Hello all.
Regarding the perplexing matter of gold formation, and how does it seem to renew supplies of itself in supposedly worked out areas.
Who knows how gold was actually created in the first instance!
Did it just appear as a “Singularity”, as “Perfect” gold ,without any other make-up in its consistency whatsoever, or, was it composed through “Nuclear” processes from a combination of essential ingredients that just happened to be floating around in a fissionable/fusionable sea of electronic particles?
If it did not appear as a singularity, then it “Must” consist of two or more components. This begs the question of what components could possibly make gold as we know it today?
And does it actually “Renew” itself to replace its supplies in worked out areas?
The above makes a very intriguing subject to contemplate.(if your interested of course), but somebody on the forum did ask a sort of comparable question!
O.K.
First we have to realize that the Alluvial gold which is gathered from rivers (or anywhere that a river existed in the past) was not actually “Formed” within or by any of the rivers resources. Any gold within a river was firstly deposited into the river by being eroded away from some sort of gold bearing volcanic “Primary” source (usually a group of Quartz reefs or veins somewhere along its course.) because somewhere along the paths that lead to these reefs the gold was transported to the rivers channel by the rain waters shed down the sides of the hills that contained the reef/s.
What was the “Origin” of this gold that was contained within the reefs?
(My personal opinion is gathered from intensive research into this happening, which points to the entrapment off extremely fine gold particles in the first instance, within a mineral called “Pyroxene”, a small, usually green colored glassy looking mineral which is prominent in most volcanic magmas.)
But that’s just my theory.
The Pyroxenes are a group of important rock-forming Silicates found in many igneous and metamorphic rocks. They share a common structure, and most of the “Common” minerals can occur in them. They are early-forming minerals that crystallized before the lava erupted. The Upper Mantle of the Earth is mainly composed of Olivines and Pyroxenes, a good host rock of which is “Basalt”.
Basalt which erupts into the open air forms three distinct types of lava flows, or volcanic deposits: Scoria, Ash (or cinder) and Breccias.
Basalt is one of the most common rock types in the world, and is most typical in igneous areas They are most important within metamorphic areas, and they also weather fairly fast.
Second O.K.
Sea water contains extremely fine gold particles in suspension. This also infers that it is trapped and contained within the sediments that settle and cover the oceans bottom over the millenniums, where extreme pressure compresses it into a sort of sedimentary mudstone rock.
Now comes the interesting part!
At some future point in time, and long after this sedimentary rock is formed, molten magma eats its way up from the depths of the earth under these great sheets of mudrock and basically gobbles them up within itself carrying all the constituent parts(including the gold) of this rock upwards to the surface of the earth where it is erupted in the spewing fury of a possible land forming, and mountain forming Vulcanism.
Note that when this mudstone melts completely, it too becomes magma, and when this magma solidifies it becomes an “Igneous” rock
This molten sedimentary “mudrock” when it reforms, hardens to an “Igneous” rock within the ground or elsewhere. It is now called “Shale” which contains approx 95% of the Carbonaceous organic matter that originally exists in all sedimentary rocks. Shales also contain lots of Clay materials (or volcanic ash), termed “Greywacke”’ plus quartz grains (or silica). Their typical colour is Grey.
(Clay itself is a known filtration mineral for the precipitation of gold)
The geological term for this change is termed “Low grade Regional Metamorphism”. (which basically means altered by heat and pressure in the place of deposition.)
So from starting with a single “Shale Parent” rock-form, this type of metamorphism produces a series of different rock formations that alter from Shale, to Slate, to Phyllite, to Schist, and finally to Gneiss. ( its sort of a bit unimaginable that all these different rock types can emanate from one and the same sedimentary parent mudstone type formation.
(South Island members take note of this rock sequence, as you have got “All” of these rocks in your gold bearing areas.)
This process of metamorphism teaches us how many of the best known differing rock formations on earth were formed
Third O.K.
By understanding the above sequence of events, we also have to realize the extremely possible chances that these different rock types have of containing some of the gold that was dissolved in the sea water that originally permeated through these mudrocks when situated on the sea bottom, and is locked up in their constituent parts which are now exposed to the “Atmospheric” conditions which prevail upon the surface of this earth. These, conditions are in a continual operation of creating a process of “Weathering” which dissolves and destroys the structures of all land forms. This includes the usually mountainous regions where the reefs etc are predominantly situated.
It is mainly by this system of weathering, that all the different alkaline and acidic chemicals, plus waters that preside within the earth and above it to the limits of the troposphere, that help to re-dissolve those fine golden particles from the “Shales” First. and deposit these into the “Slates”, and from them into the “Phyllites“, to the “Schists“, and finally to the “Gneiss”, or some of the other rock forms that may intrude into each and every one of them. (Slates are typically associated with Major Mountain building events when Shales or clay rich sandstones (Greywackes) undergo “Low” grade regional metamorphism.)
All these different metamorphosed rock forms have usually been subjected to what they call “Tectonic” fracturing (sometimes more than once, by some sorts of events like more volcanic eruptions, or earth shudders like earthquakes etc.) after they were formed, and these events cause extensive fracturing called Faults, and where these faults are very numerous within an area that has been subjected to volcanic actions, then, that is where gold is most likely to be found.
These faults create open channels that seem to be very favorable for the deposition of Quartzes and Calcites etc, as the Vulcanism wanes and cools down from its initial fiery start, and begins to enter its “Hydrothermal” sequences of boiling waters, accompanied by the lessening of the heat and pressures.
These events are mainly confined within the open fault channels, but which in a “Major” way also dissolves and leaches the surrounding country rocks of their contained minerals and metals etc, which migrate into those open channels where they re-Crystalize and contribute to filling the channels up with themselves.
As this sequence of events continues, it tends to block and close the fault channels up with precipitated materials as the waters continues to cool and dissipate the heat from the Hydrothermal actions during these depositions.
The minerals and metals carried into these fault zones precipitate out with the quartz or calcite into reefs etc which then contain varying amounts of any minerals or metals that were present in the surrounding country rocks that were subjected to the hydrothermal actions, and it is these that get weathered out to the relevant waterways of the area. As long as the hills contain vestiges of these reefs, the gold etc will continue to be shed into the rivers etc.
Note that if this reef gold has made its way into a river in times gone past, and has been river deposited in a placer gold situation, this deposit of gold may have been left high and dry at some point as a terrace/bench deposit as the river has cut its bed lower into the landscape, or it may have been uplifted to its present position high above the river by other traumatic earth actions. In this case, it is possible that this already deposited gold can begin another journey on its way to the sea by the rain/flood/landslip or earthquake actions that contribute to the redistribution and deposits of the contents somewhere further down the river.
How’s that for a thesis/theory/explanation/ or just a lot of codswallop.
Cheers--- Colin.
WWW
