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A New Occurrence Model for National Assessment of Undiscovered Volcanogenic Massive Sulfide Deposits

By W.C. Pat Shanks III, Cynthia Dusel-Bacon, Randolph Koski, Lisa A. Morgan, Dan Mosier, Nadine M. Piatak, Ian Ridley, Robert R. Seal II, Klaus J. Schulz, John F. Slack, Roland Thurston

Volcanogenic massive sulfide (VMS) deposits are very significant current and historical resources of Cu-Pb-Zn-Au-Ag, are active exploration targets in several areas of the United States and potentially have significant environmental effects. This new USGS VMS deposit model provides a comprehensive review of deposit occurrence and ore genesis, and fully integrates recent advances in the understanding of active seafloor VMS-forming environments, and integrates consideration of geoenvironmental consequences of mining VMS deposits. Because VMS deposits exhibit a broad range of geological and geochemical characteristics, a suitable classification system is required to incorporate these variations into the mineral deposit model. We classify VMS deposits based on compositional variations in volcanic and sedimentary host rocks. The advantage of the classification method is that it provides a closer linkage between tectonic setting and lithostratigraphic assemblages, and an increased predictive capability during field-based studies.

First posted October 9, 2009 Report PDF (345 kB) 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:

Shanks, W.C.P., III, Dusel-Bacon, Cynthia, Koski, Randolph, Morgan, L.A., Mosier, Dan, Piatak, N.M., Ridley, Ian, Seal, R.R., II, Schulz, K.J., Slack, J.F., Thurston, Roland, 2009, A new occurrence model for national assessment of undiscovered volcanogenic massive sulfide deposits: U.S. Geological Survey Open-File Report 2009–1235, 27 p.

Contents

Introduction

Deposit Type and Associated Commodities

Physical Volcanology

Regional Environment

Physical Description of Deposits

Geophysical Characteristics of VMS Deposits

Ore Characteristics

Supergene Ore and Gangue Characteristics

Exhalites

Hydrothermal Alteration

Weathering Processes

Geochemical Characteristics

Petrology of Igneous Rocks Associated with VMS Deposits

Petrology of Sedimentary Rocks Associated with VMS Deposits

Effects of Metamorphism and Deformation on VMS Host Rocks and Deposits

Theory of Deposit Formation

Exploration and Resource Assessment Guides

Geoenvironmental Features

References