| Over
the last 48 months, a previously
ignored group of metals has forced its way into the collective consciousness of
the world's minerals industry. These metals are referred to as Platinum
Group Elements (PGE's) and normally include platinum, palladium,
rhodium, ruthenium, osmium and iridium. Of these elements, only platinum and palladium
are mined as primary metals. The other four PGEs are recovered as byproducts,
primarily from platinum, palladium and/or copper-nickel production. Research conducted
by Avalon Development suggests Alaska contains significant potential to
host economically attractive PGE occurrences in a wide variety of geologic settings.
With few exceptions, there has been virtually no targeted exploration of the nearly
200 known Alaskan PGE occurrences. Extremely favorable current and future PGE
supply - demand fundamentals suggest Alaska's prospective PGE potential will come
of age in the new millennium.
General
Geology of Alaska PGE Deposits There
are five main geologic settings that favor PGE deposition in Alaska. This classification
is modified from one recently suggested by Foley and others in Economic Geology
Monograph 9 (1997):
| Summary
of Alaska PGE Occurances | |
Deposit
Model | Number
of Alaska Occurances | Past
Pt. Production | Past
Pd. Production | Pt
resources (troy oz) | Pd
resources (troy oz) | | 1 |
27 |
321 |
0 |
0 |
72,000 |
| 2 |
31 |
83 |
0 |
0 |
0 |
| 3 |
10 |
0 |
0 |
525,100 |
0 |
| 4 |
63 |
30 |
0 |
0 |
0 |
| 5 |
35 |
648,812 |
20,500 |
0 |
0 |
| 6 |
32 |
100 |
0 |
0 |
0 |
| Totals |
198 |
649,346 |
20,500 |
525,100 |
72,000 |
Deposit
Model 1: Alkaline-to-subalkaline Composite
plutons: There are 27 known PGE-bearing
alkaline to subalkaline composite plutonic occurrences in Alaska. Composite plutons
are the least well documented and least understood of the potential PGE hosts
in Alaska. These composite plutonic complexes are highly variable in age and their
associated igneous rocks range from granitic to mafic to ultramafic. Alkaline
and silica-saturated plutonic rocks are volumetrically more common than mafic
to ultramafic intrusives. Many are concentrically zoned, with granitic cores and
more alkaline and mafic outer zones. They form above active subduction zones in
convergent plate margin tectonic settings and are thought to be the result of
interaction between mantle and crustal melts. There is a growing body of evidence
that suggests composite plutons and Ural - Alaska plutons are end-members of a
range of plutonic complexes whose gross tectonic origins are similar. Zoned plutonic
bodies which exhibit alkaline to subalkaline plutonic phases may have been generated
under extensional conditions within a back-arc basin setting. Zoned plutonic bodies
which are dominated by mafic and ultramafic rocks (Ural - Alaska) have chemical
and physical characteristics suggestive of derivation within compressive regimes
above active subduction zones. A number of the Alaskan composite plutons are associated
with substantial placer gold deposits which contain PGEs in minor amounts in heavy
mineral concentrates. Composite plutonic complexes also have potential for precious
metal, base metal, uranium, tin-tantalum-niobium and rare earth deposits. Deposit
Model 2: Differentiated sill-form
complexes: There are 31 known PGE-bearing differentiated sill-form type occurrences
in Alaska. The best known Alaskan sill-form complexes are of Late Triassic age
and are interpreted to be comagmatic feeders to the extensive Nikolai basalts
of the Wrangellia terrane of southcentral Alaska. This belt of rocks extends into
the western Yukon where it hosts the past producing Wellgreen copper - nickel
- PGE deposit. These complexes consist of ultramafic and lessor mafic rocks with
associated PGE mineralization in placer deposits as well as lode deposits associated
with copper - nickel sulfide mineralization. Recent exploration in the central
Alaska Range has identified a number of untested prospects containing anomalous
PGEs. A number of these prospects were known to contain copper and nickel mineralization
but were not evaluated for their PGE content until recently. Deposit
Model 3:
Synorogenic Layered complexes: There are 10 known
PGE-bearing synorogenic layered occurrences in Alaska. The bulk of the world's
platinum production is derived from synorogenic mafic intrusive layered complexes,
primarily the Bushveld and Stillwater complexes. Sulfide and/or chromite and/or
PGE minerals accumulate in distinct layers which form under quiescent conditions
within a large magma chamber. In Alaska, all known layered complexes are Tertiary
in age and are composed primarily of gabbro and norite with lesser gabbronorite,
troctolite and anorthosite. Alaska deposits are hosted within the allochthonous
Chugach Terrane in northern southeast Alaska. These prospects are essentially
copper-nickel sulfide deposits with secondary amounts of PGEs. For example, the
Brady Glacier deposit resources contain 100 million tons grading 0.5% nickel and
0.3% copper with 171 parts per billion total PGEs (approx. 0.005 oz/ton). Deposit
Model 4: Ophiolitic complexes:
There are 63 known PGE-bearing ophiolite type occurrences in Alaska. Ophiolitic
complexes originate at ocean ridge spreading centers and are commonly composed
of a basal unit consisting of differentiated ultramafic and mafic rocks overlain
by sheeted mafic dikes which are in turn overlain by submarine basaltic lava flows
often associated with deep-water marine cherts. Ophiolites are typically more
complex structurally than other PGE-permissive settings due to transport on the
host oceanic plate and their subsequent obduction at convergent plate margins.
Jurassic age ophiolites are common throughout Alaska's major mountain belts but
the distribution of PGEs in them is poorly documented. Ophiolites commonly contain
anomalous chromium, copper and nickel but the distribution of PGEs in Alaskan
ophiolites is poorly documented. Deposit
Model 5: Ural-Alaska type complexes:
There are 35 known PGE-bearing Ural - Alaska type occurrences in Alaska. Ural-Alaska
type complexes are mafic to ultramafic plutonic bodies that commonly are associated
with basal portions of Mesozoic volcanic arc terranes. These complexes commonly
are associated with linear orogenic belts which range in length up to 1,000 kilometers.
Ural-Alaska type complexes normally are concentrically zoned, with dunite or peridotite
cores surrounded by pyroxene-bearing rocks (pyroxenite, websterite and lherzolite)
which are in turn rimmed by more differentiated rocks including gabbro and norite.
Ural-Alaska complexes commonly range in size from 1 to 10 miles in diameter and
cause variable sized contact metamorphic aureoles in surrounding country rocks.
The world's first platinum producers were the Choco placers derived from Ural
- Alaska type complexes in Columbia however these types of complexes are best
known from their type localities in the Ural Mountains of west-central Russia
and from southwestern and southeastern Alaska and northwestern British Columbia.
Several of these complexes, including the Goodnews Bay complex in southwestern
Alaska and the Kondeur deposits in the Urals, have been deeply eroded resulting
in formation of significant placer PGE deposits. With the exception of the Salt
Chuck and Goodnews Bay prospects, little recent exploration has been directed
toward PGE mineralization in Ural - Alaska type complexes in Alaska. Deposit
Model 1: Unclassified type
complexes: Any other model type not previously mentioned.
DESTINATION
2008
- ALEXANDER PLATINUM BELT
 |
| Click
on image for larger view | One
of the most important and often overlooked details regarding PGEs in Alaska is
that 100% of its historic palladium production and over 99% of its historic platinum
production has been derived from one type of geologic setting, the Ural - Alaska
type mafic/ultramafic complexes. Ural - Alaska type complexes were recognized
as a distinct geologic entity in the early 1900's in both the Ural Mountains of
central Russia and in Alaska and northwestern British Columbia. However, these
complexes were the world's first and only sources of platinum until the 1920s.
It was about this time the Russian, Canadian and American geologists began to
realize that most of world's platinum had been derived from geologic settings
which were remarkably similar in composition, size, geometry and other geologic
characteristics. One such belt, the Alexander Platinum Belt, stretches
for over 350 miles though southeast Alaska and hosts at least 11 Ural - Alaska
type complexes. Only one of these occurrences has had past PGE production and
only one other occurrence was explored specifically for its PGE potential in 2000.
Both returned extremely promising PGE results from 2000 field programs. The Alexander
Platinum Belt represents one of the least explored metallogenic belts in Alaska
and is expected to become an active destination for corporations and individuals
conducting PGE exploration in 2002 and beyond.
PGE's
for the New Millennium The
future of PGE exploration, development and production seems bright despite the
difficult political, social and environmental hurdles which face the mining industry
on a global scale. Some of the factors which contribute to this conclusion include:
1. Platinum is still the rarest
of the precious metals and retains its historic role as a store of value and as
an investment commodity. 2.
Both the growing autocatalyst technology sector and several platinum-group mines
now in and nearing production are the direct result of government intervention
to clean vehicle exhaust emissions. This is a rare instance in which an environmental
policy is the cause of expanded mining activity. 3.
In contrast with gold and silver, there are no large above-ground platinum stockpiles
that can be sold into the market to fill the gap against significant supply shortfalls
or disruptions. 4. The only
known above-ground palladium stockpiles are in Russia and these are rapidly dwindling
as Russia has met annual demand shortfalls over the last 10 years from their above-ground
stockpiles.
Alaska
PGE Potential Alaska
is well positioned to take advantage of a unique situation in the metals industry.
Unlike virtually every other metal, the PGEs are facing a strongly increasing
future demand coupled with a dwindling or flat supply. Conditions such as these
encourage active exploration for and development of PGE resources. Alaska's diverse
geological history has left it well endowed with prospective PGE prospects which
have been ignored for most of the last century. With few exceptions, what we know
about Alaska PGE occurrences was derived as a secondary benefit of exploration
for other metals such as copper, nickel, chromium or gold. Avalon Development
has taken the first steps to identify, categorize and prioritize the most promising
PGE prospects in Alaska. The first two targets acquired for our clients have returned
extremely encouraging results from properties that were previously available for
staking and acquisition. We have identified other high priority PGE targets, several
of which are currently open to location. Avalon Development's experience and expertise
can help you achieve your acquisition goals quietly and efficiently, without you
having to invest the time and money to create the database and targeting tools
you need to become competitive. If
you are interested in learning more about PGE opportunities in Alaska, contact
Avalon Development and request a free
copy of the "white paper" Exploration Potential for
the Platinum Group Elements in Alaska and let us help you explore for the
metals of the new millennium. | 
