SMEDG - Notice of Meeting

Thursday, 25th March, 2004. 5.30pm for 6pm Rugby Club, Rugby Place, Circular Quay

David Roots

"THE REMAINING SILVER AT YERRANDERIE"

Yerranderie lies close to Sydney, and produced well over $50,000,000 of silver at 1980 values. Mining ceased when the filling of Warragamba Dam closed the road to the coast. A Devonian volcano on the edge of a vast caldera describes the geological structure that controlled the location of the silver. Examination of the several historic mines reveals they all lay within the central cone of the volcano, following the dip of bedded debris within the crater. The paying mines all occured within a ~90 degree sector of the volcano. Mines outside this sector were non-productive. Half of the volcano, however, is still covered by thick Sydney Basin sandstone, and was never explored. The volcano structure was not recognised when the mines were active. Structural symmetry suggests that half of the ore remains in the opposite sector to the productive one, and the geometry of volcanoes makes its location easy. Yerranderie lies within the Greater Blue Mountains National Park. David Roots is a retired Senior Lecturer from Macquarie University. His Doctoral study was a mix of geology and geophysics, solving the structure of ocean floor magnetic patterns in locations where spreading was oblique to rifting margins. He continues to research on the plate motor. He has specialised in field teaching, and for the last decade has toured the world to locations of geological interest, taking geology to the travelling public. David has authored a book, explaining why plate tectonics is a predictor for the location of scenery, rocks and fossils. He currently works at Sancta Sophia College, Sydney University.

E-mail David