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Gold/Mining/Energy : Precious and Base Metal Investing -- Ignore unavailable to you. Want to Upgrade?

To: croesus1111 who wrote (26809)	1/11/2004 9:23:45 AM
From: E. Charters	Read Replies (1) \| Respond to of 39344

Apart from gas, the effect of increased dust in the atmosphere is to cool the planet, it is thought. Really large scale explosions of volcanic material, such as the kimberlite instrusions of the cretaceous were believed to have caused this effect in prehistoric times. Kimberlite's most frequent expression is as a sudden instrusion, creating a tuffaceous (vocanic dust or micro ejecta) explosive volcano. Another word for this is diatreme. The diatreme spreads out from a very narrow, 50 foot wide conduit at perhaps 3000 feet in depth to up to 1/2 mile wide at the surface. The volume of dust ejection is enormous and the fragments cover several tens of square miles outside the crater. This latter process takes only seconds from this depth. The velocity of the kimberlite extrusion is said to have reached supersonic speeds and attained several kilometres in height. Interestingly by Bernoulli's principle when all this energy goes into speed, the temperature drops. Cooling of the lava dust takes places very fast due to two effect, dispersal speed and Bernoulli effect. So the extrusion of the diatreme is a cold tropospheric dust dispersal at high speed. Worldwide thousands of these volcanoes probably increased the dust level in the upper atmosphere by an order of magnitude and probably induced the climate change that precipitated wide scale extinctions and the ice ages. It may have been a huge cosmic event of shock such as the possible Sudbury asteroid hit, or the Manicougan or Hudson Bay meteor collisions, that initiated the shock and subsequent pressure waves educing magma ascent through so many widespread conduits. Canada has many shockwave features near what are called Astrobleme areas. From the air, areas such as Armstrong, Ontario Sudbury, Manicougan, and Carswell, Saskatchewan show rock patterns that are clearly radiating shock features. Whole river systems in 300 feet deep rock canyons near Armstrong traverse flat table rocks thousands of square miles wide, with obvious crazed fracture zig-zags remniscent of broken pottery patterns. This may account for the many kimberlite fields that Canada is blessed with, as they are most often clustered near these astrobleme areas, not really co-incidentally, the central locus of widespread alkaline volcanism. One may explore for kimberlite by radiating a search patterns outwards from these alkaline centres with good effect. So far, except for DeBeers, whose diamond hunt began in Canada near Rouyn and North Bay in 1963, no company has systematically done this. The Geological survey of Canada did some research into this area starting in the mid 50's and published findings indicating what have been subsequently known to be the surface expressions of kimberlite in such areas as Lac Dubawnt and Lac de Gras in the North West territories. The kimberlites did not intrude all at once but over millions of years continually during certain broad geologic periods. Popular ones for diamonds are 1.2 billion year, 300,000 million years, 160, million years, 30 million years and 16 million years ago. At these times the continents were moving in different directions. This leads to a very confusing pattern of emplacent as we shall see below. We know this because the same type of kimberlite intruded along hundred mile long "transform faults" and these kimberlites have been aged by their contained zircon. The progessive age successions of the intrusions correspond exactly to the intrusions' movement in the very direction of continental drift along the fault. We know in fact that it must be that the kimberlite source is immobile and the continent itself moves over it, causing the successive kimberlites along the fault to get older or younger as you move along the fault. This makes it easy to explore for like-mineralized kimberlite by following the fault and that era's continental drift direction. This is known as the hotspot theory, and it is operative for any sort of shear or fault injected ore, including gold. It was first discovered by W. J. Atkinson of Australia in Namibia The study of the pattern effect of fractures , and shears to predict their volume, shape and direction in materials or fabrics is that branch of geology called structural geology. It is most important to the study of ore deposits as it helps to aim drill holes at ore targets. That is what is meant by the structure of an ore deposit. It is alluded that it has a certain pattern of fracture and shear filling of solidified fluid which can be probed for scientifically. EC<:-}