基于ASTER VNIR-SWIR多光谱遥感数据识别与提取干旱地区岩性信息——以西南天山柯坪隆起东部为例

Detecting lithologic features from ASTER VNIR-SWIR multispectral data in the arid region:A case study in the eastern Kalpin uplift,southwest Tian Shan

ASTER多光谱遥感数据目前可以用于岩石矿物资源信息的识别和提取。本研究尝试利用ASTER可见光近红外(VNIR)和短波红外(SWIR)的多光谱遥感数据提取干旱地区的岩石与矿物信息。基于新疆天山西南缘柯坪隆起东部不同地层单元岩石的化学组成和矿物成份以及VNIR-SWIR谱域光谱吸收特征的分析,我们采用相关吸收波段深度(RBD)和波段比值(BR)方法对研究区的多光谱遥感数据进行图像处理,有效区分和识别了白云岩、石灰岩、砂岩以及阿克苏群的蓝片岩—绿片岩和砂质片岩。白云岩的CO_3^(2-)吸收谱带中心波长位于2.32μm,与灰岩的CO_3^(2-)吸收谱带中心波长位置2.35μm相比,具有向短波长方向移动的特点,据此可以利用RBD7、RBD8分别有效的识别白云岩和灰岩;长英质岩石显示Al-OH和Fe^(3+)VNIR-SWIR吸收特征,而基性-超基性岩石显示Fe^(2+)和Fe、Mg-OH特征,利用不同的铁价态和次要矿物可以区分它们:ASTER band2/band1代表了含Fe^(3+)矿物分布信息、ASTER band5/band4代表了含Fe^(2+)矿物分布信息、RBD6可以估计Al-OH矿物的丰度;砂质/泥质片岩含较多的多硅白云母、绿泥石、黑硬绿泥石以及风化后表面覆盖的其它粘土矿物,在2.21μm(band6)存在有特征的吸收谱带,并且在1.65μm(band 4)具有较高的反射率,而蓝片/绿片岩在2.21μm(band 6)反射率较高,不具有明显特征吸收谱带,同时其在1.65μm(band 4)反射率较低,因此蓝片/绿片岩ASTER band4/band6比值低。应用ASTER band4/band6波段比值可以有效的区分开砂质/泥质片岩与蓝片岩/绿片岩。

Spaceborne Thermal Emission and Reflection Radiometer（ASTER）can provide high quality of muhispectral data for detecting lithology. This study attempted to extract lithlogical and mineralogical information in the arid region using the ASTER muhispectral data. Based on the analysis of chemical composition, mineral composition and the spectral absorption characteristics of different lithostratigraphic units, the Relative Absorption Band-Depth （RBD） and the bands-ratio method were adopted to process ASTER Visible-Near Infrared（VNIR） and Shortwave-Infrared （SWIR）multispectral data from the east Kalpin Uplift, southwest Tian Shan. Limestone,dolomite, sandstone, blueschist/greenschist and psammitic schist/pelitic schist, in the study area were well discriminated. The absorption spectrum center wavelength of dolomite is near 2.32 μm is shorter than 2.35 μm of limestone, and thus RBD7 and RBD8 can be employed effectively to identify dolomite and limestone,respectively. Felsic rocks show Al-OH and Fe^3＋ absorption characteristics in the VNIR-SWIR region,while the mafic-ultramafic rocks show Fe^2＋ and Fe, Mg-OH absorption features, hence the use of different valence state of iron and secondary minerals can distinguish them：ASTER band2/bandl represent Fe^3＋ distribution, ASTER band2/bandl represent the Fe^2＋ distribution, RBD6 can estimate the Al-OH mineral abundance. Psammitic/pelitic schist containing phengite,chlorite, stilpnomelane,as well as the weathered surface covered by clay minerals, exist characteristic absorption spectrum in the 2.21 μm（ band 6）,and has a high reflectance in 1.65μm（ band 4）,while the blueschist/ greenschist show high reflectance in the 2.21μm （ band 6） , and it exit low reflectance in 1. 65 μm （band 4 ）, and blueschist/greenschist appear low ASTER band4/band6 ratio. Therefore,the band ratio of ASTER band 4 and band 6 can effectively distinguish blueschist/ greenschist and psammitic/pelitic schist.