基于辐射传输模型的月球撞击坑中央峰矿物反演

发布时间：2018-02-20 02:39

  本文关键词： 月球矿物 月球矿物绘图仪 辐射传输模型 月壳成分　出处：《山东大学》2016年硕士论文　论文类型：学位论文

【摘要】：Apollo样品返回以后,科学家们发现高地样品中的斜长石含量非常高(可高达90%以上),因而提出了岩浆洋模型来解释月壳的形成。模型指出在岩浆洋结晶晚期,斜长石开始结晶并且由于其密度较小而上升到月表,形成了古老的斜长岩质月壳。然而已有的月球样品采集点主要集中在月球正面,而且分布区域有限。月球遥感研究则可以从全球化的视角来研究月壳的成分和矿物分布,特别是月球中央峰由撞击形成,代表了月壳深部的物质。研究不同大小的撞击坑中央峰,通过撞击坑直径-挖掘深度的关系,就可以得到月壳不同深度下的成分和矿物分布,进而对月壳起源的岩浆洋模型进行验证或者改进。本研究通过建立辐射传输模型对月表撞击坑中央峰的矿物组分进行反演。首先反演得到橄榄石的光学常数虚部k随着Fo(橄榄石中Mg/(Mg+Fe)摩尔比)的变化规律,考虑空间风化效应、月壤孔隙度和背向散射效应对月球光谱的影响,加入SMFe(亚微米Fe),采用橄榄石、单斜辉石、斜方辉石和斜长石四种端元矿物,矿物含量从0%变化到100%,精度为5%,建立矿物混合光谱库,利用查找表和光谱匹配算法对中央峰的矿物模式进行反演。我们利用月球矿物绘图仪(M3)数据提取了全月101个直径为～30-200 km的撞击坑中央峰光谱,并利用辐射传输模型对其中86个存在可识别矿物特征的中央峰进行光谱匹配,获得其矿物组成模式。整体来看,全月中央峰矿物反演结果显示,月壳中的主要矿物为斜长石,主要镁铁质矿物为斜方辉石,其次为橄榄石和单斜辉石,与高地样品的成分研究结果一致。我们将全月中央峰矿物在长石质高地地体(FHT)、风暴洋克里普地体(PKT)和南极艾肯盆地地体(SPAT)的分布进行针对性分析,发现：1)FHT的斜长石含量要高于PKT和SPAT,而且FHT所在的月壳厚度明显大于PKT和SPAT,暗示月壳越薄,镁铁质矿物含量越高。2)FHT的中央峰岩石类型主要为纯斜长岩、苏长斜长岩、斜长苏长岩,和少量的斜长橄长岩,苏长岩到橄榄石苏长岩组成；PKT的中央峰主要包含纯斜长岩,苏长／辉长斜长岩,斜长橄长岩和苏长岩；SPAT的中央峰主要包含辉长苏长岩,苏长岩,斜长苏长岩和纯斜长岩。另外,我们在FHT,PKT和SPAT共选择了6个典型中央峰,利用修正高斯模型(MGM)进一步分析其主要矿物成分信息,结果发现FHT中央峰镁指数较高(Mg'90), PKT中央峰镁指数相对较低(Mg'-25-57),而且变化范围较大。PKT地区中央峰的镁铁质矿物的镁指数远低于镁质岩套(Mg'80)。SPA撞击坑的中央峰斜方辉石一般含量较高(30%),主要以苏长岩为主。我们分别将全月、FHT、PKT和SPAT的斜长石含量(或镁铁质矿物含量)与中央峰代表的岩层到月幔距离作关联,发现无论是从全球角度还是分三个月球地体来看,斜长石的含量(或镁铁质矿物含量)变化与其到月幔距离都没有显著地相关性。我们对存在PAN出露的中央峰的月幔距离进行了统计,发现其变化范围较大,约为25-60 km。因此月壳中可能并不存在一个纯斜长岩地层,或者这个地层已经被后期的月幔岩浆侵入作用或一些大型盆地撞击作用所改造,导致月壳成分在纵向和横向上都变得不均匀。三大地体的成分在次表层存在一定差异,可能主要是由于其岩浆洋时期的成分和演化阶段不同导致,FHT偏镁,其岩浆演化程度低,PKT偏铁,其岩浆演化程度高。
[Abstract]:After the Apollo sample return, the scientists found that the plagioclase content highland samples is very high (up to 90%), is proposed to explain the formation of the magma ocean model. The model indicates that the lunar crust in the late magma ocean crystallization, plagioclase began to crystallize and because of its low density and rise to the surface, the formation of anorthositic month old shell. However, samples of moon existing mainly in the lunar surface, and the distribution area is limited. Composition and mineral distribution of remote sensing research can study the moon shell from the perspective of globalization, especially the central peak caused by the formation of the moon, on behalf of the deep crust material crater central. The peak of different size, the relationship between crater diameter - mining depth, can composition and mineral distribution of lunar crust at different depths, and the origin of the magma ocean model on shell for verification or To improve. This study through the establishment of radiative transfer model of the lunar crater central peak mineral component inversion. First inversion of optical constants of olivine in the imaginary part of K with Fo (Mg/ in olivine (Mg+Fe) molar ratio) changes in the law, considering the space weathering effect, soil porosity and the backscattering effect on lunar spectral the effects of adding SMFe (sub micron Fe), using four kinds of olivine, clinopyroxene, orthopyroxene and plagioclase endmember minerals, mineral content changes from 0% to 100%, the accuracy was 5%, the establishment of mixed mineral spectral library, matching on the central peak mineral model inversion using look-up table and spectrum. We use the moon mineral plotter (M3) data. The whole month 101 diameter crater central peak spectra of 30-200 ~ km, and the use of the radiative transfer model of 86 of them have identifiable mineral characteristics of the central peak of the spectrum. With its mineral composition model. Overall, the whole month central peak mineral inversion results show that the main minerals in the lunar crust is mainly mafic minerals are plagioclase, orthopyroxene, and olivine and clinopyroxene, and high sample composition research results. We will full month the central peak of minerals in the feldspathic highlands block (FHT), ocean storm Kerrey (PKT) and Pu body pole Aitken basin body (SPAT) distribution for the analysis, it is found that: 1) the content of plagioclase FHT was higher than that of PKT and SPAT, and the shell thickness of FHT months was significantly higher than that of PKT and SPAT, suggesting that the lunar crust is thin, magnesium the higher the content of iron mineral.2) central peak rock type FHT mainly for pure anorthosite, Su Xie Changyan, Su Changyan and a small amount of plagioclase plagioclase, troctolite, olivine norite to norite; PKT central peak consists mainly of pure anorthosite, Su Hui Long / long oblique 闀垮博,鏂滈暱姗勯暱宀╁拰鑻忛暱宀╋紱SPAT鐨勪腑澶�宄颁富瑕佸寘鍚�杈夐暱鑻忛暱宀，

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