Digital map of hydrothermal alteration type, key mineral groups, and green vegetation of the southwestern United States derived from automated analysis of ASTER satellite data

Mineral groups identified through automated analysis of remote sensing data acquired by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) were used to generate a map showing the type and spatial distribution of hydrothermal alteration, other exposed mineral groups, and green vegetation across the southwestern conterminous United States. Boolean algebra was used to combine mineral groups identified through analysis of visible, near-infrared, and shortwave-infrared ASTER data into attributed alteration types and mineral classes based on common mineralogical definitions of such types and the minerals present within the mineral groups. Alteration types modeled in this way can be stratified relative to acid producing and neutralizing potential to aid in geoenvironmental watershed studies. This mapping was performed in support of multidisciplinary studies involving the predictive modeling of mineral deposit occurrence and geochemical environments at watershed to regional scales. These studies seek to determine the relative effects of mining and non-anthropogenic hydrothermal alteration on watershed surface water geochemistry and faunal populations. The presence or absence of hydrothermally-altered rocks and (or) specific mineral groups can be used to model the favorability of occurrence of certain types of mineral deposits, and aid in the delineation of permissive tracts for these deposits. These data were used as a data source for the U.S. Geological Survey (USGS) Sagebrush Mineral-Resource Assessment (SaMiRA). This map, in ERDAS Imagine (.img) format, has been attributed by pixel value with material identification data that can be queried in most image processing and GIS software packages. Three files are included with this product: file with .img extension contains thematic image attributes and geographic projection data, file with .ige extension contains the raster data, and the file with .rrd extension includes pyramid data for fast display.通过对先进星载热发射和反射辐射计（Advanced Spaceborne Thermal Emission and Reflection Radiometer, ASTER）获取的遥感数据开展自动化分析所识别的矿物群，被用于生成一幅专题地图，用以展示美国本土西南部热液蚀变、其他裸露矿物群与绿色植被的类型及其空间分布。研究人员采用布尔代数，将通过可见光、近红外及短波红外ASTER数据分析得到的矿物群，依据此类蚀变类型的通用矿物学定义以及矿物群内赋存的矿物，整合为带有属性标识的蚀变类型与矿物类别。以此方式建模得到的蚀变类型可依据产酸潜力与中和潜力进行分层，以辅助地质环境流域研究。本次制图工作旨在支撑多学科研究，涵盖流域至区域尺度下的矿床产出预测建模与地球化学环境研究。此类研究旨在厘清采矿活动与非人为热液蚀变对流域地表水地球化学特征及动物种群的相对影响。热液蚀变岩石的存在与否以及（或）特定矿物群，可用于建模特定类型矿床的产出有利性，并有助于圈定此类矿床的允许分布区。上述数据被用作美国地质调查局（U.S. Geological Survey, USGS）山艾树矿产资源评估（Sagebrush Mineral-Resource Assessment, SaMiRA）项目的数据源。该地图采用ERDAS Imagine（.img）格式存储，已通过像素值赋予物质识别属性数据，可在多数图像处理与地理信息系统（GIS）软件中进行查询。本产品附带三个配套文件：扩展名为.img的文件包含专题图像属性与地理投影数据，扩展名为.ige的文件存储栅格数据，扩展名为.rrd的文件则包含用于快速显示的金字塔层级数据。