Spatial Patterns of Mineral Deposits in the Broken Hill Region New South Wales, Australia

Transcription

1 Spatial Patterns of Mineral Deposits in the Broken Hill Region New South Wales, Australia PowerPoint 6-6 All images and text are Copyright 2005 by Larry Robinson

2 Prepared as part of:

3 The Spatial and Temporal Distribution of the Metal Mineralisation in Eastern Australia and the Relationship of the Observed Patterns to Giant Ore Deposits by Larry Robinson A thesis submitted for the degree of PhD 2006

4

5 New South Wales Topography1

6

7 The High Temperature Type Deposits The Broken Hill Type Predominantly stratiform disseminations or pods of galena-sphalerite quartz gahnite lode.

8 The Giant Broken Hill Deposits The three giant ore deposits beneath and immediately south of the city contained "over 200 million tonnes of high grade lead-silver-zinc ore". Barnes (1980) 2

9 The Minor Broken Hill Deposits The production from the 525 minor deposits was "only a few thousand tonnes of ore" from each deposit. Barnes (1980) 2

10 The Giant and Minor Broken Hill Deposits

11 Pattern Recognition by Clustering the Broken Hill Type Deposits The AUTOCLUST Algorithm The approach automatically extracts boundaries based on Voronoi modelling and Delaunay Diagrams. Parameters are not specified by users in the automatic clustering. All clustering operations takes place on the Delaunay Diagram where data points become vertices and edges connect pairs of points to model spatial proximity. Estivill-Castro & Lee (2000) 3

12 Area Clustered

13 Delaunay Diagram, m = 0.8, noise = 0%

14 Voronoi Tesselation (without deposits)

15 Voronoi Tesselation and Clusters

16 Voronoi Tesselation and Boundaries

17 Voronoi Tesselation and Polygonization

18 Polygonization

19 Polygonization with Giant Deposits

20 Polygonization with Radial Trends

21 The Lower Temperature Type Deposits Thackaringa Type* Mount Robe Type* Gold Vein Type* Iron Duke Pyrite Type Ettlewood Type Silver King Type Waukeroo Type Vein Pyrite Type Great Eastern Type Vein Cu Type *These reveal the pattern adequately. New South Wales mineral exploration data package, 2004 New South Wales Department of Mineral Resources, CD-ROM

22 Thackaringa Type Deposits Narrow veins or shoots and pods in veins in fault zones of argentiferous galena bearing siderite quartz veins.

23 Thackaringa Type and Giant Broken Hill Type Deposits

24 Mount Robe Type Deposits Narrow long tabular bodies of galena-sphaleritechalcopyrite-(gold) bearing quartz fluorite veins where the veins transgress layering in host.

25 Mt Robe and Giant Broken Hill Type Deposits

26 Gold Vein Type Deposits Pyritic or cupriferous quartz vein with gold.

27 Gold Vein Type and Giant Broken Hill Type Deposits

28 The High Temperature Giant Broken Hill Type and the Three Lower Temperature Type Deposits

29 Giant High Temperature and Lower Temperature Type Deposits

30 The following image shows the probable thermal gradient in the Broken Hill Region when the giant deposits were forming.

31 The Paleothermal Thermometer

32 The HOT ZONE is delineated by the Lower Temperature Deposits.

33 The HOT ZONE in the Broken Hill Region

34 The majority of the Broken Hill Type Deposits occur in the HOT ZONE.

35 The HOT ZONE and Polygonization of Broken Hill Type Deposits

36 The ellipticity of the HOT ZONE indicates that compressional forces, in an E-W direction, distorted the original spatial distribution of the deposits.

37 The HOT ZONE with compression arrows (blue)

38 The Complex Geology in the Broken Hill Region

39

40 A prime example of the small-scale complexity in the crust and the large-scale simplicity in the underlying mantle. From 1969 to about 1972, the impact of the geological ideas stemming from plate tectonics was muted by the characteristic geological aversion to bold, rational solutions to geological problems: small-scale complexity commonly retards and obscures our understanding of larger-scale simplicity. (p. 237) John F. Dewey Plate Tectonics and Geology, 1965 to Today (Oreskes, 2001)

41 The End Thank You

42 References 1. NewSouthWales_MineralExplorationDataPackage, 2004, New South Wales mineral exploration data package: Sydney, New South Wales Department of Mineral Resources, p. 1 CD-ROM 2. Barnes, R. G., 1980, Types of mineralization in the Broken Hill Block and their relationship to stratigraphy, in Stevens, B. P. J., ed., A Guide to the Stratigraphy and Mineralization of the Broken Hill Block, New South Wales - Record 20, Geological Survey of New South Wales, p V. Estivill-Castro and I. Lee. AUTOCLUST: Automatic Clustering via Boundary Extraction for Massive Point-data Sets. In Proceedings of the 5th International Conference on Geocomputation, to appear. Extended version is available at as a technical report. 4. * 5. Oreskes, N., and Le Grand, H., 2001, Plate tectonics : an insider's history of the modern theory of the Earth, Boulder, Colo., Westview Press, xxiv, 424 p.