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GLE 2024 (Day 3) > EXPLORATION GEOLOGY (EVAL TECHNIQUES) > Flashcards

EXPLORATION GEOLOGY (EVAL TECHNIQUES) Flashcards

1
Q

expectations for an exploration geologists

A

1) Familiar with Mineral Deposit Geology
2) Understand implications of extraction on the hydrology of the mineral deposit area
3) Recognize importance of collecting geotech data as a precaution to strata control problems
4) Propose suitable mining methods
5) Assess economic viability

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2
Q

The basis of all geological evaluation

A

Sample

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3
Q

A scientific, selective process applied to a large mass or group (population) to reduce its bulk for interpretation purposes

A

Sampling

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4
Q

The portion of mineralized rock which are analyzed for elements of interest

A

Assay Portion

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5
Q

Parameters: Population = ________________: Sample

A

Statistics

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6
Q

The property that defines a population whose constituent units are strictlty identical with one another

A

Homogeneity

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7
Q

Mineralisation is what type of population?

A

Heterogeneity

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8
Q

Sampling methods which ensures that all constituent units of the pupulation have a uniform probability of being slected to form the sample and the integrity of sample is respected

A

Random Sampling

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9
Q

Mean

A

Average

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10
Q

Median

A

Middle value of an ordered sample of numerical values

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11
Q

Mode

A

Value that occurs most frequently

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12
Q

Variance

A

The measure of the spread or dispersion of values about the mean (midpoint)
Small variance - concetrated about the mean
Large - Spread out about the mean central clustering is weak

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13
Q

Standard Deviation

A

Square root of the variance

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14
Q

Normal Distribution

A

?Curve is Symmetrical and bell shaped
?Variable has a continuous and symmetrical distribution about the mean
?All three measure of central tendencies coincide
?Standard Deviation is realted to the area under the curve

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15
Q

Asymmetrical Distribution

A

?Much of Geological data
?Assymetric Cuve (Proponderance of low values with a long tail of high values - Positive Skew - nasa kanan ang tail)
?Median lies in between mode and mean

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16
Q

Mathematical Transformation of Skewed data to normal distribution

A

1) Log Normal Transformation
2) Gaussian transformation - (simulation data)

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17
Q

Type of statistics which specify conditions regarding the nature of the population being sampled

A

Parametric Statistics

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18
Q

Independent of nature of population and is necessary in Mineral exploration

A

Non Parametric Statistics

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19
Q

Three main steps of Sampling

A

1) Extraction of the samples from in-situ Minerals - involves delimitation and collection
2) Preparation of the Assay Portion - involves reduction both mass and grain size to an assay portion for chemical analyses
3) Analysis of the Assay Portion

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20
Q

Includes all errors in all the three steps of sampling

A

Global Estimation Error (GE)

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21
Q

Includes all error in extraction and preparation

A

Total Sampling error (TE)

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22
Q

Part of TE which is inherent in both extraction and Preparation (error in the procedures and decisions)

A

Selection Errors (SE)

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23
Q

Errors are restriced to mechanical processes used in sample reduction such as crushing, weighing, drying, grinding

A

Preparation Errors (PE)

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24
Q

Minimizing Selection Errors (SE)

A

1) Correct definition Sample Spacing
2) Correct definition of the Sampling Area
?Long dimension of the sample must be perpendicular to the dip of mienralisation never parallel
?Cut in plan is ideally circular, square or rectangle
?Length should penetrate the full length of the sampled area
3) Correct extraction and collection - Ideal Diamond Core Drilling
4) Correct preparation of the assay portion from original sample

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25
Q

Type of SE which comprises the inherent heterogeneity of the sample which also represents the irreducible minimum of the TE

A

Fundamental Error (FE)

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26
Q

Possible sources of Preparation Errors (PE)
Mga errors due to careless treatment of samples and can be caused by inasequate crushing and grinding equipment

A

1) Alteration due to overheating during drying (coal, sulfides of Hg, As, Sb, Bi)
2) Alteration of the the sample’s physical condition due to mishandling
3) Losses due to assay portion preparation - can be checked by consistently weighing samples at each reduction stage)
4) Sample contamination (steel chips from hammers, crushing and grinding equipments)
5) Unintentional Sampling errors (Mislabeling and mixing of fractions of different samples)

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27
Q

correct sampling techniques

A

Random Sampling

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28
Q

Variance of a larger sample tends to be

A

Smaller

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29
Q

Variability is (directly, indirectly) Proportional to sample volume

A

Indirectly (the larger the volume the smaller the variance)

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30
Q

Largest scree size which retains 5% of the material

A

Maximum Particle Size

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31
Q

How much should the dimenstions of the collection device be when sampling?

A

3X the LxWxH of the Max particle size

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32
Q

SAMPLING

A

PROCEDURE

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33
Q

Channel sampling

A

?A channel is cut in an outcrop w/ the same diameter as the core being collected
?Cut using a happer or a chisel or circular saw ACROSS the STRIKE of a mineralisation
?Cutting is allowed to fall to the floor covered a plastic sheet or sample tray from which it will be collected and bagged
?Best delimiting and extracting technique
?Provides samllest possible contribution to total error

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34
Q

Stratified Sampling

A

?Sampling relative to distinct and seaparate types of mienralisation
?Reduces Natiral Variation and variance

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35
Q

Chip Sampling

A

?Obtained by collecting rock particles “chipped” from a surface either linearly or over an area
?Rock chips from blastholes using scoops, channels or pipes pushed into heap
?Corellated with the core for corrections
?used as an ienxpensive reconnaissance tool prior to more expensive channel sampling

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36
Q

Grab Sampling

A

?Consist of already broken materials (floats)
?Handfuls or shovelfuls of Brocken rock picked at random in convenient location
?Low cost-rapid
?best used where mienralized rock as LOW VARIANCE(massive)
?Used as Quality control of mineralisation at strategic sampling points such as stope outlets and in an open pit

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37
Q

What is the ultimate purpose of sampling?

A

Estimate content by valuable constituents (mean and variance)

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38
Q

The few grams of material in subjected to chemical analysis

A

Assay Portion

39
Q

After reduction of grain size by communition what happens next?

A

Splitting

40
Q

Splitting

A

Step 1. Pile material into a Cone
Step 2. Flattened into a circular cake
Step 3. Repeat step 1 3x
Step 4: From the final cone, shovel material consecutively around its circumference alterantively into two separate piles
Step 5.Toss a coin to determine the new sample between the two smaller cones
Step 6: Repeat Steps 1 to 5 to further reduce weight

41
Q

Cone and Quartering

A

A splitting technique wherein the cone is quartered and each quarter is further resuced in the same way

42
Q

What should be the measure of the width of the hand or shovel

A

At least three times the coarsest particle sizze

43
Q

How much should be the weight of the sample for assay portion?

A

100g

44
Q

the most satisfactory of stationary instrument splitters which dive a dry sample into two equal parts

A

Jones Riffle

45
Q

Splitters capable of separating laboratory to bulk samples and uses centrifugal force to split sample into four or six containers

A

Rotary Splitters

46
Q

Splitter used at the drill site while having percussion or reverse cicrulation drilling

A

Sample Splitters

47
Q

Splits samples into 70:30 or 80:20 basis

A

Asymmetrical Splitters

48
Q

What should be done next is the observed total error in spliiting is smaller or of the same order of magnitude as the estimated total error?

A

Nothing should be changed in the reduction system

49
Q

What should be done if the observed total error in splitting is larger?

A

1) Maintain the number of sampling stages but increase the mass of the sample at each separate stage
2) Increase the number of sampling stages but maintain the mass of the smaple

50
Q

Densest of all common sulfide and six times that of quartz

A

Galena

51
Q

How to control Analytical errors?

A

Submit Duplicate sampls and reference materials

52
Q

When will pitting and trenching be expensive?

A

If it is below the water table

53
Q

In what type of Deposit is Pitting ideal?

A

Lateritic Soils (Provided soil is dry)

54
Q

Pitting Vs Trenching

A

Pitting - Square
Trenching - completed at RIGHT ANGLES to the general strike to sample over long lengths

55
Q

Purpose

A

Quality

56
Q

Reconnaissance and Exploration

A

Low

57
Q

Resource or Reserve Estimation

A

High

58
Q

Type of Drill

A

Characteristics

59
Q

Auger

A

Light drills which can be hand held or truck mounted which have rods for spiral flights that bring soft material to the surface (Bailing)

60
Q

Rotary

A

Non-coring method
Tungsten carbide rotatry bit
Flushes Rock Chips to the surface by drilling fluid / Mud
Not so mobile

61
Q

Percussion

A

Hammer unit driven by compressed air imparts a series of short rapid blows to drill rods or bit w/rotary motion at the same time:

1) Down-the hole Hammer drills -
Tungsten Carbide tipped drill bit
Holes w/ diameter of up to 20 cm
Depths of up to 200 m
Drill cutting are flushed to the surface by compressed air
Truck mounted very mobile

2) Top Hammer -
Much lighter than down the hole
Diameter of up to 10cm
Depths of up to 100m

62
Q

Reverse Circulation

A

?Air and water can be both used as the flushing medium
?Can produce both cuttings and or core
?double walled strings of drill rod

63
Q

Sonic Core Drilling

A

?Retrieves core but without the contamination caused by drilling muds
?Uses principle harmonics to drill and case a borehole - uses a variable-frequency drill head to transmit vibration energy through the drill pipe and core barrel that allows continuous core sampling to take place
?up to 2.54 m diameter an 200 m vertical

64
Q

Diamond Core Drilling

A

?Sample is cut by a diamon-aromored or impregnated bit
?Produces a cylinder of rock recovered from the inner tube of a core barel

Parts:
1. Drill bits -
a) Impreganted (Fine grained synthetic or industrial grade diamonds within metallic cement) - For though compact rocks such as chert
b) suface set (have individual diamonds sized by their number per carat) - for softer rocks such as limestone

2) Core barrels - as the core is cut by the circular motion of the drill it is forced up into the core barrel by the advancing drill rods.

3) Circulating Medium - Usually water is circulated down the inside of the drill rods to lubricate and cool the bit and to remove crushed and ground rock fragments from the bit surface

4) Casing - cylindical casing used to seal the rock face of the hole and provides a steel tube in which the drill string can operate in safety and prevents loss of drill strings caused by rock collapse

5) Speed and Cost of Drilling -
Capacity 2000-6000 m may be inclined from horizonal to vertical
Rate of advance is slower as the diameter increases, as the the hole becomes deeper.

65
Q

What should be specified in the Drilling contract between a mining company and a specialist drilling company or contractor?

A

1) Conditions of Drilling
2) Amount of Work Required (Work Program)
3) Cost of Drilling

66
Q

The choice of Drilling method or equipment depend upon

A

The experience of the project manager

67
Q

If the Project Manager is unsure and the drilling conditions are not well known what should be done first?

A

Test Work - to compare efficiency of different drilling methods

68
Q

Costs in a Drilling Contract

A

1) Mobilization and Transport of Equipment to the Drilling site
2) Setting up at each site and movement between successive borehole locations
3) Basic cost per meter of hole drilled
4) Optional or miscellanoue costs such as cementing holes, casing holes and surveing
5) Demobilization and Return of Equipment

69
Q

What are the duties of a geologist during drilling?

A

1) Monitor if the drilling proceeds according to the company’s plan and contract
2) Ensure adequate core recovery and that the hole is hitting the desired target
3) Signs documents at the completion of ech shift where progress and problems are described
4) Must be familiar with teh contract and the problems that may arise at the drill site

70
Q

Conducted as a matter of routine in all holes (To examine)

A

Borehole surveys

71
Q

Used in Borehole surveys to indicate direction (azimuth) and inclination of the hole at selected intervals commonly at 100 m

A

Small Magnetic Gyroscopic Compass

72
Q

Reconnaissance

A

Isolated Holes

73
Q

Exploration Proper

A

Up to 10 km apart

74
Q

Detailed Exploration

A

“Fenses” - lines of holes
Hole are 100-200m apart
Fenses are 200-400m apart

75
Q

What should be the inclination of indidivudal holes?

A

Right Angles to the expected average dip of the mineralisation

76
Q

Methods of Assigning zones of Influence

A

Mean Square successive Difference test
Correlation Coefficients
Semivariogram

77
Q

During exploration and initial evaluation, primary concern is

A

Geological Characteristic
Estimatio of Qualiity and Quantity of the Resource Present

78
Q

JORC stands for?

A

Australoasian Joint Ore Reserves Committee

79
Q

Whats the purpose of JORC

A

Adopt a rigorous procedures for companies to report their resources

80
Q

Increasing resource quality depends on

A

Increasing Degree of Geological Confidence and Knowledge

81
Q

For resource to be reserve what must be met

A

Modifying Factors which represent Feasibility

82
Q

What are the modifying factors?

A

1) Mining
2) Metallurgical
3) Economic
4) Marketing
5) Legal
6) Environmental
7) Social
8) Governmental 9)Infrastructure 10) Governmental

83
Q

JORC Code sets what?

A

Standard or system for classifying tonnage and grade estimates for the purpose of public reporting

84
Q

What is beyond the scope of the JORC code?

A

How the estimate should be done or how much data is needed to qualify in certain categories

85
Q

Who makes the decision based on direct knowledge of the deposit in question?

A

Competent persons

86
Q

In the JORC Code, what is the definition of Mineral Resouce?

A

?Concentration or Occurrence of Material of Intrinsic economic interest IN OR ON Earth’s crust in SUCH FORM and QUANTITY that there are REASONABLE PROSPECTS for EVENTUAL ECONOMIC EXTRACTION

87
Q

What are the information needed to define/estimate/interpret a mienral resouce?

A

Location
Quantity
Grade
Geological characteristics and Continuity

88
Q

What is a mineral resource relative to mineralsation?

A

Realistic Inventory of mineralisation, which, under assumed and justifiable technical and economic conditions might, in whole or in part, become economically extractable

89
Q

Economically minerable part of a mineral resource hich includes diluting materials and allowance for mining losses

A

Reserve

90
Q

When is reserve usually assessed?

A

Feasibility Studies (in consideratio of and modification by realistically assumed modifying factors)

91
Q

Economically mineable part of an indicated resource and in some circumstances measure mineral resource

A

Proabable Ore Reserve

92
Q

Econmonically mineable part of a measure mineral resource

A

Proved Ore Reserve

93
Q

Readily identifiable geologic boundaries of a mineralisation which needs to be defined before resource calculations

A

mineralisation Envelope

GLE 2024 (Day 3) (48 decks)

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