Understand the basic concept of Surface filed geology

WELCOME TO THE STUDENTS
5th Semester (Mining)
Bogura Polytechnic Institute, Bogura.
Md. Majedur Rahman
B. Sc (Hon’s), M. Sc in Geology & Mining, RU
Instructor (Tech)
Mining and Mine Survey Technology
Bogura Polytechnic Institute, BOGURA.
Presented By
October 26, 2019 Prepared by Md. Majedur Rahman, E-mail: majedu1r_ru6871@yahoo.com 1

Exploration Geology
Course Code No. 69351
Course Curriculum T C P
2 3 3
October 26, 2019
Prepared by Md. Majedur Rahman, E-mail:
majedu1r_ru6871@yahoo.com
2

Why we study Exploration Geology ?
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The aim of Exploration Geology
• To be able to understand the basic methods of geological exploration.
• To be able to understand the basic procedure of field geology survey.
• To be able develop knowledge, skill and attitude of methods of exploration such
as gravity, magnetic, seismic and exploratory drillings.
• To be able to understand the basic principles and methods of petroleum
exploration
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Short description of the course
Basic concept of surface and underground exploration geology;
Topographical surveying for geological work;
Geochemical method for petroleum and natural gas exploration;
Geophysical method in mineral explorations;
Drilling used in mining and geological work;
Seismic methods in mineral exploration;
Mud logging; Gamma ray logging and its basic principle and
interpretation;
Production of petroleum gas and gas condense;
Basic concept of GIS and Remote sensing
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Chapter-01
Understand the basic concept of Surface filed geology
1.1 Define Surface geological map.
1.2 Describe the basic procedures of Surface geological field mapping.
1.3 Mention the use of compass and clinometers.
1.4 Describe the methods of compass traverse.
1.5 Describe the method of outcrop studies.
1.6 Describe the drawing procedures of geological Surface mapping.
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1.1 Define Surface geological map.
What do you mean by geological map?
A map on which is recorded geologic information, such as the
distribution, nature, and age relationships of rock units (surficial
deposits may or may not be mapped separately), and the occurrence of
structural features (folds, faults, joints), mineral deposits, and fossil
localities. It may indicate geologic structure by means of formational
outcrop patterns, by conventional symbols giving the direction and
amount of dip at certain points, or by structure-contour lines.
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Surface Geological Map
A geological map is a precisely oriented scaled down diagram of the
earth’s surface. Its position on earth is shown by lines of latitude and
longitude or geographic bounderies. Sizes, orientation, and positions of
geologic features can be compared exactly with those of other maps
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1.2 Describe the basic procedures of Surface geological field mapping.
The art and science of geologic mapping involves the accurate depiction of contacts
between rock units on a base map of some sort. This is what it’s all about – being
able to draw a contact on a topo-map or air photo!
Your ability to construct a reasonable geologic map in the field fundamentally
depends on two things.
First, you must know exactly where you are on a topo-sheet or aerial photo at all
times – being lost is simply not an option!
Second, you must know where you are in the stratigraphic section.
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Procedure:
1. Keep track of your location on the map or aerial photo continuously as you traverse an area;
typically, you will want to plan your traverses perpendicular to strike, thus crossing as many
units as possible.
2. Orient the map in the direction that you are traversing: if you are walking east, then you should
be looking eastward on the map. Always look ahead to where you want to go next on the
topographic map, so when you get there you have already anticipated the topography - have a
plan!
3. When you encounter a contact between two mappable units, stick a pin through the map at
your location, turn the map over, circle the pinhole, and assign a station number to it; then,
enter the station number in your field notebook as the heading for entries relating to that map
station.
4. A typical station number might be abbreviated in the following manner:
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5. Typical notebook entries for a given station might include:
 Rock descriptions
 Identification of formations (or other mappable units) at the contact
 Nature of the contact (disconformity; gradational; fault; igneous; etc.)
 Strike-and-dip, trend-and-plunge, etc.
 Estimates of formation thickness
 Observations on topographic expression of rock units
 Structural cross-section sketch
 Stereonet sketch (to help visualize structural data)
 Sketch of complex outcrop relationships (Be sure to distinguish facts/observations from
interpretations)
Good field notes are richly illustrated with clean, clear sketches; one good picture is worth a
thousand words!
6. Next, draw the contact on your map as far as you can confidently see it, either on the
ground or the air photo (use a thin/sharp pencil with a soft touch, in case you need to
erase it). Do not forget the But don’t exaggerate the contact migration in valleys. The
contact location on your map should be accurate not generalized or theoretical. Your map
IS data. e of V’s, but
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7. Then move on quickly to the next contact. Remember, try to cover as much
ground as possible each day and NEVER plan to return to the same outcrop later
– chances are, you never will. Also, don’t stash your daypack expecting to return to
it later. Once you get to a new spot, you may see something that dictates a
different route than you planned on. Carry all your gear with you, all the time
(this is a basic USGS rule of mapping).
8. To save time and energy, plan your traverse so it crosses the structural grain at a
high angle (perpendicular to strike). Work back and forth over an area in a series of
traverses, spaced according to the topography and complexity of the geology.
9. Take advantage of hilltops to check your mapping, refine your contacts, refine your
traverse route, and predict contacts on the next leg of your traverse. Sometimes in
rugged, high mountains, the view from a peak may be your only way to map cliffs,
cirque headwalls, and other inaccessible places. In such instances, a good pair of
lightweight field binoculars may be your best friend (the so-called “Swiss rock
hammer”).
10. On your geologic map, depict the hinge lines of folds at the point of maximum
curvature and be sure that your strike-and-dip data support the interpretation. Use
medium-weight blue lines for fold hinges.
11. Use heavyweight red lines for faults and apply the appropriate design for different
fault types (e.g., barbs in the hanging wall of thrust faults).
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What to map during geological mapping?
The features recorded are the following:
• Rock types and Contacts
• Shape of the rock bodies
• Note on the sequence and relative ages
• Note on the primary porosity and permeability
• Note on the weathering and their patterns
• Note on the depositional or magmatic flow features
• Structures including
a) Folding - dip, strike, deformation, orientation of grains
b) Joints – attitude, size, open or closed
c) Faults – look for slickensides, fault gouge, breccia and their visible displacements.
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Uses of Geological Maps
A Geologic map helps to protect groundwater resources.
The geologic maps are also used for habitat prediction.
Geologic maps are used to evaluate the mineral resources.
Geologic maps are also used to delineate the landslide prone areas.
Geologic map guides to delineate the earthquake-prone areas and help in damage
prediction.
Geologic map delineates volcanic hazards and aids in the mitigation of earthquake
damage, cyclone damage, tsunami damage, etc.
Geologic maps show the locations of exploring sand and gravel resources.
Geologic maps identify the economic resources and mining areas.
A Geologic map guides transportation planning.
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1.3 Mention the use of compass and clinometers.
What is clinometer compass?
The clinometer is an optical device for measuring elevation angles above
horizontal. Compass clinometers are fundamentally just magnetic
compasses held with their plane vertical so that a plummet or its equivalent
can point to the elevation of the sight line.
What is clinometer compass?
A compass is an instrument used for navigation and orientation that shows
direction relative to the geographic cardinal directions, or "points". An
inclinometer or clinometer is an instrument for measuring angles of slope
(or tilt), elevation or depression of an object with respect to gravity.
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Uses of Compass
A compass is used for several different purposes including:
 Determine direction to a destination or landmark.
 Stay on a straight course to a destination or landmark, even if you lose sight of it.
 Avoid obstacles in the path to the destination or landmark.
 Return to your starting point.
 Pinpoint locations on a map and in the field.
 Identify what you are looking at in the field or on a map.
 Orient a map.
 Plot points on a map.
 Plot route of travel on a map.
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Parts of a Compass
The basic parts of a base-plate compass are described below and illustrated in
Figure.
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 Magnetic needle.
 Housing with cardinal points and degrees.
 Orienting arrow.
 Orienting lines.
 Index line.
 Direction of travel arrow.
 Base plate.
 Magnifying lens.
 Declination adjustment screw.
 Clinometer.
 Sighting mirror.
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1.4 Describe the methods of compass traverse.
Traversing is a method of making observation of outcrops along a path
across a country. It is a method to be repeated in roughly parallel
alignment with the earlier traverse. This method helps in covering the
ground in detail. Traverses are pre-determined rout contacts and other
geological features are extrapolated between the traverses and top
map of the geology of the area is prepared.
The major traversing methods adopted during geological mapping are:
a) Cross-section traverses
b) Stream and ridge traverses and
c) Road traverses.
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1.5 Describe the method of outcrop studies.
An outcrop or rocky outcrop is a visible exposure of bedrock or ancient
superficial deposits on the surface of the Earth.
Features
Outcrops do not cover the majority of the Earth's land surface because
in most places the bedrock or superficial deposits are covered by a
mantle of soil and vegetation and cannot be seen or examined closely.
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Description of Outcrops Study:
Outcrops allow direct observation and sampling of the bedrock in situ for geologic
analysis and creating geologic maps. In situ measurements are critical for proper
analysis of geological history and outcrops are therefore extremely important for
understanding the geologic time scale of earth history.
Some of the types of information that cannot be obtained except from bedrock
outcrops or by precise drilling and coring operations, are structural geology
features orientations (e.g. bedding planes, fold axes, foliation), depositional
features orientations (e.g. paleo-current directions, grading, facies changes),
paleomagnetic orientations.
Outcrops are also very important for understanding fossil assemblages, and paleo-
environment, and evolution as they provide a record of relative changes within
geologic strata.
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1.6 Describe the drawing procedures of geological Surface mapping.
Geological mapping is the process of making observations of geology and structure
in the field and recording them on a base map and reproduce. It is the form of a
geological map. The information recorded must be factual and thorough based on
objective examination of rocks and exposures.
There are several methods adopted during this process as traversing. Following
contacts and exposure mapping is the methodology adopted. This involves
mapping of poorly exposed region with indications of rocks from soils, vegetational
guides, topography and geomorphology and structure. Contours are the major lines
of trace involved during surface geological mapping.
A geologic map thus show the following:
• Distribution of rocks at the surface
• Geologic Structure
• Cross section in distributions of the rocks in the subsurface
• Age relation
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Surface mapping methods:
Mapping superficial Deposits, Drilling, logging and geophysical measurements,
underground mapping, pitting, trenching, augering and loaming are some of the
subsurface mapping method adopted during surface geological mapping.
What to map during geological mapping:
• The features recorded are the following:
• Rock types and Contacts
• Shape of the rock bodies
• Note on the sequence and relative ages
• Note on the primary porosity and permeability
• Note on the weathering and their patterns
• Note on the depositional or magmatic flow features
• Structures including
a) Folding - dip, strike, deformation, orientation of grains
b) Joints – attitude, size, open or closed
c) Faults – look for slickensides, fault gouge, breccia and their visible displacements.
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Drawing procedures of geological Surface mapping
The procedure of drawing a section consists of three steps:
1. Drawing a Topographic Profile
2. Determination of Dip and Strike
3. Construction of Geological Structures.
Step # 1. Drawing a Topographic Profile:
a) Suppose it is required to draw a topographic profile along a XY line on the
geological map. The map is first folded along the XY line on a drawing paper. A
horizontal line equal to the XY line is drawn, which serves as a base line to the
Geological sections to be made over this line.
b) The folded map is placed and the positions of the various contour lines along XY
lines are marked. From these points vertical lines are drawn their length being
proportional to the values of corresponding contours as per the scale of the
map. Then a Free Hand Curve joins their tops.
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Topographic Profile:
The vertical lines drawn above the base line are not desired and therefore should
be removed.
Step # 2. Determination of Dip and Strike:
a) Generally on Geological maps both the contour lines as well as boundaries of
rock beds are shown. To determine the dip of a rock bed by graphical method
such a contour is selected which cuts the particular rock boundary at two
points.
b) A line called Strike line joins these two points. Two Strike lines from contours
of different values are drawn for the same boundary. Then the distance
between them along XY line is measured.
c) And a line having the same length is drawn on the drawing paper somewhere
below the profile already made. From one end a perpendicular of length equal
to the strike of interval is constructed as per the scale of the map.
d) The angle formed by joining its top with the other end of the line will be the
dip angle. And its directions will be from the strike line of higher value to the
one that has the lower value. In this way dip of various rock beds shown on the
map are determined.
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Step # 3. Construction of Geological Structures
a) Now the map is folded along the XY line and is placed over the base line of the
profile.
b) The points of intersection of the boundary lines between different beds and the
XY line are transferred. These points are then projected to the surface profile.
From these points lines are drawn according to the Dip of the respective
boundary surfaces. This is usually done by drawing angles of Dip first at the
base line and then drawing parallel lines from the corresponding points at the
surface profile.
In the section thus constructed, the various structures present are completed as
follows:
i. If unconformity is present, an undulating line shows its plane.
ii. If a fold is present, anticlinal or synclinal structures are made accordingly.
iii. If a fault is present, strata must be shown dislocated along it.
iv. Dykes are shown running vertically. Sills are shown running parallel to the
bedding planes.
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Any Question of the Topic?
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THANKS TO ALL
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Understand the basic concept of Surface filed geology

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