Chimala Geological Mapping Field Report

My Geological Mapping Report

MINERAL RESOURCES INSTITUTE (MRI)

DODOMA, TANZANIA

DEPARTMENT OF GEOLOGY AND MINERAL EXPLORATION

INDUSTRIAL PRACTICAL TRAINING (IPT)

AT CHIMALA

LOCATION: MBALALI DISTRICT IN MBEYA REGION

STUDENT NAME:    PROTASE HERMAN              
REG NO:                    650 MID 12
COURSE PROGRAM:     INDUSTRIAL PRACTPCAL TRAINING (IPT)
                                            GET04206
INDUSTRIAL SUPERVISOR:   MR. NGOWI AND MR. GEORGE
DATE OF SUBMISSION:           27TH SEPTEMBER,  2013

Signature :......................

ACKNOWLEDGEMENT

This report is the result of the efforts of many. Firstly I would like to give my special thanks to our almighty God, he is everything to us. Also I would like to express my appreciation to the following people and organization that had contributed a lot in my field work, first of all I wish to express my deeply felt gratitude to The Principle of Mineral Resources Institute (MRI) Mr. S. A. Chiragwile for his effort, our supervisors Mr. Dickson Ngowi and Mr. George together with our bus driver Mr. Ridhiwan Msuya without forgetting Mr. Makena who was our IPT coordinator.
. 
Finally, I would like to express my sincere thanks to my parents and my relatives for their support, as well as my fellow students, especially my group members; I would like to appreciate their cooperation and understanding during field work.
 
ABSTRACT
Chimala is the area geologically composed of different lithologies of all rock types. The area we concentrated was located at the UTM of 0627000E/9024000N, 0631000E/9024000N; 0627000E/9018000N, 0631000E/9018000N.
Main purpose of conducting this field is to describe and indentify the different lithologies, rock structure, rock unit and mineralogical composition that constitute different outcrops. Mainly sedimentary rock is the type we observed in our concentrated area, sedimentary rocks observed are like shale, sandstone and conglomerate. Nevertheless the other objective was to create a geological map of the mapped area and its cross-section.
Also we had excursion at Mambi Village, Mlima Nyoka, Kongolo quarry, Isalaga and Songwe hot/warm springs were we observed vesicular basalt (olive basalt and scoriacious basalt), pyroclastic materials (bombs and lapilli tuff),  phenolite, travertine, limestone and warm springs.


 
ABBREVIATION
GPS Global Position System
UTM Universal Transverse Mercator
IPT Industrial Practical Training
E Easting’s
N Northing’s
M Meter
Mt        Mountain













 

Table of Contents

ACKNOWLEDGEMENT ii
ABSTRACT iii
ABBREVIATION iv
CHAPTER ONE 1
1.0 INTRODUCTION 1
1.1 LOCATION AND ACCESSIBLITY 1
1.1.1 LOCATION 1
1.1.2 ACCESSIBILITY 1
1.2 CLIMATE AND PHYSIOGRAPHY 1
1.2.1 CLIMATE OF THE AREA 1
1.2.2 PHYSIOGRAPHY 1
1.4. METHODOLOGY OF INVESTIGATION AND EQUIPMENTS 2
1.4.1 METHODOLOGIES 2
1.4.2 INSTRUMENTS AND EQUIPMENT 2
1.4.2.1. Compass 2
1.4.2.2. GPS (global position system) 3
1.4.2.3. Base map 3
1.4.2.4. Geological hammer 4
1.4.2.5 .Note book 5
1.4.2.6. Pencil, colored pencil, scaled rulers and maker pen 5
1.4.2.7. Sample bag 5
1.4.2.8. Hand lens 6
1.4.2.9. Tracing paper 6
1.4.2.10. HCl bottle 6
1.4.2.11 Camera 6
1.4.2.12 Magnet 6
1.4.2.13 Bush knife 6
CHAPTER TWO 7
2.0 Geology of the area/ Regional 7
2.1. The ubendian rocks 7
2.2. The ukingani rocks 7
2.3. The bukoban rocks 7
2.3.1 The lower Buanji 7
2.3.2 The Upper Buanji 8
CHAPTER THREE 9
3.0 LOCAL GEOLOGY OF THE MAPPED AREA 9
3.1.1. ROCK FORMATION 9
3.1.1.1. SEDIMENTARY ROCKS 9
3.2 NAMES OF ROCKS WHICH MAKE LITHOLOGIES OF THE MAPPED AREA ARE:- 10
3.2.1 Sandstone 10
3.2.2 Shale 10
3.2.3 Conglomerate 10
3.2.4 Alluvium 10
3.3 NATURE OF THE OUTCROP AND TOPOGRAPHIC EXPPRESSION 12
3.4 LITHOLOGICAL STRUCTURE 12
3.4.1 Bedding 12
3.4.2 Laminations 12
3.4.3 Ripple marks 13
3.4.4 Folds 13
3.4.5 Joints 13
3.4.6 Veins 13
3.5 FIELD RELATIONSHIP 15
CHAPTE FOUR 16
4.0 GEOLOGICAL HISTORY OF THE AREA 16
4.1 DESCRIPTION OF GEOLOGICAL EVENTS IN THE NATURAL SEQUENCE 16
4.2 THE MODE OF ORIGIN OF VARIOUS ROCK UNITS AND IMPORTANT STRUCTURES 16
4.2.1 Mode of origin of various rocks 17
4.2.2 Important structures 17
CHAPTER FIVE 18
5.0 CONCLUSION AND RECCOMENDATION 18
5.1 CONCLUSION 18
5.2 RECCOMENDATION 18
5.3 EXCURSION 18
REFFERENCE 24


 

CHAPTER ONE

1.0 INTRODUCTION
It was Saturday, 8th June, 2013, the day I travelled from home, Dodoma to Chimala, Mbeya. My journey began earlier in the morning at 06.00a.m, by bus. It was a bit long and tiresome journey but late in evening around 07.30p.m I arrived at Chimala Village. Our IPT program started on Monday, 10th June, 2013 with about seven days of training by our supervisor.
1.1 LOCATION AND ACCESSIBLITY
1.1.1 LOCATION
Chimala is at Mbarali district found in Mbeya Region. It is located within a quarter degree sheet 024/03. Also it is found within latitude 80 45’ to 90 00’ south of the equator and longitude 340 15’E of the Greenwich or Prime Meridian and it’s about 76km from Mbeya town.
1.1.2 ACCESSIBILITY
Chimala is accessible by road transport (Tanzania–Zambia/Malawi highway) and railway (TAZARA railway). During mapping some parts were remote due to thick thorny bushes, big river and higher mountains with steep slope but were successful mapped.
1.2 CLIMATE AND PHYSIOGRAPHY
1.2.1 CLIMATE OF THE AREA 
The climatic condition of the area is wet on September up to April and then dries from May to August. Also the annual mean temperature as about 220C and the rainfall starts on November and end up to April. Daytime maximum temperature is around 27 ºC.
1.2.2 PHYSIOGRAPHY
The area is characterized by well-vegetated low hills, mountains and flat lowland. The Southern part is uplifted or elevated. It is highland consisting of hills and mountains there are two higher mountains namely Mt. Kidofi and Mt. Chaufukwe. The Northern part is lowland with shrubs and mangrove swamps, mainly composed of massive alluvial deposits (sediments) which make this part contain fertile soil hence common for large scale paddy (rice) plantations.
 The area of Chimala is well drained by many streams most of which are seasonal, and three main rivers; Chimala River (in the west), Ruaha river (in the middle of the area) and Kimani River (in the east). Chimala All Rivers are running to the north; hence provide water for irrigation in the paddy plantations. River and Kimani River join Ruaha River to form one great Ruaha River.

The area is sparsely inhabited bush country with bushes, sparse short trees and grasslands especially in low land and in most parts of the area. There are tall trees and fewer grasses in the area around the mountain slopes. Human habitation is restricted to villages along the main Dar es Salaam to Malawi/Zambia road (Tan-Zam highway). Limited agriculture is practiced along the road and in some irrigated areas in the Northern part.


 1.3 OBJECTIVES OF THE STUDY
The main objectives of study which was done at Chimala are:
• To determine the structure of the rock in the chosen area such as joints, fault, fold and other structures.
• To measure different structures like joints, fault and fold present in the outcrops.
• To indentify different rock type that was present within the mapped 
• To determine the mineralogical composition of different rocks.
• Identification of the nature of the environment that the rocks are formed such as stream, road cut and uplifting environment.
• To measure the orientation of the bedding plane and read the altitude of the outcrops. 
• Creation of geological map and geological section by using data gathered during field work according to collection and identification of the representation sample. 
1.4. METHODOLOGY OF INVESTIGATION AND EQUIPMENTS
1.4.1 METHODOLOGIES
Our area of interest was rectangular in shape of about 4km × 6km, and we divided it into squares of about 200M sided. Our mapping was done by traversing zigzag line from north to south and back. The line and direction of traverse was perpendicular to the strike so as to descover contacts and new lithology easily. Data were collected after every 200M and where a geological feature and structure was encountered. 
1.4.2 INSTRUMENTS AND EQUIPMENT
The instruments and equipments used during field observation were;
1.4.2.1. Compass
We had two main geological compasses namely; Brunton compass and Suünton compass. Compasses are used for determining and measuring direction as well as bearing of place, position or location. Also compasses consist of inclinometer/clinometers used for measuring dip of the outcrop. Brunton compasses consist of bubble type and Suünton compasses contain pendulum type inclinometer. Generally compasses were mainly used for measuring strike, dip and dip direction of the outcrop exposed also used in plague and trend measurements and taking bearing of the features. 
1.4.2.2. GPS (global position system)
It is used to determine location and elevation on the earth’s surface by using signals from selected satellites. It determines location coordinates in two different systems depending on the one desired. The coordinate system can be UTM or latitude and longitude system. We preferred UTM coordinate system in recording location data as it is the best for mapping. A GPS requires signals from at least four (4) satellites to record accurate information and must be in open space. For instance area covered by thick forest and the period of higher cloud cover interfere the accuracy of a GPS.
1.4.2.3. Base map
It is commonly a topographical map of the area of interest used in geological mapping as a base map as it shows various features and elevation in the area by the contour lines. The base map was used for preliminary study of the nature and structure of the area, orienting our position in the field and planning traverse lines/path during field work (mapping).
HOW TO USE A BASE MAP
Before working with the base map, the followings have to be taken into account;
1. Identifying the north part of the map,
2. Scale used on the map,
3. Recognizing and identifying symbols used on the map, by the help of a legend or a key of the map,
      4.   Coordinate system used (UTM or latitude and longitude).

WORKING WITH THE BASE MAP
• The map has to be oriented the north after identifying the north part of the map sheet, with the help of the north arrow present on the map. The compass is laid on the map sheet with its edge coinciding with the grid lines. The map sheet is rotated until its north part is the pointing in the same direction as that of the compass.
• The coordinates of our present location/position were read from the GPS i.e. 0628400E/9022980N.
• Finally we find our current location position on the base map using the coordinate obtained from the GPS (corresponding base map position) and we marked/note it.

  
Figure no. 1 d). Orienting in the field
1.4.2.4. Geological hammer
It was used to break rocks in order to get fresh sample for identification and interpretation of the observed rock. And collecting samples for further study in the off the field.
Fig. geological Hammer Fig. a GPS
Fig. Hand lenses fig. Brunton compass

 Fig. Suünton compass
Illustration of some geological tools and instruments



1.4.2.5 .Note book
It is used to record or documents all observations during field work.
1.4.2.6. Pencil, colored pencil, scaled ruler and maker pen
These were used for sketching, drawing and labeling different geological features and rock types/ name in the field and during office work. Mark pens were used for labeling samples.
1.4.2.7. Sample bag
Used for carrying rock sample after collecting them from the concentrated area and has been approved not less than 500g. A sample bag were of plastic type as it reduce contamination of samples
1.4.2.8. Hand lens
The hand lens is used for rock analysis in the field to identify lineation, mineral composition and rock texture. We had two lenses; a 10× magnification lens and a 20× magnification lens. Also Suünton compass provided has lens on it.
1.4.2.9. Tracing paper
This was used for sketching and drawing various features such as contact between lithologies, dip and strike in the field and during office work.
1.4.2.10. HCl bottle
This was used to carry diluted HCl acid, which is used for testing the presence of carbonate (calciate minerals) in the rocks. It helps especially on the identification of rock such as Dolostone, Marble, Limestone and Travertine.
1.4.2.11 Camera
This is used for taking photos of interesting features, structures and rock in the field. The GPS (fig no. 3) we had consisted of a 5M pixel camera which help on taking photos.
1.4.2.12 Magnet 
A Magnet was used to test the presence of hematite and magnetite minerals (iron content) in a rock (outcrop) 

1.4.2.13 Bush knife
Bush knife are usually for clearing some bushes, thorny and trees which are obstacle to the traversing way.

CHAPTER TWO

2.0 Geology of the area/ Regional
The geology of Chimala is characterized by rocks which based on ubendian complex, Ukingan and Bukoban The ubendiani Rocks. The Ubendian rocks are intruded by a number of igneous suites of unknown age and are unconformably overlain by Neoproterozoic Bukoban Supergroup clastic over rocks (sediments) forming Buanji series. The basement area is bounded immediately to the north by the extensive Quaternary alluvial deposits of the Buhoro Flats.

2.1. The ubendian rocks
These rocks consist of Micaceous schist, gneiss, migmatites, quartzite anesthetic body and large gabbro-anesthosite mass which extends to upangwa and ukinga. The anesthetic body belongs to amphibolites faces of metamorphism.
The contact of granitic rocks and migmatities are transitional and they are defined by parallel lineation of mafic dots and dark minerals.
2.2. The ukingani rocks
These are manifested rocks of pre-Bukoban age. In this region there is granite which is post-organic showing some rapakivi texture. These are oval orthoclase crystal; occurred in mantle with soda rich plagioclase. Pseudoporphy are believed to represent transfused sediments of the ukinga series.
2.3. The bukoban rocks
This rock consists of shale made of clays, also sandstone, conglomerate and little quartzitic sandstone. Not only that but also in this three rocks regions there are another series of rocks that have crossed all three rocks and these three rocks are as follows:-
The Buanji series that are made of assemblages of continental sediments with lava which lies uncomfortably on rocks of Ubendian and Ukingani super group. These Buanji series are divided into lower, middle and upper Buanji.
2.3.1 The lower Buanji
This series is composed of reddish shale occasional quartzite sandstones horizon. Also these series shows a thin development of conglomerate composed of pebble of jasper and agate.



No table of figures entries found.This is in lower kimani area showing the development of cupriferous shale contain metatorbenite in places. Also there is a thin band of green shale with numerous bands of dolomitic limestone occasionally pyritifferous.
2.3.2 The Upper Buanji
Chaufukwe Mountain is large comprised of greenish, brownish, grayish or buff-colored shale mudstone and siltstone. The andesite capping Chaufukwe is highly vascular or amygdaloidal and its base also is much terruginised. The Buanji is folded into broad syncline pinching to the north. The folds trends approximately 100% which are parallel to gofio thrust on the southern age of the mapped area.

CHAPTER THREE

3.0 LOCAL GEOLOGY OF THE MAPPED AREA
The mapped area was located at the UTM of 0627000E/90224000N, 0631000E/9024000N; 0627000E/9018000N, 0631000E/9018000N.
This was our area of interest which includes the area of Kimani Village, Kimani River and Mbuyuni Village. The area is rectangular in shape where mainly sedimentary rocks were rocks observed.
3.1.1. ROCK FORMATION
The type of rock within the concentrated area which we observed is sedimentary rock. These rocks found in this area depend on the nature of originality and it environment that lead to its formation. The area is dominated by three rocks which were mappable units, which are shale, sandstone, and conglomerate. The formation of these sedimentary rocks was due to lithification of sediments.
3.1.1.1. SEDIMENTARY ROCKS
Clastic sedimentary rocks;
These are sedimentary rocks formed from cemented sediments grains that are fragment of pre – existing rock such as igneous rock, metamorphic and sometimes other sedimentary rocks.
The rock fragments can either be identifiable pieces of rock such as pebbles of shale or individual mineral grains such as sand sized quartz and feldspar crystals loosened from rocks by weathering and erosion processes. Examples of these rocks are sandstone, shale and conglomerate.

Chemical sedimentary rocks;
These are other types of sedimentary rocks, which are formed from precipitations of minerals from solutions. An example of such rocks are rock salt formed once sea water evaporated leaving high concentration of salt minerals in water, chemical precipitation can be also induced by organisms for instance the limestone sedimentary rocks can form by the precipitation of calcite minerals within coral reefs by corals and algaes and other marine  microorganism skeleton.

Organic sedimentary rocks;
These are formed from the accumulation of organisms remains example of organic sedimentary rocks are coal rock form from the burial and compression of the plant remains. Example of organic sedimentary rocks is Coal.

3.2 NAMES OF ROCKS WHICH MAKE LITHOLOGIES OF THE MAPPED AREA ARE:-
3.2.1 Sandstone
Sandstone is a medium grained clastic sedimentary rock formed by the cementation of sand grain. Any deposit of sand can lithify to sandstone.  Rivers deposit sand in their channel and wind piles up sand into dunes which can be lithified to form sand stone. Sandstone is commonly formed in environments where large amount of sand can accumulate, such as beaches, deserts, flood plains and deltas.  Sandstone has a mineralogical composition of quartz and feldspar. Sandstone outcrops were observed in the eastern part of the area and also form the bed of the river Kimani in most parts. We observed sandstone outcrop at different location such as at 0630943E/9023860N, at 0629833E/9021550N, at 0629235E/9021934N, at 0629307E/9021817N and at 0629020E/9022286N.
3.2.2 Shale
Shale is a fine grained clastic sedimentary rock notable for its splitting capability (called fissility), splitting take place along the surface of very thin parallel layers (called laminations). Most shale contains both silt and clay and are so fine grained that the surface of the rock feels smooth. The silt and clay deposits that lithify as shale accumulate on lake bottoms, and beside the river. Shale also contains quartz, iron oxide and feldspar. Most parts of our area of interest is covered with shale outcrops; especially in the southern, western and some of the eastern part of the mapped area. In the western part of the area near Chaufukwe Mountain, shale outcrop is highly weathered and greenish in colour due to composition of Malachite. Shale observed in western Kimani River is very thinly laminated (example at 0627970E/9018755N) while those in eastern Kimani River is relatively thinly laminated (example at 0631052E/9022559N).

3.2.3 Conglomerate
Conglomerate is also a clastic sedimentary rock containing large rounded particle sediments like sand and pebbles. The space between the particles is generally filled with smaller particles and chemical cement that binds the rock together.  We encountered conglomerate outcrops at UTM 0628907E/9022408N and at 0630878E/9020998N.
3.2.4 Alluvium
Small amounts of coarse alluvium are found along some of the larger river courses, but the main accumulations are the extensive silty deposits which form the Buhoro flats region to the north of the mapped area. These alluvium deposits provide the raw material for the formation of fertile soil for agriculture.

Fig. Sandstone Fig. Conglomerate
Fig. Grayish/greenish Shale Fig. Malachite rich Shale
Fig. Chaufukwe Mountain Fig. Dolostone boulder

Other rocks found in Chimala area
The area of Chimala is constituted of rock of all types; sedimentary rocks, metamorphic rocks and igneous rocks. The western parts; Chaufukwe Mountain and the area of Chimala River have igneous rocks. The middle parts; Kimani River area and Kidofi Mountain have sedimentary rocks while the eastern part; Mabadaga area has many varieties of metamorphic rocks.
Igneous rocks such as andesite, Diorite, granodiorite, granite, basalt were observed in the western part. Along Chimala River, there are igneous rock boulders of different rock such as Diorite, granodiorite, basalt, and gabbro with pinkish granite dominant. At Chaufukwe mountain andesite, dolostone, marble and shale were observed. In the eastern part, Mabadaga area especially along Nyangulu River, metamorphic and igneous rocks and boulders of different rocks such as granitic-gneiss, amphibolites, gabbro, granites, quartzite, schist and tonolite. Metamorphic rocks are dominant in the area of Mabadaga which is in the active shear zone as we saw mylonitic rocks. Our group did not concentrate in the area with Metamorphic and igneous rocks.
3.3 NATURE OF THE OUTCROP AND TOPOGRAPHIC EXPPRESSION
The type of rock which found on the area was sedimentary rocks. Also there we encountered various boulders of metamorphic and igneous rocks.
The outcrops observed in the mapped area had been exposed due to tectonic movement, erosion and weathering process. Example at UTM 06307999E/9019505N the rock exposed by stream (erosion) and at UTM 0630965E/9019336N the rocks exposed by weathering process.
3.4 LITHOLOGICAL STRUCTURE
Both primary and secondary structures were observed. Primary structures are structures which are formed in the rock during the time of rock formation while, secondary structures are structures which are formed in the rock after the rock has been formed. Primary structures we encountered in the field were bedding, laminations, and ripple marks. Secondary structures we observed were faults, folds and joints.
3.4.1 Bedding
Sandstone is thickly bedded in most parts especially eastern and north eastern parts of the area. We observed thick bedding of sandstone at different location like at UTM 0628406E/9023010N. Shale is thinly bedded in the east of Kimani River while very thinly bedded in the west and south of the River Kimani.
3.4.2 Laminations
Lamination is common in shale as clay and silt sized minerals forming shale are diposted in thin layers which are lithified to form rock. Laminations are primary structures. In the area we mapped, the part eastern Kimani River shale encountered appear to be moderately and thinly laminated, for example at UTM 0630922E/9021855N with elevation of 1195M. In other parts especially near Chaufukwe Mountain (western part) we observed has very thin laminations.


3.4.3 Ripple marks
These are sedimentary structure formed by deposition of material and agitation by water (currents or waves) or wind. Ripple marks are primary structures. They are formed perpendicular to the direction of wind or water floor. We encountered formed on the sandstone outcrop for example at 0630799E/9019505N with elevation of 1111M, and 0629307E/9021817N with elevation of 1093M and conglomerate outcrops with ripple marks was observed at the location 0630878E/9020998N which is 1169M above the sea level.
3.4.4 Folds
Folds are wave like structures (wrinkles) which are produced by the deformation of bedding plane or foliation of the rock. They are secondary structures. We encountered simple folds in the area near Chaufukwe Mountain as in fig. 3(a) below.
3.4.5 Joints
These are fractures in the rocks in which there is no displacement or slippage of the blocks. We observed different joints in outcrop especially on sandstone at UTM. Joints were observed in most of outcrops; 0629307E/9021817N with dip, strike and dip direction (54-204-SE), 0629039E/9021183N with elevation of 1102M its measurement was (90-075-EW), Also joint sets were observed at different location such as 0630683E/9022854N with elevation of 1215M, 0631075E/9023078N with elevation of 1279M and at 0630683E/9022854N with elevation of 1093M
3.4.6 Veins
 This is the mass of mineral matter, deposited in the fissure, crack, or crevice of a body of rock, and differing in composition from the substance in which it is embedded. We encountered quartz veins in sedimentary rocks at different locations such as at 0629027E/9022415N with elevation of 1097M.

(a) (b)
c) d)
c)
Figure 3. Field photographs of some lithological structures. (a) Very thin laminated greenish shale with simple folds. (b) Ripple marks on sandstone outcrop. (c) Quartz vein. (d) Joint sets in reddish brown Shale. (e) Bedding in reddish brown shale outcrop.
3.5 FIELD RELATIONSHIP
The field relationship of our area is age relationship and contact between lithologies (contact relationship) example at UTM 0628370E/9022950N with altitude of 1096m above the sea level, 0630959E/9019181N with elevation of 1128M, 0629969E/9020603N with elevation of 1101M and 0630735E/9022884N with elevation of 1213M above the sea level, there were observable contracts between sandstone and shale. Conglomerate encountered were formed in relation to sandstone, this is because it occurs in combination with sandstone outcrop. Again conglomerate encountered has composition almost similar to that of sandstone, hence can termed as conglomeratic sandstone, as it might have been formed from sandstone. Also relationship is according to the age of formation, as we observed sandstone were on top of the shale outcrop. This signifies that in most part sandstone is younger than shale, therefore shale form basement of all lithologies. To some area shale is underlain by sandstone despite the fact that shale is older than sandstone, this is probably due to uplift and deformation. In the other hand Conglomerate encountered were the youngest of all.
Shale was encountered in the lowland and the whole of western part, where by shale is reddish brown in most parts of the area we mapped while in the area nearby Chaufukwe Mountain shale encountered were Grey greenish in colour as it occurs with Malachite mineral

CHAPTE FOUR

4.0 GEOLOGICAL HISTORY OF THE AREA
At Chimala, the long time ago it was covered by water where the river and sea was present before the formation of different lithologies around the area of Kidofi Mountains and Chaufukwe Mountain. As time goes sediments that were originated from breaking of various rocks existed in that area.
After the formation of sediments these sediment transported by water and wind from their origin to depositional area and the compaction and cementation of deposited sediments took place which later lead to formation of sedimentary rocks such as siltstone, sandstone conglomerate and shale hence these rocks were deposited in layer according to geological deposition.
When sedimentary rocks subjected to high temperature and pressure they change to another type of rock called metamorphic rock. Metamorphic rocks occurred in different type due to different grade of metamorphism.
4.1 DESCRIPTION OF GEOLOGICAL EVENTS IN THE NATURAL SEQUENCE
The sedimentary rocks that observed at the field were shale, sandstone and conglomerate. These rocks have been deformed in some areas and tilted due to uplift. The outcrops were originally horizontally bedded. This was observed in most parts of the area where by the outcrops are dipping to small angles about 2O to10O to the horizontal plain. For example at 0630962E/9019631N, 1140m elevation and 0629833E/9021550N, 1124m elevation sandstone outcrop observed with dipping of 2o but at 06300559E/9020133N, 1140m elevation sandstone has a dip of 10O while at 0628022E/9022051N, 1109m above the sea level; shale outcrop is dipping at 11O
4.2 THE MODE OF ORIGIN OF VARIOUS ROCK UNITS AND IMPORTANT STRUCTURES
Generally in our mapped area we observed sedimentary rocks. These rocks were originated from different manner.
4.2.1 Mode of origin of various rocks
The area was mostly dominated by Shale sedimentary rocks. The other sedimentary rocks that we observed in the field were sandstone and conglomerate.
The mode of their formation is as follow:
Weathering: the process of breaking or splitting of large particle or rocks into small fragment by either chemical or mechanical means.
Erosion: this involves the removal of loosen and weathered materials by moving agents like wind and water. As particles are disintegrated can be easy removed from one place to another by action of wind and water, this involve the removal of materials on the upper part of the earth surface from one place to another.
Transportation: the movement of sediment that have been disintegrated from one place to another by the means of moving water and wind.
Deposition: this is accumulation of sediment at the same place. This occurs mostly at the base of water bodies and where there is flat/gentle slope when the speed of moving water is reduced hence the carried load is released.
Lithification: refer to the compaction and cementation of sediment to certain which is last stage for the formation of sedimentary rock.
4.2.2 Important structures
The important structures that found at our area (Kimani area) which is between Kidofi Mountain and Chaufukwe were:
1. Joints: this is the fracture which occurs at any lithologies without any displacement.
2. Fold: this is fracture that formed when ductility rock undergoes compression force and process lead to syncline and anticline of the rock.
3. Beddings: refers to parallel alignment of plate minerals when the rock is subjected to external force (confining pressure).
4. Foliation:  rock strata, usually a roughly plane surface of a rock. Bedding occurs following the principle of stratigraphy.
5. Vein: this is the mass of mineral matter, deposited in the fissure, crack, or crevice of a body of rock, and differing in composition from the substance in which it is embedded.

CHAPTER FIVE

5.0 CONCLUSION AND RECCOMENDATION
5.1 CONCLUSION
Chimala is the area of very conducive geological content, the area consist of all the three rock types which are metamorphic, sedimentary and igneous rocks; hence good area for students and geological learning.  Most parts of the area are composed of sedimentary rock with shale as dominant outcrop.
Despite the successive mapping we faced some difficulties such as thorn dense forest which is the residence of dangerous animal like snake. The River was an obstacle to our mapping as it interfered traversing and added on difficulties on planning the traverse. Also there was shortage of some equipment like magnets, bush knives, GPS (Global position system), lack of first aid kit and a tape measure for logging sections; hence it was difficult during geological mapping then we have difficult in transport since our bus was not capable to accommodate all students, as the number of students was bigger than the number of seats.
5.2 RECCOMENDATION
My  advice is fore to the Industrial Practical Training (IPT) department to provide all essential field equipment for suitable field work so that some errors may be reduced during geological mapping is conducted. Also students have to be provided with first aid kit so that the danger to the one injured is reduces. Again I would like to advise our institute leaders to improve the means of transport, for instance purchasing a bus capable of accommodating the number of student in the trip to the fields. Finally we would like to see cooperation spirit between students and supervisors which will lead to reach the goals of the field works.
5.3 EXCURSION
On 18th June we had excursion with intention to visit Kongolo quarry, Songwe hot/warm springs and mapping different outcrops, features, structure and lithologies along Chimala-Mbeya road, under the supervision of Mr. Ngowi and Mr. George. Our first site to visit was Mambi village, located at E0589109M/N9028050M with 1178m elevation where we observed volcanic materials. Materials we observed were lapill tuff, ashes, and few bombs and blocks. To some parts ashes are overlaying lapill tuff. These are pyroclstic material resulted from violent volcanic eruption, they are very fine and grayish in colour. We also encountered fault; a normal fault with dip of 53° trending NE to SW.
a) b)
c) d)
Figure no.4: Pyroclastic material at Mambi village. (a) Ashes forming lapilli tuff. (b) And (c) a normal fault. (d) Volcanic bombs.
Then we visited Kongolo quarry allocated at UTM E0687641M/N9029770M with 1199m elevation. The quarry is under Tanzania Zambia Railway Authority (TAZARA). We observed extrusive igneous rocks called Phonolite with mineralogical composition of nephline, feldspar, dark mineral, mica and little/no quartz. Phonolite rocks are extracted; blasted and crushed for morram which is commonly used for railway and highway construction. They are very hard and durable rock with unique/easy identification due their sounding ring when hit each and spot marks (guinea fowl marks/spot like).
a) b)
Figure no. 5: Extraction of Phonolite rocks at Kongolo Quarry. (a) Area of blast rocks, which is done in bench style with each bench about 12M high. (b) Crushing plants/machines and gravels (output)
We left Kongolo quarry to Inyala hill which is located at 0573398E/9023968N with elevation of 1378M, where we observed igneous rock boulders of olive-basalt (basalt rich in olivine) dark in colour with mineralogical composition of olivine, pyroxene and plagioclase. The boulder also has vesicles.
We also visited Mlima Nyoka located at 0564671E/9016833N and altitude of 1751M and 06564623E/9016829N, where we observed volcanic material named lapilli tuff and the eruption of pyroclastic material which deposit with an irregular arrangement of layers. The outcrop is very wide approximately 100M and height of 50M forming the mountain, an outcrop is subsidized and well exposed due to road cut. These rocks are very fine grained, light-grayish in colour and mostly composed of quartz, feldspar and calcite. They were formed from a felsic magma.
a) b)
Figure no. 6: volcanic/pyroclatic materials and rocks at Mlima Nyoka (a) Lapilli tuff. (b) Volcanic materials deposited in irregular layer, exposed due to road cuts.

 Another excursion was done at the Islaga hill near Uyole, with UTM 0561982E/9017670N with the elevation of 1760M from sea level. We encountered another outcrop of extrusive igneous rocks highly vesicular, dark in color, and with composition of pyroxene, amphiboles, olivine biotite muscovite micas and feldspars named Scoriacious Basalt. At this location rocks are blasted for construction purpose.
a) b)
Figure no.7. Excursion at Isalaga hill (a) Scoriacious Basalt (highly vesicular basalt). (b) Isalaga hill with Scoriacious basalt
On 19th June, we visited Songwe hot springs which is located around 0520199E/9019185N and 1130M above the sea level. We observed emergence of geothermally heated groundwater from the ground (crust) forming springs at different position. Water from the springs join one another and form a steam (tributary) which joins Songwe River. The temperature of water from the springs ranges between 60ºC and 80ºC (by approximation) and contain calciate minerals. Springs are on top of the river valley. The Songwe hot springs are in the great East Africa Rift Valley, where movements and volcanic activities within the crust are active (active volcanic environment).
Formation/Occurrence of the hot spring
Hot springs are springs with water at a temperature substantially higher than the air temperature of the surrounding region. The source of water for hot spring is any meteoric water percolating through permeable rocks. When percolating water come in contact (meet) with hot rock become is heated and discharged from the ground. Most hot springs discharge ground water that is heated by shallow intrusion of magma in volcanic zones. Some thermal springs, however, are not related to volcanic activities. In such case, the water is heated by convective circulation: where by groundwater percolating downward reaches depth of a kilometer or more where the temperature is higher because of the normal temperature gradient of the earth’s crust.
We also observed limestone and travertine rock which are formed from calciate minerals carried in hot springs water. Hot water heated by hot rocks dissolves calciate (CaCO3) minerals when become in contact with rocks containing calciate minerals. Dissolved calciate minerals are carried in hot water to the surface. At the surface hot water looses its temperature, hence calciate minerals precipitate and solidify. Solidified calciates are compacted and lithified to form rocks. Rocks we observed at the hot spring area were young and therefore weak.
On the other hand, few kilometers from Songwe Hot spring there is extraction of travertine rocks which are used for making tiles for building floor and wall decoration and furniture.

a) b)
c) d)
Figure no. 8 Songwe Hotspring. (a) One of the hot springs with travertine forming around it. (b) The largest spring with calciate (whites) precipitated in the bed of a stream channel. (c) Travertine extracted, and carved into rectangular blocks read for transportation to tile industries.

REFFERENCE

 Harpum, J.R and Brown, P.E (1958) Geological map of quarter degree sheet 71 south west (CHIMALA). Geological survey department Dodoma.
 F.H.Lahee, Field geology-sixth edition
 George H. Daviss, Structure Geology of rock and regions.
 Marland P. Billing, Structural Geology third edition.
 Norris, W Jones Laboratory, Manual for physical geology, Third edition.
 Field note book.