The San Juan Volcanic Field in Southwest Colorado comprises a prolific metallogenic province, having produced an estimated $28 billion worth of metals, including gold, silver, lead, zinc, and copper, from intermediate-sulfidation (IS) and high-sulfidation (HS) epithermal deposits. This region spans approximately 25,000 km2 and is characterized by extensive dacitic-rhyolitic ash flow sheets resulting from a series of caldera-forming ignimbrite eruptions during the Oligocene. This trip will focus on the Central and Western San Juan caldera complex, where we will explore several renowned epithermal mineral deposits. Key stops include the mineral districts of Creede, Lake City, Silverton and Telluride, as well as the high-sulfidation epithermal deposits of the Red Mountain District. Through field observations and discussions, participants will gain a deeper understanding of the volcanic and magmatic processes, examine the formation environments of epithermal deposits, discuss their proximity to intrusions, delve into ore formation processes, observe various alteration characteristics and styles of mineralization.
This course is ideal for seasoned professionals, early-career geologists, and students involved in the genesis, exploration, and mining of epithermal deposits
The Creede Mining District is one of the most prolific intermediate-sulfidation epithermal silver and base-metal deposits in the world, having produced 80 million ounces of silver along with zinc, lead and minor gold. We will visit several past-producing mines such as the Commodore, Midwest, Equity, Park Regent, Last Chance and Bulldog mines. Participants will learn about the deposit geology, volcanic stratigraphy, and the chronology of volcanism, sedimentation and ore mineralization, and will also examine vein textures and mineralogy, review drill core, and discuss ore formation processes.
We will be spending the night in Creede.
The second day of the field trip begins in Lake City, proceeding west to Engineer Pass along the northern margin of the Lake City caldera. We will observe the volcanic stratigraphy of the western San Juan Mountains (Uncompahgre, San Juan and Lake City calderas). Along the way, we will stop at several prolific polymetallic vein deposits in the Lake City District and discuss previous mineral exploration. During the descent into Silverton, we will examine post-caldera porphyry intrusions and visit additional polymetallic vein deposits in the Eureka district including the Sunnyside mine.
We will be spending the night in Silverton.
This day focuses on the Red Mountain District, a classic example of a high-sulfidation epithermal environment. Activities include background on the magmatic evolution, examining advanced argillic alteration, and visiting high-grade high-sulfidation epithermal ore deposits. These deposits feature breccia pipes, ore chimneys, and veins that zone from Ag-Zn-Pb at upper levels to Cu-Au at deeper levels. Discussions will cover past metal production, ore and gangue mineralogy, trace element geochemistry, legacy mining issues, and previous mineral exploration efforts.
Overnight stay in Silverton.
The day involves visiting several past producing gold-silver and base metal epithermal vein deposits in Governor Basin. The stops will include examining veins outcropping at surface and observing the deposit geology. We will observe exposures of the Telluride conglomerate, stratified volcanic ash flow tuff units, and post-caldera dikes and stocks. We will discuss the local igneous and mineralization chronology and ore-forming processes of the Camp Bird and Revenue Mines, as well as their current status. The route includes a scenic overlook of Telluride, which is the Day 5 destination.
We will be checking-out of our hotel in Silverton in the morning and will spend the night in Ouray.
We will spend the fifth day in Telluride, Colorado, visiting high-grade gold-silver and base metal epithermal veins that outcrop near the Idarado and Smuggler-Union mines. Stops will include examining several outcropping veins, observing the deposit geology, and visiting the Pandora Mill and Meldrum Tunnel. We will discuss the mining history, previous studies on ore mineralization of the Idarado mine, the chronology of igneous and hydrothermal activity, and the current status of mine-related operations.
This course is scheduled for July 7-11 , 2025 and costs $4500/person (if paid before March 1st). This all inclusive rate includes five nights hotel stay, all meals, snacks and drinks in the field, fuel, permits, transportation during the field trip, tuition and field guide.