Komatiitic Sulphide Deposits

A particular type of lava which flowed over parts of the Earth mainly in the Archean age is

called komatiite (koh-mat-tee-ite) after the Komati River in South Africa where it was first

described. Except for one occurrence about 80 million years in age, all komatiites are

about 2.7 billion years old or older. By definition, komatiities must:

1) contain at least 18% MgO;

2) exhibit spinifex texture(resembles a lacy mesh of acicular or needle-like olivine crystals,

typically surrounded by lighter-colored, interstitial minerals such as plagioclase, tremolite,

and/or chlorite);

3) and contain olivene. The elongated nature of the komatiite olivine crystals is quite distinct

when compared with the tabular olivine crystals seen in most basaltic rocks.

Komatiite lavas erupted from the upper mantel of the earth carrying heavy metals like iron,

nickel, cobalt, and the Platinum Group Metals (PGM's) such as platinum, palladium (and others),

and are a primary source of nickel deposits. Since a komatiite eruption has never been

observed, the fluid flow characteristics and eruption style of these lavas have been deduced

from the properties and textures of the ancient rocks. Their high eruption temperatures (1600

degrees C compared to today's typical lava eruptions of 1150 degrees C), for example, are

calculated from their olivine-rich compositions. The characteristic spinifex textures, on the other

hand, indicate that these lavas cooled very rapidly. Combined, the high eruption temperatures

and the low silica contents indicate that komatiites erupted as very fluid lavas, having excep-

tionally low viscosities (flowed like water) and low aspect ratios (inlet height to length of channel).

Komatiites can therefore be modeled by an open channel flow of hot fluid flowing over the Earth

like water in a channelized river. An interesting phenomenon occurs when a fluid flows over a top-

ographic low or around an obstacle in the path of the fluid. Hydrodynamics requires the fluid to ro-

tate as it flows over the low or around the obstacle. These rotations look like eddies or whirlpools

in a stream. The super hot rotating lava now acts like a "drill" thermally and mechanically eroding

the rocks beneath the channel and extracting sulphur from them if present. The lava can then

become sulphur saturated which forces sulphide minerals to precipitate out of the fluid as immis-

cible "blobs" and sink to the bottom of the lows or eroded channels by gravity. The result is a po-

tentially economic nickel deposit from the formation of massive sulphides.

However, the flow characteristics of the komatiite also have a great affect on the formation of the

deposits as shown in the accompanying models. A source of sulphur in the substrate with which

the komatiite thermally and mechanically interacts is also critical. Pyrite in iron formations is an

excellent source of sulphur because the pyrite can convert to pyrrhotite releasing excess sulphur

to be assimilated in the komatiite. Graphite formed from carbonization of an ancient sea floor bed

often contains pyrite so komatiite flows can also assimilate sulphur from graphitic substrates.

Conceptualizing the surface of the ancient Earth as a series of irregular hollows, craters or chan-

nels connected by "flat spots" (like a "Moon-scape") explains why komatiite deposits occur as pods,

typical of those found at Kambalda Australia, (called the "Kambalda Nickel Belt") and at the Shaw

Dome Nickel Belt near Timmins Ontario, Canada. The hollows or embayments created the most effec-

tive conditions for the thermomechanical erosion of the sulphur containing substrate and provided a

trap or a container for the deposition of the sulphur saturated nickel sulphides by gravity. An analogy

can be drawn to that of water flowing over a gravel road during a rain storm; after the storm, water

remains only in the pot-holes or "pods" of the road.

Hydrodynamics tells us many other things which affect the formation of nickel deposits from komatiite flows. For example, because the earth rotates counter clockwise in the Northern Hemisphere, the right hand side of the channel of the river will always be more eroded than the left side. This suggests the settling sulphide minerals should accumulate more on the right hand side of the komatiite flow forming a "v" shaped deposit. In Australia, being in the Southern Hemisphere, the left side of fluid flows would be more mechanically eroded.

The first five accompanying figures are computer simulations of komatiite flows over a hollow. By varying the velocity (red is fast and blue is slow) and the thickness of the flow, it can be seen how the rotational properties and therefore the formation of the pods is affected. The Reynolds number is a dimensionless quantity equal to the (velocity)(thickness of flow above its bed)(density)/(viscosity of the fluid), and represents the ratio of the inertial forces to the viscous forces.

The Shaw Dome area is quite unique because it contains approximately 5% pyrite in the rock over and around which the komatiite flowed. The pyrite was a very good source of sulphur for the scavenging lava, changing to pyrrhotite in the process which in turned formed part of the massive sulphide beds along with pentlandite. The mining lands around the Shaw Dome are therefore very prospective for finding nickel pods. Liberty's extensive nickel mining claims on the komatiite flow are shown in the accompanying Shaw Dome geology picture.

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Diagrams are all on the home site. Anyway, mineralization in any of the two new highly prospective sites could prove pretty interesting. But what if some of GCR's and ISM's theories prove true? I kind of hope ISM proves up their resource to be everything they claim.

My theory is not what the company is promoting. We are only working on Hart 1 so there is much more drilling to be anywhere close to approaching this idea. Three deposits all the same size as Hart #1 are just fine with me. Any other takers?