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72007150
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7050
7000
6950
6900
72007150
7100
7050
70006950
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RBMC-002
RBMC-003
RRBM-255
RBD05-01
RBD06-01
RBD06-03
Jqmp
Jqmp
Mc
JbxJqmp
Js
Jbx
Mc
Jqmd
Jqmp
Mc
JqmpJqmp
Mc
Jqmp
Mc Jqmp
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Jqmp
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Jqmp
Jqmp Jqmp
Jqmp
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Jbx Jqmp
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Jbx Mc
Mc
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RBM_AD_1
RBM_AD_2
RBM_AD_7
RBM_AD_10
30
35
30
30
20
20
80
60
80
30
26
5556
80
40
38
2020
50
45
50
50
40
80
52
70
76
80
70
84
80
60
86
6268
75
8560
50
45
28
35
85
8080
68
80
86
70
48
70
70
56
60
70
60
72
6044
50
6080
75
75
44
86
60
75
619900
619900
620000
620000
620100
620100
620200
620200
620300
620300
620400
620400
4422
600
4422
600
4422
700
4422
700
4422
800
4422
800
4422
900
4422
900
4423
000
4423
000
115°35'30"W
115°35'30"W
115°35'45"W
115°35'45"W
39°56'45"N
39°56'45"N
PRELIMINARY GEOLOGIC MAP OF THE RBM PIT, BALD MOUNTAIN MINE, WHITE PINE COUNTY,
NEVADA
Daniel Pace
OPEN-FILE REPORT 15-1PLATE 1 OF 2
PRELIMINARY GEOLOGIC MAP OF THE RBM PIT, BALD MOUNTAIN MINE, WHITE PINE COUNTY, NEVADANEVADA BUREAU OF MINES AND GEOLOGY
2015
UTM GRID AND 1983 MAGNETIC NORTH
DECLINATION AT CENTER OF SHEET
^
MN
15º 00'0º 55'
GN
×××
Prepared with support from Barrick Gold Corp., the Nevada Division of Minerals, and the Geological Society of Nevada
Quartz monzonite porphyry (Jurassic) Plug-like body with a diameter of at least 300 mwith associated dikes and sills composed of 5–15% partially resorbed quartz, 10-30%feldspar, 1–5% biotite, and sparse hornblende phenocrysts set in a fine-grainedgroundmass of quartz and feldspar. Hydrothermal alteration commonly masks originaligneous mineralogy. LA-ICPMS dates on zircon yielded ages of 163.5±6.8 Ma and163.0±3.4 Ma (Pace, 2009).
Diorite Porphyry (Jurassic) A 0.25 m-wide east-west-striking, steeply north-dipping dikethat cuts the quartz monzonite porphyry plug on the west side of the RBM pit. Dikes alsocut quartz monzodiorite dikes in drill core. Contains up to 10% plagioclase, 5–7%hornblende, and 3% biotite phenocrysts, as well as up to 5% rounded quartz xenocrysts,set in a groundmass of fine-grained sub-aligned feldspar laths, hornblende needles, andquartz. LA-ICPMS date on zircon yielded age of 161.8 ± 2.9 Ma (Pace, 2009).
Magmatic hydrothermal breccia (Jurassic) Northwest-striking, steeply northeast-dippingbreccia bodies that cut quartz monzonite porphyry and quartz monzodiorite dikes. Matrix-supported, composed of 30–60% subangular to subrounded fragments up to a meter indiameter in an altered, finely milled matrix of quartz, kaolinite, and sulfides. Silicified rockand quartz veinlets are the most abundant fragment types.
Quartz monzodiorite (Jurassic) North- to northwest-striking fine-grained equigranulardikes up to 15 m thick that cut quartz monzonite porphyry. Primary mineralogy everywheredestroyed by hydrothermal alteration. Up to 30% quartz, which could be largelyhydrothermal in origin, is present as ~0.2 mm anhedral quartz crystals in a matrix ofkaolinite. Similar dikes intercepted in drill holes south of the RBM pit contain up to 20%biotite. LA-ICPMS date on zircon yielded age of 163.9 ± 3.3 Ma (Pace, 2009).
GOLD MINERALIZATION
Garnet skarn (Jurassic) Andraditic garnet skarn. Interstices between garnet arecomposed of retrograde quartz, chlorite, calcite, and pyrite variably oxidized to limonite.
Diamond Peak Formation (Mississippian) Predominantly sandstone with interbeds ofsiltstone. Sandstone ranges from white quartzite to poorly-sorted, medium-grainedheterolithic arenites containing conspicuous chert clasts. Contact with underlying ChainmanShale is gradational and was mapped by the last occurrence of coarse-grained sandstonelenses with chert clasts.
Chainman Shale (Mississippian) Pale white to tan, siltstone that is locallymetamorphosed to quartz-albite-epidote hornfels and variably hydrothermally leached andsilicified.
>0.01 opt gold
Contact Solid where certain and location accurate, dashed where approximate. Arrow showing dip of bedding contact.
Normal fault Solid where certain and location accurate, dashed where approximate. Arrow showing dip of fault.
Strike and dip of beddingInclinedo41
Benches Mapped benches, solid where certain and location accurate
!
Location of blast holes by elevation (ft)6825 ! 6800
S
S
Jdp
Jqmd
Js
Jqmp
Mdp
Mc
Jbx
Suggested citation:Pace, D., 2015, Preliminary geologic map of the RBM pit, Bald Mountain Mine, White Pine County, Nevada; Nevada Bureau of Mines and Geology Open-File Report 15-1, scale 1:1000.
ReferencesPace, D. W., 2009, Relationship between magmatism and mineralization in the RBM gold deposit, White Pine County, Nevada: Unpublished Master’s thesis, University of Nevada Reno, 172 p.
AcknowledgmentsBarrick Gold Corp. and Nevada Bureau of Mines and Geology provided financial support for Dan Pace’s Master’s thesis, of which this map was a major component. The Nevada Division of Minerals and the Geological Society of Nevada provided funds to prepare the map for release as a Nevada Bureau of Mines and Geology Open-File Report.
RBM_AD_3
"
Location of dated sample
RBMC-002
RBM_AD_3
#
Location of logged drill holes
40
70
1:1,000
Field work done in June–August, 2007Prepared with support from Barrick Gold Corp., the Nevada Division of Minerals, and the Geological Society of NevadaDRAFT Preliminary geologic map Has not undergone office or field reviewCartography and map production in ESRI ArcGIS v10.1 (ArcGeology v1.3) by Daniel Pace and Katie RyanSymbology per FGDC-STD-013-2006First Edition, January 2015Printed by Nevada Bureau of Mines and GeologyThis map was printed on an electronic plotter directly from digital files. Dimensional calibration may vary between electronic plotters and X and Y directions on the same plotter, and paper may change size; therefore, scale and proportions may not be exact on copies of this map.
For sale by: Nevada Bureau of Mines and Geology 2175 Raggio Pkwy. Reno, Nevada 89512 ph. (775) 682-8766 www.nbmg.unr.edu; [email protected] 2423
Projection: Universal Transverse Mercator, Zone 11, North American Datum 1983 (m)Contour interval 5 feet. Base contour lines provided by Barrick Gold Corp.
Scale 1:1000
0 0.025 0.05 Miles
0 0.025 0.05 Kilometers
0 100 200 Feet1 Walker Canyon2 Sherman Mountain3 Station Butte4 Cold Creek Ranch NW5 Big Bald Mountain6 Tognini Spring7 Cold Creek Ranch8 Mooney Basin Summit9 Long Valley Slough
Adjoining 7.5'quadrangle names
1 2
4 6
7
3
5
8 9
Map location
Plate 1 of 2
GEOLOGY
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