Structural Model for Cooke Mountain in Republic Gold District, NE Washington
Oversight Points to an
Overlooked Structural Model
for Cooke Mountain,
Republic Gold District,
NE Washington
Michael Rasmussen,
PhD, CPG
Nine Mile Falls, WA
Calgary
Spokane
●
●
Canada
US
100 km
CM
Quesnellia
Nelson
Sea Level
Quesnellia
after Hoy and Andrew, 1997
Late Triassic
North
America
Cache Creek
melange
Nicola
arc
Harper Ranch
Kootenay
Brooklyn
Quesnel Terrane
Late Triassic
S
outheast British Columbia
Sea Level
Early Jurassic
North
America
after Hoy and Andrew, 1997
Knob Hill
Hall
Elise
Nicola
Cache Creek
melange
Quesnellia
Quesnel Terrane
S
outheast British Columbia
Early Jurassic
Jurassic Fold and Thrust Deformation
Growth of Metamorphic Core Complexes
with Synformal Grabens and Half-Grabens
Box, 1992
Toroda Graben
Republic Graben
Republic Graben
Lamefoot Mine
530,000 oz Au @ 0.21 opt
Key East & West Pits
Kettle River Mill Site
Republic District
(Golden Eagle)
Republic
Overlook Mine
280,000 oz Au @ 0.15 opt
A -------A’
Sherman Fault
Chesaw Fault
Cooke Mtn
Sericite 197 Ma
40
Ar/
39
Ar
Bedded pyrite
with reaction rim.
Pyrite Clasts
Felsic tuffaceous siltite
Felsic tuff
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LF-xsecs.ppt
KCA 10-25-96
Evidence for sea-floor deposition of massive mag+po+Au
•
Metamorphic foliation in massive sulfides
•
Au-bearing clasts in ls-mag-po conglomerate at ls contact
•
Zoned decrease in Cu/Cu+Zn from strat base upward
•
40
Ar/
39
Ar sericite age 197 Ma in mineralized tuff
•
S isotope consistent w/ uPermian marine settings
•
Pb isotopes consistent with Permian Pb, later overprint
c
E.S. Cheney in 1996 at about
26700 N
,
using data collected up to 11/19/94 by geologists
and consultants of Echo Bay Mines, Ltd.
Lamefoot Isoclinal Fold Model
Oversight
Overlook
Key West
Key East
Adamera Drilling 2014, Oversight Prospect, 50 m depth
Downhole
Section is upright.
Overlook
Cooke Mountain
Mark Kolebaba, Pres/CEO, Adamera Minerals,
Oversight Prospect, Cooke Mtn,
Republic District, Washington
1. View to the SW from upper slopes of Cooke Mtn, at a prospect referred to as Oversight, a historically mapped magnetiferous metallic showing with anomalous gold nearby. Adamera Minerals conducted drilling on Oversight this summer, and determined that a structural model proposed in the 1990’s should be applied to this setting.
2. The Echo Bay tailings pond is in the middle distance, and
3. The now-reclaimed adits for Echo Bay’s Overlook underground gold mine (280,000 oz, at 0.15 opt) are downslope to the right (west) in this field of view.
This article presents an overlooked structural model for Cooke Mountain in the Republic Gold District of NE Washington. It covers various geological aspects such as the Quesnel Terrane, growth of metamorphic core complexes, and the geology of the Republic, WA area. Detailed descriptions and images of key features like Lamefoot Mine and Pyrite Clasts are provided. The study sheds light on the geological history and important mineral deposits in the region.
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Presentation Transcript
Oversight Points to an Overlooked Structural Model for Cooke Mountain, Republic Gold District, NE Washington Michael Rasmussen, PhD, CPG Nine Mile Falls, WA
Calgary 100 km Nelson Quesnellia Canada US CM Spokane
Quesnel Terrane Late Triassic Southeast British Columbia Quesnellia Nicola arc Cache Creek melange North America Kootenay Brooklyn Sea Level Harper Ranch Late Triassic after Hoy and Andrew, 1997
Quesnel Terrane Southeast British Columbia Early Jurassic Quesnellia Cache Creek melange North America Elise Hall Nicola Sea Level Knob Hill Early Jurassic after Hoy and Andrew, 1997
Growth of Metamorphic Core Complexes with Synformal Grabens and Half-Grabens Jurassic Fold and Thrust Deformation Box, 1992
Geology of the Republic, WA Area UD R.30 E. R.32 E. R.33 E. R.31 E. Buckhorn Mt Vancover B.C. T.40.N T.40.N Kettle Mine K2 Mine & East Veins Curlew Emanuel Creek UD T.39.N T.39.N U D 0 100 200 300 400 500 UD Scale in Miles UD Fault UD Lamefoot Mine T.38.N T.38.N Key East & West Pits Explanation: Republic District (Golden Eagle) Overlook Mine Volcanics T.37.N T.37.N Kettle River Mill Site Intrusives UD Republic UD Greenstone U High Grade Metamorphic D Locations Washington-BC.dwg U T.36.N T.36.N D Claim Block(s) UD 0 1 2 3 4 5 R.33 E. R.30 E. R.34 E. R.31 E. R.32 E. Scale in Miles UD Geology of the Republic Graben Area
Lamefoot Mine 530,000 oz Au @ 0.21 opt Key East & West Pits Republic District (Golden Eagle) Overlook Mine 280,000 oz Au @ 0.15 opt Kettle River Mill Site Republic
Pyrite Clasts Felsic tuff Bedded pyrite with reaction rim. Felsic tuffaceous siltite Sericite 197 Ma 40Ar/39Ar
Overlook Project Generalized Geology Section 10210 Evidence for sea-floor deposition of massive mag+po+Au Metamorphic foliation in massive sulfides Au-bearing clasts in ls-mag-po conglomerate at ls contact Zoned decrease in Cu/Cu+Zn from strat base upward 40Ar/39Ar sericite age 197 Ma in mineralized tuff S isotope consistent w/ uPermian marine settings Pb isotopes consistent with Permian Pb, later overprint SE NW 4400 Pcl Pcl Pcl Veinlet Ore Zone 4200 Low-Angle Shear Pvcl Low-Angle Shear Tsc-1 Pvcl Ore Zone Tsc-2 Pyrrhotite Magnetite Pls Magnetite 4000 Pls LF-xsecs.ppt KCA 10-25-96 Po+Mag+Au clasts in limestone basal conglomerate 200 Feet
Lamefoot Isoclinal Fold Model E.S. Cheney in 1996 at about 26700 N, using data collected up to 11/19/94 by geologists and consultants of Echo Bay Mines, Ltd. c ~ 250 m
Key West Key East Oversight Overlook
Adamera Drilling 2014, Oversight Prospect, 50 m depth Downhole Section is upright.
Overlook Cooke Mountain Cooke Mountain Oversight
Cooke Mountain Oversight
Mark Kolebaba, Pres/CEO, Adamera Minerals, Oversight Prospect, Cooke Mtn, Republic District, Washington
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