| . The Alaska Freegold Company, Inc. . |
| The Blue Ribbon Mine, Alaska |
This page will provide information about the Blue Ribbon Mine. A little history, a little production, and little geology. (Note: This page written by Dennis R. Garrett, who bears sole responsibility for the accuracy of the statements herein. This page is for information only.)
Preface:
I first came to what would become The Blue Ribbon Mine in 1985. The first reported mining in what was to become The Blue Ribbon Mine took place in 1906. Except for some stretches when no mining took place, some gold has probably been recovered every year since. The total amount recovered is unknown, but at least 20,000 ounces have been reported recovered, mostly by small-scale hand or mechanized methods. At least that much, and probably more, remain. The Blue Ribbon Mine is located on a road that takes off at the end of the Petersville Road, T28N-T29N, and R8W-R9W, Seward Meridian, Alaska. See U.S.G.S. Talkeetna C-2 quadrangle map for details.
Today, over one hundred years since the first gold rush in south-central Alaska, a renewed interest is taking place in the Yentna mining district. This report will focus on one mine, abandoned when the owners were murdered in 1939, and reopened in 1992.The mine is located on Gopher Gulch, a tributary of Willow Creek and Ramsdyke Creek; We also have claims or interests on Poorman Creek; Cottonwood Creek; Peters Creek, and some on no creeks above these; and on tributaries of Cache Creek to the south.
In 1990 I began an earnest search for the possible lode sources of the placer gold found in the streams draining the eastern flanks of the northern Dutch Hills. One source, the major one in fact, turned out to be the abandoned mine known as 'The Potato Patch'. This report will describe that deposit, and include information released as as recently as 2 months ago. That information will include results of an airborne geophysical survey and related ground-truth follow up studies, and occurences discovered by this author and not previously described in the available literature.
I will be regularly adding to and updating this page. Most recent update: 11 June 1999.
Note: This will be a stripped-down version of the Mineral Property Evaluation Report compiled on the subject property. That report is available from the author.
* Blue Ribbon Mine as used in this report includes those claims on Gopher Mountain, located in sections 24 and 25, T29N R9W of the Seward Meridian, Alaska. This report is not to be construed as a solicitation for the sale of securities. Such solicitation may only be done through a prospectus. This report is for information on the companys business, projects, and properties.
INTRODUCTION.
The recent release of an Airborne Geophysical Survey and follow up ground-truthing surveys, coincident with the discovery of additional veins and mineralized outcrops in and around the Blue Ribbon Mine, has spurred a renewal of exploration of the mineral potential of the area. This report will focus on the known mineralization, history, and past production, and finally how this new information fits into the model.
The southern part of the Chulitna-Yentna mineral belt, reported on by Clark and Hawley in USGS Professional Paper 758-A, lies within the Yentna Mining District. The known portion "..extends from a few miles south of Collinsville to the Tokositna River;" on the north.
Geography and Environment: Located in the transition zone between Maritime and Continental climatic zones. The topography is dominated by the high, spectacularly glaciated Alaska Range, which forms a northeast-trending arc of mountains in this part of Alaska. North Americas' tallest mountain lies approx. 30 miles to the northwest. South-central Alaska Range foothills, of low vertical relief (1800' - 4000' above sea level), is the primary topography within the property, which is located on the eastern flank of the Dutch Hills. Precipitation is relatively high, (average annual rainfall is 30" and average mean annual snowfall is about 130") owing to the barrier created by the Alaska Range. Temperature ranges from +70o F in the summer to -20oF in winter. The region is protected from the harsh continental extremes of the Interior by the Alaska Range. Vegetation is primarily sub-alpine brush or mosses, and a few stunted trees are widely scattered about. Existing environmental baseline data are incomplete at this time.
History and Past Production : Gold was first reported in the area in 1898, and claim staking and production had begun on this property by 1906. Three operations were being conducted on Willow Creek and two of its' headwater tributaries, Gopher and Ruby Gulch, by 1917. It is known that at least 1500 ounces of gold was produced from an area smaller than 320 by 660 feet. About 2000 ounces were reported produced from Little Willow Creek, which drains the Potato patch area in the mid-30's. Hydrauliking and hand-mining operations continued yearly under then-owners Frank and Helena Jenkins, until 1939, when they and 2 other persons were murdered on these claims. Since1992, pilot-plant and bulk testing of the area known as the "Potato Patch" has been conducted. Click HERE for a picture of some of the gold. The area was actively prospected and mined before WWII. Essentially no new exploration work was done from the early '50s' until 1972, (except for Clark and Hawley, USGS 1968) when the price of gold started to move up. A number of reports, both Government and private, have been generated since then, and new data are being generated from recent surveys conducted by the Alaska Division of Geological and Geophysical Surveys and this author.
The following excerpt is from a report written in 1973:
"By ditching water around Gopher Mountain from Judy Gulch, Jenkins , the prior owner, was able to sluice some of the surface gravels above Gopher Creek and along its northerly tri butaries. A scar is still visible on the hillside {This is the location of the present-day Blue Ribbon Mine} and by measurement from the air photos an area of 320 ft. by 660 ft., or 4.85 acres, was cleaned to bedrock. The sketch map (ref #24){ These numbers refer to citations from that report.} notes that this sluicing was done " 1930 and prior ", and " This of record as more than $30,000 Jenkins paid royalty to Rice- check in file- August, 1 ft. to BR (Serpentine) approximately 640 ft. square - (less than 1 acre)." The measurement described would enclose an area of 9.4 acres. The Nasenius map (Ref. #8) contains the following notes: " Approximately three acres of ground worked on this steep hill where two or more highly decomposed quartz leads as marked" . (This notation subsequently marked over to say "1" acre). Above and to the NE is shown " Highly decomposed quartz" , with the note: " Some of this quartz so highly decomposed as to resemble a white paste and walking into fall onto your knees." Above and to the NW is the note: " somewhat harder quartz" " A small creek bisects the sluiced area and extends south to Gopher Creek" Grade 12-1/2% " , " large amount quartz boulders." Also the note: " 32,000 recoved by Jenkins." Another old map (ref #25) has the note: " Approximately three acres of ground worked on decomposed BR under moss, plus $32,000 reported recovered by Jenkins, very small amount of actual decomposed material handled @ $18.00 oz. - Prior to 1930----." And the further note indicating a location several hundred feet NW of Jenkins work: " Took one small pan of decomposed bedrock-counted over 70 very small colors" (A.L. Renshaw, 1973. Unpubl.)
Except for the "very small amount of actual decomposed material handled", the tailings left are primarily larger rocks piled up after being thrown from the sluice or pit. The other claims that make up this property, on the west and north sides of Gopher Mountain, were mined at some time by persons unknown. They are included in this report whenever it is referring to the Blue Ribbon Mine, unless otherwise noted. The geology and other features are the same.
Numerous lode claims were staked at various times in the past, and some work was done, but all evidence in the field has long since been lost, as is the case with most, if not all, of the written documentation.
Current Development : Pilot-plant testing of the "Potato Patch", including test pits, equipment, settling ponds, and other infrastructure is in place, with camp facilities. All permits, licenses, etc. are current for 1999. Refer to narrative below for details and mining method.
NOTE: Details of this report pertaining to reserves, assays, ore grades, and other proprietary information have been deleted.
Geologic nature of the exploration target : Lode deposits, primarily auriferous quartz veins in slate and argillite, shear zones, and other mineralized areas have assayed from a few ppm { Parts per million. 1 ppm = 1 gram/metric tonne } to XX.5 oz/ton. This is no doubt an anomalous high reading. An unusual number of samples have assayed at ~0.3 oz/ton, after visible gold was removed. See Table of Results for details. An unknown amount of lode gold was produced from the property. Estimated >1.5 million tons in shear zones, veins, and mineralized areas. Unknown volume of auriferous alluvial and bench gravels, grading at 0.0xx ounces of gold per yard. Closer examination of this deposit is indicated.
Quantity and quality of information : The author endeavored to obtain all information available, from any source, and this was accomplished before verification began. A review of published material relating to the property was accomplished as part of the initial study and reconnaissance program, and the information thus obtained was a great time saver, as some details of regional and local geology has been worked out previously by qualified observers. Please refer to References and Acknowledgements. Except for x0,000 cubic yards of economic grade gold bearing gravels, which is limited to those areas on both sides of Gopher Gulch, the remainder of the deposit must be classified as "uninvestigated" or "underinvestigated", at least as far as required for the classification of reserves. Detailed exploration, in an increasing level of collection and analysis, is indicated.
Regional Geology : Most of this information taken from or based on U.S. Geological Survey Map I-1174, Geologic Map of the Talkeetna Quadrangle, Alaska, by Bruce Reed and Steven Nelson, and from U.S. Geological Survey Open-File report #68-1, Clark and Hawley, unless otherwise noted.
SURFICIAL DEPOSITS
Qau-Alluvium, undivided. -Includes alluvium on active flood plains, older alluvium on terraces of major streams, alluvial fans, etc. Locally auriferous, chiefly gravel, sand, and boulders, with areas of silt and clay.
Qn-Drift of the Naptowne Glaciation.-Includes end, lateral, and ground moraine, postglacial alluvial, pond, and swamp deposits, fluvialglacial deposits of all stages of Naptowne Glaciation, and glaciolacustrine deposits. At higher elevations, deposits merge with and are covered by colluvium and locally contain drift of the Alaska Glaciation.
SEDIMENTARY and VOLCANIC ROCKS
Tk-Kenai Group, undivided. Fluvial sedimentary rocks correlative with estuarine and nonmarine clastic sedimentary Tertiary formations assigned to the Kenai Group in the Cook Inlet basin by Calderwood and Fackler (1972). Exposures of the Kenai Group in the project area are limited to gently to moderately southeast dipping beds (see map). The group is locally divided into the Sterling (?) Formation and the Tyonek (?) Formation. The Sterling (?) unconformably overlies the Tyonek (?), and the Tyonek (?) rests with angular unconformity on Mesozoic rocks.
Tps-Sterling (?) Formation (Pliocene).- Orange, light-tan, or light-gray, massive-bedded conglomerate, distinguished from conglomerate in the Tyonek (?) by its' color, relative coarseness, and clast lithology. Clasts are well rounded and equant and average 2-8 " in diameter, although much larger clasts are not uncommon. The conglomerate is poorly to moderately well indurated with a clayey and, locally, ferruginous matrix. Clasts consist of the same lithologies but occur in proportions different from those in the Tyonek (?) member, which occurs in the same locality. Crossbed sets in orange and tan sandstone lenses in conglomerate nearby (T27N R13W) suggest that current directions were to the east or southeast. Thickness is unknown, but is probably less than 500'.
Tts-Tyonek (?) Formation (Miocene), Sandstone member.- Approx. 80% sandstone, 20% siltstone and claystone, and less than 1% conglomerate, coal, and volcanic ash. The member occurs in repetitive cycles 20-70' thick that grade upward from conglomerate or coarse sandstone to finer grained sandstone, to interbedded silt and clay with coal or bony coal. Conglomerate occurs in beds as much as 15' thick; clasts have an average size of 1-4" and a maximum size of 6". Sandstone is tan or light gray, coarse to medium grained, poorly indurated, and consists of about 75-85% chert and quartz grains, 10-20% feldspar, and about 5% mafic grains which include biotite, hornblende, clinozoisite, and chlorite. Sandstone beds are as much as 200' thick, although the thicker ones were probably not deposited as a single unit. Interbedded claystone and siltstone occur in units as much as 50' thick, are light to medium gray, and contain rootlets and coaly partings. Coal or bone, if present, is found above clay beds. Coal, in beds as much as 10' thick with an average thickness of less that 3', ranges in this area from platy or papery and soft to hard and glassy, and in many places contains shaly or bony partings. Coal beds contain volcanic ash layers up to 15" thick, and rootlets and other plant materials are present in the ash.
Kjs-Undivided Marine Sedimentary Rocks.-Medium-to dark-gray, generally isoclinally folded, thick sequence of lithic graywacke, phyllite, and shale with local lenses of quartz-chert conglomerate. The unit includes minor fossiliferous limestone, radiolarian chert, and red ferruginous sandstone and siltstone. Lithic graywacke is thin to massive bedded and locally shows graded bedding, ripple marks, cross bedding, and pull-apart structures. Graywacke is poorly to moderately well sorted and consists of angular to subangular, fine to coarse sand size detritus, of which quartz and lithic fragments comprise about 50%. Lithic fragments are fine-grained recrystallized quartzite or metachert with lesser amounts of dark siltstone or argillite, muscovite schist, and fine-grained volcanic rocks (including porphyry). Plagioclase, potassium feldspar, and detrital muscovite are subordinate. Common, though not abundant, heavy minerals include zircon and tourmaline. Contemporaneous volcanism is suggested by rare interbedded light-colored tuffaceous sediments in the Yenlo Hills. Argillaceous rocks are locally thermally metamorphosed to spotted cordierite and andalusite hornfels. Graywacke is thermally metamorphosed to biotite-quartz hornfels. Elsewhere, low-grade metamorphism is indicated by the presence of metamorphic chlorite and biotite. Hydrothermal activity, probably related to the emplacement of plutonic rocks at depth, locally has altered the graywackes to a soft orange-weathering quartz, chlorite, sericite, iron-oxide rock that locally contains vuggy and brecciated quartz. Gold can be panned from the streams draining these altered zones.
One of these zones has been traced over eight miles, trending approx. N42oE, the same as the main fault zones in this area, and is known to be a significant source of placer gold. More about this is presented in the section on resources.
Fossils found in this formation indicate a Late Cretaceous and/or Early Jurassic age. The contact relation of the Early Jurassic to Cretaceous strata is uncertain. The thickness of the unit is unknown but is probably more than 9000'.
Tmk- Kahiltna Pluton.- A relatively large mass of granite and granodiorite,described as fine- to coarse-grained, hypidiomorphic-granular biotite and biotite-muscovite granite and granodiorite. Apatite and zircon are characteristic accessory minerals, but tourmaline, garnet, and allanite are locally present, and minor tin anomalies are associated with a quartz-tourmaline-muscovite greisen zone at the head of Hidden Creek (T30N R10W). Average color index of 10 samples is 8. A small satellitic body of fine- to coarse- grained biotite-hornblende graniodiorite (T31N R9W) is included with the Kahiltna Pluton.
Tki- Undivided Intrusive Rocks.- Small intrusive bodies of Late Cretaceous or Tertiary age with compositions that preclude definite assignment to the above intrusive sequence. Owing to difficult accessibility, many of these bodies were not sampled; their contacts were mapped from the air. The petrography and composition of these rocks are incompletely known.
This author has discovered a number of previously undescribed igneous occurences and altered zones. A brief description of them follows:
"Approximately 1300 feet north of the Potato Patch is an outcrop of greenish granitic rock, greatly weathered and fractured. The surface was stained quite rusty, and mica is abundant. The exposure was about 20'h and several hundred feet along the north side of the creek. Milky white quartz, probably from veins that weren't visible, was also abundant."
"On the west side of Gopher Mountain is an area that is composed of orange to light tan, weathered rock with abundant small quartz veinlets. There appears to have been some mining in the past, and there was a claim shown on the older maps. This saddle is also the head of Ramsdyke Creek, which has had historic mining activity. Visible gold was recovered in numerous pan samples."
"A different type of rock outcrops on the north side of Gopher Mountain. This rock is quite hard, weathered only a fraction of an inch below the surface, dark green to greenish-gray. The color resulted from abundant striated green crystals in the rock. Analyses of this rock indicate that it is of mafic composition, with elevated levels of chromium and other metals. Possibly gabbro. Externally it is no different than the local sedimentary rocks, (i.e. covered by a growth of lichens) but it is visible as a ridge on the airphotos."
Structural Features- The sedimentary rock units described above are fault-bounded, and their bases are not exposed. In this part of the Alaska Range, The McKinley sequence of the Denali fault system has undergone right-lateral displacement of about 24 miles in the last 38 m. y. Furthermore, the straight north-facing scarp along this part of the range indicates that as much as 2 miles of south-side-up verticle component of movement may have occurred since middle Tertiary time. The Peters Hills Lineament and Dutch Hills Lineaments ( Clark and Hawley, USGS 1968) are major faults, and are consistent with the areas' typical N50o-70o E strike and are steeply dipping. The Denali fault described above also trends N60oE. Detailed mapping, particularly along Willow and Dollar Creeks, show a definite pattern of faulting. The major faults strike approx. N65oE and dip steeply. The major faults are intersected by minor high-angle faults which strike approx. N40o-50oE. The result is an acute grid pattern. The faults have been active in Tertiary time, as evidenced by steeply dipping to verticle beds of the Kenai Formation along faults. These faults have played a large role in controlling the emplacement of igneous bodies and apparently the subsequent formation of placer deposits.
A cluster of deposits is in the main part of the Yentna district, near the Dutch Hills. The productive deposits here have been placer gold deposits with byproduct platinum and locally abundant cassiterite. Because these deposits are secondary, the validity of a hypogene mineral belt crossing the district is dependent on the existence of lode deposits of gold, tin, and other metals within the belt. "...Mertie (1919, p. 257-260, p. 261-262) stated specifically that the gold and cassiterite in Poorman, Willow, Long, and Canyon Creeks were largely derived from visibly mineralized rocks of their drainage areas. Prospecting done since the visits of Capps (1913) and Mertie has resulted in the discovery of additional lode sources." "Gold-bearing lodes in the Yentna district, which have not been as well described, include small and locally very rich deposits associated with felsic dikes and apparently low-grade deposits in major shear and altered zones." Assays exceeding 1 ounce of gold per ton have been obtained from three of these areas, and selected quartz-arsenopyrite vein material from one prospect assayed about 200 ounces of gold per ton.
Placer deposits of gold are abundant in the Yentna district. In the Yentna district, most of the streams draining the Dutch Hills have auriferous deposits. Placer gold is locally present on the north flank of the Dutch Hills. "In the Yentna district, the variety of placer deposits, together with the difficulty of finding bench or buried channel-type deposits in extensively alluviated terrain, suggests that undiscovered deposits exist in the area. Some of the small vein deposits of the Yentna district are locally rich enough in gold and tungsten to be exploited profitably if mined on a small scale.
"The Chulitna-Yentna mineral belt has produced gold valued at more than $7 million (at $35 per ounce) [in 1968] from the placer deposits of the Yentna district..." "Although the highly productive Cache Creek basin of the Yentna district has been mined extensively, there are unmined bench and buried-channel deposits near Cache Creek ..." "One deposit near Bird Creek has drilled reserves of more than $1 million (at $35 per ounce); very likely there are other deposits whose approximate reserves are known by the owners, but this information is not available. Because of the possibility of undiscovered placers...and the multiple types and ages of placers, it is not unreasonable to assume that as much gold remains in the Yentna district as has been mined."
"The region is, when compared with most other terranes or areas, strongly mineralized, and if it existed in a more accessible or climatically hospitable region, would certainly have had much more extensive mineral production, and the mineral potential remains factual, needing mostly human desires and ingenuity for it to be realized. All studies suggests a potential for new additional placer and lode deposits in the district. " (From U.S.G.S. PP 758-A).
Geology of the Deposit : The presently productive deposits are placer deposits of several types and ages. The most productive to date have been in alluvial channels of Holocene age in creeks, but gold has also been produced from glaciofluviatile deposits of Quaternary age and from the conglomerate units described above, as well as residual and eluvial placers. Some placers are in or head into conglomerates and breccias composed chiefly of white quartz. Although some of these bodies are of fluviatile origin, others are essentially fault breccias in hydrothermally altered zones, and their occurrence strongly suggests that gold was derived from the fault zones. The placer deposits range from mid- Tertiary to Holocene in age. Although gold is the main product from the placers, platinum metals and cassiterite have been recovered. The white quartz conglomerates form important paystreakes in the district, and have been traced in Dollar, Thunder, Willow, and Bunco Creeks. They have been described variously; however, according to Capps (1925, p. 54), the white quartz conglomerate is the basal unit of the Kenai Formation. Capps interpreted the conglomerate as follows: "The lower portion of the Eocene beds, in places having a thickness of 60 feet, consists primarily of subangular or partly rounded fragments of quartz, with some imperfectly rounded graywacke fragments, and a smaller amount of well-rounded pebbles of quartz and graywacke. The pebble-sand fragments are embedded in a bluish-white clayey matrix that is itself composed largely of broken vein quartz and siliceous clay. This quartzose stratum is gold bearing throughout, though there is a main concentration." Three features of the white quartz conglomerate generally agreed on by all observers are noteworthy:
1. Fragments are generally angular to subangular.
2. Matrix is primarily clay and very fine grained quartz, and
3. The white quartz conglomerate is overlain, probably disconformably, by sediments more typical of the Kenai Formation.
The first two features indicate that the white quartz conglomerates are not typical fluviatile sediments. Any extensive reworking of the white quartz conglomerate would have rounded the pebbles and destroyed the clay matrix. Therefore, the white quartz conglomerate is very near its' source. The disconformable contact between the conglomerate member and the Kenai Formation is suggested by the following:
- Rock fragments of the Kenai Formation are of fluvial origin and generally well rounded, whereas those in the white quartz conglomerate are not.
- The matrix of the white quartz conglomerate is highly altered, whereas those of the Kenai Formation are not. The present study indicates that the white quartz conglomerate is very near its original source and is an older unit upon which sediments of the Kenai Formation were deposited.
Controls of occurrence of the white quartz conglomerates. Detailed mapping in Willow, Dollar, and Thunder Creeks showed that in each area the white quartz conglomerates are near major faults. The strong general structural control of the white quartz conglomerates in the district is indicated by:
- The linear alignment of white quartz conglomerate placers over 8 miles strongly suggests a fault control.
- Except for the occurrence south of the Peters Hills at Bunco Creek, the known white quartz conglomerate occur only north and west of the Peters Hills Lineament, indicating that they are structurally controlled, and not fluvial deposits, or they would be more widespread.
- Detailed mapping in other parts of the region indicate that major faults of the area have the same trend as the Peters Hills Lineament, substantiating the present mapping that indicates that the streams of the Yentna District are fault controlled.
Source rocks of the white quartz conglomerates. The white quartz conglomerates apparently were derived from strongly altered quartz-bearing rocks near fault zones. The high quartz, muscovite, and clay content of the matrix of the white quartz conglomerate and altered intrusive, plus their proximity to the placers, leave little doubt that the altered igneous rock is the source rock for the auriferous white quartz conglomerate placers. An additional indication that the placer gold was derived from the altered intrusive rocks is the high gold content of these rocks and their associated quartz veins.[Photo] We will further discuss the veins below.
Placer gold characteristics. Characteristics of gold from the placers indicate that the gold is associated with faulting, veining, and igneous intrusives, and that the gold is very near its' source. The following characteristics have been noted:
- Most of the gold is coarse and angular to subangular, and crystalline particles and wire gold are common. Some coarse gold grains are subrounded. Shapes of grains suggest that the gold has not been extensively reworked.
- Much of the gold is slickensided. Many samples show oxidized slickensided surfaces that cannot be attributed to the placer operations. The close association of the placers with known faults, the small amount of reworking, and the large number of slickensided particles strongly suggest that the slickensided gold is genetically connected with faulting in the area.
- Detailed studies of the fineness (purity) of gold in the area (Smith, 1941, p. 175-176), showed that the gold is very uniform, averaging 865 fine. Since Fisher(1945) has demonstrated that the fineness of gold increases with increasing distance from the source, the uniform fineness of the gold in this area strongly suggests that the placer gold is near its' source. The uniform fineness also indicates a common source or type of source (Fisher, 1956).
- Some fragments of placer gold have cassiterite included, indicating that the gold has not moved far and has not been reworked. Cassiterite is also common in the heavy sand concentrates, and this association suggests the source rock is high in tin. Only the intrusives in the area are high in tin.
Alteration- Many of the placers in the Yentna District are associated with large zones of argillic alteration. In other areas the arkosic sandstone, siltite, and argillite have been strongly argillically altered along fault zones so that all that remains is a varicolored greenish-black clay. Near small intrusives a thin zone of hornfels is common. Generally there is also minor silicification and sericitization. All igneous dikes and plugs of the area are strongly quartz-sericite altered and locally silicified. The basal part of the Kenai Formation is locally strongly altered by weathering and has a limonite matrix.
Origin of the Placers
Present Hypothesis: Available data indicate that the auriferous white quartz conglomerates are the product of shearing and weathering in situ of argillic altered auriferous quartz porphyry intrusives and associated auriferous quartz veins. The characteristics of the placer gold show it has a common source, has not moved far from its' source, and has not been reworked. All of the observed features indicate that the following sequence of events produced the auriferous white quartz conglomerate placers.
- In late Mesozoic or early Tertiary time, the Yentna District was cut by a series of deep, northeast-trending, high angle, normal faults. Closely following, or contemporaneous with the faulting, small auriferous quartz porphyry bodies and associated auriferous veins were emplaced along the pre-existing faults. The igneous bodies were strongly hydrothermally altered.
- Following the emplacement of the auriferous bodies recurrent faulting crushed the quartz veins and igneous bodies. The faulting was followed by a period of weathering, erosion, and nearby deposition of the auriferous fault material as white quartz conglomerate.
- Subsequently the Kenai Formation was deposited unconformably on the white quartz conglomerate. Continuing faulting caused local mixing of the white quartz conglomerate and Kenai Formation. Following the deposition of the Kenai Formation, portions of the white quartz conglomerates were reworked locally during the ensuing glacial events. (Parts were adapted from U.S. Geological Survey Open-File report #68-1, Clark and Hawley).
THIS SECTION IN PROGRESS (10 June 1999)
REFERENCES As most of the references are listed in the reports noted below, the reader is advised to review the references listed in these reports.
U.S. Geological Survey, Circular 775; Bull. 520, p. 174-200; Bull. 534 p. 75; Bull 773-A, p. A63-A69. Open-File Report # 68-35. Geologic Map of the Talkeenta Quadrangle, I-1174. Professional Paper 758-A; U.S. Bureau of Mines Open-File Report # 24-78.
NEAR SURFACE PLACER DEPOSIT MODEL and Proposed Low-Sulfide Gold Quartz Vein Model
The near surface placer deposit model evaluated herein is based on current geologic knowledge of the Blue Ribbon Mine Project placer and lode deposit and nearby placer and lode deposits in the Dutch Hills, Alaska. For details see the part of the Mineral Property Evaluation Report describing these deposits. The geometry of the deposit is horizontally oriented and generally tabular in shape. The ore body is buried by a maximum of 4' of overburden, which consists of unfrozen glacial till, glacially derived fluvial sediments, and soil with vegetative matter. The ore body is composed of fluvially deposited, well-to poorly sorted gravel, and the gold is disseminated throughout the ore body, with some concentration on the bedrock, and the gold may extend 2' into the bedrock. The bedrock is a weathered, gray or green-gray pebbly conglomerate of Tertiary age (unit Tps) which is itself gold-bearing, or where this conglomerate has been removed by erosion, the bedrock is a slate or graywacke of late Jurassic or early Cretaceous age (unit Kjs). Swell factor of the gravel is estimated to be 20%. Ore body dimensions are from 4' to 15' thick, up to 300' wide, and of variable length. Stripping factor averages .27:1. The mining and reclamation plan is based on open-pit, mechanical cut-and-fill techniques. Pit walls are designed for a maximum 45 degree slope. Mining occurs up to 140 days per year at a maximum of 16 hours per day, @ 60LCY (loose cubic yards) per hour. Any overburden is stripped by bulldozers and stockpiled for future reclamation. Process water is 100% recycle, and makeup process water (to compensate for evaporation and other losses) is obtained from seepage infiltration into the pit and runoff from rain. Ore is excavated by bulldozers or hydraulic excavators, transported by bulldozers or front end loaders, and fed to the plant by hydraulic excavator or front end loader. Average one-way haul distances are less than 100'. The initial processing plant will consist of a feed hopper, shaking screen or trommel, sluices, and a waste conveyor. Concentrates recovered from the sluices are further processed on-site by jigs and/or shaking tables, and further processed by the best available technology to produce several grades of concentrate and enhance co-product recovery. Sluice and/or jig tailings are caught in a series of ponds, dewatered, and stockpiled for future reclamation, and the water is reused for processing. Excess surface and groundwater is diverted around the operation. Reclamation is conducted as much as possible concurrent to the mining operation. Pits, settling ponds, and other mine infrastructure are stabilized prior to the end-of-season closure. See attached diagram. Exploration to support the mining operation will continue ahead of the operation in the direction of mining to define the limits of the pay zone as well as to determine the parameters of the processing operations, which will be modified as needed to achieve maximum recovery. Final closure of the mine site will occur when the ore is exhausted, and will consist of final grading of the tailings and spreading of the organic overburden, reseeding the site, and removal of the mine equipment and surface structures.
Proposed Low-Sulfide Gold Quartz Vein Model (Go To Part 2-In Progress 10 June 1999)
The current status of the mine and associated reserves are as follows:
Equipment on-site consists of a Drott 35D excavator, trommel washplant, a 30 LCY/hr testplant, a 25 LCY/hr testplant, (either may be used as a small production plant), a D-6 and a D-7 "Cat" dozer(s), (1) each 4" and 6" pumps, and misc. support equipment and camp facilities too extensive to list. The equipment on-site is generally in good to very good condition, and the additional equipment needed to scale up to full production is available and ready to mobilize to the site. Other equipment, needing repairs, is available. The mine infrastructure consists of several small pits, from which gold and other metals have been produced, settling ponds, tailing piles, ditches, test pits, some stripped ground, access roads, an access road from the Petersville Road, a good landing strip, and a number of cabins, trailer campers, and other buildings.
Permits have been applied for and received for test or pilot plant operations for the years 1988-99, and should present no problem in the future.
Adjusted value-A sample value that has been increased or decreased by an amount deemed necessary to offset known variables or other factors that may cause discrepancies in the initially collected value. See indicated value.
Alluvial-1. Deposited by a stream or river. 2. Relating to deposits made by flowing water.
Assay-To determine the amount of metal contained in an ore. Au Chemical symbol for gold
Auriferous-Containing gold.
Batholith-A large plutonic intrusive body at least partially igneous, the bottom of which is not clearly marked, and with margins that are often gradational and that widen with depth.
BCY -Bank Cubic Yard, the measurement of gravels in place. See also LCY and Swell Factor. One cubic yard is 27 cubic feet.
Bedrock-The solid rock underlying auriferous deposits. The term bedrock may be applied to any consolidated formation underlying the gold-bearing gravel. See also false bedrock.
Bench Deposit-Gravel deposits in ancient stream channels which are above the present streams.
Black Sand-Heavy grains of various minerals which have a dark color, and are usually found with gold in placer deposits.
Blue Gravel-Some of the deeper, water-saturated gravels have a distinctive bluish-gray color. At one time they were believed to represent a separate gravel flow, distinct from the overlying red gravels. Actually, these blue gravels represent unoxidized portions of the gravel channels, whereas the red gravels represent the oxidized portions of the same material.
Eluvial Deposit or Eluvium-Loose material resulting from the decomposition of rock. Eluvial material may have slumped or washed downhill for a short distance, but it has not been transported by a stream.
Eocene-An epoch of the Tertiary period between the Paleocene and Oligocene.
False Bedrock-A hard or relatively tight formation within a placer deposit, at some distance above the true bedrock, upon which gold concentrations are found. Clay, volcanic ash, or tight gravel formations can serve as false bedrock. A deposit may have gold concentrations on one or more false bedrocks, with or without a concentration on true bedrock.
Fineness-The proportion of pure gold expressed in parts per thousand. For example, a piece of natural gold containing 150 parts of silver and 50 parts of copper per thousand, and the remainder pure gold, would be 800 fine.
Float-Piece of ore or rock which have fallen from veins or strata, or have been separated from the parent vein or strata by weathering agencies.
Fluvial-Of or pertaining to streams or rivers.
Gangue-The noneconomic mineral components of a mineral deposit.
Glacial-Pertaining to, characteristic of, produced or deposited by, or derived from a glacier.
Gm-Gram
Greisen-Igneous rock that has been altered by the action of fluids rich in volatile elements.
Hydrothermal Vein-A vein formed by the crystallization of minerals from predominantly hot water solutions of igneous origin.
Indicated Value-The value of a placer sample before making adjustments for shaft factors, boulder factors, or other empirical corrections.
Lacustrine-Deposits Deposits formed in the bottom of a lake.
Overburden-Worthless or subeconomic surface material covering an ore deposit.
Oz-Ounce, Troy
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