Density and Magnetic Properties of Selected Rock Samples from the Western U.S. and Alaska

The U.S. Geological Survey (USGS) has collected or incorporated over 20,000 physical property measurements into an ASCII database. These data are primarily from the western U.S. and Alaska and are dominated by granitic rock samples from the Sierra Nevada (compiled by Sikora and others, 1991), but also include a range of other commonly found rocks types. The data include density, magnetic susceptibility, and in some cases, remanent magnetic properties. Density data for more recently collected samples include grain, dry-bulk, and saturated-bulk density measurements. Sample locations are in the North American Datum of 1927 (NAD27) and elevations are in the National Geodetic Vertical Datum of 1929 (NGVD29). These physical property data are particularly useful for potential-field (gravity and magnetic) investigations and modeling of regional crustal structures and subsurface geology as an aid to understanding geologic framework. The ASCII formatted data release includes physical property data, a data dictionary describing the data fields, and a rock dictionary describing the rock types.

美国地质调查局（U.S. Geological Survey, USGS）已收集并整合逾20000项物理性质测量数据至ASCII格式数据库中。该数据集主要源自美国西部与阿拉斯加地区，其中以内华达山脉的花岗岩类岩石样品为主（由Sikora等人于1991年汇编），同时涵盖多种其他常见岩石类型。数据包含密度、磁化率两类参数，部分样品还包含剩余磁性相关测量结果。针对新近采集的样品，其密度数据包含颗粒密度、干体积密度与饱和体积密度三项细分指标。样品位置采用1927年北美大地基准面（North American Datum of 1927, NAD27），高程基准则采用1929年国家大地垂直基准面（National Geodetic Vertical Datum of 1927, NGVD29）。此类物理性质数据可用于位场（重力与磁法）调查、区域地壳结构及地下地质建模工作，辅助理解区域地质构造框架。本次以ASCII格式发布的数据包含物理性质原始数据、描述各数据字段的数据字典，以及说明岩石类型的岩石字典。