Georgetown-Silver Plume District, Clear Creek Co., Colorado, USA
|Latitude & Longitude (WGS84):||39° 41' 58'' North , 105° 42' 45'' West|
|Latitude & Longitude (decimal):||39.69947,-105.71253|
Also known as Griffith or Silver Plume. Ag, Zn, Pb, Au, Cu.
Location and history: The Georgetown-Silver Plume District occupies an area of about 25 square miles in the west-central part of Clear Creek County, surrounding the towns of Silver Plume and Georgetown. Georgetown is situated at the junction of Clear Creek and South Clear Creek and Silver Plume is on Clear Creek 2 miles southwest of Georgetown. The principal mines are on the south slope of Republican Mountain, just north of Silver Plume, but there are some important mines to the southwest, northeast, and northwest of Georgetown. The district is well watered by the drainage of Clear Creek and is very rugged, ranging from 8,400 to 12,400 feet in altitude.
Precious metals were first discovered in the district in 1859, when several lodes were located near Georgetown, at that time called Elizabethtown. The rich surface ores were worked chiefly for gold, although most of the veins in depth have since produced more silver than gold. Among the most prominent was one located on August 1, 1859, by George Griffith. In 1864 a rich silver vein, the "Belmont lode," was discovered in the Argentine district southwest of Silver Plume, and as silver at that time was worth $1.34 an ounce there was a rush of prospectors to the Silver Plume-Georgetown region seeking silver lodes. During 1865 and 1866, many silver-bearing veins were discovered near Georgetown and Silver Plume. In 1867 the Blackhawk smelter began to operate and greatly stimulated mining in the Front Range. In 1870 mining in the region was further helped by the completion of two railroads to Denver and one from Denver to Golden. The period of important silver-lead mining really commenced in 1872, reached its peak in 1894, and gradually declined thereafter.
Mineralogy and Geology: The chief metals produced in the Silver Plume-Georgetown district are silver, lead, gold, and zinc, but in general the gold occurs in separate areas. In the very productive area covering about 2 square miles just north of Silver Plume, the veins contain silver, lead, and zinc almost to the exclusion of gold, and this is also true of the veins on Republican Mountain and on Democrat Mountain, 1½ to 2½ miles north-northeast. In these areas veins of both northeast and northwest trend are prominent and important, but commonly the trends are nearer east-west than north. One and a half to 2 miles south of Georgetown is a smaller but important silver mining area-that of the Colorado Central group-the abundant ores of which are largely of high grade and very similar to those of the Silver Plume area. This silver belt is represented farther to the northeast by the Conlet-Aetna and Magnet veins, about a mile east of Georgetown. In this belt the predominant strike of the veins is northeast.
Between the two silver belts is a narrow gold belt about three-fourths of a mile wide extending from Leavenworth Mountain, 1½ miles south of Georgetown, northeastward to Saxon Mountain. In this belt the important veins. all trend northeastward. The gold- bearing veins commonly contain some silver, and at the northern end of the belt the value of the silver content is somewhat higher than that of the gold. On Lincoln Mountain, 3½ miles northwest of Georgetown, some veins are chiefly valuable for silver and others for gold.
Mineralogically the two groups of ores may be classified as (1) galena-sphalerite ores with some pyrite, chalcopyrite, gray copper, and polybasite, and (2) pyritic ores containing chiefly pyrite and chalcopyrite, with subordinate quantities of galena and sphalerite, and less commonly tetrahedrite.
30 valid minerals.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
1000 - 1600 Ma
|Silver Plume Granite|
Age: Mesoproterozoic (1000 - 1600 Ma)
Description: Gray to pinkish-gray, medium- to coarsegrained, equigranular, seriate, or porphyritic, massive to flow-foliated, biotite-muscovite peraluminous syenogranite and monzogranite. Porphyritic varieties contain tabular microcline phenocrysts. Locally includes muscovite-bearing pegmatite, alaskite, and aplite. Muscovite in equivalent rocks north of quadrangle is almost entirely subsolidus, indicating that it formed during retrograde crystallization (J.C. Cole, written commun., 2005). Rb-Sr whole-rock age is 1,409±40 Ma (Hedge, 1969); preliminary U-Pb zircon ages are 1,424±6 Ma (W.R. Premo, unpub. data, 2005) and 1,422 Ma (no error given; Graubard and Mattison, 1990)
Reference: Kellogg, K.S., Shroba, R.R., Bryant, Bruce, and Premo, W.R. Geologic Map of the Denver West 30' x 60' Quadrangle, North- Central Colorado. USGS Geologic Investigations Series 3000. 
1000 - 1600 Ma
|Granitic rocks of 1400-m.y. age group|
Age: Mesoproterozoic (1000 - 1600 Ma)
Description: Includes Silver Plume, Sherman, Cripple Creek, St. Kevin, Vernal Mesa, Curecanti, Eolus, and Trimble Granites or Quartz Monzonites; also, San Isabel Granite of Boyer (1962) and unnamed granitic rocks
Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052.