EXPLORATION FOR

GEOTHERMAL RESOURCES

USING GEOLOGICAL

STRUCTURES-FAULTS

BY

CHARLESON NAMANDWA ELIYASI

GEOLOGICAL SURVEY OF MALAWI

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OUTLINE

• Introduction

• Structural setting of the study area

• Surface manifestations

• Methodology

• Relationship between faults and geothermal springs

• Fault density analysis

• Discussion

• Conclusion

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INTRODUCTION

MALAWI’S GEOGRAPHICAL

LOCATION

• Located in the SE part of

Africa

• Within within latitudes 90s and

180s and longitudes 32

0e and

360e

• The Study area is located to

the Northern part of Malawi

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Source: Google map

STRUCTURAL SETTING

• The area lies at the meeting point of three major

mobile belts formed during the orogenic

episodes.

• The Ubendian mobile belt: originates from the

Sw-Tanzania and extend into Malawi in a SE

direction.

• Irumide belt of Zambia: well pronounced in the N

& and Southern province of the Malawi rift.

• The Mozambique is the last mobile belt that

affected the country including northern Malawi.

• This was followed by the rifting episodes and

initiated the Malawi rifting.

• Geothermal occurrences in Malawi are

influenced by these tectonic activities.

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SURFACE

MANIFESTATIONS

• Surface

indicators/manifestations

are in form of warm and

hot springs.

• Surface temperatures

ranging from 300C to over

700C

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Source: Field photo

CHIWETA

METHODOLOGY FLOW CHART

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FAULTS ORIENTATION AND RELATIONSHIP

BETWEEN FAULTS AND GEOTHERMAL

SPRING OCCURENCES

Faults overlain on

SRTM DEM (A)) and

Rose diagram (B)

showing two main

prominent NE-SW,

NW-SE trending

pattern and less

prominent NS

trending pattern

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FAULT SETS ASSOCIATED WITH

GEOTHERMAL SPRINGS

• Known geothermal

spring locations and

their temperature,

border faults and major

faults were overlain on

SRTM DEM (arrows

show areas where

higher temperatures

were recorded)

• High temperature

geothermal springs

located within border

faults (above 700C)

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FAULT DENSITY ANALYSIS

• Fault density analysis is a method that is used to calculate the number

of faults per unit area

• Areas with more faults per unit area are considered as high fault

density areas while those with less faults per unit area , low density

areas

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FAULT DENSITY ANALYSIS CONT’D

• The Density analysis

showed high occurrence of

geothermal springs in high

density areas, followed by

medium density areas.

• In terms of percentage: out

of 12 geothermal spring

sites 50% of them occur in

high density areas, 42% in

medium density areas and

8% in low density areas

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DISCUSSION

• The study has shown that the orogenic processes that affected the

area resulted into formation of structures such as faults which have

two main NW-SE, and NE-SW general orientation and less pronounced

N-S orientation.

• It was also noted that the general occurrence of geothermal springs

mainly follows a similar trend.

• Geothermal spring occurrences in the study area are mainly controlled

by two sets of faults namely major faults and border faults.

• High temperature geothermal springs are located in border fault zones

• Exploration for geothermal resources in the study area should be

concentrated in high and medium fault density zone areas.

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CONCLUSION

• It is possible to use geological structures such as faults for

geothermal exploration

• The technique can be applied to other areas of similar geological

setting.

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THANK YOU ALL FOR YOUR ATTENTION

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STRUCTURAL SETTING

• The area lies at the meeting point of

three major mobile belts formed during

the orogenic episodes.

• The orogenic episode was followed by

rifting and faulting within the Malawi rift.

• Ubendian –originates from the Sw-

Tanzania

• Irumide belt of Zambia

• The Mozambique

• This was followed by the rifting episodes

and initiated the Malawi rifting.

• Geothermal occurrences in Malawi are

influenced by these tectonic activities.

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FAULTS

• Faults were digitized from the geological map of Malawi using arc Gis

software 10.2 and a shapefile was created. it was displayed on SRTM

DEM data to see how it correlates spatially with the structural features

(figure 5a). the shapefile containing faults was exported from arc gis to

PCI Geomatica software and saved as AutoCAD vectors in a data

interchange file (dxf) format in order to be compatible with rockworks

software where the rose diagrams were plotted. the rose diagram

(figure 5b) was plotted in rockworks using the linear algorithm under

the utilities function.

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ROSE DIAGRAM

• A Rose diagram is a circular histogram plot which displays directional

data and frequency of each class (PRABU ET AL., 1964). These

diagrams have been used in many studies to define structural trend.

for instance CHENRAI, (2012) used rose diagrams to interpret

geological structures in koh samui area in gulf of thailand. further,

prabu et al., (2013) used rose diagrams to analyse orientation of

lineaments in the mapping of lineaments for groundwater study in

india.

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• SRTM-SHUTTLE RADAR TOPOGRAPHY MISSION

• A HALF-GRABEN IS A GEOLOGICAL STRUCTURE BOUNDED BY A FAULT ALONG ONE SIDE OF

ITS BOUNDARIES, UNLIKE A FULL GRABEN WHERE A DEPRESSED BLOCK OF LAND IS BORDERED

BY PARALLEL FAULTS.

•

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OROGENIC PROCESS

• OROGENY REFERS TO FORCES AND EVENTS LEADING TO A LARGE STRUCTURAL

DEFORMATION OF THE EARTH'S LITHOSPHERE (CRUSTAND UPPERMOST MANTLE) DUE TO THE

INTERACTION BETWEEN TECTONIC PLATES. OROGENS OR OROGENIC BELTS DEVELOP WHEN A

CONTINENTAL PLATE IS CRUMPLED AND IS PUSHED UPWARDS TO FORM MOUNTAIN RANGES,

AND INVOLVE A GREAT RANGE OF GEOLOGICAL PROCESSES COLLECTIVELY

CALLED OROGENESIS.[1][2]

•

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