EXPLORATION GEOLOGY (PROSPECTING TO PRE-FS) Flashcards by Sean Levi Abiera

The scale and speed of exploration primarily depend on?

1)The land Acquisition Agreements
2)Overall Budget

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A geologist who heads an exploration project with a separate budget allocation

Project Geologist

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Whats the recommended distance of in house facility for staff to the site?

Less that 1 hour commuting time

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If the areas is really remote what would be the possible setup?

In field camps and commute by air

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Difference of Reconnaissance budget to Prospecting Budget?

More expensive because of Driling

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Estimates of a contractor for geochemical and geophysical surveys are usually on the basis of?

Cost per line-Kilometer or Sample

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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

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Surveying Methods

1) GPS - Problematic in Forested Areas
2) Tape and Compass

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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

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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

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How is leveling done?

Measures height difference between a pair of station using a surveyor’s level

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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%)

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a more accurate survey equipment than compass?

Theodolite

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What is the scale of the Map needed at the prospecting stage?

1:10,000 to 1:2,500

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What instruments can be used for accurate mapping?

1) Telescopic Alidade - used to plot points
2) Plane table or Differential GPS

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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

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Conventional wat of producing Maps

Indian Ink Pen on Transparent Film

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Computer softwares that aid in Map Making

1) Autocad
2) ArcGIS
3) MapInfo

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Intervals of sampling for vein gold deposit?

1m intervals

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Intervals for copper deposit?

5 or 10 m

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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

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A form needed to be accomplished when sending samples to the lab?

Sample Control Form

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What error instances must one be alerted?

Gold values of several Percent
Copper values in ppb range

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Who must discuss or decide about the lements that needs to be tested?

Project Manager
Field Staff
Chief Geologist

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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

1. Visual description of weathered rocks 2. Examination for relic textures 3. 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