Mining Exploration - Présentation PowerPoint

ExploringGeosciences –

12 Thematic Lessons-

Block 2Mining Exploration

Lesson 3

Geochemical Surveys

September 30th,, 2020

Your Host:Francine Fallara, P. Geo., M.Sc.A (OGQ #433)

Exploration geologist with over 25 years of field experience in various difficult geological environments

Consultant in analytical data analysis specialized in complex geological exploration studies

Expert in 3D geological modeling and digital targeting of mineralswww.ffexplore3d.com

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Thematic Bloc 2 - Overview

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Thematic Block 2 Lesson Subtitle Date - 2020 English

Mining Exploration

1 Cartography Surveys September 2nd 1:30 – 3:30 PM

2 Geophysical Surveys September 16th 1:30 – 3:30 PM

3 Geochemical Surveys September 30th 1:30 – 3:30 PM

Exploring Geosciences: B2-Mining Exploration: L3- Geochemical Surveys

Lesson 3 – Geochemical Surveys

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Lesson 3 Sub-lessons September 30th

GeochemicalSurveys

a. Intro to geochemistry

1:30 – 3:30 PM

b. Overview of field techniques

c. Using geochemistry data

d. Validating and interpreting geological surveys with geochemistry


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Geochemistry studies the origin, evolution and distribution of chemical elements on Earth which are contained in the rock-forming minerals and the products derived from it, as well as in living beings, water and atmosphere.

One of the goals of geochemistry is to determine the abundance of elements in nature, as this information is essential to hypotheses development about the origin and structure of our planet and the universe.


What is Geochemistry?

https://www.gob.mx/sgm

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Geochemistry uses chemistry to understand various processes on Earth

Geochemistry = Chemistry of the Earth’s materials — Minerals and rocks:

Study of the chemical composition of the Earth and other planets:

The chemical processes and reactions that govern the composition of rocks, water, and soils.

The cycles of matter and energy that transport the Earth's chemical components in time and space, and their interaction with the hydrosphere and the atmosphere.



The Geochemistry of Rocks and Natural Waters, A. Koschinsky

7Exploring Geosciences: B2-Mining Exploration: L3- Geochemical Surveys



Victor Moritz Goldschmidt 1888 - 1947

Swiss chemist Victor Moritz Goldschmidt is the founder, characterizing, in 1933, the major role of geochemistry as:

The task to investigate the composition of the Earth as a whole and of its various components and to uncover the laws that control the distribution of the various elements.

Based on a comprehensive collection of analytical data of terrestrial material:

• Rocks, waters and atmosphere• Meteorites• Astrophysical data about the composition of other cosmic

bodies and geophysical data about the nature of the Earth’s inside.

• Information from the synthesis of minerals in the lab and from the observation of their mode of formation and stability conditions

Goldschmidt System - eduqas


Main Layers that form the Earth


Earth’s Interior


The Earth's crust is a thin hard outer shell of rock. Under the crust, there is a deep layer of hot soft rock called the mantle.


The crust and upper mantle can be divided into three layers according to their rigidity:

The lithosphere is the upper, rigid layer of the Earth:

Consists of the crust and the top of the mantle

About 100 km thickThe Geochemistry of Rocks and Natural Waters, A. Koschinsky

Earth’s Interior




The asthenosphere, below the lithosphere, in the Earth's mantle, is the hot, soft rock of the asthenosphere:

This boundary between the lithosphere and the asthenosphere occurs at the point where temperatures climb above 1300°C


Earth’s Interior




The mesosphere is the solid part of the earth's mantle lying between the asthenosphere and the core.


Earth’s Interior



Geochemistry of the Earth’s Minerals and Rocks


Earth’s Interior Earth’s Geo-Chemistry

The bulk of the Earth is made from iron, oxygen, magnesium and silicon.

More than 80 chemical elements occur naturally in the Earth and its atmosphere.

Mostly Earth is composed of three parts:• Crust• Mantle (Upper & Lower)• Core




Earth’s Geo-Chemistry

The Earth's crust is a thin layer of rock that floats on the mantle.

The Earth’s crust is made mostly from oxygen and silicon:

• Silicate minerals such as quartz, with aluminum, iron, calcium, magnesium, sodium, potassium, titanium and traces of 64 other elements.

Earth’s Interior





The upper mantle is made up of iron and magnesium silicates.

The lower mantle is mostly silicon and magnesium sulfides and oxides.

The core is mostly iron, with little nickel and traces of sulfur, carbon, oxygen and potassium.

Earth’s Interior





The outer core is so hot (4500°C -6000°C) that it is always molten.

The inner core is even hotter (up to 7000°C) but it stays solid because the pressure is 6000 times greater than on the surface.

Earth’s Interior




Earth’s Interior Earth’s Mass Distribution

• Inner core = 1.7% of the Earth's mass• Outer core = 30.8%• Core - mantle boundary = 3%• Lower mantle = 49%• Upper mantle = 15%• Ocean crust = 0.099%• Continental crust = 0.374%


Elemental Composition of the Earth’s Crust


99% of the earth’s crust by weight is made up of just eight elements: Oxygen Silicon Aluminum Iron Calcium Sodium Potassium Magnesium


Geochemistry of the Earth’s Processes


Geochemistry is the study of the composition of geological materials and the behavior of

individual elements during geological processes.


Geochemistry of the Earth’s Processes


Geochemical analysis is now a vital tool in most fields of geological and environmental research for studies of:

Water, soil, and air quality, Formation of rocks and minerals Fossilization mechanisms Metal accumulation in

organisms from contaminated water and soil

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Isotope geochemistry: Determination of the relative and absolute concentrations of the elements and their isotopes in the earth and on earth's surface.

Trace element, petro, soil, sediment and marine geochemistry: Examination of the distribution and movements of elements in different parts of the earth (crust, mantle, hydrosphere etc.) and in minerals with the goal to determine the underlying system of distribution and movement.

Planetary geochemistry and Cosmo geochemistry: Analysis of the distribution of elements and their isotopes in the cosmos.


Geochemistry Subdivisions

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Biogeochemistry: Field of study focusing on the effect of life on the chemistry of the earth.

Organic geochemistry: A study of the role of processes and compounds that are derived from living or once-living organisms.

Inorganic geochemistry

Aquatic geochemistry: Understanding the role of various elements in watersheds.

Regional, environmental and exploration geochemistry: Applications to environmental, hydrological and mineral exploration studies.


Geochemistry Subdivisions


The Goldschmidt Classification of Elements


Victor Moritz Goldschmidt 1888 - 1947

Swedish born mineralogist considered to be one of the founders of modern geochemistry and crystal chemistry

Chemical elements on the periodic table are classified into 4 groups according to their preferred host phases:

Lithophile Siderophile Chalcophile Atmophile







In Goldschmidt’s classification, elements are divided on how they partition between coexisting silicate liquid, sulfide liquid, metallic liquid, and gas phase:

Silicate Liquid

Sulfide Liquid

Metallic Liquid

Gas Phase

Siderophile

Chalcophile

Lithophile

Atmophile H, He, N, Noble gases

Alkalis, Alkaline Earths,Halogens, B, O, Al, Si, Sc, Ti, V, Cr, Mn, Y, Zr, Nb,Lanthanides, Hf, Ta, Th, U

Cu, Zn, Ga, Ag, Cd, In, Hg,Tl, As, S, Sb, Se, Pb, Bi, Te

Fe, Co, Ni, Ru, Rh, Pd, Os,Ir, Pt, Mo, Re, Au, C, P, Ge, Sn



Lithophile (rock loving) elements are found:

Close to the Earth’s surface

They combine readily with oxygen

Form compounds that do not sink into the core

Lithophile Elements: Concentrated in the Crust



Lithophile elements include:

Aluminium Calcium Potassium Magnesium Sodium Oxygen Silicon Titanium





Lithophile are found in the silicate minerals which make up 93% of the crust by mass and constitute the common rock-forming minerals:

Quartz Orthoclase Feldspar Plagioclase Feldspar Biotite Mica Muscovite Mica Hornblende (Amphibole) Augite (Pyroxene) Olivine Garnet Clay Minerals (Kaolinite)



Siderophile Elements: Concentrated in the Core

Siderophile (iron-loving) elements:

High density metals

Sink into the Earth’s core

Do not combine with oxygen

Dissolve in iron as solid solutions or in the molten state



Siderophile elements include:

Gold Iridium Iron Molybdenum Nickel Platinum

Siderophile Elements: Concentrated in the Core



Chalcophile Elements: Trace amounts in the Crust

Chalcophile (ore-loving) elements:

Combine readily with sulfur

Form compounds that do not sink to the core

Make up just 0.046% of crust by mass:

• Concentrated in mineral veins



Chalcophile elements include:

Arsenic Cadmium Copper Lead Silver Sulphur Tin Zinc

Chalcophile Elements: Trace amounts in the Crust



Atmophile (atmosphere-loving) elements:

Known as volatile elements

Occur in gases and liquids close to the Earth’s surface

Atmophile Elements: Concentrated in the Atmosphere & Hydrosphere



Atmophile elements include:

Carbon Hydrogen Nitrogen Argon Helium Neon Krypton Xenon

Atmophile Elements: Concentrated in the Atmosphere & Hydrosphere


The Exploration Challenge

A New Search Space

Deep Exploration Targeting

CSIRO, 2013, James S. Cleverley

Geochemical Geological Exploration

Until two decades ago, geological exploration was restricted to easily detectable outcropping mineralized bodies.


The Exploration Challenge

A New Search Space

Deep Exploration Targeting


Geochemical Geological Exploration

Nowadays, exploration leads to deposits that are not exposed to the surface and therefore are difficult to locate: For indirect exploration,

different methods were developed for the detection of hidden mineralized bodies:

Geochemical prospection based on established principles of geochemistry cycle and distribution of elements.


Geochemistry exploration applied to mining has three main purposes:

Search for metals in different adjacent parts to a known deposit, defining its limits, reiterate and new mineral bodies.

Finding deposits in unexplored areas.

Definition and delimitation of mineralized belts and/or metallogenic provinces.

Geochemical Geological Exploration Objectives




How do I explore for a mineral system?


Geochemistry has a direct connection to the commodity that is sought: Geophysics, though

indisputably useful, cannot make the same claim.

Geochemical responses are often larger than the target itself: Which makes it easier

(and cheaper) to detect



How do I explore for a mineral system?


Where is the next ore body?

Inputs from:

Data Integration

New technology

3D Analytics

The Why Question

Why is the ore body there?

The Where Question


Among the fundamental principles of geochemistry is the recognition of geochemical environments that are developed in the earth's crust and are grouped into:

Surface geochemical environment: Supergene, secondary and exogenous Geochemical reactions: Weathering, erosion, sedimentation

and soil occurs: Clear superficial conditions and features, such as:

• Low temperature and pressure• Free fluids movement• Plenty oxygen, water and carbon dioxidehttps://www.gob.mx/sgm

Geochemical Geological Exploration Principles


Dispersion: Formation of a mineral deposit with a certain distribution of the ore

minerals or elements associated with them: A halo around the deposit is formed from a few centimeters to

kilometers of extension

Types of dispersion: Primary dispersion:

• Involves all emplacement processes during the formation of how the mineralized body was formed.

Secondary dispersion: • Involves the redistribution of primary models, by any

subsequent process• Often under low temperature and pressure conditions




Dispersion: Primary and Secondary

Both types depend on:

The geochemical mobility of elements which depends on the:

Mechanical properties (mobile stage of mineral):

• Viscosity, solution, size, shape and density of the grains and the physic- chemical features of each element.




We may sample material derived from the rocks on the assumption that if the rocks are enriched in metals of interest, the derived material will be too.

CIM Short Course, 2013, Steve Amor

Schematic diagram of primary and secondary dispersions



We may sample material derived from the rocks on the assumption that if the rocks are enriched in metals of interest, the derived material will be too.

Eric Grunsky, 2015

Schematic diagram of primary and secondary dispersions


Mineral deposits represent anomalous concentrations of specific elements, usually within a relatively confined volume of the Earth's crust.

Most mineral deposits include a central zone, or core, in which the valuable elements or minerals are concentrated.

This zone surrounding the core deposit is known as a primary halo or anomaly

H. E. Hawkes and J. S. Webb (1979) Geochemistry in mineral exploration, 2nd edition, p.535-548.


We may sample solid material derived directly from the rock as soil, or sediment created by the mass-wasting of soil into streams, or sediment on which metals transported in solution (ground-, creek- or lake-water) are precipitated, or the waters themselves CIM Short Course, 2013, Steve Amor

Dispersion of metals from sulfide deposits by groundwater and streams into lakes and lake sediments.(Allan et al. (1973), reproduced in Levinson (1980))



We also may be sampling material that has been transported by glaciers, or stream or lakesediment derived from it.


Glacial dispersion from metals from sulfide deposit into till (Miller, 1984).



Overview of Geochemical Exploration Methods

Regional Prospecting ...1850

Goldoz.com.au



Until 20 years ago, geological exploration was restricted to easily detectable outcropping mineralized bodies, however, today exploration has led to deposits that are not exposed to the surface and therefore are difficult to locate: The purpose is the possible discovery of a geochemical "anomaly" or area where the

chemical pattern indicates the presence of ore in the vicinity.

As a result, geochemical exploration focuses on the determination of the elements of the ore or elements associated with the ore that are dispersed, called respectively indicator elements and guide elements:

For example, in a deposit of lead-zinc (Pb-Zn) sulfide: The indicator elements are lead and zinc A possible guide element will be mercury (Hg)


Why Use Geochemical Exploration Methods?


The different types of studies performed by sampling elements are:

Lake and stream-sediment and water geochemistry Soil geochemistry Till geochemistry Rock geochemistry Gas geochemistry Vegetation geochemistry

Types of Geochemical Exploration Methods



Lake and stream-sediment and water geochemistry: The method of sampling lake sediments and waters is ideally suited to

large-scale regional projects that only a government or large company could undertake, although some prospectors carry out lake surveys of more limited scope, particularly in winter when access is easier.



There are also large online databases of lake data collected

by both the Provincial and Federal governments

Coverage of lake-sediment and water sample collection by Geological Survey of Canada (GSC).


Lake and stream-sediment and water geochemistry: Lake water samples are collected in Nalgene bottles; normally before

collecting sediment samples, so that disturbed sediment does not get into the sampled water.


CIM Short Course, 2013, Steve AmorRetrieving a lake-sediment sample from a “Hornbrook bomb”

Collecting lake-water samples in Nalgene bottles.

Lake and stream sampling should be considered as a first-pass method that can be used to identify targets prior to more detailed geochemical work (soil or till sampling) or prospecting.


Soil geochemistry: The soils are mainly humoferric and ferrohumic podzols, both consist of

an: Organic-rich Ah horizon and an ash-grey leached Ae horizon:

• Neither of which should be sampled Underlain by a rusty brown B horizon:

• The preferred sample medium for many prospectors as it is enriched in metals leached from the A horizons

The base of the soil profile is the C horizon:• Consisting of the relatively unweathered source material of

the soil



Unweathered mineral matter.

Effects of groundwater, vegetation, oxidation.(not sampled)

Oxidized, bioturbated and organic debris, extensive weathering of mineral matter.

Top Layer = 0 to 5cm. Organic debris with little mineral matter.

Progressive weathering of mineral matter up the profile.

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Sampling the Soil Profile



Soil geochemistry: Soil sampling may be a second-stage prospecting procedure used to follow up a

drainage anomaly OR may also constitute the first geochemical work to be carried out, if mineralization is already known to occur nearby.

Soil samples are laid out on a grid, normally in the form of regularly spaced cut lines


Sampling lines are spaced so that any important feature should be cut by at least two of them

Samples are spaced so the key feature is sampled in at least two adjacent samples

Normally, this means that the spacing between the samples is much less than the spacing between the lines: Samples are spaced at intervals of 10 to 25 metres Lines are 100 to 200 metres apart.Selection of line and sample spacing should reflect

the size of the expected target.



Till geochemistry: Till (sometimes called drift) is the sediment from the movement of glacier ice over

the land surface and the plucking and grinding of bedrock. Typically unsorted, meaning that fragments of all sizes are intimately mixed together


Typical rocky till, exposed in a road cut



Till geochemistry:


The interpretation of till geochemistry requires knowledge of the glacial history of the area; in particular, the direction(s) of ice movement.

Usually, ice-movement direction is generally towards the coast, but large- and small-scale deviations from this rule are not uncommon.

Several field methods are used to determine the direction of ice movement:

Most common is to measure the direction of striations on glaciated rock surfaces.

Downloadable database of striation measurements exist

Striations on a flat rocksurface

Striations directions map



Till geochemistry:


Glacial dispersion of beryllium (Be) from the Strange Lake rare earth-rare metal deposit, Labrador (Batterson 1989).



Schematic sections and plan of glacial dispersion from an ore zone

Assuming a single till-depositing event: Distance “up-ice” to

the bedrock source of a geochemical anomaly, or mineralized boulder, detected at surface is dependent on the till thickness.CIM Short Course, 2013, Steve Amor

(from Miller, 1984)

Till geochemistry:


Select the geochemical survey study area:

The main purpose of this stage is to select areas or regions that have good mineral potential and that can be prospected effectively.

Initial selection of areas should be based on a most thorough review of the known geology and records of past mining and prospecting activity:

“To get some idea of background for an area of interest, prospectors should examine regional and local historical survey data with respect to their area of interest”

Based on recorded mineralization and on the geological environment.

Geochemical Mineral Exploration: How to?




Define the geochemical survey scale:


Continental Scale – > 1:500,000 & < 1:1,000,000Mapping large crustal blocks/tectonic assemblages

Regional Scale - > 1:50,000 & < 1:500,000Regional geological mapping

Local/Camp Scale < 1:50,000Exploration scale studies and detailed geologic mapping

Eric Grunsky, 2015


Characterize the target size and geometry:

Some features of ore environment, such as favorable host rocks, geological structures, or geochemical provinces, are related to the genesis and localization.

Each geological, geophysical, and geochemical features of the ore environment defines a target area of characteristic size, shape, and relationship to the ore.




Choose the exploration technique: For greatest overall effectiveness, an optimum balance must be struck

between the various geological, geophysical, and geochemical methods that are known to be applicable.

The choice must be based on relevant previous experience and case-history data.

Fit with the chosen scale of the study area.

Selection of methods is also strongly influenced by the size of the target and by property control.




Rely on the chosen geochemical survey method:

Reliability depends not only on how effective the exploration method is in locating the target, but also extent to which an anomaly is specifically related to ore and the abundance of non-significance anomalies that may confuse interpretation and require fallow-up survey.




Link the cost of the method based on the value of the expected ore:

The expected value of the ore body being sought and the chances of success may have an appreciable bearing on the applicability of a given method.

Thus a high-cost survey is justified for large ore bodies are expected and there is relatively little chances of overlooking a deposit.

Conversely, a low cost-survey is justified in areas of small targets.




Assure high quality control for geochemical surveys:

Geochemical methods of exploration constitutes an important tool in the investigation of the economic mineral deposits.

Any geochemical investigation to be effective, must take into consideration several aspects of the ore body, including genesis and cost at various stages of exploration.




Justify the role of geochemistry in an exploration program:

Geochemistry is an essential component in most modern integrated mineral exploration programs, for the following reasons:

1. Economic mineral deposits are commonly characterized by their low grade and large tonnage. Discovery, assessment and development are highly dependent upon geochemical methods and analyses.

2. Exploration activity is mostly carried out in tropical and subtropical environments where chemical weathering has predominated and where geochemical prospecting techniques have proven most effective.

Recent estimates suggest that between 10 and 25% of exploration budgets are allocated to geochemistry.




Choose the elements to analyze:

“Primary Targets”: Metal elements that are most commonly sought by prospectors

“Secondary Targets”: Metals (except fluorine) which may be sought under special geological and

economic circumstances

“Pathfinders”: Uneconomic elements useful in discovering a deposit of an element other than

themselves:• Usually, the target have sampling or analytical challenges that the pathfinders do not.







Reduce ‘nugget’ effects:

Gold analyses in geochemical samples are subject to the “nugget effect” which can cause an anomaly to be missed, or alternately for an unrealistically high value to be returned; the outcome depends very much on chance



“Nugget” or “particle sparsity” effect illustration:

Gold’s sample material represented by the smaller square will return a very low assay

If the scoop picks up the single gold particle (represented by the larger dot), the assay will be very high.

As indicators of the bulk gold composition of the sample, neither will be correct (Harris, 1981).

A pathfinder element like arsenic is more evenly distributed and not subject to this problem.


Understand analytical certificates:

Analyses preceded by the “less than” (<) sign: Means there is so little of the element in question in the sample that

the analytical method is not sensitive enough to measure it. The < sign is sometimes replaced by a minus sign (-) Rarely (though it may turn up in old assessment documents) the

words “ND” meaning “Not detected”.

“Greater than” (>) sign: Indicates an analysis that exceeds the method’s upper range



Field Cartography

A long tradition

Exploring Geosciences: B2-Mining Exploration: L3- Geochemical Surveys70

Helicopter Outcrop Stripping

In compliance with all the regulations 71


Outcrop Stripping

In compliance with all the regulations


Trenching and Sampling

Experienced and efficient


More than 50,000 lakes to our credit

Sampling of Lake Sediments


Sampling and Characterization

Lake Sediments

Surface Water


Till Sampling

Quaternary Geology76


Soil Sampling

Highly skilled experience


Trenching Sampling Drill Hole Sampling

Drilling tailings within abandoned sitesCollecting soil samples

Soil Sampling and Characterization


Pedogeochemistry:LiftIndex, Double-normalization and Probabilism

Beyond statistics


Preparation of Soil Samples

Super-clean work by reducing all risk of contamination



PLANNING AND SAMPLING General influences

EXPLORATION GEOCHEMISTRY: From planning to interpretation, with all its complexity

http://www.iosgeo.com/en/

MEDIUM ADAPTED TO THE CONTEXT REGIONAL OR LOCAL ENVIRONMENT TYPE AVAILABILITY AND HOMOGENEITY BEHAVIOR OF TARGETED METAL

USE THE MOST SUITABLE MEDIUM, THE RIGHT ANALYTICAL METHOD FOR THE MEDIUM, AND THE ONE YOU MASTER THE MOST

EFFICIENCY vs COSTS


PLANNING AND SAMPLING Problems



80% OF QUALITY PROBLEMS ARE FROM SAMPLING * Numbering errors Localization errors Bad material No description of the material No description of the environment Contamination problem Poorly trained staff Not very robust working method *Project Manager


PLANNING AND SAMPLING Numbering



MOST SERIOUS ERRORS If there is an anomaly, the tracking takes place in

the wrong place SIMPLE, DIGITAL SYSTEM

Avoid letters Avoid complexities (i.e. no line)

• Example: 92951125, project 929, 5 for soils, sample 1125

CUSTOM COUPON BOOKS With barcode

REDUNDANCY Bag, coupon, aluminum ticket, ribbon


PLANNING AND SAMPLING Location



GPS with external antenna (± 1 m) Pay attention to the coordinate system (NAD27

and NAD83) Planning traverses Digital transfer AND handwritten notes

Watch out for numbering shifts GPS corroborated with line / station numbers

GPS inaccuracy causes zigzags in the lines


PLANNING AND SAMPLING Material selection



The quality of the survey depends on the homogeneity of the medium collected.

Samples representing material other than the targeted material generate noise

Must be performed by trained employees (not just supervised)

Dramatic effects on results and interpretation: Not filterable Difficult to detect after GARBAGE IN, GARBAGE OUT!


PLANNING AND SAMPLING Material selection



The meaning of the geochemical signature depends on the study area and therefore on its environment

The sample environment must be adequately described (expensive to do after).

Topography, slope, drainage, hydrography, forest cover, geomorphology, outcrops, etc.

Soil profile Anthropogenic influence Eliminate false anomalies


PLANNING AND SAMPLING Describe the sample



Necessary for interpretation Required for QCQA (Redundancy) Granulometry, color, humidity, cohesion, etc. Constituents:

Silt, sand, gravel Type of pebbles Presence of a glaze Organic matter:

Humus, twigs, fibers, sphagnum, etc. Crusts:

• Ferrochelate, calcrete, gypsum, etc.


PLANNING AND SAMPLING Describe the color



MUNSELL'S CHART Required for QCQA (Redundancy) Too subjective to be just descriptive

Ex.: Red brown, Goose poo brown, chocolate brown Cannot be used in a database

TVC (perception) versus RGB (measurement) Tint (Base color)

• R: red; Y: yellow, V: green, B: cyan, P: purple• YR, GY, BG, PB, RP• 5: pure, 10: hybridized

Value (tint brightness) 1: white, 10: black

Chromaticity (Purity of perceived color) 1: gray, 12: saturated color


PLANNING AND SAMPLING Sample size



CATIONIC METHODS 300-1000 grams wet

CHEMISTRY OF DETRITICAL FRACTIONS 300 gr for the fines 1-5 kg for BLEG 10 kg for heavy minerals

MINERALOGICAL METHODS 10 kg for nugget gold 20-30 kg for the tills 20-50 kg for eskers


SAMPLING PATTERNS OPTIMAL SCALES OF SURVEYS



Regional

Local

MEDIUM TRANSPORT RESOLUTION

RIVERS AND ESKERS 1 - 300 km > 10 km Detrital

LAKES 1-5 km > 1 km Cat> Det

TILLS 300 m-30 km > 500 m Detrital

STREAMS 0-5 km > 500 m Det or Cat

SOILS 0-1 km <100 m Cationic

Unusual methods (plants, water, termite mounds, etc.) are far less well precise


PLANNING AND SAMPLING LAKES



Mileage spacing Heavy logistics Gyttja in the darkest part of the lake

Under the hypolimnion Avoid sampling near riverbanks, mouths, or in bog

lakes Helicopter torpedo sampling

BLIND Tight sampling of the same lake: NOT USEFUL


PLANNING AND SAMPLING RIVERS AND ESKERS



Pluri-kilometric spacing Sifted and clean gravel

• Heart of the esker or swimming pool in the rapids Avoid shoulders or sandy dunes Rapid dilution of chemical signal Oxidizing system, no sulfide Heavy mineral studies only


PLANNING AND SAMPLING STREAMS: DETRITAL



Detrital material Sub-kilometer spacing Alluvial plain, meanders High energy zone

• Confluences, rapids, traps Concentration of heavy minerals Mineralogy or chemistry Oxidizing medium: destroyed sulfides


PLANNING AND SAMPLING STREAMS: ORGANIC



Organic banks Flood zones Organic material Adsorption of water cations Restricted watershed influx


PLANNING AND SAMPLING GLACIAL SEDIMENTS: DETRITAL



Bottom till and melting till Geomorphological study (specialist)

Material availability Flow direction Complex stratigraphy, palimpsest Doesn't work everywhere Presence of wind glacis or runoff

Mineralogical study (10-30 kg) Chemical analysis (0.5-2 kg) Fence 2-20 km, perpendicular to the dominant flow Spacing on fences: According to target


PLANNING AND SAMPLING SOILS



Only local grid method Line 100 - 400 meters Station 25 - 100 meters Different horizons do not have the same signature

Humus "A": cationic Ferrochelate "B": cat + detrital Horizon "C": detrital


PLANNING AND SAMPLING SOILS SAMPLING



Inverted plastic bag used as a glove to

avoid contamination

Hole crossing the target horizon

Kraft paper bag Barcode label


PLANNING AND SAMPLING SOILS SAMPLING

Fibrisol: Organic peaty soils



PEAT

Pierre-Luc> 6 feet


PLANNING AND SAMPLING SOILS PROFILES



L-F : Fibrous materialAh : Humic matterAe : Leached area

B : Ferruginous zone

C : Non altered overburden


PLANNING AND SAMPLING SOILS PROFILES: PODZOL



Leached soil, poorly developed Typically thin Dominant on the tills

Very acidic Cold climate Typical forest floor of the taiga

Conifers Ericaceae

Dominated by chelation Organic-iron-aluminum complex Horizon B poorly developed

Easy to sample


PLANNING AND SAMPLING SOILS PROFILES: BRUNISOL



Very well drained soil Hardwoods, pine forests, etc.

Permeable terrain (sand and gravel) Positive water balance, dominated by downward flow Oxidizing environment

Intense ferrochelate Highly developed Horizon B

Complex structure, can be thick No leached zone Ae

Easy-to-sample humus Horizon B: can be difficult Presence of ferricrust Destroyed by forest fires


PLANNING AND SAMPLING SOILS PROFILES: BRUNISOL



FERRICRUST HARDSTEIN


PLANNING AND SAMPLING SOILS PROFILES: GLEYSOL



Continuously waterlogged soil Swamp, bog, sphagnum moss

Poorly drained, waterproof land Anoxic, reducing

No ferrochelate Horizon B absent Enrichment of clays

Humus sits directly on the clay

Can be deep Holes 1-2 meters Dutch Auger

http://www.soilsofcanada.ca/gallery/image/1718381974_Humic Luvic Gleysol.jpg

http://www.soilsofcanada.ca/gallery/image/1718381974_Humic Luvic Gleysol.jpg


PLANNING AND SAMPLING SOILS PROFILES: LUVISOL



Leaching soil Agricultural plains, herbaceous plants Good drainage

Weathering and production of clays Positive water balance, dominated by downward

eluviation / illuviation Complex structure Easy to sample

Can be thick and disturbed


PLANNING AND SAMPLING SOILS PROFILES: OTHERS



MOLLISOL: Accumulation of organic matter in herbaceous plains REGOSOL: Poorly developed profiles CRYOSOL: Developed on permafrost VERTISOL: Clay soils with poorly developed profiles and argilopedoturbation FIBRISOL: Organic peaty soils

https://soilweb.ca/


Data for major elements are generally reported in the form of oxides as weight per cent (e.g. silica, SiO2 wt. percent) and trace elements in parts per million (ppm) or micrograms per gram (μg g−1).

An important consideration in the interpretation of data is analytical uncertainty, particularly when evaluating the existence or significance of small variations in composition.

Some of the most common sources of uncertainty are sample contamination, incomplete sample digestion (some minerals are extremely resistant to acids), interferences between elements, and poor instrument calibration.

Geochemical Data Interpretation



The extent of these problems is best limited at the time of analysis by taking necessary precautions and through discussion with experienced laboratory staff.

They are, however, impossible to eliminate completely and an indication of analytical uncertainty should therefore be reported with the data, ideally as ‘error bars’ on geochemical diagrams.

Uncertainties can be estimated from the regular analysis of reference materials of known composition and from the analysis of two or more samples.




To help in interpretation, data are often imported into graphing and statistical computer programs.

A wide variety of diagrams can be produced to compare the data with those from previous studies and to demonstrate trends or new interpretations.





1) 2D and 3D quantitative punctual data:

a) Added analyzes of cartographic surveys, compilation and drilling (DDH)

2) 2D and 3D qualitative punctual data:

b) Alteration and mineralization observed (in %)

2D and 3D Geochemistry

Fallara, Rabeau, Cheng and de Kemp (2008)


Targeting Proximal and Distal Footprints


Fisher et al; 2013




Golden Mile

Kanowna Belle

Paddington

Mt Pleasant

Kundana

Binduli10 km

Scott HalleyMinmap

Fisher et al; 2013




Fisher et al; 2013

Whole rock geochemistry / mineralogy, mineral chemistry

Immobile geochemistry / mineralogy, mineral chemistry

<50 meters - Gas, hydrogeochemistry biogeochemistry (trees/shrubs)

> 50-100 meters - Hydrogeochemistry


Real time integrated data while drilling


Fisher et al; 2013


Real time integrated data while drilling


Fisher et al; 2013

Geochemistry


Linking geophysics and geochemistry


Fisher et al; 2013


Geochemical surveys are conducted to provide baseline information for: Mineral exploration Geologic mapping Baseline values for environment/land use purposes

Geochemical survey data: Contains various information for geological, geochemical, environmental and

climatic processes. Uses more than 50 elements can be analyzed at sufficiently low detection

limits. Reflects processes that form or affect mineralogy. Represents a multivariate data space over a two or three dimensional

geographic space and time.


E. C. Grunsky and P. de Caritat Geochemistry: Exploration, Environment, Analysis 2019; Geochem2019-031



Melville Peninsula Case Study

117


Regional basement rock type map of Nunavut, Canada, showing the location of the Melville Peninsula study area.


118


Regional scale of geochemical surveys 1:250,000


1 site/13km2

119


Geological map of the southern part of the Melville Peninsula, Nunavut, Canada, with lake sediment sample sites (shown as black dots)


120


Mineral occurrences obtained from NUMIN (2017)


121


Map of the residual values of Au (ppb) estimated from a robust interpretation of lake sediment geochemical data, Melville Peninsula.


122


Map of the residual values of Ni (ppm) estimated from a robust interpretation of lake sediment geochemical data, Melville Peninsula.


123


Map of the residual values of Zn (ppm) estimated from a robust interpretation of lake sediment geochemical data, Melville Peninsula.


124


Map of the residual values of Cu (ppm) estimated from a robust interpretation of lake sediment geochemical data, Melville Peninsula.


125

3D Spatial Interpretations and Geochemical Quantification: Used to identify and illustrate possible anomalies found within the

vicinity of known mineral deposits.


Fisher et al; 2013126




Fisher et al; 2013

Gold isosurfaces: 0.05,0.1, 0.5, 1.0 ppm

127




Fisher et al; 2013

Favorable Alteration

Isosurfaces (0.5, 0.6, 0.7)

128


B2: Lesson 3: Geochemical Surveys: Videos

THE GEOLOGICAL MAP "Drawing the Earth's skin"(9.47min)

https://youtu.be/qdz9DN74ukY

Mineral Exploration Geologist (5.02min)

https://youtu.be/3uXyZ3FGTCo

Tellus geochemical sampling: collecting soil samples (6.2min)

https://youtu.be/sDAtLfSP9SU

Geochemical Prospecting (28.06min)

https://youtu.be/-Ys0LH7sYWg

Geochemical Techniques for Undercover Exploration: The 'New Geophysics'?- James Cleverley, 2013 (56.45)

https://youtu.be/ag2JLP5vIkQ

https://youtu.be/qdz9DN74ukY

https://youtu.be/3uXyZ3FGTCo

https://youtu.be/sDAtLfSP9SU

https://youtu.be/-Ys0LH7sYWg

https://youtu.be/ag2JLP5vIkQ

FNQLSDI.CA

Questions?

Thanks!


Mining Exploration - Présentation PowerPoint

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