Geological Mapping in Exploration

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Exploration Geology @ PetMin 2014 1

GE – 03 Geological Mapping

GEOLOGICAL MAPPING IN EXPLORATION

By:Mega F. Rosana, Ir., MSc., PhD

Euis Tintin Yuningsih, ST., MT., Ph.D.Dr. Ir. Ildrem Syafrie, DEA.

Emi Sukiyah, Ir. MT.Yuyun Yuniardi, ST., MT.Adi Hardiono, ST., MT.

Ir. Cecep Yandri Sunarie., MengIr. Undang Mardiana, MT.

Aton Patonah, ST., MT.

Part 1: (2) INTRODUCTION Introduction Concept exploration

Part 2: (3) GEOLOGICAL MAPPING IN EXPLORATION Geological Mapping Remote Sensing

PART 4: (4) EXPLORATION GEOCHEMISTRY Stream Sediment & Heavy Minerals Sampling Soil Sampling Rocks Sampling Biogeochemistry, Hydrogeochemistry, Gasgeochemistry Assaying

PART 4: (2) EXPLORATION GEOPHYSYC Airborne geophysics Ground geophysics Submarine geophyscs

PART 5: (2) EXPLORATION DRILLING Type drilling Drilling method Logging

PART 6: (3) EVALUATION Seminar (Presentation, Groups Discussion) Mid Test Final Test Fieldtrip

Courses Outline

Exploration Geology @ PetMin 20149/11/2014

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EXPLORATION METHODS

B. Ground Mapping

Topographic mapping

Aero‐geochemical surveys

Aero‐geophysical surveys

• Aeromagnetic

• Electromagnetic

• Radiometric

• Gravimetric

Preliminary/Regional mapping

• Scale 1 : 250,000 ~ 1 : 50,000

Detail mapping

• Scale 1 : 20,000 ~ 1 : 1,000

Exploration Geology @ PetMin 2014

A. Airbone Mapping

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Why make a map ?

The nature of Geological Mapping

Smart Mapping

Choosing the best

technique

Choosing the best scale

The use of satellite

navigation (GPS)


GENERAL CONSIDERATIONS

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WHY MAKE A MAP?

Geological map is graphical presentation of geological

observations and interpretations on a horizontal plane

Geological map is graphical presentation of geological

observations and interpretations on a horizontal plane

Geological section is identical in nature to a map except that data are

recorded and interpreted on a vertical rather then a horizontal surface

Geological section is identical in nature to a map except that data are

recorded and interpreted on a vertical rather then a horizontal surface

Maps and sections are essential tools in visualizing spatial, three‐

dimensional, geological relationships

Maps and sections are essential tools in visualizing spatial, three‐

dimensional, geological relationships

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WHY MAKE A MAP?

Making a geological map is invariably the first step in any mineral exploration

programs

Geological map is important control document for all subsequent stages of exploration and mining (including drilling, geochemistry, geophysics, geostatistics and mine planning)

Making a geological map is a fundamental skill for any exploration or mine geologist

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Constructed according to the theories of geology and the intellectual abilities of its author

Constructed according to the theories of geology and the intellectual abilities of its author

Presents a selection of field observations and useful to the extent that is permits prediction of things which cannot

be observed

Presents a selection of field observations and useful to the extent that is permits prediction of things which cannot

be observed

Two different kinds of geological map

• large‐scale “fact or observational or outcrop maps”

• small‐scale “interpolation made by remote sensed image data : satellite, radar, air photographs, aeromagnetic maps

Two different kinds of geological map

• large‐scale “fact or observational or outcrop maps”

• small‐scale “interpolation made by remote sensed image data : satellite, radar, air photographs, aeromagnetic maps

THE NATURE OF GEOLOGICAL MAP

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SMART MAPPING

Geologist start the fieldwork with ideas about the geology which has to

be mapped

The ideas are developed from looking at published

maps; interpreting air photos, remote sensing; aeromagnetic data; aero geochemical data; or followed an intuitive

hunch

The mapping sequence depends on the postulated geology driven from the

ideas

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Air photo mapping

Mapping with plane table

Mapping on pegged

grid

Mapping with tape

and compass

MAPPING TECHNIQUE

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CHOOSING THE BEST TECHNIQUE

Depends upon the availability of suitable maps bases on which to record the field

observation.

The ideal base is an air photographs

Satellite imagery provide suitable base for regional mapping

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Remote sensing is the science of remotely acquiring, processing and interpreting spectral

information about the earth’s surface and recording interactions between matter and

electromagnetic energy.

GROUND

Alumbrera, Ar

SATELLITE

AIRBORNE

CUPRITE, NVGoldfield, NV

Pengumpulan data dari citra satelit dan sensor airbone. Kemudian data tsbt dikalibarasi dan diverifikasi menggunkan spectrometer di lapangan

Field Spectrometer

LANDSAT

HYPERSPECTRAL

Geological mapping procedure

Survey Establishing control points

Compass and tape traverse

GPS traverse

Fact geology data collection Pit and trench mapping Prospect scale surface mapping District scale mapping Use of field manual for standard symbols and

codes

Map generation and archiving Map scales

Map folio system

Map interpretation

GIS maps generation

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Survey procedure Establishing control points

Establish one differential GPS control point for early stage mapping works. Tie all traverses from this point.

For grid mapping – establish corner points of grid using differential GPS or Total station EDM.

Compass and tape traverse To be conducted only if GPS cannot be used. Important in gridding if area has poor GPS

signal. Traverses should be corrected using CSS

GPS traverse Use Garmin 60Csx for 2‐d mapping in early‐stage

mapping works

Use differential GPS for gridding in open areas.

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Mapping – fact geology data collection

Pit mapping map at 1:500 scale (100 metres per A‐4

map sheet)

project data from mid‐bench

map rock type by colouring the ground side of the bench line with appropriate lithology colour (field manual)

map alteration by colouring the air side of the bench line

indicate structural contacts (dip/dip direction) using appropriate symbol

sketch (or photograph) the bench face as an offset diagram parallel to the bench map.

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Trench mapping map at 1:100 scale (10 metres per A‐4

map sheet)

map the floor of the trench

colour the map based on lithology

describe features in long hand using abbreviations in field manual (format: texture‐litho‐alteration‐mineralisation)

indicate structural contacts using appropriate symbol

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Organizational hints for efficient mappingFaults, joint and contact lithology measurement


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Trench mapping map at 1:100 scale (10 metres per A‐4 map

sheet)

map the floor of the trench




sketch one wall of the trench as offset diagrams parallel to the trench floor map.

decide on the sampling cut (either along wall or floor) and interval

tabulate “from‐to” sampling interval on the A‐4 map

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Detailed prospect scale mapping map at 1:1000 scale (data plotted in field

book or A‐4 millimeter sheets and transfer to map folios in camp)

draw‐out configuration of outcrop as actually measured (use solid line for outcrop and dash lines for floats or subcrops)




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District mapping map at 1:5,000 scale (plot data on a

1:5000 scale topo map), use GPS for locating in the field

sketch configuration of outcrop (use solid line for outcrop and dash lines for floats or subcrops)




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Map Generation and Archiving Map consolidation

Pit mapping: consolidate maps into 1:500 bench plans

Trench maps: plot trench maps onto 1:1000 fact map

Prospect scale mapping: maintain a folio map system (do not digitise fact maps, can be scanned and then register in GIS)

Map interpretation Pit mapping: Use overlays on the bench fact

maps to interpret geology (with structures) and alteration in separate sheets.

Prospect and district‐scale mapping: Use overlays of the same size as the map to interpret geology and alteration as above.

Generate interpretive sections at the same scale as the maps.

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Mapping outcrops : use multiple overlays

Color separation is maintained by plotting :

Lithologic contacts, faults, veins, and other structural on base map

Pervasive alteration and alteration halos on the first overlay

Mineral or their oxidation products on second overlay


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Map Generation and Archiving Map filing

Maintain an orderly filing system of hardcopy maps in the project office (hangers or map cabinets)

Map interps are to be digitised and included in the GIS files for the project

Ensure that file name of shape files are correct and updated every month with the central server

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Comparison of mapping techniquesMapping Technique

Scales Indications Advantages Disadvantages

Pace & compass

1:100 ~ 1:1000

Rough prospect map. Infill between survey points

Quick. No assistance and minimal equipment needed

Poor survey accuracy especially on uneven ground

Tape & compass

1:100 ~ 1:1000

Detailed prospect maps: Linear traverse maps. Mine mapping

Quick. Good accuracy. No preparation needed

May need assistance. Slow for large equidimensional areas

Grid 1:500 ~ 1:2500

Detailed maps of established prospects

Fair survey accuracy. Relatively quick

Expensive. Requires advance preparation.

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Mapping Technique

Scales Indications Advantages Disadvantages

Plane table 1:50 ~ 1:1000

Detailed prospect mapping in complex areas

High survey accuracy. No ground preparation required

Slow. Requires assistance. Geological observation and map making are separate steps

Topographic map sheet

1:2500 ~ 1:100 000

Regional mapping & reconnaissance where no photography available. Base for GPS observations

Accurate map base with regional coordinates. Height contours

Difficulty in exact location. Irrelevant map detail obscures geology. Not available in large scale

Air photographs

1:500 ~ 1:100 000

Ideal geological mapping technique at all scales

Geological interpretation on photo. Stereo viewing. Easy location on features.

Scale distortion. Expensive survey if standard coverage not available

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CHOOSING THE BASE SCALEThe scale chosen for mapping controls the types of data which can be recorded and types of observations in the

field

Small scale map shows broad regional patterns of rock distribution and major structures

Intermediate range scale could be described as detailed regional mapping; ideal scale when combining geological

mapping with regional prospecting or regional geochemistry

Large scale map is appropriate for showing the features which directly control and localize ore

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Geological map at 1 : 50009/11/2014


Geological map at : 1 : 25009/11/2014

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Geological map at : 1 : 10009/11/2014


THE USE OF SATELLITE NAVIGATION (GPS)

Ideal for regional geological mapping onto published map bases

Ideal for regional prospecting and regional and detailed geochemical and geophysical data collection

Some limitations should be noted :

• GPS needs an unobstructed line of sight to the satellite which provide the location signal

• Relying exclusively on GPS for navigation can create serious problems

• GPS cannot provide accurate positioning on air photographs

• Plotting latitude and longitude coordinates in the field is difficult

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Exploration Geology @ PetMin 2014 Example of Tape and Compass map9/11/2014


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REMOTE SENSING APPLICATION


Documents

Geological Mapping in Exploration