Prospecting for Ores

Question 1

Why do you need to use prospecting techniques?

Answer 1

• to find out where an ore/resource is
• to find out how much of an ore/resource there is
• to work out the grade of the resource
• if there are any geological problems

Question 2

What is random sampling?

Answer 2

points chosen at random to sample

Question 3

What is stratified sampling?

Answer 3

picking out areas with geological differences and then randomly choosing points within these areas

Question 4

What is systematic sampling?

Answer 4

points are a set distance apart and orderly

Question 5

What would you use to measure a gravity survey?

Answer 5

A gravimeter

Question 6

What does a positive gravity anomaly mean?

Answer 6

there is an excess of mass which could suggest a metallic ore or a high density mafic intrusion

Question 7

What does a negative gravity anomaly mean?

Answer 7

there a deficit in mass which could suggest a low density silicic intrusion

Question 8

What do you use to carry out a magnetic survey and what are you measuring?

Answer 8

A magnetometer

small variations in magnetic field strength

Question 9

What are the two types of magnetic survey?

Answer 9

• transect survey which has measurements takes along a single line
• map survey which has values plotted onto a map and isobars drawn on so anomalies can be identified

Question 10

What does a positive magnetic anomaly mean?

Answer 10

the rock is rich in iron such as a mafic/ultra mafic intrusion or magnetite

Question 11

How could you use electrical resistivity to find resources?

Answer 11

• two electrodes are placed in the ground and current is pass between them
• if a rock is a good conductor the resistivity will be low
• metallic ores are good conductors so if an area is low resistivity then there is likely to a metallic ore such as gold

Question 12

What are the advantages of Geophysical surveys?

Answer 12

• quick, accurate
• relatively cheap in terms of equipment and labour
• covers a wide a wide area
• can find deposits hidden under recent deposits
• determine the extent and orientation of the structure
• access may not be a problem as you can use aerial techniques

Question 13

What are the disadvantages of Geophysical surveys?

Answer 13

• you can’t identify the type of ore present
• only detects structures if there is a good enough contrast between units
• based on interpretation and there is usually several solutions
• further exploration/investigation is required (boreholes and drilling)

Question 14

What does Geochemical exploration rely on?

Answer 14

-the fact that metal ores will undergo dispersion by weathering, erosion and transportation

Question 15

How can stream sediment and water surveys tell you where there are resources?

Answer 15

• the stream will sample the chemistry of the rocks its flowing over affecting the water
• concentration of the element will be highest just downstream from the ore
• samples of sediment can contain grains of ore minerals which can been panned to concentrate them

Question 16

What are the advantages of Geochemical surveys?

Answer 16

• samples allow a large catchment area to be investigated quickly
• all elements have a characteristic signature which may show up in vegetation, soil and water samples indicating their presence
• very dependable
• cost effective

Question 17

What are the disadvantages of Geochemical surveys?

Answer 17

• contamination
• background rocks need to be known
• variations in water pH or water levels affecting metal concentrations
• access might be difficult over a wider area
• sediment sampling only in temperate climate otherwise no streams
• tributaries may have lower concentrations

Question 18

How can you use satellite survey to locate resources?

Answer 18

• different rocks reflect visible and infrared light in different ways
• initial survey technique to target areas for further exploration
• pick out random rock units and landforms (with folds and faults)
• pick out areas of alterations and other signs of mineralization as clues to subsurface deposits of ore minerals, oil, gas and groundwater

Question 19

What are the advantages satellite surveys?

Answer 19

• provides large scales for relatively cheap without need for ground-truthing
• inaccessible areas studied easily
• satellites are in place just need to buy the image

Question 20

What are the disadvantages to satellite survey?

Answer 20

• only for basic reconnaissance, it needs ground-truthing
• not stereo images
• colours can misleading

Question 21

What is ground truthing?

Answer 21

-asses the 3D shape and size of the ore-body by carrying out chemical analysis and looking at the physical and structural properties