Birr~R GEOLOGICAL SURVEY -,Llli!RYSERVICES

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REPUBLIC OF BOTSWANA

ANNUAL REPORT

OFTHE

GEOLOGICAL SURVEY

DEPARTMENT

FOR THE YEAR

1981

PRli'\TED BY THE GOVERl\'MEI'T PRl!'\TER, G,\BOROl'\E, BOTSWM":,\

)

_/--

1. GENERAL

1.1 Introduction

The organisation of the department was amended

slightly by the amalgamation of the Regional Mapping

and Economic Geology divisions into a single Field

Geology division. In recent years it was apparent that

strict separation of the functions between field

mapping and certain aspects of economic geology was at

times more artificial than real and the amalgamation

improved the allocation of duties between staff. The

Geophysics unit was upgraded to an operational division,

largely in response to the increasing amount of geo­

physical work being undertaken throughout Botswana,

particularly in the Kgalagadi. The three main divisions

of Field Geology, Hydrogeology and Geophysics continued

to be supported by the technical service branches of

the Chemistry Laboratory, Mineral Dressing Laboratory,

Drawing Office, Library and Records, and Drilling; plus

Administration. A departmental organisation chart is

included in this report.

The serious shortage of professional staff

experienced in 1980 was to SOITe extent overcome during

1981 and by the year's end only three professional

posts, that of geophysicist, chemist and coal geologist,

remained vacant. Mr. C.D.G. Black arrived in June to

1

fill the vacant Deputy Director post and Dr. C. Mortimer

joined the department in April as Assistant Director.

Both officers are on secondment from the Institute of

Geological Sciences, U.K. Other posts were filled by

Dr. D.T. Aldiss (geologist), Mr. S. Bruno (hydrogeologist

on secondment from Holland) and Mr. D. Buckley (hydro­

geologist). Mr. Sekwale returned after successfully

completing his post graduate studies in U.K. and took up

his duties as hydrogeologist. The duties of principal

administrative officer were taken over by Mr. M.D. Tau

on transfer of Mr. L. Botlhole to the Department of Water

Affairs on January 1st 1981.

In the Field Geology division staff shortages

continued to hinder progress in the geological field

mapping programme. With the completion of work on the

Mmathethe sheet early in the year field surveys came to

a halt and only recommenced in August with the initiation

of a full re-survey of the Tsetsebjwe area (2228A), in

preparation for the production of the first full colour

edition of this sheet. Other field work undertaken was

directed towards the evaluation of industrial minerals,

with particular emphasis being placed on brickclays and

carbonate deposits. The division continued to be

responsible for monitoring the exploration activities of

the private sector, as well as advising the Minister on

the issue of new prospecting licences. Private sector

interest in mineral exploration continued at a

2

very satisfactory level throughout the year. Seventy­

three prospecting licences were on issue in January and

seventy-eight were active by the year's end. Expenditure

on prospecting by the private sector in licence areas

outSide the existing mine leases exceeded eight million

pula.

The Hydrogeology division was fully staffed by

the year's end, a staffing situation that was a welcome

relief from the acute shortage of personnel that has

existed in this division for several years. The

complement of five hydrogeologists devoted most of their

efforts towards major groundwater studies in the

eastern part of the country and the production of the

1: 500 000 hydrogeological reconnaissance maps,

temporarily halted during the year, will hopefully

re-commence in 1982. The U.K. funded bi-lateral aid

project, "Evaluation of Undergrcund water Resources" was

completed in March and a final report prepared.

The activities of the Geophysics division were

largely devoted to the on-going groundwater search

studies and providing input into various donor funded

mineral exploration projects. These technical aid

projects were largely undertaken in the Kalahari area

and have a strong geophysical input in their work

programmes. The technical service branches functioned

satisfactorily throughout the year. The Chemistry

Laboratory, as well as providing routine analyticsl

3

support work, conducted a field oriented hydrogeo­

chemical project in the Molopo Farms area, whereby

analyses of groundwater were examined for concentration

of elements which may be related to sub-Kalahari bedorck.

The new Mineral Dressing Laboratory is proving to be a

well used addition to the department's facilities and

the work load in the laboratory was largely derived

from the on-going programme of evaluation of brickclay

deposits. An X-ray diffraction unit has been donated

by the Japanese government and after installation will

form a very useful item to the laboratory's equipment.

The equipment of the drilling unit was improved by

the replacement of old compressors with three new units.

The Ingersoll Rand rig was re-conditioned by the

manufacturers but it is apparent that it is reaching the

end of its useful life and will need replacing in the

very near future. The Hydreq Gryphon rig was used

successfully in drilling groundwater exploration holes

and for ftost of the year this rig was used almost

exclusively for this purpose.

The departmental activities received strong support

from several donor funded bi-lateral aid projects.

These projects were related to groundwater search (GS10,

funded by the U.K.) to mineral exploration (GS17, funded

by Japan, West Germany and the U.K.) and to further

elucidation of the sub-Kalahari geology (GS12, the final

phase of the airborne magnetic survey, funded by Canada).

4

All these projects require departmental support in either

expertise, personnel, transport or equipment and they

are all providing much new information on the geology

of Botswana. The department's facilities have been

supplemented and, in some directions, greatly expanded

by equipment purchased from donor funding, such as GS18,

Geological Survey Equipment, funded by West Germany, as

well as other items supplied from the Canadian and

Japanese projects.

With the improved equipment, a return to almost

full staffing, departmental activity, through its own

resources and those of bi-lateral aid projects, will

continue to make satisfactory input into the broad

development and growth of Botswana.

In May the department was honoured by a visit of

H.E. the President and Mrs. Masire, who were accompanied

by Dr. Chiepe, Minister for Mineral Resources and Water

Affairs, Mr. C. Blackbeard, Minister for Works and

Communications, Mr. Tibone, Permanent Secretary, Mineral

Resources & Water Affairs, Mr. Steenkamp, Permanent

Secretory, Office of the President.

5

FIELD GEOLOGY Assistam Director ,-_Or

"IN EX:~~I:~TiON~"APPING Geologist

Ge~~~ist Ger9isi . Technic<ll ASs!.

""m' Geologist Officer

I Publication OffICer

I

'T STA/TA STAjTA STAjT,A

"- --

HYOROGEOlOGy Principal Geoklgisl

I Seninr

Geologist

I Geoklgist

131

STA/TA 16)

GEOPHYSICS Principal GeologISt

I Senior

Geoklgis\

Geologist I Electronics (2) Engmeer

, :TA/TA TA 13) 110)

I RECORDS MANAGEMENT REGIONAL GEOLOGICAL SALE Of PUBUCATIONS MAPPING

SAMPLE STORAGE GfOTECHNICAL SURVEYS

GEQCHRONOtOGY MINERALOGY/PETROLOGY

El r tQPHVSICAl SURVEYS ECTRONIC EQUIPMENT

DESIGN AND MAINTENANCE

ADMINISTRATION OF REGIONAL HYOROGEOLOGlCAl PRIVATE SECTOR MAPPING WATER BOREHOlE

EXPlORATION RECORDS O{~ARTME~! EXPLO~TlON _ GRO~~QWAI~B STUp~

MINISTRY OF MINERAL RESOURCES AND WATER AFFAIRS DEPARTMENT OF GEOLOGICAL SURVEY

DIRECTOR J 1---- ?el${lnal

SllCfetalY

DEPUTY 0'iRECTiiR I

ADMINISTRATION

I Principal

Adminisll11tion officer

Personal Secretary

Admin. O!hcel Admin. Officer Admin.Officfr

~ro_) A"1.ffi ~"'"I""I °t"ll SAA/A S"hand TYPISt $AA/AA SAJi/AA

Typist

STAFF ACCOUNTS STORES TRANSPORT

REGISTRY TYPING

CHEMISTRY LABORATORY

Principal Chemist

,-l, Chemist

I Senior

TeChnical OffICer

Chemist Chemist

Tethni:al 0"",

slAllA 12)

i Chemist

OR~WING OFFICE

Chie! Tedmical 0"""

lCaf1ography) I

Senior Senior Technical Technical OffICer Officer

I Technital

OffICer

sllllA SIA~IA 12) { )

PRODUCTION OF MAPS DRAWINGS AND

PHOTOGRAPHS fOR PUBliCATIONS AND INTERNAL REPORTS

DRILLING SECTION

1 Senior Senior

Technical Technical OffICer OffICer

lA lA

ORILlING FOR

MINERAL LABORATORY

Technital Officer

I STAlTA

12)

MINERAL EXPLORATION GROUNOWAHR

STRATIGRAPHIC SURVEYS GEOTECHNlrAL SURVEyS

ROCK AND MINERAL SAMPLE PREPARATION

INDUSTRIAL MINERALS TtSTING

. __ .. __ .

"

5. HYDROGEOLOGY DIVISION

5.1 Introduction

A large part of the year's programme was taken up

with field work for the Serowe groundwater study.

Towards the end of the year, when three more hydro­

geologists were appointed, long outstanding commitments

were re-generated and new projects were initiated.

The consultative work always rendered to various

bodies inside and outside Government was continued

throughout the year at almost the same level as in the

past.

Dr. Goldberg remained as Principal Hydrogeologist

and was assisted throughout the year by the Senior

Hydrogeologist Dr. Neurnann-Redlin, both officers

seconded from West German Government Service.

Towards the end of the year there was a great

improvement in the staffing situation. Through the

appointment of Messrs S.A. Bruno from the Netherlands

(6.10.81) and D. Buckley from the U.K. (23.12.81) the

number of professional staff increased to five after

Mr. M. Sekwale successfully passed his higher degree

(MSc) course at the University College in London and

re-joined the Division in October.

Mr. C. Cheney (GS10 project staff member) remained

20

with the Survey for a further three months after

completion of the project on the 31st March. His

contract was extended specifically for setting up

equipment for the determination on core samples of

aquifer parameters such as porosity and permeability.

5.2 Staff Deployment

For most of the year Dr. Goldberg and Dr. Neumann­

Redlin were mainly engaged in three major groundwater

studies. Early in the year the consultative work to

the Gaborone Additional Water Supply Exploratory

Programme by Messrs. Wellfield Consulting Services (pty)

Ltd. in the Ramotswa area was brought to an end. The

Letshana Groundwater Resources Study was completed by

Dr. Neumann-Redlin. His conclusions regarding the

potential for groundwater development are included in

his report CNR/2/81 (53 p., 50 fig., 5 tab., 3 encl.).

In February the work on the Serowe Water Supply

Augmentation Study commenced which kept the then two

hydrogeologists alternately occupied until the end of

year, finally assisted by Mr. Sekwale after his return

from his overseas study tour. For the study 20 holes

were drilled by the Hydreq-Gryphon rig of Geological

Survey, the metreage totalling 1759 metres. In addition

three observation holes were cored with the Boyles 17A

rig, with a total metreage of 342 metres. Altogether

21

135 km of lines were cut for geophysical surveys along 6

traverses. 2340 hours of test pumping were carried out

and 52 water samples taken.

Since the activities of the two professional staff

were completely absorbed by this study the hydrogeological

mapping programme had to be postponed until the time when

additional staff arrived late in the year. Consequently

no other map sheet was compiled. However Dr. Neumann­

Redlin was able to carry out final checks on the proof

prints of sheets Nos. 1 and 2 and so complete the

editorial work. Due to technical conversions of the

printing machinery at Government Printers these two maps

were subjected to format changes and, therefore, could

not be published before the end of the year. With the

arrival of Mr. Bruno the compilation work on sheet No. 7

was recommenced.

Dr. Goldberg apart from attending to all divisional

activities, was also engaged in various types of

consultative work to Central Government, other Government

institutions, parastatal organisations and the private

sector. Special prominence was rendered to the Central

Eastern Botswana Water Resources Study, Orapa Mine 'Water

Supply Review and Extension Study, Domestic Water Law

Consultancy and meetings of the Water Apportionment

Board.

Within the last week of the year Mr. D. Buckley upon

22

request from the Department of Water Affairs started

working on two groundwater assessment studies for Mochudi

Bnd Kanye villages water supplies. The work involved

desk top studies comprising the evaluation of all

available data on groundwater occurrences and quality

that is stored in the Geological Survey archives or

contained in reports, coupled with field investigations.

Mr. Bruno, besides compiling map sheet No. 7,

carried out preliminary studies for the assessment of

the groundwater potential around Hukuntsi for the

Ministry of Agriculture's Research Station and the

Matsheng Land Use Plan Project, i.e. work which has to

be continued in 1982.

23

HYDROGEOLOGICAL RECONNAISSANCE MAP OF THE REPUBLIC OF BOTSWANA AT SCALE 1 : 500 000 PROGRESS IN MAPPING AS AT 1. 1.1882

Published [ill]] Under production in Drawing Office

a AI press Under preparation ........

El] Awaiting production D ...... Prepar"ion 1981/83 in Drawing Office

mJ Under revision ----

26°

6. GEOPHYSICS DIVISION

6.1 Introduction

A considerable proportion of the division's activities

were related to assisting the various development projects

funded and staffed from overseas donor countries. As a

result of this commitment to the development projects

additional geophysical investigations were largely confined

to hydrogeophysical studies.

Several new items of geophysi=l equipment were

received during the year and are listed below. The

equipment was purchased as part of the GS18 development

project which was funded by the Federal Republic of

Germany.

6.2 Development Projects

GS10 Evaluation of Underground Water

This project was completed during the year and the

final report included a contribution from the geophysics

division (R.J. Peart) outlining the use of hydrogeophysical

techniques in Karoo lithologies and the use of geophysics

in the delineation and extrapolation of Karoo aquifers

into those areas covered by recent Kalahari sediments.

In addition Technical Note No. 10 and Report No. 3 were

25

completed early in the year (see 8.3.1).

GS12 Aeromagnetic Survey Phase III - Ground Follow-up

Assistance to this CIDA-funded project continued

throughout the year. The interpretation of ground

magnetic anomalies to locate drill targets and estimate

depths and magnetic susceptibilities was conducted for

all sites prior to drilling~ In some cases additional

field surveys were conducted to locate accurately the

drill site on the ground.

One additional site, located some 10 kms. east of

Maun along the old Francistown Road, was surveyed

magnetically to provide an alternative drill site. A

total of 40 kms. of magnetic traversing located a magnetic

high presumed to be associated with the northeasterly

extension of the Toteng diabase.

Early in the project it was realised that the lack of

water would hinder drilling operations in some localities,

particularly in the north west. To overcome this problem

water well drill sites were located near sites 12 and 12A

using electrical and magnetic techniques.

GS17 Mineral Exporation of the Kalahari

Assistance was given to the three bilateral aid teams

engaged in this project. In addition to logistical

26

support of the field parties and the loan of geophysical

equipment, a field survey was conducted for the Molopo

farms project to ascertain the thickness of Kalahari cover.

Eleven vertical electrical soundings conducted in the

northern sector of the project area indicated a close

correlation between depth to bedrock and total longitudinal

conductance. Further soundings will be conducted throughout

the project area, prior to drilling, to eliminate those

areas of thick Kalahari cover.

6.3 Departmental activities

Serowe Underground Water Study

An area to the west and southwest of Serowe was

surveyed geophysically to assist in the location of test

well-sites for the provision of a village water supply.

73 kms. of line were cut and surveyed magnetically and

a total of 36 electrical soundings were conducted at

selected localities to determine the thickness of the

basalt and Cave sandstone. Areas of shallow and thin

basalt were identified and several borehole sites

recommended. In the southern part of the survey area,

where basalt is absent, the resistivity values indicated

that the Cave sandstone was relatIvely thin, with

transition beds and red beds predominating.

27

Hukuntsi Underground Water Study

Cut lines were prepared and surveyed magnetically in

an area around Hukuntsi to locate possible areas suitable

for hand-dug wells. This preliminary phase was conducted

in December and further work, to include electrical

soundings and traversing, will be conducted in the new

year.

Selebi-North geophysical study

A geophysical survey was conducted over the Selebi­

North prospect in north-east Botswana. The surveys were

conducted with the full cooperation of B.C.L. and the

objectives were twofold; firstly to test the newly

acquired Pulse E.M. and I.P. equipment over known massive

sulphide deposits and secondly to locate a possible

extension of the Selebi-North ore body.

The equipment trials proved successful in locating

the known ore body, and supported the geological inter­

pretation. Unfortunately no obvious extensions to the ore

body were located although a faint anomaly on later

channels of the Pulse E.M. warrants further investigation

using the Crone Deep-EM system.

Pan Study

Further geophysical traverses (gravity) were conducted

28

it!' Illl Wl 11'11

" It! ,Ill

design consultancy. In early December a local firm of

structural engineers was appointed to consult on the new

design. A review of core held on site at Lobatse 'head-

quarters was undertaken to assist in producing realistic

design options. It transpired that the Survey had at

that time approximately 5,300 boxes of core, with an

aggregate length of about 49 kilometres and weighing

about 260 tons.

7.2 Evaluation of Underground Water Resources (GS10)

(U.K. funded technical co-operation)

The early part of the year was devoted to completing

the computer storage of hydrogeological data from the

study area and to writing up the final report. The

project was formally completed on 31st March.

The project leader Mr. J.L. Farr, returned to U.K.

leaving Mr. C.S. Cheney, who had been granted a 3-month

extension, to set up a rock permeability and porosity

testing facility.

This aim was only partially realised due to delays

in delivering of equipment. However, the final report

was completed and sent for printing and binding.

32

Two portable pH meters

Scintrex HGG-3 mercury analyzer

Scintrex UA-3 uranium analyzer

Stainless steel fume cupboard

Dionex - 10 ion chromatograph

Perkin-Elmer 2280 atomic absorption spectrophotometer

8.1.2 Analytical Development

A scheme of rapid instrumental silicate analysis

was introduced which allowed determination of all

traditional parameters with a slightly reduced precision

in less than a quarter of the time of previous methods.

The old methoffiwere retained for cases where higher

precision is required.

A method was developed using differential pulse

polarography for the determination of chromium in natural

waters down to 50 parts per billion.

A pyrolysis apparatus was constructed which, together

with background corrected atomic absorption, enabled the

direct determination of mercury in soils to be made at

the parts per billion level.

8.1.3 Assistance with Development Projects

GS10 - Underground Water Evaluation

Until the completion of this project on 31st March

41

P. Francks continued to assist with programing the Hewlett

Packard 9845 for hydrogeological data storage and

manipulation.

GS12 - Aeromagnetic Survey

A limited amount of assay work was carried out.

GS17 (UK) - Mineral Exploration of the Kalahari

Some 8600 samples were analyzed for Cu, Ni, Zn and Cr.

GS17 (W. Germany)

Owing to delays in the sampling programme only a few

samples were analyzed for Hg.

8.1.4 Internal investigations

Molopo Farms Hydrogeochemistry

Field work on this project was undertaken from 8th

May until the end of July. Analysis was carried out as

far as possible in the field using the mobile laboratory.

Forty one samples were analyzed for 10 trace elements in

addition to the usual range of major ions. Contamination

from borehole equipment was shown to be negligible and

chromium and nickel anomalies indicated the existence of

the ultrabasic body suggested by geophysics. Several

42

Sheet No. 2425D Gaborone (2nd Colour Edition)

Sheet No. 2525B Lobatse (2nd Colour Edition)

8.2.2 Hydrogeological Mapping

The following maps at a scale of 1: 500 000 were

under production for printing in full colour.

Sheets Nos. 1 and 2

8.2.3 Kalatraverse Maps

The four colour maps in this series were produced

and lithographed. These maps at a scale of 1: 250 000

are included in the Kalatraverse 1 Bulletin and depict

the surface geology and sub-surface geology of Rysana Pan

and Deception Pan.

8.2.4 Map of the Karoo in Botswana

The map at a scale of 1: 2 000 000 was produced and

printed in full colour.

8.2.5 Special purpose Maps

Two maps showing areas held under prospecting licences

and mining leases as at 1st January, 1981 and 1st July,

1981 respectively were produced and printed. Two maps

47