Lost Creek Mine GIS Project: Economic Analysis using ArcGIS, Study Guides, Projects, Research of Geology

Download Lost Creek Mine GIS Project: Economic Analysis using ArcGIS and more Study Guides, Projects, Research Geology in PDF only on Docsity! GY461 Computer Mapping & GIS Technology Lost Creek Mine GIS Project Page -1- I. Introduction Last Update: October 13, 2006 For your Geographic Information System (GIS) project, you will determine the economic viability of the Lost Creek Mine claim that has been purchased by a major mining corporation. The ArcGIS 9.1 GIS software will be used to analyze and solve the assigned problems. The base maps containing the raw data will be available on the following web site: http://www.usouthal.edu/geography/allison/gy461/gy461_project_resources.htm or at an alternative location designated by your course instructor. Look for the “LostCreek.exe” link to download the self-extracting ZIP file. This project is intended to teach and reinforce the capability of a GIS system to analyze data that is attached to digital maps. In this project, the worth of the mine property is a function of the abundance of the three ore minerals: Chalcopyrite (CuFeS2), Galena (PbS), and Sphalerite (ZnS). Because the base elements in each mineral have different market values, and because the ore minerals vary in abundance throughout the ore deposit independently, the calculation for net worth over the entire claim is rather complex. Additional complications include the fact that overburden must be removed at significant cost. Because the ore body underlies a road system and processing plant, the strip mine cannot effectively extract any ore closer than 50 meters to the plant or roads. Strip mine operations closer than this distance could undermine the plant or road. The capability of the GIS to track polygon data and calculate values using attributes makes this project practical on the computer workstation, whereas it would be extremely time consuming with manual methods (and much more error prone). After completion of the project you will be familiar with fundamental GIS concepts, and you will have successfully solved a complex economic geology problem that is based on drill core data from a Colorado massive sulfide deposit. Note that although the data that this project is based on is actual data, the location of the mine has been modified to obscure the true location. II. Raw Data, Constants, and Other Constraints You should first create a subdirectory folder using your initials under the C:\ArcGIS_Data\XXX\ subdirectory. Then create a “LostCreek” child directory under your initials. For the rest of these instructions, the initials “XXX” will be used in examples – these should be replaced by your own initials when you work through the project. Download the starting files from the web site (or alternative location if so instructed) as the raw data for the problem. Note that in the “real world”, you would probably have to create these files from scratch: Border.shp, Border.shx, Border.dbf, Border.prj CuFeS2.shp, CuFeS2.shx, CuFeS2.dbf, CuFeS2.prj GY461 Computer Mapping & GIS Technology Lost Creek Mine GIS Project Page -2- PbS.shp, PbS.shx, PbS.dbf, PbS.prj Plant.shp, Plant.shx, Plant.dbf, Plant.prj Roads.shp, Roads.shx, Roads.dbf, Roads.prj Topography.shp, Topography.shx, Topography.dbf, Topography.prj ZnS.shp, ZnS.shx, ZnS.dbf, ZnS.prj The above maps contain the topography of the mine area, volume percent ore mineralogy for three ores, roads, and the plan of the processing plant structure. Note that the (x, y) coordinate system of the mine area is the UTM system, zone 14, NAD27, therefore, (x, y) units are in meters. The topographic contour interval value units are feet. The contours of the volume percent abundance of the three ore minerals are based on thin section petrography from drill cores. The ore body structure consists of a tabular horizontal granite porphyry sill that underlies the entire area. The drilling program that the mining corporation just completed has determined that the top and bottom of the sill are relatively horizontal and planar, therefore, you can assume that the structure is tabular and laterally continuous throughout the mine area. The elevation of the top of the sill is 3400 feet above sea level. The base of the structure is 3072 feet above sea level, therefore, the sill thickness is 100 meters. You also can assume that the contours in Figures 1-3 of mineral volume percent is representative of the entire ore body from top to bottom. In other words, the drill cores were sampled from top to bottom, with each sample depth counted for volume percent of the three ore sulfide minerals. Therefore, the contour values on the base maps are assumed to represent averages of the entire drill hole. Figure 4 displays the topography, road system, and processing plant on the mine property. Note that the values for each polygon defined by the contours in Figures 1-4 are labeled with the appropriate values. For all four of the contour maps you should consider contour lines as being the bounding limits of polygons with the interior of the polygon possessing a value that falls at one half the contour interval between the adjacent contour lines. If the adjacent contour lines are equal in value you should estimate the value of the polygon based on whether or not the contours represent a "hill" or "valley" trend. In addition to the data maps, use the following definitions/data in your calculations: Ore Body: includes both the ore minerals and the host granite sill. Ore minerals: Chalcopyrite (CuFeS2), Sphalerite (ZnS), and Galena (PbS) are sulfide minerals that form this particular massive sulfide ore deposit. 1 meter = 3.28 feet. Density Values: Overburden rock: 2.90 Ore Rock: 2.95 GY461 Computer Mapping & GIS Technology Lost Creek Mine GIS Project Page -5- To begin the process double-click the toolbox icon in ArcMap. From the toolbox window expand the “Analysis Tools” > “Overlay” > “Union” utility. Double-click on the icon to start the union operation and specify “Topography” and “CuFeS2" as the 2 input layers. In addition, specify the output as a geodatabase named “Union1" stored in “LostCreek” geodatabase. Select the optional “No FID” option to avoid conflicting field names in future union operations. Figure 8 displays the setup of the union dialog- note that the “No_FID” option of the join attributes list box should be selected. Figure 9 displays the ArcMap arrangement of the project after the union operation. The figure also displays the results of the “information” tool after clicking on a polygon. Note that “Elevation” and “CuFeS2" fields contain numeric data, and that the area of the polygon is contained in “Shape_Area”. Continue using the same overlay union tool to create “Union2" and “Union3". Figure 10 contains the layout of this combination of all 4 data layers. Be sure to check the results of Union 3 with the information icon. All 4 data layers should be represented in each polygon. The info tool (dark blue circle with white “i” in the center) should be used to verify this before proceeding to the next step. If you have problems getting to this point seek help from your instructor. STEP 4: The next step involves creating buffer zones around the road system and processing plant that are located on the mine property. The ore cannot be strip-mined closer than 50 meters to any of these features because of the danger of rock slides undermining them. To make allowances for this problem a 50 meter “buffer” zone will be created around the roads and processing plant. This will be done in 2 independent steps. These 2 buffers will then be merged into a single buffer zone, and then “unioned” with the Combo3 topology to mark the portions of polygons that cannot be mined. To begin creating the buffer zones double-click on the toolbox icon to open the toolbox window if it is not already open. Expand the tools hierarchy until you can find “Analysis Tools” > “Proximity” > “Buffer”. Double-click on the Buffer icon to start the utility. Indicate “Roads” as the input topology, “RoadBuf” as the output topology, and 50 meters as the buffer distance. Name the new buffer as “RoadBuf”. Figure 11 displays the dialog window setup for the buffer operation. Note that the dissolve_type is set to all so that the result is one continuous polygon buffer. Your ArcMap project should appear as Figure 12 at this point. Create a buffer of 50 meters around the processing plant using the same method just described. Call this buffer polygon “PlantBuf”. Start the overlay union utility to union together “RoadBuf” and “PlantBuf”. Call the result “Buffer”. In the union dialog window set “JoinAttributes” list box to “No_FID”. The results should appear as in Figure 13. GY461 Computer Mapping & GIS Technology Lost Creek Mine GIS Project Page -6- STEP 5: In this step the Union3 and Buffer polygon topologies will be combined with another union operation. Use the overlay union tool with Union3 and Buffer as the input topology, and Union3Buf as the output topology. Set the “JoinAttributes” list box to “ALL”. With the info tool you can now verify that the Union3Buf polygon topology inherited all of the attributes of Union3, but also the field “FID_Buffer”. Any polygons that fall outside the buffer zone will have this field set to -1, all polygons inside the buffer will have a value of 1. We can use this fact to extract all of the polygons inside the buffer zone out of the polygon topology. Open the toolbox window and select “Analysis Tools” > “Extract” > “Select”. Double-click to run the utility. Setup the dialog window as in Figure 14. Note that the field name “FID_Buffer” must be enclosed in square brackets in the expression edit box. The results of the extraction of the buffer zone can be seen in Figure 15. Note that the ArcMap project has the buffer zone removed, and that each polygon has the 4 data layer values attached to it. Make sure you save your project at this time. The next series of steps will be processed as calculations within the attribute table of the “Results” layer. Right-click on the “Results” layer, and select “Open Attribute Table”. You should see the attribute table in a separate window at this time. You should note that each row in the table represents a single polygon, and you will also see the values for CuFeS2, PbS, ZnS and Elevation. Using the “Options” button, and then the “Add Field” option, add the following fields to the attribute table: OBT (Overburden tonnage per polygon) ORT (Ore rock tonnage per polygon) Cu (Copper tonnage per polygon) Zn (Zinc tonnage per polygon) Pb (Lead tonnage per polygon) Ore_Value (Dollar value per polygon) Use the precision and scale settings indicated in Figure 16 for all of the new fields. Next set ArcMap in “Edit” mode by selecting “Start Editing” from the Editor button bar. Edit mode allows you to discard changes to the attribute table if your calculations go awry. Right-click on the “OBT’ field name in the attribute table. Select “Calculate Values”, and enter the calculation for OBT as indicated in Figure 17. Proceed to calculate the ORT, Cu, Zn, Pb, and Ore_Value fields using field calculations based on the below equations. As with the OBT calculation, play it safe by putting ArcMap into edit mode before typing in the calculation equation. If the results are reasonable in the attribute table then select the “Save Edits” from the editor drop-down list. When you are done with the GY461 Computer Mapping & GIS Technology Lost Creek Mine GIS Project Page -7- calculations be sure to select “Stop Editing” from the editor drop-down list. A) Overburden tonnage per polygon: [OBT] = [Shape_Area]* ([Elevation]-3400)* 0.3048*2.90 The 0.3048 converts feet to meters. Overburden rock density is 2.90. B) Ore rock tonnage per polygon: [ORT]=[Shape_Area]* (100)* (2.95) Use the item name [ORT] to hold this value. Note that the sill thickness is 100 meters, and the ore rock density is 2.95. C) element tonnage per polygon: = [ORT]* (vol. % mineralX)/100*(density mineralX/density ore)* (wt. % elementX)/100 1. [Cu] = [ORT]*[CuFeS2]/100*4.20/2.95*34.6/100 2. [Pb] = [ORT]*[PbS]/100*7.50/2.95*86.6/100 3. [Zn] = [ORT]*[ZnS]/100*4.00/2.95*67.0/100 Create the items [Cu], [Zn], and [Pb] respectively to hold the calculated values of metric tonnage of a specific element on a per polygon basis. D) Value of commodities per ton mined: [Ore_Value] = [Cu]/[ORT]* (2360) + [Zn]/[ORT]* (1300) + [Pb]/[ORT]* (790) [Ore_Value] will hold this calculation. Market prices for each commodities are volatile, therefore, different values may be assigned compared to those given in this handout. In this example Cu=$2,360, Zn=$1,300, and Pb=$790. STEP 6: This step composes a final map product with legend information. The goal is to visually display levels of color indication the economic worth of each polygon based on all the relevant factors. Start the ArcMap application and load the LostCreek project. Use the identity tool on the FinalResults layer to make sure that all calculations are “seen” by ArcGIS. If you cannot find the “Ore_Value” calculation see your instructor at this time. Right-click on the “Results” layer in the layer control window, and then select “Properties”. Then select the “Symbology” tab. Select “quantities” on the left side of the dialog window, and “Graduated colors”. For the value field select “Ore_Value” with no normalization. Under “Classification pick 6 classes and use the “Classify” button to choose equal intervals. Next right