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Prepared in cooperation with the U.S. Environmental Protection Agency

Characterization of Geologic Structures and Host Rock Properties Relevant to the Hydrogeology of the Standard Mine in Elk Basin, Gunnison County, Colorado

By Jonathan Saul Caine, Andrew H. Manning, Byron R. Berger, Yannick Kremer, Mario A. Guzman, Dennis D. Eberl, and Kathryn Schuller

Abstract The Standard Mine Superfund Site is a source of mine drainage and associated heavy metal contamination of surface and groundwaters. The site contains Tertiary polymetallic quartz veins and fault zones that host precious and base metal sulfide mineralization common in Colorado. To assist the U.S. Environmental Protection Agency in its effort to remediate mine-related contamination, we characterized geologic structures, host rocks, and their potential hydraulic properties to better understand the sources of contaminants and the local hydrogeology. Real time kinematic and handheld global positioning systems were used to locate and map precisely the geometry of the surface traces of structures and mine-related features, such as portals. New reconnaissance geologic mapping, field and x-ray diffraction mineralogy, rock sample collection, thin-section analysis, and elemental geochemical analysis were completed to characterize hydrothermal alteration, mineralization, and subsequent leaching of metallic phases. Surface and subsurface observations, fault vein and fracture network characterization, borehole geophysical logging, and mercury injection capillary entry pressure data were used to document potential controls on the hydrologic system.

First posted March 5, 2010 Report PDF (4.3 MB) For additional information contact: Team Chief Scientist, USGS Crustal Imaging and Characterization Box 25046, Mail Stop 964 Denver, CO 80225 http://crustal.usgs.gov/ Part or all of this report is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge.

Suggested citation:

Caine, J.S., Manning, A.H., Berger, B.R., Kremer, Y., Guzman, M.A., Eberl. D.D., and Schuller, K., 2010, Characterization of geologic structures and host rock properties relevant to the hydrogeology of the Standard Mine in Elk Basin, Gunnison County, Colorado: U.S. Geological Survey Open-File Report 2010–1008, 56 p.

Contents

Abstract

Introduction

Definitions of Brittle Structures

Site Description

Location, Ecosystem, and Climate

Geological and Hydrological Overview

Methods

Reconnaissance Geologic Mapping

Fault Zone Characterization

Borehole Geophysical Logging

Drill Core Logging

Estimates of Intergranular Porosity and Permeability by MICP

55-Element ICP–AES–MS Rock Geochemistry

Mineralogy by X-Ray Diffraction

Observations and Data

Map to Sample Scale Features

Stratigraphy, Bedforms, Lithologic Contacts, and Geomorphology

Spot Mineralogy, Petrography, and Alteration

Ground Surface Elevation Gradients as a Proxy for Surface and Groundwater Flow

Petrophysics

Geologic Structures

Joints and Televiewer Log Data

Faults, Fault Veins, and Fault-Related Fluid Flow

Veins

Summary of Key Observations and Hypotheses

Acknowledgments

References