学载荷获得更多新的数据,我们对于火星表面的成分,岩石热物理性质和古环境特征都有新的认识。可见光/近红外仪器虽然具有较高的空间分辨率,并且对含水矿物的探测的灵敏度比较高的,但是通常无法得到全部造岩矿物的含量(如长石和石英)。热红外仪器通常具有较低的空间分辨率,然而热红外发射光谱的吸收特征的深度是直接和观测视域中各种矿物的含量成正比的。利用热红外发射光谱的线性解谱可以定量获得结晶的火成岩的矿物成分(准确度为5-15%),而传统岩相学分析的准确度也在5-10%,因此热红外测谱学能够适用于矿物含量的定量分析。本文报道了新开发的热红外多光谱解谱方法——最小剩余循环光谱混合分析(LRISMA:Least Residual Iterative Spectral Mixture Analysis)。该方法能够根据先验知识,半定量的获得主要造岩矿物的含量：对于长石,辉石,橄榄石,高硅相和石英的精确度可以达到4-16%,准确度可以达到5-20%。本方法可以应用于高质量的THEMIS数据(较高表面温度,较低的大气水汽含量和灰尘含量)得到小尺度地质单元的主要造岩矿物的含量,从而更好的研究区域地质演化。2.南部高原古老火山的形貌学和年代学的研究火山作用在所有类地行星层圈结构的形成和演化中都起了重要的作用。前人对火星上的火山做了大量的研究,普遍认为它们的火山作用始于诺亚纪(>3.7Ga),一直持续到晚亚马逊纪(<0.1Ga)。但是古老火山作用的形式,它们和最早期火山建造以及与整个火星热演化的联系尚不清楚。本文展示了许多分布在南部高原的早诺亚纪(>4.0Ga)的火山。在空间分布上它们大多毗邻萨西斯(Tharsis)火山省和环海拉斯(Hellas)火山省。相比以前的研究结论,本文认为这两个火山省的火山作用时间跨度更长,强度更大。这些火山建造的表面大都被放射状的河谷所切割,是早期流水侵蚀的痕迹,而这些侵蚀作用在西方纪熔岩平原形成的时候已经停止,证明火星早期曾经潮湿温暖。3.火星表面岩石热物理性质及岩墙(群)研究萨西斯隆起是火星表面最显著的火山省,确定其岩浆成分对于研究火星的岩浆和热的演化非常重要。由于其表面大部分的区域覆盖了较厚的灰尘,以往岩浆的成分确定主要是利用火山形貌数据反演获得的。叙利亚-萨梅斯亚地块是一个和萨西斯隆起紧密联系的复杂的构造-火山区域。其中的熔岩平原具有不同的表面模式年龄,研究这些熔岩平原的岩浆成分为我们提供了研究萨西斯隆起前后岩浆成分是否变化的机会。本文利用TES数据研究了叙利亚-萨梅斯亚地块中的熔岩平原的表面岩石的热物理性质和成分；利用THEMIS红外图像,CTX (Context Camera)图像和HiRISE (High Resolution Imaging Science Experiment)图像展示了新发现的长距离熔岩渠道和熔岩管道。这些火山构造为广泛分布的岩浆的长距离运输提供了通道。皱脊的分布指示了诺亚纪-西方纪皱脊平原物质单元(HNr)和西方纪皱脊平原物质单元(Hr)的岩浆喷发时间早于萨西斯隆起,而西方纪下部熔岩流物质单元(Hsl)和西方纪上部熔岩流物质单元(Hsu)的岩浆喷发晚于该隆起。本文通过光谱数据的分析,发现这四个熔岩平原的成分有一定的变化,并且表面热物理性质指示这些变化是来自于原位的成分差异,受风成堆积物的影响很小。据此,我们认为萨西斯隆起前后,构成熔岩平原的岩浆成分发生了变化。这个结果表明了萨西斯地幔柱对于广泛发育的熔岩平原的岩浆成分和演化机制产生的复杂影响,对于了解早期火山作用具有重要的意义。尽管火星是一个强烈火山作用并且火山形貌得到了很好保存的行星,但是由于缺少构造抬升和较低的剥蚀速率,岩墙很少在表面暴露(而地球上主要是通过这两种方式暴露次表层的岩墙)。火星表面连续的凹陷,较窄的地堑,线性或拉长的槽型凹陷以及磁场的异常可以用来推测岩墙的存在。近年来随着探测数据的增多以及分辨率的提高,前人报道了一些直接观测到的可能的侵蚀暴露的岩墙,有些成分还比较独特。本文报道了利用图像和光谱数据在萨梅斯亚平原(Thaumasia Planum)新发现的岩墙。岩墙分布的区域发育了大量的蜿蜒的皱脊,这些区域在前人的地质填图的结果中显示为较老的具有皱脊的平原物质,其年龄在晚诺亚纪到早西方纪。这些岩墙相对与周围的物质具有独特的热物理性质和成分特征。对于它们的空间分布和成分特征以及和周围地质单元的地层关系,为萨西斯隆起和水手大峡谷的打开提供了限制条件。总之,本论文的研究成果可以加深我们对于火星古老火山作用(包括火山作用形迹的形貌,成分,表面热物理性质,岩浆侵位机制和成分演化)的认识,为各种地球物理模型和数值模拟模型提供了切实的地质观测证据,对了解太阳系类地行星的早期火山作用的特征和比较行星学研究具有重要的意义。更多还原

【Abstract】 Mars has a unique position in solar system exploration:many important planetary scientific questions can be answered by systematic and relatively short-period exploration. The main scientific objectives of the Mars exploration are to decipher the geological evolution of the planet, to understand the interaction of tectonics and climate, and to search for a habitable environment for life.41Mars exploration missions have been carried out:the first spacecraft flew by the red planet in1965, followed by orbiters, landers, and rovers on the surface. These systematic exploration missions have shown us many important characteristics of Mars, including the global topography, geological tectonic and process, mineralogical and elemental composition of the surface, distribution of near-surface water, remnant magnetic field, gravity field and crustal structure, and time-varying atmospheric composition. The study of martian geology and comparative planetary geology started late in China, and the foundation is weak. However, with the constant enhancement of China’s national strength, the country has developed a medium-and long-term deep space exploration plan that will continue to carry out a series of deep space exploration projects. With the success of the Chang’E lunar missions and the space station project, independent missions to Mars and other celestial bodies in the solar system will be launched in the next5-10years. Meanwhile, the construction of planetary science programs also continues to receive attention. Therefore, using the existing data to study the morphology, topography, chronology, mineralogy, and volcanology of Mars is not only a forefront research topic, but it also provides a necessary knowledge basis for China’s future exploration of Mars. It is in line with national strategic requirements and of scientific significance.Terrestrial planets have experienced similar formation and early evolution history (>3Ga), but their subsequent geological evolution differed greatly and resulted in variations of the surface morphology, composition, and internal structure. For example, the Earth’s tectonics have been so active that the average surface age is about100Ma, and the early (>2.5Ga in Archean and Proterozoic) volcanic magma records rarely survive. Mars has a large amount of volcanic features (volcanoes and lava plains), and it is the planet with both the best-preserved ancient volcanic features and the most prominent volcanic processes. It is very important to study the geomorphology, composition, and modification of these volcanic features to reveal the early thermal evolution and subsequent geologic processes. In addition, it is important to understand the relationship between terrestrial planets and comparative planetary studies.In this paper, we summarized the volcanic features on the surface of Mars, reported a new method and its application for the semi-quantitative determination of major rock-forming minerals, presented the morphology and chronology of newly identified ancient volcanoes on the southern highlands, showed a newly discovered dike in Thaumasia planum, and revealed the surface composition and thermophysical properties of lava plains in Syria-Thaumasia Block.We have developed a new method (LRISMA:Least Residual Iterative Spectral Mixture Analysis) to semi-quantitatively determine major rock forming minerals (feldspar, pyroxene, olivine, high-silica phases and quartz) with multispectral data. Sub-libraries of minerals, generated from a master library of minerals based on prior knowledge, are used to produce every possible mineral end-member combination to fit the target spectra. Mineral abundances that correspond to the least root-mean-square (RMS) errors (best fit) generally agree best with previous petrographic and hyperspectral studies, given the greatly reduced spectral range and resolution. The accuracy and reproducibility of LRISMA is～4-16%and～5-20%respectively, while the accuracy of petrographic and previous hyperspectral studies is～5-15%. LRISMA can be applied to semi-quantitatively characterize the bulk surface mineralogy of small-scale geologic features with high quality Thermal Emission Imaging System (THEMIS) spectral data (high surface temperature, low atmospheric opacity) with the ultimate goal of better understanding regional geologic processes.Volcanism plays an important role in the formation and thermal evolution of the crusts of all terrestrial planets. Martian volcanoes have been extensively studied, and it has been suggested that the volcanism on Mars that created the visible volcanic features was initiated in the Noachian (>3.7Ga) and continued to the Late Amazonian (<0.1Ga). However, styles of ancient volcanism, their links with the earliest volcanic constructions, and the thermal evolution of the planet are still not well understood. Here we show that numerous Early Noachian (>4.0Ga) volcanoes are preserved in the heavily cratered southern highlands. Most of these are central volcanoes with diameters ranging from50to100km and heights of2-3km. Most of them are spatially adjacent to and temporally continuous with the Tharsis and circum-Hellas volcanic provinces, suggesting that these two volcanic provinces have experienced more extensive and longer duration volcanism than previously thought. These edifices are heavily cut by radial channels, suggesting that an early phase of aqueous erosion initiated and ended prior to the emplacement of the encircling Hesperian lava fields.Tharsis is the most prominent volcanic province on Mars, yet the composition of its lava flows and the relationship of composition to the development of Tharsis are poorly known. Most of Tharsis is covered with air-fall dust, which inhibits spectroscopic determination of lava mineralogy. The Syria-Thaumasia block (STB) is a complex tectono-volcanic province closely related to the Tharsis bulge. The lava plains of STB have different emplacement ages, which provide an opportunity to examine whether magma composition changed with the evolution of Tharsis. In this study, we assessed the lava plains using Thermal Emission Spectrometer (TES) data. Using derived physical properties, we targeted dust-free regions from four different-aged surfaces. We determined the mineralogical composition by modeling the average TES surface spectrum from each of the four surfaces. All units have similar mineralogy, but the younger two units have more high-SiO2phases. We also identified long distance lava channels/tubes in this region for the first time using data of the THEMIS instrument, Context Camera (CTX) and High Resolution Imaging Science Experiment (HiRISE). They provided an efficient mechanism for observing long-distance and widely distributed lava emplacement. The spatial distribution of wrinkle ridges indicates that lava emplacement in the lava plains units HNr (older ridged plains material) and Hr (younger ridged plains material) happened before the rise of Tharsis. Finally, lava was emplaced in the lava plains of units Hsl (flows of lower member) and Hsu (Upper members). We showed the magma composition changed in the lava plains of STB before and after the uplift of Tharsis. This helps to characterize both the composition and evolution of the early martian magma as well as to provide insight into the mechanism of emplacement of lava plains and early volcanism.Finally, we have identified several exposed dikes in Thaumasia Planum Mars using THEMIS, CTX, HiRISE and CRISM data. These dikes extend from tens to～100kilometers in length with average widths of～50m. They display classic’en echelon’ patterns while cross-cutting preexisting geologic features, including extensive wrinkle ridges. Both the dikes and associated fissure eruption products have very blocky morphologies with～38%higher thermal inertia than the surrounding regions. The dikes are all enriched in Mg-rich olivine relative to the surrounding terrain, while a subset also contains elevated high-calcium pyroxene, both of which indicate relatively primitive magma compositions. We propose that these dikes might have served as feeders for the olivine-enriched flood basalts in this region, and may be derived from the Tharsis plume. These observations provide further evidence that the opening of Valles Marineris was facilitated by tectonic stresses following paths of preferential weakness along preexisting structures—such as fractures and faults like those indicated by these dikes.In summary, the results in this paper can improve our understanding about ancient volcanism on Mars (including the morphology, composition, thermophysics, mechanism of emplacement, and evolution of magma), and they provide geologic evidence for various geophysical and numerical models. They are important in learning the early history of volcanism in the solar system and comparative planetary geology.更多还原