EXPLORATION GEOLOGY (PROSPECTING TO PRE-FS) Flashcards
The scale and speed of exploration primarily depend on?
1)The land Acquisition Agreements
2)Overall Budget
A geologist who heads an exploration project with a separate budget allocation
Project Geologist
Whats the recommended distance of in house facility for staff to the site?
Less that 1 hour commuting time
If the areas is really remote what would be the possible setup?
In field camps and commute by air
Difference of Reconnaissance budget to Prospecting Budget?
More expensive because of Driling
Estimates of a contractor for geochemical and geophysical surveys are usually on the basis of?
Cost per line-Kilometer or Sample
What should be the first thing to be done when starting work on a prospect?
Define a local grid for the Prospect using GPS :
-Relate to the national grid system
-Must be parallel to the regional strike
Surveying Methods
1) GPS - Problematic in Forested Areas
2) Tape and Compass
Type of traverse which is often used to minimize erros in Tape and Compass Survery and done by starting and retusning to the initial point
Closed Traverses
The most accurate method of obtaining height difference between stations and is used to obtain the elevation of each station when undertaking gravity survey
Leveling
How is leveling done?
Measures height difference between a pair of station using a surveyor’s level
Where is leveling required?
?In an underground mine - Determine minimum slope to drain an adit or drive
?In a surface mine - Determine the max gradient up which load, haul and dump trucks can climb when fully laden (<10%)
a more accurate survey equipment than compass?
Theodolite
What is the scale of the Map needed at the prospecting stage?
1:10,000 to 1:2,500
What instruments can be used for accurate mapping?
1) Telescopic Alidade - used to plot points
2) Plane table or Differential GPS
What must be highlighted in Geol Mapping in terms of prospecting?
?Known Mineralisation or any discovered during survey
?Geological Relationship of the mineralisation to the geological model sought
?Mapping of Hydrothermal Alteration
Conventional wat of producing Maps
Indian Ink Pen on Transparent Film
Computer softwares that aid in Map Making
1) Autocad
2) ArcGIS
3) MapInfo
Intervals of sampling for vein gold deposit?
1m intervals
Intervals for copper deposit?
5 or 10 m
What must be specified when bagged and labelled samples are sent to the laboratory for analysis?
1) Elements of Interest
2) Type of Analytical Procedure
A form needed to be accomplished when sending samples to the lab?
Sample Control Form
What error instances must one be alerted?
Gold values of several Percent
Copper values in ppb range
Who must discuss or decide about the lements that needs to be tested?
Project Manager
Field Staff
Chief Geologist
A relatively inexpensive method of analysis
AAS (Atomic Absorption Spectometry)
Detailed identification of individual minerals
SEM
EPMA
Sequence of Activities on site during Prospecting
1) Estabilishing Organization and bugdeting
2) Topographic Surveying
3) Geologic Mapping
4) Sampling
5) Testing and Analysis
6) Prospecting
When is prospecting usually conducted?
1) Follow up to Geochem and Geophysical anomalies
2) Routine Geol Mapping
Field characteristics of Copper deposits
Green stained top
Field Chracteristics of Iron deposits
Protruding
Field characteristics of Hydrothermal deposits?
Smaller scale silicification resulting in slight topographical ridges
Karst hosted deposits are characterized by?
Distinct Depressions
Kimberlite pipes usually occur under
Under lakes in glaciated areas
Iron Rich Rocks contraining sulfides
Ironstones
Iron oxides overlying Metallic sulfide deposits
Gossans or Iron Hats
Relict Red Oxides
Hematite
Relict Yellow Borwn Hydroxides
Limonite
Copper suflides oxidize to secondary minerals that have distictive green or blue colors such as
Malachite (Green)
Azurite (Blue)
Secondary minerals of Lead and Zinc are colored
White
Recognizable traces or spaces or relic textures left by Sulfides after Weathering due to their instability
Boxworks
Minerals that frequently infill boxworks
Limonite and Goethite
Difference of ironestones overlying sulfides over the ironstones of nonsulfide origin?
sulfide origin: Alternation of color and texture - “Live Ironstones”
non sulfide: shows little variaton “Dead Ironstones”
What are the techniques which can be used to investigate weathered overbuden ironstons
- Visual description of weathered rocks
- Examination for relic textures
- Chemical Analysis
What can be a confirmatory to visual description in identification of rock types?
Chemical Analyses for Trace and Major Elements (Zr-TiO2)
Recommended samples to be representative of a gossan?
20 Samples
Multielement analysis which can be used to anlyse gossan samples
1) XRF
2) ICP-ES
*Following a total attack to dissolve silica
Geophysical Instruments which are portable to be used in-situ?
1)Scintillometer - detects gamma radiation
2) Magnetic Susceptibility Meter - Rock Type
What is the use of ultraviolet lamps?
Detect fluorescene of Minerals at Night particularly SCHEELITE (CaWO4)
In situ chemical tests for lead minerals?
HCl + Potassium Iodide (KI)
Lead Minerals forms Bright Yellow Lead Iodide
In situ chemical tests for Zinc Minerals?
Potassium Ferrocyanide in Oxalic Acid w/ Diethylaniline
Red Precipitates
In situ chemical tests for Gray Copper Minerals?
Acidified Mixture of Ammonium Pyrophosphate
In Situ Chemical test for Molybdates and Nickel Sulfides?
Dimethyl Glyoxine
Zones of Supergene Enrichement in Cu?
From Surface to Bottom
1) Leaching
2) Oxide Enrichment
-Water Table-
3) Secondary Sulfide Enrichment
4) Primary Sulfide Zone
In which zone is the Cu grade the highest?
Secondary enrichment zone due to transformation of Chalcopyrite (30%Cu) to Chalcocite (80%Cu)
In which zone is Gold grade the highest?
Oxide Zone
Mienrals in the Leaching Zone
Iron Oxides
Minerals in the Oxide enrichment
Malachite
Azurite
Chrysocolla
Cuprite
Native Cu
Minerals in the secondary sulfide enrichment?
Chalcocite
Bornite
Covellite
Chalcopyrite
Pyrite
Minerals in the Primary Sulfide Zone
Chalcopyrite
Pyrite
What is the environment below the water table
Reducing
Wha is the environment above the water table
Oxidising
The skill of tracing mineralized boulders or rock fragments which is extremely valuable in mountainous areas with poor exposures
Float Mapping and Sampling
What should be the next procedure if the area has poor to moderate outcrop
Trenching or Pitting
What should be done during trenching or Pitting?
Trench (Linear) or Pit (Square) walls whould be described and ilutsrtrated thoroughly
Large sampling for accurate grade estimation
Alternative to Trenching?
Hand Held Drill for shallow drilling
Whats the end result of prospecting?
Drill Target
Whats the next step after obtaining data from exploration?
Overlay data (Surface and subsurface) on the base map to allow rapid integration and analysis of data
Trenching and pitting are more likely to discover what?
Mineralogy, mineralized structure
Continuity of Deposit
Setting up a Drill Program
Considerations in Setting up a Drilling Program
1) Drilling Type Required
2) Drillhole Spacing
3) Timing of Drilling
4) Contractor
Drilling pattern id dependent on
Assumed Attitude and Thickness of Drill targets
Easiest and cheapest to Drill
Used for shallow dipped mineralisation and
Disseminated Deposits
Vertical Boreholes
Preferred for targets with steep dips
Inclined Boreholes
Whats the primary aim of Drilling
?To cut/intersect the mineralisation at 90 degress with the initial hole
?Cutting immediately below the zone of oxidation/weathered zone
What is the most crucial in drilling?
1st hole which is normally aimed at down dip projection of surface anomalies or the interpreted centre of subsuracae geology
Succeeding drills will depend on the success of the first holes
Typical borehole spacing for a vein deposit?
25-50 m
Typical borehole spacing for a stratiform deposit?
100m to several hundres of meters
Usuall pattern in an accessible area
Square with regular rows of holes offset from adjacent holes
Why is it vital to closely monitor the geology and mineralisation intersercted during drilling programs?
to Controll the costs
How often should a geologists monitor drilling?
1) Precussion - Stay beside the rig
2) Diamong 0 Twice a day visit to examine core, make initial logs and decide next drill holes
Data on mineralisation, lithologies and structures hosting its should be recorded on this log as soon as the information becomes available
Graphic Log
A continuous graphic and written record used to describe obvserved features from drilling
Strip Drill lOgs
Typical Sophisticated methods to plot data fro boreholes
1) Structure Contour Plans
2) Isopach (equal Thickness map)
3) Grade
4) Thickness
5) Grade x Thickness (Accumulation Maps)
How to determine the continuity of mineralisation?
Once a reasonable sized body has been defines,
holes are to be drilled immediately adjacent to others (Closer Spcing)
When to Stop?
1) No mineralisation has been ecnountered
2) Mineralisation has been intersected but not of economic grade or width
3) Limited continuity of an economic grae mienralisation or too small to be of interest
4) Body of potential economic grade and size has been established
5) Budget is exhausted
When and why is recycling prospects an option?
In order to recover some of the investments in the propsect
What does Joint venture or farm out means?
The original owner still has a share of the prospect and is partly sold to other investors
Valuation Methods of Prospects
Subjective valuation since the project is still at an early stage
Methods of Valuation (At exploration Stage)
1) Comparable Transaction Method - the value of similar transaction is compared
2) Multiple of Exploration Spending - the value of the prospect is some multiple (0.5-3x) of the amount that has been spent on the property
3) Joint Venture Comparison - value is assigned based on the value of a JV of the property
4) Replacement Value - the value is a multiple of the cost of aquisition and maintenance of the property
5) Geoscience rating method - based on a series of geological parameters such as alteration, width and grade of any minerals intersected, proximity to deposit using weightings
