Compositional Study Of Mare Imbrium Basalts Of The Moon Based On Remote Sensing Data

Compositional study of the Moon is an indispensable part of Moon exploration, which is of great importance to both researches of origin and evolution of the Moon and exploitation and utilization of lunar resource. Mare Imbrium is the second largest basaltic region on the Moon, it has well preserved lava flows and emplacements, which has always been the subject of intense researches. In2013, the Chang’E-3has successfully landed in the north of Mare Imbrium, its scientific exploration goals is closely related with geology and magma evolution of Mare Imbrium. The spectral resolution of hyper-spectral data is very high, and it has lots of bands. Which is sensitive to the diagnostic absorption properties of minerals. Thus it can be used for compositional identification. This paper makes use of hyper-spectral data from Moon Mineralogy Mapper (M3) onboard Chandrayaan-1and Interference Imaging Spectrometer (IIM) onboard Chang’E-1to study the composition of Mare Imbrium basalts, thereby understanding the characteristics of iron and titanium contents and mineralogy of Mare Imbrium basalts, enriching the geological evolution, and providing basics for Chang’E-3scientific research.First, this paper makes use of data from different optical periods (OP IB, OP2C) of M3and two calibrated data sets (pc1, pc2) of IIM to extract iron and titanium contents of the Sinus Iridum region. The results are as followed:FeO peak value obtained by OP1B and OP2C is17.80wt.%and17.60wt.%respectively, which is higher than pcl’s 15.80wt.%and pc2’s14.00wt.%. FeO average value achieved by OP1B and OP2C is16.91wt.%and16.79wt.%respectively, higher than pcl’s14.11wt.%and pc2’s13.46wt.%.0-4wt.%titanium contents percentage acquired by OP2C is74.46%. higher than pcl’s54.66%and pc2’s62.46%, while OPIB’s is37.55%. TiO2average value obtained by OP1B and OP2C is5.35wt.%and3.16wt.%respectively. TiO2average value achieved by pcl and pc2is4.25wt.%and3.65wt.%respectively.Second, very low and low titanium basalt of the Sinus Iridum area nearly approach50%and40%respectively, which mainly locate on Iml and Im2units. High titanium basalt that account for nearly10%percentage locates on Elm unit. On the whole, titanium content of basalt obtained by optical data show a unimodal distribution, low titanium basalt dominates, which differs from the bimodal distribution of the samples’ titanium. Iron and titanium contents of the Sinus Iridum’s basalt, with its age become younger, present a growing tendency. Among the four data sets, the photometric calibration of pc2data is the best, the precision of photometric calibration of pcl is rather low, the reflectance of various optical periods of M3differs, and the precision of photometric calibration of M3data from different optical periods needs to be improved.Third, M3OP1B data have been utilized to obtain an Integrated Band Depth (IBD) mosaic of the Imbrium basin. Based on spectral variations observed in the IBD mosaic,16spectral units have been mapped in Mare Imbrium region, we have also derived spectral band parameters, namely, band center, band depth, band area, band area ratio and slope from the M3data to study the mineralogical and compositional variations amongst the basaltic units of the studied basin. On the basis of spectral band parameters analysis, the younger basalts of Mare Imbrium (Unit S1, S2, S3and S10) are found to be abundant with olivine. Furthermore, we found the presence of olivine in some older basalts in the northeast of Imbrium region (Unit S11and S12). We suggest that space weathering effect obviously weakens the characteristics of1μm and2μm by analyzing the spectral parameters of crater pairs. With the maturation of craters, slopes of1μm and2μm increase, while, band areas and band depths both decrease. Which might be related with the generation of nanometer Fe of lunar regolith during space weathering process. Fourth, We conclude that the pyroxene compositions of the basaltic vary from low to intermediate end of the pyroxene and probably represent a sub-calcic to moderate-calcic augite compositional range by analyzing scatter plot of band I center and band II center and scatter plot of band I center and band area ratio. Based on the equations between Wo pyroxene and Fs pyroxene and band center, We calculate the contents of Wo pyroxene and Fs pyroxene of each unit. The Wo pyroxenes and Fs pyroxenes of Unit S1, S2, S3and S10are very same, the Wo pyroxenes contents range from34%to35%, whereas the Fs pyroxenes vary from17.5%to17.6%that suggests that the compositions of these units are alike. Unlike the younger basaltic units, the Wo pyroxenes contents of which are lower than that of younger basalts, however, the Fs pyroxenes contents are higher, and vary from45.51%to51.50%.This paper makes an investigation on composition of Mare Imbrium basalts based on available data, and hopes to provide references for subsequent researches.