Geology Of Gold In Alaska

Intoduction:

By: Dr. Stéphane D. Deganay

650 kilometers long and up to more than 6,000 meters above sea level, the "Alaska Range" covers part of Alaska, and gives rise in its eastern part to the sources of the famous "Yukon" river.

It is the mineral lung of Alaska and Canada with these 3 million lakes, its 3000 rivers, where the Yukon is the most majestic of them for more than 2000 kilometers.

This fantastic mountain range is arguably the most beautiful place in the world  in terms of geology, mineralogy and adventure in the world...

It is here and in these bowels that hundreds of millions of years ago, this fantastic birth is located between 600 and 800 million years ago, exactly in the Proterozoic, due to the metamorphism of the shale, the sandstone and the  mudstone along the western continental margin.

It is at the heart of these rare earths and these extremely ancient rocks that a fabulous mineralized treasure was born in the contact zones buried very deep under the earth's crust.

During the uplift of these mountains, metamorphism will give rise, through hydrothermal flows and gigantic pressure, to the elements sufficient to bring to light rare gases and chlorides, which will generate the conditions for the birth of rare elements, such as  gold or platinum.....

From this immense force and this moving chemical mass will then be born the gold of the earth, and one of the most fabulous traces of these major events in the history of our planet....

The gold from Alaska will then make a long journey towards the surface of the earth's crust, first in the crust under infrachemical flow, and strong sources of aqueous chloride solutions loaded with elements...

Then subsequently, crystallizing in veins of high temperatures, with extremely powerful isobaric pressures, gold will become a stable element of the periodic table.

The age of erosion and the partial release of these gigantic vein banks will come, which slowly and probably over nearly 180 million years and after a very ancient metamorphic age, will release with another collosal hydrogeological force the gold which  had been waiting there for over 560 million years.

This first stage will follow a very long storage of gold in the post-Proterozoic plains.   It is during this period that the largest fossil alluvial pudding formations will form, immensely loaded with heavy elements, such as mineralized sands or even elements, such as gold.

Tectonics and the mechanical working of plates, and contact zones, will shape until today, these geological landscapes where we find these ancient fossil deposits, loaded with minerals and important gold deposits.  .

The gold thus shaped, crushed, ground then metamorphosed, will find its place in the different geographical landscapes of Alaska today.

Added to this understanding of these phenomena is the almost continuous work on the geochemistry of these rocks, which to this day continues to make the chemical elements of these very ancient deposits more complex.

 Chemical Gold Complexes in Alaska

Gold in physical form continues to fascinate people today, but to understand it, find it and appreciate it, we still need to study its origin and its physics.

Gold has continued to travel from the depths of the earth, transforming itself in turn into chemical solutions then into crystallization, this is what we call “Transmutation”.  The gold which will travel through the rocks, in the form of gold chlorides and selenides, will "transmute" when the ambient environment gives it the possibility of precipitating in the form of complex chlorite salts.

It will be able either to rush with enormous pressures into sulphide veins, then leave these conditions, to return to the rocks in the form of chlorides, and sometimes stay there, to travel even today, in hydrothermal zones under  complex chemical forms.

This Alaskan gold, so coveted for its renowned title as one of the finest golds in the world, is naturally not an accident of nature.....

We now know that the formation of certain surface veins, such as alluvial nuggets or ancient placer banks, owe their richness to phenomena of nourishment and deposition, by chlorinated solutions loaded with chemical gold.

Indeed certain nuggets or (angular vein elements) detached from the veins, then rolled by the alluvium, continue under certain conditions to grow, thanks to this unexpected and recently discovered chemical precipitation...

These phenomena, still unknown and unexplained by science, still remained mysterious 30 years ago.

They partly explain the mysterious and sometimes incomprehensible richness of certain veins or sites that are poorly established geologically or incompatible with their geological histories.

Alaska is full of these formidable deposits, sometimes strategically and geologically isolated from their anchoring points.

 Gold Mineralogy In Alaska

Very efficient, the geochemistry of gold in place, whether primary or secondary deposits, are becoming records.

First of all, Alaskan gold is up to 99% chemically pure, in some places contact metamorphism has reshaped several phases of these numerous deposits.

The gold of the "Range ALASKA" chain is heavy.  The elluvionary gold retains these crystallographic forms for quite a long time, in question, the hydrothermal torrential evacuation, of the hydrogeological systems, in fact we travel along the face of the chain, through violent and torrential episodes.

These torrential leaps favor the extension and reduction of the erosion of heavy elements.

Thus the storage of gold on the platforms of the "bed Roch" of alluvial slabs, is organized in micro "Dow", these mini placers are strongholds, where one could find record masses of gold  .
The participation and tectonic shift accentuates the extension of these impromptu deposits.

The alluvial sources of these deposits contain different forms of gold:

(1) granular spherules:
For the metal deposits of metamorphism, gold will nourish the low zones of alluvial emissions in light “concave grains” of 0.01 microns up to 0.10 g.  These gold spheres will accumulate in the deep gravel and fill only micro faults to concentrate in the ejection mud at the bottom of the alluvial streams.

(2) powders and fine links:
Always and mainly of metamorphic origin, the micro crystals scattered across the miles of metamorphic rocks, once released, they will be heavily mechanized, we will find them in the form of "straws" of the order of a few microns, capable  to float thanks to the alluvial emulsions which trap air under these straws.  They will have eratic deposits of no interest and will be very poor geitological indicators for the engineer who will look for placement clues.

(3) (Sequins) “beans”:
We now move on to alluvial sources, particularly ancient rocks, the gold will then be found in fairly strong grains, to form during the alluvial descents, beans, i.e. quite thick flattened grains.  These grains, which sometimes can be slightly crystallized into failed octahedrons, then form golden pegs inside the convection pots, either on the surface of the streams, or in the erosion vacuoles, against the Roch bed at depth.  These deformed grains will reach up to 2 grams.

(4) Vein masses - nuggets.
The pieces of veins more or less accompanied by quartz and parent rocks, after alluvial leaching, become shapeless, losing their angular origins.  The crushing will depend on the position of the gold in the sample, the dispersion of the center of gravity of 19.6 plays a role in the conservation of the gold in the center of the sample.  The location of these masses is slow, due to the density, the nuggets rarely jump beyond the first 3 kilometers of the primary deposits.  That said for some pieces, it is possible during the configuration of the torrents, that blocks which have vein pieces are carried further downstream, thus depositing ounces of gold, at abnormally high distances.  For Alaska, elluvium pieces of several ounces are more than likely, up to 300 or 400 g.

 Geological Contexts

The exploration of vein or placer deposits has never reached the level that the region deserves, in fact the geographical and structural impossibility added to climatic difficulties prevents any evolution and structural development of the developed exploitation zones.

The distribution of vein and placer deposits on the peninsula, is the point of certain areas where exploration could be most productive.  (Newest Placer Gold Deposit of the major Gold and Placer Districts of the Seward Peninsula).

By far the most important geological factor in the location of placer gold, on the Seward Peninsula are the famous primary deposits of York Slate.

It is clear that almost all areas with
Many Placer gold deposits either lie on large areas of York Slate, or contain York Slate where it has been intensely deformed as it approaches faulting.

We can observe that if York Slate is absent, gold placers will not be there in significant quantities.  Unquestionably, a large part of the placer gold is essentially native to the gold initially present in this precise movement represented by the York slate.

The second factor in regional extent for Alaskan placer gold is the proximity of granitic intrusives in the York Slate.

Once again, everywhere a granitic stock intrudes into the York slate, it was then noted that the placental gold was
extracted in certain streams near these phenomena.

If the granite outcrop is not obvious, there are geologic and geodetic signs that granite is present at shallow depths, such as at Dahl Creek, Hannum Creek, and Potato Mountain.

In many localities, placer gold is associated with hydrothermally altered York slate along fractures marked by quartz veins, sericitic alteration, and very prominent sulphide minerals in nearby placers.

Placers are particularly notable and rich in the upper Kougarok area, where piling and dredging at Taylor have shown the exposed bedrock to have extensive alteration into sericitic clay and quartz veins.

The concentrates, for example, from placers come from Washington Creek, from the upper west course of the Kougarck River, contain a fairly heavy mineral, cassiterite as well as numerous grains of pyrite, silvery galena and a silvery sulphide containing mainly  silver, tin and bismuth.

These markers suggest that the Serpentine granite extends southwestward beneath this area, and clearly thermally metamorphosed rocks, with development of limestone formations, are present.

Silicate rocks are also found on the west side of Kougarok Mountain.

Serpentine granite was present on the first placers exploited on
the Anikovik River in the western Seward Peninsula for over 100 miles.


The west also yielded gold and cassiterite.  This relationship between the placental gold and the intrusions which outcrop or are buried at shallow depth by the bedrock, indicates intense erosional uprooting, it seems that many streams which flow towards intrusive elements, such as those on the  north, take part of their gold concentration through these mineralized banks which cross the path of these watercourses on the surface.

The granite north of the bend of the Kugruk River in the Bendeleben quadrangle, or on the north side of the Serpentine,  contains placer gold.

Intrusive rocks are lacking, but where York Slate is present deformation is intense in the primary continental landscape of Alaska.

The clearest relationship of this type of geologic deformation is found in Budd Creek and nearby streams in the eastern Teller Quadrangle, where small deposits of placer gold are located immediately downstream where the York Slate Ribbon is delineated  by flaws.

The relationship between placer gold and tectonism involving the York Slate is evident along Telegraph Creek in the northern part of the western Solomon's Quadrangle.

A few very small tectogenic deposits of copper oxide are known near the placers.  All the placental gold is located along a section of the watershed underlain by York Slate.

Most important are the vast and rich deposits of placer gold in the Solomon Central Quadrangle Council area.  Geology here
is complex, with York Slate, Kanauguk and Paleozoic limestone formations are complexly mixed by thrust faults and normal faults.

The York Slate is under tectonic influence intensely deformed and recrystallized with innumerable quartz veins.
The gneiss mantle lies to the north next to the York Slate.

The geological factor which, combined with one or more of the above, produces the largest and richest deposits of placer gold on the Seward Peninsula.

As for the presence of
continuous fault zones cutting York Slate, which are marked by numerous gold-bearing sulphide veins exposed in places in the Anvil valleys, e.g. the Penny River, crossing the Nome River upstream of the Anvil has gold mineralization
across lower Osborn Creek (Osborn Fault).

As soon as one leaves the slate belt in almost any direction, the percentage of placer gold suddenly falls and quickly disappears.  The quarrel of these two events seems to indicate one of the mysteries of this immense mountain range....

(On placental gold deposits in the Nome region with glacial deposits)

Moraines and their features are called to provide placer gold, this simply means that detrital gold, gold derived from eroded veins, was incorporated into the moraines, where it was mechanically ground to produce extremely fine gold  beaches of Nome.

Glacial moraines are geographically widespread northwest of Nome, but the placer deposits are literally more extensive.  there are small sections of it found on York Slate below the main moraines

In the Solomons, large deposits of placer gold were dredged after the beginnings of sluice mining.  Although placer deposits have been mined to a limited extent over much of the outcrop area of the York Slate, which extends in a continuous belt north of Solomon.

Most of the deposits were of low grade.  Only in the lower Salomon River and up to Big Hurray Creek were the placers particularly rich.

As in the Nome Area, two gold-bearing quartz veins, as at the Big Hurray Mine, and the antimony-lead-silver gold-bearing vein, as on the ridge north of Big Hurray Creek (Stepovich Mine) are correlative with the  richest area of the placer gold deposit.

The gold deposits of Hannum Creek, the western upper reaches of the Inmachuk River, lie downstream of a vein that lies along a series of strong northwest-trending faults.

This vein is marked by sulfide-containing vein material up to several feet thick.

Within these important veins we can observe sulphides such as: Veins of, galena, pyrite, arsenopyrite, chalcopyrite, sphalerite, gold.

(Silver and Electrum Veins)

the money is visible or highlighted by the analyses.
The vein, which dips steeply to the southwest, is exposed on the northwest bank of Hannum Creek, a short
distance upstream from Camp Foster which is a remarkable gold deposit.

It should be noted that the first geolocations of most of the Seward Peninsula predicted the existence of a hidden vein
precisely where she was found.

Faults in the general area may be gold bearing.  The deposits may be related to a granitic intrusive which probably underlies the thin-bedded argillaceous limestone on the ridge line about five to seven miles north-west of Hannum Creek.  There, the limestone is partly converted to tactite, which clearly indicates a nearby heat source.

The final factor that governed the distribution of placer gold
on the Seward Peninsula lies the distribution of glaciers.  In places where rich gold or tin placers might be expected, notably downstream of the Lost River Tin Mine.  The placers were small and produced only a tiny fraction of the tin or gold that must have entered the flow following the erosion of the veins also releasing white gold or electron.

The rich tin placers with some gold that have been mined
near Potato Mountain, and in the deep channel of Cape Creek,  west of the Seward Peninsula, were preserved because the areas were not glaciated during the Wisconsin glaciations that were so prevalent in the York Mountains,  Kigluaik, Bendeleben and Darby.

The electron is dispersed randomly and by theoretical concentration.

Gold & Platinum

Alaska and its fabulous gold heritage contains in its depths many minerals which are effective indicators of the search for gold.....

Such minerals as galena, chalcopyrite, sphalerite, arsenopyrite, the probability exists that bedrock loaches are nearby.

Platinum in placer areas is believed to have been recovered from the deep channels of Gold Run, south of Teller.

Platinum may exist in this area due to the rather unusual concentration of intrusive rocks in the York Slate, as does gold in the Gold Run drainage

Many of these intrusives are complexly altered and most contain silica in the 40-44% range, indicating that they are malfic enough to be accompanied by platinum.

Placer platinum has also been reported in gravels near the complex intrusive zone at Granite Mountain, east of the Kiwalik River and in the Candle quadrangle area.

The bedrock of the area consists primarily of weathered malfic volcanics and rocks that date from the Jurassic, and there are numerous oxidized areas that contain strong geochemical anomalies and, locally, significant amounts of galena and base metal sulfides  .

Despite the unusual concentration of weathered bedrock and placer gold deposits in the area, they were small, shallow and of marginal quality....

Platinum may be derived from the decomposition of malfic inclusions in metavolcanic rocks, for fragments of pyroxenite and eclogite can be observed in the gravels of many Alaskan streams.