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Delta Property Full Report
- Location And Access
The Delta property is located in the eastern Alaska Range, approximately 58 km southwest of Tok, Alaska. Map coverage is provided by the Mt. Hayes and Tanacross 1:250,000 AMS maps and the 1:63,360 scale Mt. Hayes A-1 and B-1 and Tanacross A-6 and B-6 quadrangles.
Relief in the property areas is steep and elevations range from 670 m to 2,470 m above sea level (a.s.l.). Willow, alder and low brush are common in stream valleys and on slopes below 1370 m a.s.l. Outcrop exposure is approximately 25% and extensive talus covers the upper non-vegetated slopes. The massive sulphide zones weather recessively and are commonly covered by talus derived from overlying blocky units. The larger valleys are filled by glacial moraine and contain remnant glaciers above 1,675 m a.s.l.
Summers are usually mild with alternate periods of sun and cool, rainy intervals. Freezing temperatures can occur above 1,830 m a.s.l. at any time, but the lower elevations are generally frost-free for two to three months. The field season in the higher elevations is approximately 75 to 100 days. Frozen ground conditions are intermittent at the lower elevations and pervasive above 1,500 m a.s.l. Winter is cold, with temperatures to -50oC. Snowfall in the area is usually moderate, amounting to less than 2 m in non-drifted areas. Gullies at higher elevations commonly retain greater than 10 m of snow in early June, which melts completely by the end of July.
Tok (population 900) is 333 km southeast of Fairbanks via the Alaska Highway and 520 km northeast of Anchorage via the Glenn Highway. Both routes are paved and maintained on a year-round basis.
ACNC established a camp on an island in the Robertson River valley from which exploration is based. Access is by light fixed-wing aircraft to a 400 m gravel airstrip. Exploration activities are supported by helicopter.
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- Property Description
The Delta property currently consists of 51 claims, all in the name of Grayd Resources (USA) Inc. Grayd currently owns 100% of the claims, including all underlying rights, title and royalties. The claims are on state land and the property is not encumbered by any nearby wilderness or park status land.
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- History and Development
Pre-ACNC Exploration
| 1976: |
The massive sulphide deposits of the Delta District were discovered by geologists working for Resource Associates of Alaska (RAA) under contract to Cook Inlet Region, Inc. (CIRI). RAA staked the claims for CIRI and then leased the property from CIRI. RAA acted as the operator under a number of agreements with various companies during the following years. |
| 1977-78: |
A joint venture consisting of Placer Amex and Gulf Mineral Resources Company optioned the original claims from RAA and conducted extensive geologic and ground geophysical surveys and core drilling. The Joint Venture greatly increased the claim position, but terminated the agreement after the 1978 field season. |
| 1979-81: |
Anaconda Minerals Company participated in a joint venture on the claims and conducted a program of geologic mapping, ground geophysics, and core drilling. During this period, RAA was acquired by Nerco Minerals Company (Nerco). |
| 1982-85: |
Nerco continued a limited exploration program to satisfy obligations on the claims and develop gold targets. During 1984, Utah International reviewed the base metal deposits and generated a valuable summary document and analysis of the prior RAA-Nerco work. The property comprised approximately 2,300 claims at this time. |
| 1986: |
Nerco and Meridian Minerals Company entered into a joint venture to explore gold targets developed by RAA during 1984 and 1985. |
| 1987: |
Nerco and Western Mining conducted a one-year gold program in the eastern part of the district known as the AR Project. |
| 1990: |
Phelps Dodge entered into a joint venture on nearly all of Nerco's Alaska properties, including the Delta District. They conducted ground geophysical surveys and limited core drilling on the previously-identified targets. The Phelps Dodge joint venture was terminated in late 1990. |
| 1993: |
Nerco divested itself of metal mining assets and Pacific Northwest Resources Corporation (PNR) acquired Nerco's interest in the Delta District, which by this time comprised 581 claims. |
From 1976 through 1990, a total of approximately $10 million was spent exploring for base metal and gold deposits in the Delta District. Geologic mapping at scales from 1:1,200 to 1:30,000 was completed. Approximately 24,000 soil, rock, drill core, stream sediment and pan concentrate samples were collected and analyzed. Geophysical surveys consisting of CEM, PEM, magnetics, Max-Min EM (HLEM), IP, Airborne EM 225 line-km (140 line-miles}), gravity, down-hole PEM and seismic techniques totaling approximately 1,255 line-km (780 line-miles) were completed in the district. Core drilling totaled 16,746 m (54,940 ft) in 134 holes.
ACNC Exploration
| 1993: |
ACNC entered into a Joint Venture agreement with PNR on September 30, 1993. Compilation of all available data commenced. |
| 1994: |
Following the examination and sampling of available drill core and a study of the district utilizing Landsat images, ACNC conducted a two-month exploration program. Fieldwork included the examination of all massive sulphide showings in the district, regional lithochemical sampling to define favorable stratigraphy away from the deposits, examination of altered areas interpreted from Landsat images, and an orientation vertical-loop geophysical survey. A total of 966 rock samples, 128 core samples, and one stream sediment sample were collected and analyzed. |
| 1995: |
An airborne magnetic-electromagnetic (AEM) survey totaling 2,992 line-km (1,855 line-miles) was flown in April. One-hundred and sixty-nine EM responses were identified that warranted follow-up. During the three-month exploration program, regional geologic mapping was carried out concurrent with follow-up of the AEM anomalies. Ground geophysical surveys totaling 69 line-km (43 line-miles) utilized HLEM, Genie and magnetic methods and were deployed in areas of observed alteration or mineralization, or where overburden covers airborne conductors in favorable geologic settings. A total of 927 rock samples, nine core samples, 293 soil samples and 94 stream sediment samples were collected and analyzed. |
| 1996: |
A re-examination of all core from prior drilling stored in Fairbanks, and a stratigraphic reinterpretation were completed prior to the field season. Drilling in 14 holes totaled 3,650 m (11,976 ft) testing targets in the DD, MID, Ward's Saddle, Super Cub East and Tushtena Pass areas (Delta property). Borehole UTEM surveys were conducted in seven of the holes. Ground geophysical surveys totaling 97.6 line-km (60.6 line-miles) utilizing large-loop UTEM, HLEM, and magnetic methods were deployed at the Super Cub East, HD South, Peak 7057, PP2 and DD areas where overburden precluded geologic target definition. Reconnaissance geologic mapping, prospecting and detailed geologic mapping in support of drilling were done concurrently. A total of 193 rock samples, 270 core samples, 1,784 soil samples and 110 stream sediment samples were collected and analyzed, and 245 new claims and 16 prospecting sites were staked to cover projections of target horizons and anomalous areas. |
| 1997: |
Drilling in 20 holes totaled 4,470 m (14,664 ft) testing targets in the PP2, LP, DW deposits, and the HDS, LZ East, and Rum North prospects. Borehole UTEM surveys were conducted in two of the holes. A ground UTEM geophysical survey covered 5.8 line-km (3.6 line-miles) at the DD Southwest anomaly. FLAIRTEM Geophysical surveys totaled 670 line-km (415 line-miles). Geologic mapping and prospecting focused on target development in the lower-Lagoon SuperCub-Trio, LZ East and PP horizons and the lower Drum HDS horizon. A total of 619 rock samples, 1479 core samples, 1584 soil samples and 155 stream sediment samples were collected and analyzed. To cover down-dip projections at the PP prospect, 15 new claims (called OPP) were staked in 1997. Development of a three-dimensional model of the drilled sulphide deposits and enclosing geology was initiated. |
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1998:
1999-2004:
2005:
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Ten holes totaling 2,673 m (8,770 ft) were drilled on the Delta property. ACNC and the Company formed the Rumble Creek Joint Venture to jointly explore for VMS and Gold targets in prospective areas outside of the Delta Joint Venture. 367 claims were staked covering unprotected targets and prospective geology. Nine man days were spent following up strong gold targets outlined in 1997. No work was attempted on any of the Rumble Creek VMS prospects in 1998.
No exploration was conducted on the property in the period from 1999 – 2001.In 1999 and 2000, most of the camp and drill equipment was removed from site.In 2002 and 2003, a very limited program to test for platinum and palladium potential within the mafic intrusions was undertaken.This involved sampling core available in Fairbanksand on the property. Analytical results for both platinum and palladium were mostly low, with a few very weakly anomalous results.In 2004, minimum assessment work requirements were satisfied by reclamation of drill sites and camp combined with payment in Lieu of work.
A small program of prospecting and channel sampling was undertaken at mineralized exposures along the receding margins of the LP glacier. Sawn channel samples collected across a zone of mineralized chlorite schist averaged3.0 m grading 6.1 g/t Au, 374.8 g/t Ag, 0.4% Cu and 14.8% Pb and 0.6 m grading 4.7 g/t Au, 547.3 g/t Ag, 0.4% Cu and 22.6 % Pb.The 5 cm wide by 7 cm deep channel samples were collected using a portable diamond-blade saw across the limited exposure of a glacially striated outcrop in moraine.Mineralization is open laterally beyond the endpoints of the samples.The thickness of mineralization is unknown.It is believed that the zone represents the deformed footwall stringer-alteration zone to the LP deposit, which outcrops 200 m to the west of the new samples |
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- Regional Geology
The Delta property is located within the eastern Alaska Range along the southern margin of the Devonian to Mississippian Yukon Tanana Terrane (YTT). The YTT underlies a large portion of east-central Alaska and extends through central and western Yukon into northern British Columbia. This assemblage of poly-deformed metamorphic rocks lies between the autochthonous North American continental margin to the northeast and allochthonous terranes to the southwest. The YTT in east-central Alaska is separated from Wrangellia Terrane to the southwest by the major dextral Denali Fault.
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- Property Geology
Stratigraphy
Rocks underlying the Delta property are a structural/stratigraphic assemblage of middle to late Devonian metavolcanic and metasedimentary phyllites and schists, known as the Delta Schist Belt (Jarvis Creek Subterrane -- USGS nomenclature). These rocks were intruded by a suite of Jurassic(?) age gabbroic sills. Rocks in the belt have undergone middle to upper greenschist facies regional metamorphism and include quartzite, phyllite, schist, marble, hornfels, cataclasite, and a variety of transitional lithologies that combine these textural and compositional characteristics. There have been at least two major deformational events. A third, more recent, deformational event is evidenced by widespread brittle faulting and fault-controlled intrusion of Cretaceous-Tertiary dikes. Cretaceous felsic intrusive stocks are less common in the Belt.
Delta Schist rocks have been mapped based on the recognition of five structural/stratigraphic units or "series". (From structurally lowest to highest: Tushtena Pass, Lagoon, Tiger, Drum, and Tok River). The series designation permits correlation between work areas and provides a framework for a comprehensible interpretation of the gross structure. Internally, however, each series is a complex and contorted mix of intercalated metasedimentary and metavolcanic rocks that can be difficult to correlate at the outcrop scale. Contacts between the series that comprise the Delta Schist Belt appear to be transitional facies changes occurring through 3 to over 30 m.
Massive sulphides are most commonly associated with the metarhyolite to metadacite volcanics of the Lagoon Series and the structurally higher Drum Series. These two important series are separated by the barren, metadacite dominated Tiger Series. Less-studied volcanic-hosted sulphides have been found in the sediment-dominated section of the lower Lagoon Series and in the underlying metasedimentary/metavolcanic Tushtena Pass Series.
Tushtena Pass Series includes chloritic and calcareous, medium to coarse-grained schists. Metavolcanic protoliths range from felsic to intermediate, with local mafic volcanics in the lower section. Interbedded metasediments have calc-arenite and lesser siltstone protoliths. Lenses and sills of fresh to altered gabbro are distributed throughout the section. The Tushtena Pass Series is truncated on the east by the west-dipping Elting Creek (Itra) fault, which is locally typified by a chloritic mylonitic breccia. The thickness of the series is undetermined.
Lagoon Series rocks include banded, medium to coarse-grained, quartz sericite (+ chlorite) schists and graphitic schists in the basal portion, contrasting with finer-grained schists and phyllites in the upper section. Metavolcanic protoliths are primarily rhyodacite to dacite with less-common rhyolite units. Metasedimentary protoliths include immature sediments or wackes and arenites with lesser calc-arenites. Thick gabbroic sills and lenses are common and appear to inflate the sequence significantly. The thickness of the Lagoon Series is uncertain, but is estimated at 300 to 450 m.
Tiger Series is a distinctive metavolcanic package that serves as a regional marker unit between the prospective Lagoon and Drum Series. The Tiger Series is composed primarily of banded chlorite schists with variable quartz, sericite and dark brown stilpnomelane. Protoliths are dacitic to rhyodacitic in composition, with minor rhyolite and thin phyllitic metasedimentary interbeds. Metagabbroic rocks are rare. The Tiger Series is 360 to 790 m thick. A horizon containing magnetite porphyroblasts is commonly found in the basal section of the Tiger Series.
Drum Series is a relatively thin felsic schist unit composed of quartz-sericite (+ chlorite) schists with lesser grey to black phyllite. Protoliths are primarily rhyolite and rhyodacite, with minor dacite, arenite and siltstone. Metagabbroic intrusions are common and form thick sills that locally crosscut stratigraphy. The Drum Series is estimated to be 60 to 150 m thick.
Tok River Series metasediments constitute the uppermost rocks in the Delta Schist Belt. The Tok River Series is an assemblage of chloritic phyllites, quartz-sericite (+ chlorite) schist, grit, graphitic phyllite and minor marble. Protoliths are arenites, wackes, limestones and siltstones with thin interbeds of felsic to intermediate volcanics. Gabbro is uncommon in the Tok River Series. The thickness of the series is undetermined, but estimated to exceed 600 m.
Intrusive Rocks include several varieties of metagabbro (described by prior workers as diorite), greenstone and granodiorite to monzonite. The gabbros are widely-distributed throughout the work area, but are much less common in the Tiger and Tok River Series. Field evidence indicates that most of the gabbros are sills that post-date VMS mineralization. Undeformed late Cretaceous to Tertiary granodiorite to monzonite dikes and stocks and a suite of mafic alkaline dikes are widely distributed and intrude all rocks in the area.
Structure
The most obvious structural fabric in the rocks on the Delta property is a well developed cleavage related to Mesozoic (Jurassic?) compressive, recumbent fold and thrust-fault-dominant deformation. Cretaceous to recent transtensional, dip-slip, high-angle faults cut all units in the area, producing both vertical and lateral offsets of the stratigraphy (and the sulphide deposits). Displacements range from centimetres to kilometres. The major high-angle fault sets predominantly trend west-northwest and north-northeast. Mineralization
In the Delta area, massive sulphide deposits associated with the metavolcanic assemblages have been found in a number of localities. Pyrite and pyrrhotite are the most common sulphides. All of the massive sulphide deposits are polymetallic with zinc > lead >> copper. Gold is erratically distributed and locally significant, while silver is ubiquitous. Metal zoning on a district scale is not well-defined, but the metal ratios and abundances are characteristic of volcanogenic mineralization in rifted arc settings (e.g. Kuroko, Myra Falls). Some of the deposits which appear to have formed in a sediment-dominated environment have notably high concentrations of precious and base metals.
Localized hydrothermal veins and mineralized shear zones containing varying amounts of gold, silver, arsenic, lead and zinc have been found both on the Delta property. More extensive hydrothermal mineralization has been found regionally, notably at the White Gold and AR prospects. Stibnite mineralization was mined on a small scale in the 1930's at Stibnite Creek.
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- Summary of Main Deposits and Prospects
At Delta over 40 mineral occurrences have been discovered and an inferred resource has been calculated for eight deposits. There are three known stratigraphic levels with sulphide mineralization within the Lagoon series. The DW-LP consists of five deposits which are fault-bounded sections of what was once a continuous 3.2 kilometre-long sulphide sheet. The PP2 deposit occurs stratigraphically below the DW-LP series of deposits and has potential to be a very large deposit. The high-grade Trio and Supercub prospects occur within the sediment-dominated lower part of the Lagoon series. High-grade intersections from previous drilling in the Trio area are postulated to be within a large area of landslide material. At the Supercub prospect, boulders were found which consistently assay over 25% combined copper, lead and zinc with 200 g/t silver and 11.3 g/t gold. The 2,500 metre long area encompassing the two prospects is relatively unexplored. The DD South and DD North deposits occur within the Drum series. Drilling has shown these deposits to be trough-shaped with keels up to 10.7 metres thick. The grades of the DD deposits are generally higher than that of the drilled portions of the DW-LP and PP2 deposits.
Massive sulphide mineralization occurs in at least four stratigraphic levels on the property. There are three known stratigraphic levels with sulphide mineralization within the Lagoon series. The DW-LP area consists of five deposits which are fault-bounded sections of what was once a continuous 3.2 kilometre-long sulphide sheet. The PP2 deposit occurs stratigraphically below the DW-LP series of deposits and has the potential to be a very large deposit. The high-grade Trio and SuperCub prospects occur within the sediment-dominated lower part of the Lagoon series. The DD South and DD North deposits occur within the overlying Drum series.
DW-LP Deposits
The DW-LP is a series of massive sulphide deposits (LP, Nunatak, MID, DW, VAL) which are interpreted to be down-faulted sections of what was once a contiguous 3.2 kilometre-long sulphide sheet. Sulphides intersected in drill holes are generally 2.4 to 5.5 metres thick, with the thickest intersection having a true width of 10.4 metres. A total inferred resource of 8.8 million tonnes has been calculated for the DW-LP. While the average grade of this resource is relatively low, there are intersections with substantially higher grades. Drill intersections are widely spaced, and most of the deposits are open on at least three sides.
PP2 Deposit
The PP2 was originally thought to be part of the DW-LP system but work in 1997 showed it to be a separate sulphide horizon lying stratigraphically below the DW-LP. It has similar large size potential as the overlying DW-LP system. Intersections to-date are up to 8.8 metres thick, but are more commonly in the order of 3 metres thick. Grades are low to moderate, but only a small portion of the potential area of this zone has been tested, and indications of a grade vector increasing to the southeast can be seen in results from prior drilling.
DDN and DDS Deposits
The DDN and DDS deposits occur in the felsic dominated Drum series. The deposits occur as gently northwest plunging keels of sulphide accumulation up to 14.7 metres thick. The DDS has been traced over a strike length of 430 metres with a 120 to 150 metre width to the sulphide deposit. The DDN is less well defined, but has a similar keel shape as the DDS. The average grade of the 3.2 million tonne inferred resource on these deposits is significantly higher than the average of the DW-LP and PP2 systems, and compares favourably with currently operating mines. Gold content is relatively high at 2.6 g/t. Both deposits are still open in multiple directions. There is approximately 1,200 metres of untested stratigraphy between the two deposits. Steep topography complicates exploration, but the size and grades of the known deposits makes the DD area a prime exploration target.
A large UTEM anomaly located to the south of the DDS deposit remains unexplained and requires drill testing.
Trio-SuperCub Prospects
The Trio and SuperCub prospects occur in the sedimentary dominated lower part of the Lagoon series. Mineralization found in these prospects to date is high grade. These prospects may have formed in a shallow marine environment, which suggests potential for precious metal enriched VMS deposits such as Eskay Creek or Greens Creek.
The Trio prospect was discovered when large sulphide boulders averaging 1.3% Cu, 7.3% Pb, 5.6% Zn, 113 g/t Ag and 0.7 g/t Au were found. Eight holes were drilled to test the prospect prior to 1993, and some intersected similar tenor mineralization. However, intersections did not correlate well and the area was thought to be highly deformed. Work by ACNC has shown that complications were not due to structurally complicated geology, but because the sulphide showing and the relatively shallow drill holes were all within an area of landslide debris. Finding a potential deposit will require finding in-situ sulphides below the base of the landslide. Three wide spaced holes were drilled on this target in 1998. Intensely quartz-sericite-pyrite altered rocks were intersected, but no significant massive sulphides were found. The area is underlain by a large geophysical conductor and the size of the alteration system combined with the high grades of the known sulphides continues to make the Trio a prospective exploration target.
The SuperCub prospect is located 1,500 metres northwest of the Trio prospect, and in approximately the same stratigraphic position. At the SuperCub prospect, boulders were found in 1995 which consistently assay over 25% combined copper, lead and zinc with 200 g/t silver and 11.3 g/t gold. Four holes were drilled in the area topographically above the boulders in 1996, but none intersected massive sulphide mineralization. Work in 1997 indicated that the boulders did not come directly down slope, but were lying in a kame terrace, transported to the location by a small alpine glacier. One hole was drilled in 1998 based on the projected origin of the boulders and a geophysical conductor from previous surveys. The hole intersected quartz-sericite-pyrite altered rocks, but did not locate the source of the boulders. This is the only hole which tests the prospective stratigraphy that spans a distance exceeding 1 kilometre.
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Inferred Resource
An inferred resource calculation completed by ACNC in 1998 is summarized in the following table. The manual calculation is based on drilling done by previous operators, as well as that done by the former Grayd/ACNC joint venture, and includes results from the 1998 program. Before the new calculation was made, sample databases were checked with original assay certificates and a number of massive sulphide intercepts from previous operators were re-sampled and assayed. The resource was checked by Inco personnel at Inco's Copper Cliff office, but was not independently verified. The resource was calculated for the purpose of guiding further exploration only, and does not imply economic viability. Higher grade zones occur within all deposits. Most of the resource zones are still open and there are a large number of unexplored targets on the property.
Delta Project - Massive Sulphide Inferred Resource Summary
Block Deposit M
tonnes Cu % Pb % Zn % Ag g/t Au g/t
DD DDN 1.6 1.4 1.8 2.4 82 3.3
DDS 1.8 1.0 2.1 5.7 77 1.8
Total DD 3.4 1.2 2.0 4.1 79 2.5
DW-LP DW 0.3 0.4 1.2 4.0 44 0.9
MID 5.9 0.4 1.6 3.9 58 1.6
LP 0.8 0.4 1.7 4.2 56 2.0
LPH 0.7 0.4 2.2 4.4 66 1.6
Total DW-LP 7.7 0.4 1.7 4.0 58 1.6
PP2 PP2 4.2 0.5 1.5 3.4 55 1.4TOTALS 15.4 0.6 1.7 3.8 62 1.7
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- Exploration Potential
The Delta property covers a large area that is prospective for polymetallic massive sulphide mineralization. The inferred resource identified to-date is an indication of the potential of the property. Most resource zones open, and there are several additional exploration targets, some of which are essentially untested.
The potential for the large DW-LP sulphide system is in the range of 50 to 100 million tonnes, based on the size of known deposits and the area between deposits and along strike and dip extensions. It remains to be determined whether sufficient tonnage exists in a mineable configuration at higher grades, but a 20 to 30 million tonne deposit of sufficient grade to be economic is a realistic target. Exploration should focus on potentially higher-grade areas in this system. Untested geophysical anomalies outside of the area currently drilled provide defined targets and may provide valuable vectoring information for the whole system.
Prior drilling on the LP deposit identified a trend of increasing grade and increasing thickness to the southwest (down-dip). A large off-hole anomaly in a previous hole supports the potential for a significant volume of sulphides in the direction of the grade + thickness vector. Drilling is required to test this conductor. A large, broad UTEM anomaly remains in the PP2 basin to the south of current drilling. Isolated outcrops of Tiger Series rocks have been mapped in the basin, and the stratigraphic horizon that hosts the DW-LP system should underlie the area. If drilling is successful, this could significantly increase the size of the DW-LP system and open up a large area of exploration potential.
The PP2 horizon is open in three directions. A grade vector indicates potential for higher grades to the southeast of current drilling. Additional drilling on the PP2 should keep in mind the potential for further stacked systems.
The higher-grade nature of mineralization in the DD deposits make them a priority exploration target. Two holes targeted on the DDS zone in 1998 did not intersect significant sulphides; however they did supply additional evidence that the deposit could occur adjacent to a relatively undeformed rhyolite dome and as such may have significantly more potential than just the relatively narrow trough that has been pursued to date. The 1,200 m (4,000 ft) of untested stratigraphy between the DDS and DDN is a prime exploration target, though steep topography complicates drill positioning and results in increased target depth.
The location of the undisturbed extension of the Trio mineralization and the source of the high-grade SuperCub massive sulphide float remain undetermined. Drilling has outlined a large hydrothermal system in the area. There is several thousand feet of untested strike length of stratigraphy between the Trio and SuperCub prospects that requires further drill testing. The potentially very high-grade nature of any deposit makes this area a compelling target.
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 Technical Report
Delta Property - Maps and Photos
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La India, Sonora, Mexico 