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Gold/Mining/Energy : ECHARTERS -- Ignore unavailable to you. Want to Upgrade?

To: brian krause who wrote (2810)	7/26/1998 1:47:00 PM
From: Pete Mimmack	Respond to of 3744

Brian - I think he's speaking in terms of an idealized ore body lying "flat". The true width (or thickness) would be vertical. But it is not lying flat, rather it plunges from horizontal. The true width might still be referred to as "vertically". Try substituting "true width" and it should make more sense. Pete

To: brian krause who wrote (2810)	7/26/1998 3:30:00 PM
From: E. Charters	Read Replies (3) \| Respond to of 3744

Take a door hinge and fold it until the plates are about a quarter inch apart. The pin of the hinge is the orebody, long and narrow. It exists to a degree in the plates away from the pin. the distance down the plate away from the pin and in a vertical sense is its thickness. Across the pin and perhaps the two plates or in the thickness of the plate and/or the pin is its width. These terms are sometimes used interchangeably by texts (width and thickness). Now point the pin of the hinge at an angle to the floor. This is the angle of the plunge. If you cant the hinge to the left or right looking down the pin, that cant is the dip. a line that falls by gravity down one of the plates is the true dip. At 90 degree to that true dip line and horizontal, in the compass direction of the pin is the strike direction. Rake is another word that relates to plunge but it would confuse the issue. The two plates are very apropos here. Often the geological strata is folded just like the plates. The orebody oft forms at the hinge line and is draped with the strata around the hinge line or pin. When you drill, you drill at 90 degree to the strike (in a plan sense) across the plates near the pin. The drill hole opposes the dip and crosses the true width of the orebody. If you go above the pin or below the ore extent as it extends down dip away from the pin, you missed as they missed here. You may drill in other ways to test an orebody too. You may set up on the strike and opposing the plunge drill through the pin in the opposite direction to its plunge. You may parallel the dip here but what you are looking for is the thickness of the orebody vertically. Note that the hinge plates can point down or up. Down is an anticline up is a syncline. There are many variations on where and how orebodies come to form on these plates. Some are pushed into cracks at the hinge pin in simple shears (axial planar shearing). Some cross the plates at an angle in tension fractures or shears, some are conformable to the plates and are called syngenetic or epigenetic with the plate formation, some are pods on the surface of the plate. The terms strike, dip and plunge refer to all these types are geometrically the same in relation to the hinge fabric. In geology the pin is called the hinge line or axis and the plates are called the limbs of the fold. A plane that splits hinge is called the axial plane. Almost all geology has some folding in it particularly the older archean and proterozoic volcanic geology. Most mountainous terranes as well are extremely folded as in the Andes and BC. echarter@vianet.on.ca ====================================