Ulanga/Songea Districts

The HQ-P20656 is located between two districts of Ulanga and Songea.It is 169 km north east of Songea town in  Ruvuma which is in south east of Tanzania, from Songea it is accessible  through Songea-Mahanje road.

LOCAL GEOLOGY OF THE AREA WHERE THE LICENCE IS LOCATED

Based on lithological characteristics,the following rocks can be distinguished;
  1. Luwegu Formation
       a. Mbaliwali Member
       b. Ligombe Member

2. Lirondo Complex
       a Nygeya Unit
       b .Luhira Unit
       c. Itekela Unit

The Luwegu Formation
The Luwegu Formation consist of non-metamorphic sedimentary rocks. The Lirondo complex is composed of a vast of regionally metamorphosed rocks, including many types of gneisses, migmatites,amphibolites and other rock types. it is characterized by complicated tectonic structure

The Luwegu Formation is subdivided into two members.These rocks units are considered formal Lithostratigraphic units, as is expressed by their rank terms “formation and member”

The Ligombe member overlies the Mbaliwali member, so is supposed to be younger. The former consist of succession of grey clays,the alter of arkoses,arenites and conglomeratic sandstones.

The Mbaliwali member may be correlated with the Nambao member of Winkler(1973);likewise,the Ligombe member may be the equivalent of Njewe Formation.

In the East and Southeast, the Luwegu Formation is separated from the Lilondo complex by fault. In the northern part of the sheet, this fault is expressed in the Topography by large escarpment. In the southern part this fault is evident. Near the contact the sedimentary rocks of the Luwegu Formation may be tectonically disturbed. Further east, the rocks have a sub horizontal position

According to the strike of this fault, a relation to the East-African rift valley seems possible.
In the southwestern part of the sheet, flat lying rocks of the Luwegu overly unconformably the metamorphic rocks of the Lirondo complex.
Boundaries are inferred on basis of study of air-photogragraphs, contacts are checked on a few places only.

The mbaliwali member occurs in an elongated zone running north from the southern border of the sheet.

STRUCTURAL GEOLOGY & GEOPHYSICAL INTERPRETATION

Regionally passing from the southwestern to the northwestern part of the QDS 277 an eastward dipping succession gradually merges into rocks which dip in an approximate southeastward direction.

The fault, separating the Luwegu formation from Lirondo complex is expressed in the northern part the area by rather steep escarpment and is sharply defined. The fault trends approximately NNE-SSW.

The fault trends are partly characteristic for the great East African rift valley system and a mutual relation seems probable.

The coincidence of an eastward bend of schistocity in the gneiss of the Nyegeya Unit and an Eastward bend of the fault in the northeastern part of the area suggest that the location of the fault is at least partly dependent on the ancient Precambrian structures. On regionally scale, the same has been suggested by Holmes (1965)

METAMORPHISM
With the exception of the sedimentary rocks of the Luwengu Formation, all rocks of this area have been affected metamorphism

On the basis of mineral assemblages, two different stages of metamorphism can be distinguished.

1. An older stage o high-grade metamorphism in the amphibolite facies.

1. A younger stage of low grade metamorphism in thegreenschist facies.