4.0 STRUCTURES
Within the geologic environment (Area
of study), the major geologic structures observed are fold, faults, dyke,
foliation and vein/veinlet. However, the analysis of the structure was carried
out with detailed measurement and interpretation.
4.1 FAULTS
These are structures displacement of
geologic units, due to tectonic activities. They are found in many location. It
serves as channel through which server eruption can take place.
It
can be used to detect change in colour of some minerals which show some
movement. Within location11 are dextrital fault of about few cm displacement
and the trend is North-South.
4.2 FOLDS
These
are observed in almost all the location visited, they are mainly asymmetrical
folds as seen in location within the basement complexes.
Fold
also signifies the evidence of movement and it occurs as a result of tectonic.
4.3 LINEATION
This
is the arrangement of mineral grain in a linear orientation with distinguished
boundaries. Lineation can be diagnosed as a structure formed due to flowage
structure of magma. This structure is most visible in gneisses and schist
activities.
4.4 FOLIATION
This is the alignment of platy
minerals like micas and feldspars. They are found in the areas of gneiss and
migmatite complexes and at the schist belt.
Foliation
is one of the major features that are seen in metamorphic environment and it is
almost well pronounced in many of the location visited during this studies.
Finally,
the general trend is N – N direction which signifies that it controls the
younger granite in Jurassic age.
4.5 VEINS/VEINLET
This
is a joint filled with quartz minerals or they are quartz –feldsparthic
component seen to have been filled by some minerals. In some areas they appear
to be continuous which may be due to tectonic displacement. These structures are seen in many locations like 1, 6, 5 and 11
respectively. It is called veinlets when it is less than 4mm.
4.6 TECTONIC STRUCTURE
These are structure in the rock which
have resulted due to series of movement associated with earth disturbance. They
are said to be as a result of tectonic or orogenic activities. Examples of
tectonic structure are faults, folds, joints etc.
4.7 DYKES
These
are tabular intrusion that cuts across the basement discordantly, apart from
this intrusion of the older granitic complex which were include among the major
rock units of the basement complex and the younger granite complexes.
Others
were ring dykes of rhyrolite and aplite composition with characterized
porphyritic and aplitic texture as observed in location 2. Others are quartz
dyke, quartz-feldsparthic dyke as seen in location 4 these are known to be the
major structural characteristics of the basement complex i.e migmatite and
granite.
4.8 XENOLITHS
Actually, this is resistant relict of
rock fragments that intro magma so when this rock solidified to form rock this
fragments are included into the rock.
It
is important to note that this rock characteristic was observed in the older
granite, most especially in location 10 i.e Bazange along kiffi road.
Table 5: Showing the
different xenoliths where measure in terms of their dimension, the measurements
reads thus
S/No |
Different xenoliths where measure in terms
of their dimension
|
|
1
|
40cm - 29cm
|
|
2
|
40cm - 27cm
|
|
3
|
22cm - 14cm
|
|
4
|
21cm - 7.5cm
|
4.9 PINCH
AND SWELL STRUCTURES (BOUDINS OR BONDINATES)
These sansase–shaped
structures are commonly developed and quartz–rich layers in the migmatic
gneisses and schists. These layers alternate with less competent ones which are
rich in micas.