【目的】地貌是地球表层系统最重要的自然地理要素,其形态划分对地学空间分异研究具有重要意义。【方法】以山西省西山矿区作为研究区,利用该区ALOS 12.5 m DEM数据,通过窗口递增分析和均值变点分析得到地形因子最佳分析窗口为13×1...【目的】地貌是地球表层系统最重要的自然地理要素,其形态划分对地学空间分异研究具有重要意义。【方法】以山西省西山矿区作为研究区,利用该区ALOS 12.5 m DEM数据,通过窗口递增分析和均值变点分析得到地形因子最佳分析窗口为13×13(0.0264 km^(2));利用相关性分析获得最佳地形因子为地形起伏度、海拔高度、坡度、地表切割深度和地表粗糙度;利用区域统计分析得到典型地形因子的分布状况,结合叠加分析提取了西山矿区30种地貌类型,其中浅切割陡小起伏中山为主要地貌,占总面积比为21.23%.【结果】通过与1∶100万地貌类型图的图斑数和地貌分类界线对比,得出地貌类型增加了21类,图斑数目增加了296个,分类界线更为准确,验证了研究结果具有一定可靠性和可行性。【结论】本地貌划分方法较以往更加科学可行,为进一步研究西山矿区灾害防治、开发利用等问题提供了数据参考。展开更多
The quasi-monomineralic composition and huge spatial extent of massif-type anorthosites make detecting lithological regions and boundaries challenging.We use processed Landsat 8 OLI multispectral images and ALOS digit...The quasi-monomineralic composition and huge spatial extent of massif-type anorthosites make detecting lithological regions and boundaries challenging.We use processed Landsat 8 OLI multispectral images and ALOS digital elevation models integrated with field and petrographic observations to characterize the architecture of the≥17,000 km2 Mesoproterozoic Kunene Complex(KC)anorthosite suite in Angola and Namibia.Images of false colour composite bands 6,4 and 1 and band ratios 4/2(ferric minerals),6/5(ferrous minerals)and 6/7(OH-bearing minerals),as well as assessment of the PCA and MNF matrices of eigenvectors and eigenvalues from Landsat 8 data using available spectral libraries,have substantially improved the interpretation of the Kunene Complex rock types and structures.The dataset shows that the reflectance signature of KC anorthositic rocks is primarily a function of the degree of metasomatism,which is most significant in olivine-poor rock types.The weathering intensity of the olivine-bearing anorthosite substrate is another control on the remote sensing signal.Our remote sensing and field-based approach has enabled us to divide the KC anorthosite suite into six distinct spectral and architecture domains and at least four distinct magmatic plutons when considering available high-precision geochronological data.The northernmost pluton(ca.1380 Ma)of massive,olivine-bearing anorthosite shows distinct remote sensing signatures in the band ratio and MNF images marked by the dominance of OH-bearing and subordinate ferric minerals.The central pluton(1412–1400 Ma)is composed of NNE-to N-striking steeply dipping interlayered olivine-bearing and olivinepoor anorthosite,which correspond to ridges of dark-coloured,low albedo rocks with subordinate slightly oxidised ferrous mineral spectral signatures,and valleys of low albedo and OH-bearing mineral spectral signatures.A NNE-striking tectonic zone along a linear belt of KC granite gneiss separates the northern and central plutons.To the south is a NNW-to NNE-striking layered pluton(ca.1390 Ma),marked by olivine-bearing anorthosite that forms ridges and metasomatized olivine-poor and pyroxene-bearing anorthosite that forms valleys.This domain is separated from the similarly layered and E–W-striking Zebra Lobe–Oryeheke anorthosite by a top-to-the north thrust zone.A small domain of ca.1438 Ma olivine-bearing anorthosite sensu lato is situated to the SE of the main Kunene Complex.This work highlights the variability in layered and massive textures,the extent of metasomatism,and the importance of internal tectonic boundaries in the architecture of the Kunene Complex anorthosite suite.Our approach can be applied in other anorthositic terrains and large igneous bodies elsewhere on Earth,especially those where outcrop is poor,or access is inhibited.展开更多
文摘【目的】地貌是地球表层系统最重要的自然地理要素,其形态划分对地学空间分异研究具有重要意义。【方法】以山西省西山矿区作为研究区,利用该区ALOS 12.5 m DEM数据,通过窗口递增分析和均值变点分析得到地形因子最佳分析窗口为13×13(0.0264 km^(2));利用相关性分析获得最佳地形因子为地形起伏度、海拔高度、坡度、地表切割深度和地表粗糙度;利用区域统计分析得到典型地形因子的分布状况,结合叠加分析提取了西山矿区30种地貌类型,其中浅切割陡小起伏中山为主要地貌,占总面积比为21.23%.【结果】通过与1∶100万地貌类型图的图斑数和地貌分类界线对比,得出地貌类型增加了21类,图斑数目增加了296个,分类界线更为准确,验证了研究结果具有一定可靠性和可行性。【结论】本地貌划分方法较以往更加科学可行,为进一步研究西山矿区灾害防治、开发利用等问题提供了数据参考。
基金supported by a National Research Foundation(NRF)Thuthuka Grant(TTK14052367805)the DSI-NRF Centre of Excellence for Integrated Mineral and Energy Resource Analysis(DSI-NRF CIMERA)。
文摘The quasi-monomineralic composition and huge spatial extent of massif-type anorthosites make detecting lithological regions and boundaries challenging.We use processed Landsat 8 OLI multispectral images and ALOS digital elevation models integrated with field and petrographic observations to characterize the architecture of the≥17,000 km2 Mesoproterozoic Kunene Complex(KC)anorthosite suite in Angola and Namibia.Images of false colour composite bands 6,4 and 1 and band ratios 4/2(ferric minerals),6/5(ferrous minerals)and 6/7(OH-bearing minerals),as well as assessment of the PCA and MNF matrices of eigenvectors and eigenvalues from Landsat 8 data using available spectral libraries,have substantially improved the interpretation of the Kunene Complex rock types and structures.The dataset shows that the reflectance signature of KC anorthositic rocks is primarily a function of the degree of metasomatism,which is most significant in olivine-poor rock types.The weathering intensity of the olivine-bearing anorthosite substrate is another control on the remote sensing signal.Our remote sensing and field-based approach has enabled us to divide the KC anorthosite suite into six distinct spectral and architecture domains and at least four distinct magmatic plutons when considering available high-precision geochronological data.The northernmost pluton(ca.1380 Ma)of massive,olivine-bearing anorthosite shows distinct remote sensing signatures in the band ratio and MNF images marked by the dominance of OH-bearing and subordinate ferric minerals.The central pluton(1412–1400 Ma)is composed of NNE-to N-striking steeply dipping interlayered olivine-bearing and olivinepoor anorthosite,which correspond to ridges of dark-coloured,low albedo rocks with subordinate slightly oxidised ferrous mineral spectral signatures,and valleys of low albedo and OH-bearing mineral spectral signatures.A NNE-striking tectonic zone along a linear belt of KC granite gneiss separates the northern and central plutons.To the south is a NNW-to NNE-striking layered pluton(ca.1390 Ma),marked by olivine-bearing anorthosite that forms ridges and metasomatized olivine-poor and pyroxene-bearing anorthosite that forms valleys.This domain is separated from the similarly layered and E–W-striking Zebra Lobe–Oryeheke anorthosite by a top-to-the north thrust zone.A small domain of ca.1438 Ma olivine-bearing anorthosite sensu lato is situated to the SE of the main Kunene Complex.This work highlights the variability in layered and massive textures,the extent of metasomatism,and the importance of internal tectonic boundaries in the architecture of the Kunene Complex anorthosite suite.Our approach can be applied in other anorthositic terrains and large igneous bodies elsewhere on Earth,especially those where outcrop is poor,or access is inhibited.
