National mineral assessment tract SB31 (Epithermal vein, Sado)

Tract SB31
Geographic region Southern Basin and Range
Tract area 39,700sq km
Deposit type Epithermal vein, Sado
Deposit age Tertiary

Deposit model

Model code 25d
Model type descriptive
Title Descriptive model of Sado epithermal veins
Authors Dan L. Mosier, Byron R. Berger and Donald A. Singer
URL https://pubs.usgs.gov/bul/b1693/html/bull7khf.htm
Source https://pubs.er.usgs.gov/publication/b1693

Estimates

Confidence Number of
deposits
90% 0
50% 0
10% 1
5% 1
1% 2

P(none): 0.9

Estimators: Tosdal, Rytuba, Theodore, Ludington, Bagby, Jachens, Singer

Rationale

Explained by James J. Rytuba
On the choice of deposit models
Miocene volcanic centers and associated subvolcanic intrusive rocks of intermediate to felsic composition are present in the west Mojave part of the south Basin and Range province. These consist of dacite to rhyolite dome fields and lava flow and ash-flow fields with similar compositions. Active geothermal systems are present in the Coso Range. The prevolcanic basement is made up largely of plutonic igneous rocks. These environments are permissive for Sado gold deposits (Mosier and others, 1986). One Sado gold deposit has been mined but is now inactive. Several epithermal gold prospects and deposits and large areas of alteration are present in all of the volcanic centers. Most of these deposits and prospects occur in areas of subvolcanic Miocene intrusive rocks and vein mineralization occurs in these rocks as well as in the crystalline basement rocks. Associated mineral deposits include quartz-alunite gold deposits, Comstock epithermal veins, and hot spring Au-Ag deposits.
On the delineation of permissive tracts
The permissive tract for Sado gold deposits was delineated on the basis of areas of known gold prospects and deposits, Miocene volcanic centers, and areas of shallow cover where buried extensions of volcanic centers may occur. Included within the tract are three known gold deposits of this type. Only one, the Yellow Aster deposit, is currently active.
Important examples of this type of deposit
There are several examples of this type of deposit within the three gold districts located in the permissive tract, including the Soledad gold deposit in the Soledad Mountain volcanic center, and the Kelly and Yellow Aster mines in the Randsburg district, all of which have been major producers of gold and silver in California.
On the numerical estimates made
Three factors contributed to the numerical estimate for undiscovered resources. One is the presence of one mine developed for this deposit type and the presence of several prospects and deposits with alteration and mineralization characteristics of this deposit type. The second factor is the presence of quartz-alunite type deposits and prospects which are associated with this deposit type. The third factor is the presence of several large volcanic centers, parts of which are buried beneath a thin veneer of alluvium or sedimentary rock that underlies parts of the permissive terrane. For the 90th, 50th, 10th, 5th, and 1st percentiles, the team estimated 0, 0, 1, 1, and 2 or more deposits consistent with the grade and tonnage model of Mosier and Sato (1986).
References
Mosier, D.L., and Sato, Takeo, 1986, Grade and tonnage model of Sado epithermal veins, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 155-157.
Mosier, D.L., Berger, B.R., and Singer, D.A., 1986, Descriptive model of Sado epithermal veins, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 154.

Geographic coverage

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