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Published in Ansett's inflight magazine Pacific Panora when I was a staff journalist, I've added it here for readers of Stargate SG-1 fans to explain the premise of geothermal naquadah used in City of the Gods
In tiny, microscopic quantities it lay waiting beneath the Pacific. Deep under the seabed it sat, trapped in the fragile layers of crust covering the vast, molten interior. The Earth revolved, as it has from the beginning, and in doing so, the hot fluid interior moved, driving the frozen crustal plates into each other, forcing one to rise above the other. Subduction the geologists call it. As the plates ground against each other, earthquakes fractured the frozen crust and the molten heart of the planet burst to the surface in fiery, bubbly, underwater explosions. The volcanoes grew and finally reached out above the surface of the sea to become islands. Men arrived and gave them names; Indonesia, New Guinea, Solomons, Fiji, New Zealand and Vanuatu.
Some volcanoes aged and grew tired. Many could no longer belch flames but like tired dragons, could only belch out steam. Yet the steam was rich! For below the surface, cool acidic groundwater leached the gold and other minerals upwards from the rocks while superheated magmatic, chlorine rich water took it from below. As the volcanoes continued to cool, the overlaying rocks also cooled and shrunk and cracks developed. And through these cracks—faults—the superheated mineral rich water forced its way to the surface to form hot springs.
Close to the surface, silicas had slowly been deposited around the cracks, gradually narrowing them and eventually constricting the flow. This constriction caused backpressure, allowing the super-heated magmatic waters to rise from great depths without boiling. Every so often the pressure was so great, the liquid would burst through the constriction—geysers—and the sudden drop of pressure deep below caused the water there to boil—instantly. Here, down in the boiling zone, the gold, along with other minerals, escaped from the water and lay down. A precipitate was formed. A simple process, really, like the white scaly build-up called calcium precipitate seen inside old kettles.
It happened time and time again, irregularly but repetitively. The shrinkage cracks cause by the general cooling of the area and the fracture zones caused by hydraulic pressures were the new home of this relatively concentrated gold. Eventually the whole system cooled and froze into solid rock.
And the gold waited.
The rains came, and the wind too. In many places they eroded away much of the earth overlaying the gold. Sometimes the gold, too, was carried far away. Then man discovered the precious yellow metal. He sank shallow mine shafts, reaped it from the surface or mined it far from the source, where the water had carried it. For years he took it from the earth, mining all the countries upthrust eons before. All except one—Vanuatu.
Geologists have long known that certain gold deposits could be found near ancient, fossil volcanoes. They also knew that the hot springs of dying volcanoes were rich in dissolved precious metals. But it was not until the late 1970's, with the price of gold shooting upwards, that these and other keys were fitted together and the theory of epithermal (association with superheated water) gold deposits was formulated
So the geologists traipsed across old volcanoes and hot springs and discovered new gold
deposits, confirming the general theory and developing guidelines that could be used in
exploration. Then the Lahir mine in New Guinea was discovered, signalling the beginning of a latter day gold rush.
The entire article can be downloaded above.