Hydrothermal Alteration Targeting and Geophysical Mineral Exploration of Eureka and Sylvanite Mining Districts, Southwest New Mexico

Abstract

As part of the southwestern North American porphyry copper province, mining of natural resources in New Mexico has historically played a crucial role in economic development for over 150 years including this project area in the Little Hatchet Mountains. The northern half of the Little Hatchet Mountains lies in Grant County and includes the Eureka Mining District (EMD) whereas the southern half is in Hidalgo County and includes the Sylvanite Mining District (SMD), 38 miles southeast of Lordsburg. The EMD, a copper and silver-lead mining district from 1880-1961, had a total estimated production from the Laramide veins of 2.9 million lbs. Pb, 1.7 million lbs. Zn, 500,000 lbs. Cu, 5,000 ounces Au, and 450,000 ounces Ag (McLemore et. al, 1996). The SMD, a silver-gold mining district from Laramide skarn, vein, and placer deposits occur in the district and production including 2,500 ounces Au, 130,000 lbs. Cu, and 8,000 lbs. Pb from 1902-1957. This study focuses on remote sensing hydrothermal mineral alteration zones detected using Mars 2014 USGS shapefiles in the Basin and Range province, which assisted in the targeting of subsequent electromagnetic and electrical resistivity surveys that were conducted of potential mineral deposits. Electromagnetics survey readings, using the Geonics EM34-3XL that reach a depth of 180 ft, have resulted in interesting anomalies. These surveys have also allowed us to determine where the electrical resistivity surveys, using the SuperSting R8 112 electrode 5 m interval spacing for a max depth profile of 111 m, were performed. Spectral microscopy on 18 samples was conducted to test remote sensing ground truth certainty. X-ray diffraction was performed on 7 of the samples to test the accuracy of the mineral spectroscopy results. The present study is enhancing the knowledge base of these mining districts and southwest New Mexico as well as providing providing new geophysical results for future exploration.