Airborne electromagnetic and magnetic survey data, Stillwater Complex, Montana, May 2000 (ver. 2.0, June 2020)

A helicopter-borne electromagnetic/magnetic survey was flown over the Stillwater area, southwest Montana from May 5 to May 16, 2000. The survey was conducted over the Stillwater Igneous Complex, a Precambrian layered mafic-ultramafic intrusion which is characterized by igneous layering. Electromagnetic data were acquired using DIGHEM helicopter-borne electromagnetic system. Magnetic data were collected with optically pumped Cesium Vapor Geometrics G822 magnetometer. Sensor elevation above ground was measured with Honeywell/Sperry AA220 radar. The nominal elevation of the sensor was 60 meters. Survey coverage comprises 1,914 line kilometers, including tie lines. Flight lines were flown in an azimuthal direction of 020 degrees with a nominal line separation of 200 meters. In the southeastern portion of the survey area, in-fill lines were flown for coverage every 100 meters. Two tie lines were flown perpendicular to the flight lines. Version 2.0 includes an updated version of the StillwaterMagEM.csv file (StillwaterMagEM_v2.csv) that contains the data for an additional 66 out of the 266 flight lines that were missing from the original version. For access to the previous version of this report contact Heather Parks (509-368-3114) at the Spokane, WA USGS office.