Cascade Arc

U.S. part of a continental margin arc that formed during subduction of the Pacific and Juan de Fuca plates beneath western North America
Tract ID 003pCu9014
Country United States of America
Commodity Cu
Study area name United States revised
Tectonic setting continental margin
Deposit type porphyry copper
Grade-tonnage model General porphyry copper model (Singer and others, 2008)
Geologic age
Geologic feature age Tertiary
Generalized age Tertiary
Oldest rocks age 60Ma
Youngest rocks age 0Ma
Age range 60Ma
Identified Cu resources 9,200,000metric tons
Mean Cu (t/sq km) 147t/sq km
Map scales used 500K

Results of the assessment

Assessment date 2010
Estimators Steve Ludington, Jane Hammarstrom, Gilpin Robinson, and 1996 Team
Assessment depth 1km
Quantitative assessment Yes

Estimated number of deposits

Number of deposits Confidence level
1 90%
8 50%
14 10%
14 5%
14 1%
Mean estimated deposits 7.63 ±4.45 (0.58%)
Probability of mean 0.33
Probability of no copper 0.06

Estimated deposit density

(sq km)
Deposit density
per 100,000 sq km
6 13.63 203,703 7

Mean estimated tonnage

Copper 30,000,000
Molybdenum 840,000
Gold 750
Silver 9,600
Ore 6,000

Undiscovered copper resource

Confidence level 90% 50% 10% 5%
Tonnage 760,000 19,000,000 73,000,000 100,000,000

Economic analysis

Fraser country Washington*-Oregon
Fraser type 0.69%
Fraser high 0.31%
Typical cost 1%
High cost 0%
Infrastructure setting Typical
Comments on depth default
Expected depth distribution
0 - 250m 0.25
250m - 500m 0.25
500m - 1km 0.5
Economically recoverable resources
Copper 20,000,000t
Molybdenum 410,000t
Gold 390t
Silver 5,900t
Probability no econ recoverable 0.11
Econ NPV 5,500x $1M
Exp dollars 24.49x $1M/100,000 sq km
Exp value class Medium

Bibliographic references

General U.S. Geological Survey National Mineral Resource Assessment Team (2002)
Economic Robinson and Menzie (2012)

Deposits and prospects associated with this tract

Name Type State Country Development Details
Glacier Peak deposit Washington United States Occurrence Details
Gold Mountain deposit Washington United States Occurrence Details
Margaret deposit Washington United States Occurrence Details
Mazama deposit Washington United States Prospect Details
Middle Fork deposit Washington United States Occurrence Details
North Fork Snoqualmie River deposit Washington United States Occurrence Details
Sunrise deposit Washington United States Occurrence Details