|  Florissant Scientific Society notes—23
Location: The Nature Place
Brief Program Summary:
At 30-35ma, it is believed a large deep batholith underlying the San Juan region was present, sourcing small discrete stratavolcanoes of andesitic composition. At 26.5 ma, the batholith moved close to the surface and a series of distinct, overlapping calderas formed. Doming, extrusion, and collapse were repetitive processes. The broader La Garita complex is the largest in the world, characterized by massive cooling units producing dramatic topography. Magmatic differentiation through time produced viscous, explosive rhyolites capable of very significant and destructive nuee ardentes.
Martinique is a small-scale example nuee ardente destructive power. One famous eruption killed 20,000 people and only two witnesses—one in a harbor boat and one sheltered within a prison—survived.
Much of the presentation was about the history of the Creede Mining District. Creede was originally called Jimtown. A silver discovery at the Alpha mine was staked as early as 1873, and the Bachelor mine in 1876. The “boom” started in the early 1890s, but was short-lived, lasting only 2 ½- 3 years. During the summer of 1891, 300 people were arriving per day. The silver panic of 1893 was precipitated by the shut down of a mint in India stamping coins for the British Empire. It had been a major buyer of silver. Around 1870, the silver price was $1.36/oz. There was a fairly steady decline—not a precipitous drop-- through the 1890s, down to $.60/oz. There was a devastating fire at Creede on June 5, 1892.
Several famous characters were involved in early Creede: Bob Ford, Jesse James, Ed O’Kelly, Soapy Smith, Poker Alice, David Moffat, Bat Masterson, etc.
Ed showed many pictures of mines. The amethyst vein system produced >90% of district production until the discovery of the Bulldog mine. Tom Stevens did field work in the San Juans from 1952-1975, and his work was instrumental in the Bulldog find. He recognized that a subsidiary fault was connected to the Amethyst vein at depth, providing the necessary plumbing. The Bulldog operated 1969-85, making Homestake a lot of money.
Next meeting is 27 June at new Florissant library. Ed Raines will continue discussion of Creede, with emphasis on mineralogy.
A field trip to Creede is contemplated w/ Ed and Tom as goeoscience leads. This will be 10-12 September, 2004. David has graciously volunteered to handle logistics. Plan is to rent a van and meet at a convenient location.