In 1875, miners began extracting gold ore from the Phoenix Gold Mine, striking it rich with this valuable resource. The mine eventually closed commercial operations due to the beginning of World War 2. Yet, how the gold came here remains a fascinating tale worth exploring.
Traveling back 1.8 billion years, the landscape where the Phoenix Gold Mine now sits looked vastly different. During the Precambrian Era, Idaho Spring, Colorado was a desert where the sand and sediment gradually hardened into sandstone and shale throughout millions of years. These layers were buried under more sediment, pushing them miles below the surface.
As the sandstone and shale sank deeper into the Earth, Intense heat and pressure exposed them, transforming them into new rock types that would accommodate these extreme conditions. This process, known as metamorphism, caused the rock to twist and contort and alter the minerals in the rock before rapidly hardening into biotite gneiss (pronounced 'nice') and schist.
Over time, these rocks were disturbed, forming faults and joints. Faults are dramatic breaks in rock that have moved or shifted relative from one side to another. Joints are breaks or fractures that form in rock that result from the rock being pulled apart in one direction by natural forces. These breaks created perfect pathways for hydrothermal fluids to rise from deep in the Earth, carrying the essential elements to form various minerals. Under complex conditions, the hydrothermal fluids deposited material that filled the breaks and fractures. This material contained a variety of minerals, including some of economic importance, such as copper, silver, and gold.
Imagine it like baking a cake: all the ingredients for the ore veins we see today came together at just the right moment. When you step into either of our mine tours, the Phoenix or the Centurion, you're not just stepping into the history known by the miners—you're delving into a story 1.8 billion years in the making.
Sources:
file:///C:/Users/Octoo/Downloads/USGS%20precambriean%20earth%20report.pdf
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