As the Alta Stock began to cool an enormous volume of super heated water developed within and near the top of the magma body. This hydrothermal fluid transported lead, silver and other minerals, depositing them in fractures and receptive rock layers in the sedimentary rocks, forming the bonanza lead-silver deposits of the Little Cottonwood Canyon Mining District

Mine dumps from the Little Cottonwood Mining District litter the north slopes of Little Cottonwood Canyon north of Alta. Bonanza silver ore was mined from fractures and limestone lenses from the 1860s to the 1940s. There are believed to be over 100 miles of underground mine workings in the district.