Projects
Nevada
- Why Nevada
- CORTEZ TREND PROPERTIES
- Angel Wing
- Iron Point
- Redlich
- Big Blue
- East Spruce
- Kibby Flat
- Mustang
Colombia
- Why Colombia
- Pavo Real
Big Blue
Summary
Big Blue is a Carlin-Type sediment-hosted gold project 13 mi (21 km) north-northeast of Austin in south-central Lander County, Nevada (Fig. 1). The property's 255 contiguous unpatented mining claims encompass 8.2 sq mi (21.2 sq km). The claim block covers a portion of the Callaghan Window, an erosional exposure of lower Paleozoic continental platform and slope carbonate units under the siliclastic upper plate units of the Roberts Mountains Thrust.
Exploration work through 2012 identifies at least five target areas variably defined by hydrothermal alteration (bleaching, decalcification, silicification); gold and pathfinder element anomalous stream sediments, rocks, and soils; and drill-intersected gold mineralization. Rock chips range up to 56.4 ppm Au (1.6 oz Au/ton), 10,000 ppm As, 1,040 ppm Sb, and 5,080 ppm Hg. Soils range up to 3.9 ppm Au and 315 ppm As.
Only two of the target areas have drill holes within their boundaries. Upper plate drilled gold intercepts range up to 30 ft (10-40 ft) of 0.048 oz Au/ton (9.1 m of 1.631 g Au/t) containing 5 ft of 0.178 oz Au/ton (1.5 m of 6.110 g Au/t). Lower plate gold intercepts range up to 5 ft (1,040-1,045 ft) of 0.048 oz Au/ton (1.5 m of 1.660 g Au/t).
Miranda believes the existence of a favorable structural setting, including the Roberts Mountains Thrust, favorable carbonate host rocks, widespread strong surface gold and pathfinder geochemical anomalies, and drilled gold up to 0.178 oz Au/ton in the upper plate and 0.048 oz Au/ton in the lower plate of the thrust together indicate the Big Blue project area has potential to contain a multi-million ounce gold orebody.
Miranda Gold is seeking a joint venture partner for its Big Blue project.
Location
Big Blue project is on the east flank of the Toiyabe Range approximately 13 miles (21 km) north-northeast of Austin, Nevada (Fig. 1). Road access from Austin is east via highway U.S. 50, northeast on the Grass Valley road (Nevada state route 306), and a series of two-track dirt roads within the project area. The region is typified by north-northeast trending mountain ranges separated by broad, alluvium filled valleys. Property elevations vary from 6,800 ft (2,100m) to 8,700 ft (2,700m).
Geology
The project area is in a west-northwest-trending structural corridor and covers a portion of the Callaghan Window (Fig. 2). The structural corridor may extend at least 18 mi (30 km) westward to the Ravenswood district in the Shoshone Mountains. The Callaghan Window is an erosional exposure through the Nevada-scale Roberts Mountains Thrust (RMT) into lower Paleozoic carbonate rocks in the lower plate of the thrust fault. The exposure trace of the RMT roughly trends east-west through the southern portion of the Big Blue claim block. The upper plate of the RMT consists of the Ordovician Vinini and the Devonian Slaven Chert formations. These siliciclastic rocks (chert-pebble conglomerate, quartzite, sandstone, siltstone, chert, mudstone, argillite, phyllite) with minor sandy limestone were originally deposited in a marine basin to the west and tectonically transported easterly over the continental shelf by the RMT during Devonian/Mississippian time. The lower plate carbonate section, deposited on the continental shelf and slope, consists of the following Silurian through Cambrian age units (Fig. 2):
Igneous rocks crop out in and near the project area. Within the claim block small altered dikes of unknown age, some striking west-northwest, cut upper and lower plate stratigraphy. The northern margin of the Jurassic Austin stock forms a three-mile wide exposure two miles southwest of the claims. Tertiary (Oligocene or older) volcanic rocks crop out 1.5 mi southeast and 2 mi northeast of the claims.
Structure in the Big Blue project area is complex. Regionally, Big Blue is in a west-northwest-trending structural corridor that traverses upper and lower plate rocks of the RMT and includes the irregular trace of the RMT in the southern part of Big Blue. The structure zone extends through Ox Corral and Cottonwood drainage basins in the project area. Additionally, both the upper and lower plates of the RMT are cut by imbricate thrusts and high angle northeast- and northwest-trending faults.
A gravity survey (200 m grid, 313 stations) defines a doughnut-shaped residual gravity high between Ox Corral and Cottonwood creeks (Fig. 3). The anomaly is about 8,000 ft (2,400 m) in diameter with a central low about 2,000 ft (600 m) wide. The residual gravity high is interpreted to be caused by limestone at depth, to be fault-bounded, and to encompass possibly altered rock (the central low).
Gold-associated hydrothermal alteration affects both the upper and lower plates of the RMT in the project area. Alteration in the upper plate includes silicified and heavily iron stained fault breccias, patchy and linear zones of quartz veins and veinlets, bleaching, and clay alteration. Lower plate alteration includes bleaching, decalcification, and pervasive silicification (jasperoids).
Quadrangle-scale geology (Fig. 2) is shown on the Mount Callaghan 7-1/2 deg. U.S.G.S. GQ-730 geologic map (Stewart, J.H., and McKee, E.H., 1968).
Geochemistry
Miranda has data for approximately 500 rock chip and 1,500 soil samples within the Big Blue claim block as well as about 100 stream sediment samples from the region. Most of the rock and all of the soil sampling is concentrated in the southern half of the claim block. Figures 4, 5, and 6 show the distributions of stream sediment---As, rock chip---Au, and soil---Au and As samples, respectively. Table I summarizes maximum values of Au, As, Sb, and Hg in stream sediment, soil, rock, and drill hole samples from within the project area. Gold ranges up to 0.589 ppm Au in stream sediments, 3.9 ppm Au in soils, 56.4 ppm (1.645 oz Au/ton) in rock chips, and 6.11 ppm Au (0.178 oz Au/ton) in drill samples.
Drilling
From about 1981 through 2012, 21 holes totaling 12,440 ft (3,792 m) were collared within the Big Blue claim block, all within the southern part of the property (Figs. 2 and 3). Of these, 16 are less than 600 ft (183 m) deep. Table II summarizes all drill intercepts greater than 0.01 oz Au/ton (>0.034 g Au/t). The highest gold intercept is from the upper plate of the RMT in drill hole BBR11-01 with 5 ft of 0.178 oz Au/t (1.5 m of 6.110 g Au/t). All holes with greater than 0.01 oz Au/ton are in the Anomaly Ridge target area.
Exploration Targets
Anomalous geochemistry, especially for Au and As, in stream sediments, rock chips, soil samples, and drill intercepts help define five exploration target areas only two of which contain drill holes. Table I summarizes maximum element values by sample medium in these target areas which are outlined and identified by target area abbreviation in Figures 2-6.
Moxen (MT): The north end of the claim block (Moxen claims) is about 2 sq mi of mostly pediment with exposures of Cambrian Crane Creek and Ordovician Antelope Valley limestone. Highly anomalous stream sediment (max.: 0.586 ppm Au) and rock chip (max.: 6,080 ppm As, 1,040 ppm Sb) samples require detailed follow-up field work. .
Callaghan (CT): The approximately 8,000 x 6,000 ft (2,440 x 1,830 m) target area along Callaghan Creek is underlain by thin bedded to laminated Cambrian Crane Creek limestone locally replaced by jasperoid. Anomalous stream (max.: 96.1 ppm As) and highly anomalous rock chip (max.: 2.842 ppm Au, 3,710 ppm As, 123 ppm Sb, 208 ppm Hg) samples require detailed follow-up field work.
Upper Oxen (UOT): Upper Ox Corral Creek (Oxen claims) aligns with the WNW structural corridor, is underlain by the trace of the RMT, and contains a WNW-elongate region approximately 6,000 x 2,000 ft (1,830 x 610 m) of anomalous gold and pathfinder elements in rock (max.: 0.593 ppm Au, 1,130 ppm As, 88 ppm Hg) and soil (max.: 0.115 ppm Au, 228 ppm As, 3 ppm Hg). The target area has not been drill tested.
Mid Oxen (MOT): Near the middle reach of Ox Corral Creek is a crescent-shaped geochemical anomaly with 4,500 ft (1,370 m) arc length. It coincides with the projected intersection of NE-trending faults with the WNW structural corridor followed by the creek and is generally underlain by upper plate siliclastic rocks. The anomaly is also coincident with the western rim of the doughnut-shaped residual gravity high approximately 8,000 ft in diameter. The area of geochemical anomaly incorporates rock chip samples with up to 0.093 ppm Au, 9,999 ppm As, and 600 ppm Hg and soil samples with up to 0.913 ppm Au, 289 ppm As, and 2 ppm Hg. Of the three reverse circulation holes within the target area (drilled by Kerr-McGee in 1990; total 1,520 ft or 463.3 m; maximum depth 520 ft or 158 m) the strongest gold intercept is in hole 4-6: 220-230 ft, 10 ft of 0.240 ppm Au in the upper plate of the RMT.
Anomaly Ridge (ART): A 3,200 ft (975 m) long "T"-shaped geochemical anomaly elongated west-northwest with cross-bar oriented NE is aligned along Cottonwood Creek and generally follows the trace of the RMT. The target area includes highly anomalous rock chip samples (max.: 56.4 ppm Au (1.645 oz Au/ton), 10,000 ppm As, 160 ppm Sb, 5,080 ppm Hg) and anomalous soil samples (max.: 0.850 ppm Au, 315 ppm As, 66 ppm Sb, 3 ppm Hg). Of the 13 drill holes in the target area (total drilling 8,520 ft or 2,597 m), nine are less than 600 ft (183 m) deep, and all are collared in the upper plate of the RMT. All but three holes intersect >0.01 ppm in the upper plate which in drill intercepts ranges from 85 to 365 ft (26 to 111 m) deep. The strongest upper plate gold intercept is in BBR11-01: 30 ft of 0.048 oz Au/ton containing 5 ft of 0.178 oz Au/ton (9.1 m of 1.631 g Au/t containing 1.5 m of 6.110 g Au/t). Holes BBR12-01 and -02 intersect +0.01 oz Au/t in the lower plate at 1,155 ft (352.0 m) and 1,005 ft (306.3 m), respectively. The strongest lower plate gold intercept is in BBR12-02: 1,040-1,045 ft, 5 ft of 0.048 oz Au/ton (317.0-318.5 m, 1.5 m of 1.660 g Au/t) contained within 80 ft of 0.005 oz Au/ton (24.4 m of 0.176 g Au/t). Table II summarizes the drilled gold intercepts over 0.01 oz Au/ton (0.343 g Au/t) in the target area.
Significantly, hole BBR11-05 displays Carlin-Type pathfinder element dispersion from an interpreted source below the bottom of the hole. In BBR11-05, terminated due to caving at 835 ft (254.5 m), pathfinder elements in the lower plate carbonate sequence from about 600 ft to the bottom of the hole show an approximate 10-fold increase to strongly anomalous values: As from 109 to 1,360 ppm, Sb from 9.95 to 116 ppm, Hg from 0.52 to 5.54 ppm, and Tl from 0.17 to 0.91 ppm (maximum = 1.92 ppm). In this same interval gold increases from 0.008 to 0.055 ppm (maximum = 0.074 ppm Au). The interpreted target beneath BBR11-05 has not been drill tested.
Exploration History
A historic turquoise mine in the upper plate Slaven Chert south of the claims is the only known mineral production in the area. From about 1980 to 1998 several companies, including Anaconda, FMC Corp., U.S. Borax, Kerr-McGee, Homestake Mining, Cordex, and Hemlo, explored in and near the Callaghan window. They conducted geological mapping, stream sediment, rock chip, and soil sampling surveys, resistivity surveys, and drilling; however, most of this exploration work was done near Cottonwood Springs east of Big Blue claims or in McGuinness Hills southeast of Big Blue. Of the approximately 125 drill holes collared within and adjacent to the Callaghan Window, only 12 were on the Big Blue claim block. These holes range from 190 to 1000 feet deep and only four are known to have intersected the lower plate carbonate section. The deepest hole, drilled by Kennecott in 1998 on the east edge of the claim block, bottomed in the upper plate siliclastic sequence. All holes targeted shallow oxide gold.
In 2010 Miranda Gold identified sediment-hosted gold exploration potential in the Callaghan Window through generative regional exploration concepts. Miranda negotiated a lease (3% NSR with buy-down) on 76 existing claims, staked additional claims, and conducted district-scale stream sediment and rock chip sampling. Ramelius Resources Ltd., an Australian gold mining company, entered into joint-venture agreement with Miranda in 2010. From 2010 to 2012 Ramelius' project work included staking additional claims, geologic mapping, rock chip sampling, grid soil sampling, gravity and ground magnetic surveys, and drilling nine reverse circulation holes for a total of 7,210 ft (2,197.6 m). Their work proved the lower plate carbonate sequence at Big Blue hosts Carlin-Type gold mineralization.
Big Blue is a Carlin-Type sediment-hosted gold project 13 mi (21 km) north-northeast of Austin in south-central Lander County, Nevada (Fig. 1). The property's 255 contiguous unpatented mining claims encompass 8.2 sq mi (21.2 sq km). The claim block covers a portion of the Callaghan Window, an erosional exposure of lower Paleozoic continental platform and slope carbonate units under the siliclastic upper plate units of the Roberts Mountains Thrust.
Exploration work through 2012 identifies at least five target areas variably defined by hydrothermal alteration (bleaching, decalcification, silicification); gold and pathfinder element anomalous stream sediments, rocks, and soils; and drill-intersected gold mineralization. Rock chips range up to 56.4 ppm Au (1.6 oz Au/ton), 10,000 ppm As, 1,040 ppm Sb, and 5,080 ppm Hg. Soils range up to 3.9 ppm Au and 315 ppm As.
Only two of the target areas have drill holes within their boundaries. Upper plate drilled gold intercepts range up to 30 ft (10-40 ft) of 0.048 oz Au/ton (9.1 m of 1.631 g Au/t) containing 5 ft of 0.178 oz Au/ton (1.5 m of 6.110 g Au/t). Lower plate gold intercepts range up to 5 ft (1,040-1,045 ft) of 0.048 oz Au/ton (1.5 m of 1.660 g Au/t).
Miranda believes the existence of a favorable structural setting, including the Roberts Mountains Thrust, favorable carbonate host rocks, widespread strong surface gold and pathfinder geochemical anomalies, and drilled gold up to 0.178 oz Au/ton in the upper plate and 0.048 oz Au/ton in the lower plate of the thrust together indicate the Big Blue project area has potential to contain a multi-million ounce gold orebody.
Miranda Gold is seeking a joint venture partner for its Big Blue project.
Location
Big Blue project is on the east flank of the Toiyabe Range approximately 13 miles (21 km) north-northeast of Austin, Nevada (Fig. 1). Road access from Austin is east via highway U.S. 50, northeast on the Grass Valley road (Nevada state route 306), and a series of two-track dirt roads within the project area. The region is typified by north-northeast trending mountain ranges separated by broad, alluvium filled valleys. Property elevations vary from 6,800 ft (2,100m) to 8,700 ft (2,700m).
Geology
The project area is in a west-northwest-trending structural corridor and covers a portion of the Callaghan Window (Fig. 2). The structural corridor may extend at least 18 mi (30 km) westward to the Ravenswood district in the Shoshone Mountains. The Callaghan Window is an erosional exposure through the Nevada-scale Roberts Mountains Thrust (RMT) into lower Paleozoic carbonate rocks in the lower plate of the thrust fault. The exposure trace of the RMT roughly trends east-west through the southern portion of the Big Blue claim block. The upper plate of the RMT consists of the Ordovician Vinini and the Devonian Slaven Chert formations. These siliciclastic rocks (chert-pebble conglomerate, quartzite, sandstone, siltstone, chert, mudstone, argillite, phyllite) with minor sandy limestone were originally deposited in a marine basin to the west and tectonically transported easterly over the continental shelf by the RMT during Devonian/Mississippian time. The lower plate carbonate section, deposited on the continental shelf and slope, consists of the following Silurian through Cambrian age units (Fig. 2):
- Silurian Roberts Mountain Formation silty limestone;
- Ordovician Hanson Creek Formation dolomite and limestone;
- Ordovician Antelope Valley Limestone, Ninemile Formation, and Goodwin Limestone which together comprise the Ordovician Pogonip Group; and
- Cambrian Crane Creek sequence of thin bedded and platy limestone, shale, and siltstone that are the oldest rocks exposed within the claim block.
Igneous rocks crop out in and near the project area. Within the claim block small altered dikes of unknown age, some striking west-northwest, cut upper and lower plate stratigraphy. The northern margin of the Jurassic Austin stock forms a three-mile wide exposure two miles southwest of the claims. Tertiary (Oligocene or older) volcanic rocks crop out 1.5 mi southeast and 2 mi northeast of the claims.
Structure in the Big Blue project area is complex. Regionally, Big Blue is in a west-northwest-trending structural corridor that traverses upper and lower plate rocks of the RMT and includes the irregular trace of the RMT in the southern part of Big Blue. The structure zone extends through Ox Corral and Cottonwood drainage basins in the project area. Additionally, both the upper and lower plates of the RMT are cut by imbricate thrusts and high angle northeast- and northwest-trending faults.
A gravity survey (200 m grid, 313 stations) defines a doughnut-shaped residual gravity high between Ox Corral and Cottonwood creeks (Fig. 3). The anomaly is about 8,000 ft (2,400 m) in diameter with a central low about 2,000 ft (600 m) wide. The residual gravity high is interpreted to be caused by limestone at depth, to be fault-bounded, and to encompass possibly altered rock (the central low).
Gold-associated hydrothermal alteration affects both the upper and lower plates of the RMT in the project area. Alteration in the upper plate includes silicified and heavily iron stained fault breccias, patchy and linear zones of quartz veins and veinlets, bleaching, and clay alteration. Lower plate alteration includes bleaching, decalcification, and pervasive silicification (jasperoids).
Quadrangle-scale geology (Fig. 2) is shown on the Mount Callaghan 7-1/2 deg. U.S.G.S. GQ-730 geologic map (Stewart, J.H., and McKee, E.H., 1968).
Geochemistry
Miranda has data for approximately 500 rock chip and 1,500 soil samples within the Big Blue claim block as well as about 100 stream sediment samples from the region. Most of the rock and all of the soil sampling is concentrated in the southern half of the claim block. Figures 4, 5, and 6 show the distributions of stream sediment---As, rock chip---Au, and soil---Au and As samples, respectively. Table I summarizes maximum values of Au, As, Sb, and Hg in stream sediment, soil, rock, and drill hole samples from within the project area. Gold ranges up to 0.589 ppm Au in stream sediments, 3.9 ppm Au in soils, 56.4 ppm (1.645 oz Au/ton) in rock chips, and 6.11 ppm Au (0.178 oz Au/ton) in drill samples.
| Table I: Big Blue Project Area Maximum Geochemical Values in Sampled Medium | ||||
|---|---|---|---|---|
| Sample Type | Au ppm | As ppm | Sb ppm | Hg ppm |
| Big Blue Project All | ||||
| Stream | 0.589 | 96.1 | 21.3 | 1.08 |
| Soil | 3.9 | 315 | 66 | 3 |
| Rock | 56.4 | 10000 | 1040 | 5080 |
| Drill hole | 6.11 | 10000 | 212 | 45.2 |
| Moxen Target (MT) | ||||
| Stream | 0.589 | 54.8 | 6.25 | 0.06 |
| Rock | 0.089 | 6080 | 1040 | 4.11 |
| Callaghan Target (CT) | ||||
| Stream | 0.021 | 96.1 | 13.25 | 0.17 |
| Rock | 2.842 | 3710 | 123 | 208 |
| Upper Oxen Target (UOT) | ||||
| Stream | 0.003 | 28.3 | ||
| Soil | 0.115 | 228 | 8 | 3 |
| Rock | 0.593 | 1130 | 26 | 88 |
| Middle OxenTarget (MOT) | ||||
| Stream | 0.006 | 29.3 | ||
| Soil | 0.913 | 289 | 8 | 2 |
| Rock | 0.093 | 9999 | 51 | 600 |
| Drill hole (10 ft) | 0.240 | ND | ND | ND |
| Anomaly Ridge Target (ART) | ||||
| Stream | 0.028 | 72.3 | ||
| Soil | 0.850 | 315 | 66 | 3 |
| Rock | 56.4 | 10000 | 160 | 5080 |
| Drill hole (5 ft) | 6.11 | 10000 | 212 | 45.2 |
| *ND = No Data | ||||
Drilling
From about 1981 through 2012, 21 holes totaling 12,440 ft (3,792 m) were collared within the Big Blue claim block, all within the southern part of the property (Figs. 2 and 3). Of these, 16 are less than 600 ft (183 m) deep. Table II summarizes all drill intercepts greater than 0.01 oz Au/ton (>0.034 g Au/t). The highest gold intercept is from the upper plate of the RMT in drill hole BBR11-01 with 5 ft of 0.178 oz Au/t (1.5 m of 6.110 g Au/t). All holes with greater than 0.01 oz Au/ton are in the Anomaly Ridge target area.
| Table II: Big Blue Project Area Drill Intercepts >0.01 oz Au/ton (>0.343 g Au/t) | |||||||
|---|---|---|---|---|---|---|---|
| Hole ID | Total Depth (ft) |
Interval (ft) | Length (ft) | Grade (oz Au/ton) |
Interval (m) (m) |
Length (m) (m) |
Grade (g Au/t) |
| Anomaly Ridge Target (ART) | |||||||
| MC-7 | 420 | 40-50 | 10 | 0.071 | 12.2-15.2 | 3.0 | 2.44 |
| COT-1 | 500 | 115-120 | 5 | 0.032 | 35.1-36.6 | 1.5 | 1.080 |
| 33-2 | 190 | 40-45 | 5 | 0.017 | 12.2-13.7 | 1.5 | 0.583 |
| BBR11-01 | 1,120 | 10-40 | 30 | 0.048 | 3.0-12.2 | 9.1 | 1.631 |
Includes |
15-20 | 5 | 0.178 | 4.6-6.1 | 1.5 | 6.110 | |
| 70-80 | 10 | 0.019 | 21.3-24.4 | 3.0 | 0.651 | ||
| BBR11-02 | 475 | 70-75 | 5 | 0.015 | 21.3-22.9 | 1.5 | 0.515 |
| 90-95 | 5 | 0.018 | 27.4-29.0 | 1.5 | 0.624 | ||
| BBR11-03 | 275 | 55-80 | 25 | 0.043 | 16.8-24.4 | 7.6 | 1.491 |
| Includes | 55-60 | 5 | 0.149 | 16.8-18.3 | 1.5 | 5.100 | |
| 90-95 | 5 | 0.033 | 27.4-29.0 | 1.5 | 1.135 | ||
| BBR11-04 | 575 | 45-65 | 20 | 0.018 | 13.7-19.8 | 6.1 | 0.617 |
| 195-200 | 5 | 0.017 | 59.4-61.0 | 1.5 | 0.573 | ||
| BBR11-05 | 835 | 125-130 | 5 | 0.011 | 38.1-39.6 | 1.5 | 0.375 |
| 185-190 | 5 | 0.012 | 56.4-57.9 | 1.5 | 0.406 | ||
| BBR12-01 | 1,480 | 25-30 | 5 | 0.014 | 7.6-9.1 | 1.5 | 0.492 |
| 1,155-1,165 | 10 | 0.015 | 352.0-355.1 | 3.1 | 0.517 | ||
| BBR12-02 | 1,380 | 220-225 | 5 | 0.035 | 67.1-68.6 | 1.5 | 1.19 |
| 1,005-1,010 | 5 | 0.011 | 306.3-307.8 | 1.5 | 0.375 | ||
| 1,040-1,045 | 5 | 0.048 | 317.0-318.5 | 1.5 | 1.660 | ||
| 1,080-1,085 | 5 | 0.011 | 329.2-330.7 | 1.5 | 0.386 | ||
| Original data are in feet and Au ppm (g Au/t). True widths of gold intercepts are not determined. True thicknesses of gold intercepts cannot be determined. |
|||||||
Exploration Targets
Anomalous geochemistry, especially for Au and As, in stream sediments, rock chips, soil samples, and drill intercepts help define five exploration target areas only two of which contain drill holes. Table I summarizes maximum element values by sample medium in these target areas which are outlined and identified by target area abbreviation in Figures 2-6.
Moxen (MT): The north end of the claim block (Moxen claims) is about 2 sq mi of mostly pediment with exposures of Cambrian Crane Creek and Ordovician Antelope Valley limestone. Highly anomalous stream sediment (max.: 0.586 ppm Au) and rock chip (max.: 6,080 ppm As, 1,040 ppm Sb) samples require detailed follow-up field work. .
Callaghan (CT): The approximately 8,000 x 6,000 ft (2,440 x 1,830 m) target area along Callaghan Creek is underlain by thin bedded to laminated Cambrian Crane Creek limestone locally replaced by jasperoid. Anomalous stream (max.: 96.1 ppm As) and highly anomalous rock chip (max.: 2.842 ppm Au, 3,710 ppm As, 123 ppm Sb, 208 ppm Hg) samples require detailed follow-up field work.
Upper Oxen (UOT): Upper Ox Corral Creek (Oxen claims) aligns with the WNW structural corridor, is underlain by the trace of the RMT, and contains a WNW-elongate region approximately 6,000 x 2,000 ft (1,830 x 610 m) of anomalous gold and pathfinder elements in rock (max.: 0.593 ppm Au, 1,130 ppm As, 88 ppm Hg) and soil (max.: 0.115 ppm Au, 228 ppm As, 3 ppm Hg). The target area has not been drill tested.
Mid Oxen (MOT): Near the middle reach of Ox Corral Creek is a crescent-shaped geochemical anomaly with 4,500 ft (1,370 m) arc length. It coincides with the projected intersection of NE-trending faults with the WNW structural corridor followed by the creek and is generally underlain by upper plate siliclastic rocks. The anomaly is also coincident with the western rim of the doughnut-shaped residual gravity high approximately 8,000 ft in diameter. The area of geochemical anomaly incorporates rock chip samples with up to 0.093 ppm Au, 9,999 ppm As, and 600 ppm Hg and soil samples with up to 0.913 ppm Au, 289 ppm As, and 2 ppm Hg. Of the three reverse circulation holes within the target area (drilled by Kerr-McGee in 1990; total 1,520 ft or 463.3 m; maximum depth 520 ft or 158 m) the strongest gold intercept is in hole 4-6: 220-230 ft, 10 ft of 0.240 ppm Au in the upper plate of the RMT.
Anomaly Ridge (ART): A 3,200 ft (975 m) long "T"-shaped geochemical anomaly elongated west-northwest with cross-bar oriented NE is aligned along Cottonwood Creek and generally follows the trace of the RMT. The target area includes highly anomalous rock chip samples (max.: 56.4 ppm Au (1.645 oz Au/ton), 10,000 ppm As, 160 ppm Sb, 5,080 ppm Hg) and anomalous soil samples (max.: 0.850 ppm Au, 315 ppm As, 66 ppm Sb, 3 ppm Hg). Of the 13 drill holes in the target area (total drilling 8,520 ft or 2,597 m), nine are less than 600 ft (183 m) deep, and all are collared in the upper plate of the RMT. All but three holes intersect >0.01 ppm in the upper plate which in drill intercepts ranges from 85 to 365 ft (26 to 111 m) deep. The strongest upper plate gold intercept is in BBR11-01: 30 ft of 0.048 oz Au/ton containing 5 ft of 0.178 oz Au/ton (9.1 m of 1.631 g Au/t containing 1.5 m of 6.110 g Au/t). Holes BBR12-01 and -02 intersect +0.01 oz Au/t in the lower plate at 1,155 ft (352.0 m) and 1,005 ft (306.3 m), respectively. The strongest lower plate gold intercept is in BBR12-02: 1,040-1,045 ft, 5 ft of 0.048 oz Au/ton (317.0-318.5 m, 1.5 m of 1.660 g Au/t) contained within 80 ft of 0.005 oz Au/ton (24.4 m of 0.176 g Au/t). Table II summarizes the drilled gold intercepts over 0.01 oz Au/ton (0.343 g Au/t) in the target area.
Significantly, hole BBR11-05 displays Carlin-Type pathfinder element dispersion from an interpreted source below the bottom of the hole. In BBR11-05, terminated due to caving at 835 ft (254.5 m), pathfinder elements in the lower plate carbonate sequence from about 600 ft to the bottom of the hole show an approximate 10-fold increase to strongly anomalous values: As from 109 to 1,360 ppm, Sb from 9.95 to 116 ppm, Hg from 0.52 to 5.54 ppm, and Tl from 0.17 to 0.91 ppm (maximum = 1.92 ppm). In this same interval gold increases from 0.008 to 0.055 ppm (maximum = 0.074 ppm Au). The interpreted target beneath BBR11-05 has not been drill tested.
Exploration History
A historic turquoise mine in the upper plate Slaven Chert south of the claims is the only known mineral production in the area. From about 1980 to 1998 several companies, including Anaconda, FMC Corp., U.S. Borax, Kerr-McGee, Homestake Mining, Cordex, and Hemlo, explored in and near the Callaghan window. They conducted geological mapping, stream sediment, rock chip, and soil sampling surveys, resistivity surveys, and drilling; however, most of this exploration work was done near Cottonwood Springs east of Big Blue claims or in McGuinness Hills southeast of Big Blue. Of the approximately 125 drill holes collared within and adjacent to the Callaghan Window, only 12 were on the Big Blue claim block. These holes range from 190 to 1000 feet deep and only four are known to have intersected the lower plate carbonate section. The deepest hole, drilled by Kennecott in 1998 on the east edge of the claim block, bottomed in the upper plate siliclastic sequence. All holes targeted shallow oxide gold.
In 2010 Miranda Gold identified sediment-hosted gold exploration potential in the Callaghan Window through generative regional exploration concepts. Miranda negotiated a lease (3% NSR with buy-down) on 76 existing claims, staked additional claims, and conducted district-scale stream sediment and rock chip sampling. Ramelius Resources Ltd., an Australian gold mining company, entered into joint-venture agreement with Miranda in 2010. From 2010 to 2012 Ramelius' project work included staking additional claims, geologic mapping, rock chip sampling, grid soil sampling, gravity and ground magnetic surveys, and drilling nine reverse circulation holes for a total of 7,210 ft (2,197.6 m). Their work proved the lower plate carbonate sequence at Big Blue hosts Carlin-Type gold mineralization.