Gerelateerde afbeelding

Deffeyes mused his way along the cut. “There is complexity here because you have not only the upper and lower plates of the Golconda Thrust, which happened in the early Triassic; you also have basin-range faulting scarcely a hundred yards away-enormously complicating the regional picture. If you look at a geologic map of western Canada and Alaska, you can see the distinct bands of terrane that successively attached themselves to the continent. Here the zakelijke energie pattern has been all broken up and obscured by the block faulting of the Basin and Range, not to mention the great outpouring of Oligocene welded tuff. So this place is a handsome mess. If you ever want to study this sort of collision more straightforwardly, go to the Alps, where you had a continent-tocontinent collision and that was it.”
So much for theory. This roadcut contained both extremities of Deffeyes’ wide interests in geology, and his attention was now drawn to a large gap in the sandstone, faulted open probably six or seven million years ago and now filled with rock crumbs, as if a bomb had gone off there in the ground. The material was gradated outward from a very obvious core. In a country full of living hot springs, this was a dead one. Sectioned by the road builders, it remembered in its swirls and convolutions the commotion of water raging hot in rock. The dead hot spring had developed cracks, and they had been filled in by a couple of generations of calcite veins. Deffeyes was zakelijke energie vergelijken busy with his hammer, pinging, chipping samples of the calcite. “This stuff is too handsome to leave out here,” he said, filling a canvas bag. “There was a lot of thermal action here. Most of this material is not even respectable rock anymore. It’s like soil. In i903, a mining geologist named Waldemar Lindgren found cinnabar in crud like this at Steamboat, near Reno. Cinnabar is mercury sulphide. He also found cinnabar in the fissures through which water had come up from deep in the crust. He thought, Aha! Mercury deposits are hot-spring deposits! And he applied that idea to ore deposits generally. He started classifying them according to the temperature of the water from which they were deposited-warm, hot, hotter, and so on. We know now that not all metal deposits are hydrothermal in origin, but more than half of them are.

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