Publication Citation

USGS Series Open-File Report
Report Number 2005-1442
Title Questa Baseline and Pre-Mining Ground-Water Quality Investigation. 13. Mineral Microscopy and Chemistry of Mined and Unmined Porphyry Molybdenum Mineralization Along the Red River, New Mexico: Implications for Ground- and Surface-Water Quality
Edition Version 1.0 Online Only
Language ENGLISH
Author(s) Plumlee, Geoff; Lowers, Heather; Ludington, Steve; Koenig, Alan; Briggs, Paul
Year 2005
Originating office USGS New Mexico Water Science Center
USGS Library Call Number
Physical description ii, 95 p.
ISBN
Northernmost latitude 0364500
Southernmost latitude 0364000
Easternmost longitude -1052000
Westernmost longitude -1053500

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Abstract

This report is one in a series presenting results of an interdisciplinary U.S. Geological Survey (USGS) study of ground-water quality in the lower Red River watershed prior to open-pit and underground molybdenite mining at Molycorp's Questa mine. The stretch of the Red River watershed that extends from just upstream of the town of Red River to just above the town of Questa includes several mineralized areas in addition to the one mined by Molycorp. Natural erosion and weathering of pyrite-rich rocks in the mineralized areas has created a series of erosional scars along this stretch of the Red River that contribute acidic waters, as well as mineralized alluvial material and sediments, to the river. The overall goal of the USGS study is to infer the pre-mining ground-water quality at the Molycorp mine site. An integrated geologic, hydrologic, and geochemical model for ground water in the mineralized but unmined Straight Creek drainage is being used as an analogue for the geologic, geochemical, and hydrologic conditions that influenced ground-water quality and quantity at the mine site prior to mining. This report summarizes results of reconnaissance mineralogical and chemical characterization studies of rock samples collected from the various scars and the Molycorp open pit, and of drill cuttings or drill core from bedrock beneath the scars and adjacent debris fans.