GEOPRESSURED AQUIFERS AND _GEO THERMAL GRADIENT IN THE CHAD FORMATION IN BORNO STATE NIGERIA
GEOPRESSURED AQUIFERS AND _GEO THERMAL GRADIENT IN THE CHAD FORMATION IN BORNO STATE NIGERIA
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Date
1987-07
Authors
ASKIRA, Muhammad Tukur
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Abstract
Temperature maps were produced based on the data
collected on:
(a) Water temperatures from 63 boreholes tappinq water
from the artesian aquifers of the Chad Formation,
(b) Mean annual ground surface temperature for the state.
Temperatures of ground surface and water in the borehole.
were plotted on X-axis against depths to the mid screen
positions in boreholes on Y-axis of a graph. Based on
this, the map of the geothermal gradient was produced.
The map shows NW _ SE elongated geothermal anomalies
possibly correspond to troughs in the basin or correspond
to fracture zones through which intrusions took place or
represent concentrations of radioactive materials in the
sediments or in the basement below; while the cool
anomalies correspond to the ridges in the basin.
Using the graphical extrapolation method, the temperature
maps at 100m above mean sea level, at sea level.
-100m below mean sea level and at -200m below mean
sea level were produced.
The geothermal gradient in the basin ranges between
2.00 and 6„00 oC/100c and there is a general trend that
the gradients are higher towards the lake.
Areas with higher gradients reflect higher water
temperatures and this affects the PH and Eh o
rm artesian waters have low pH values and this
coupled with the high temperatures, increase the dissociation
rates of some elements (eg. Fe++ end Na+ ) and
salts. The higher iron concentrations in the waters
from the Chad formation aquifers could therefore be
related to the high temperatures.
Description
A THESIS SUBMITTED TO THE POSTGRADUATE SCHOOL,
AS PARTIAL FULFILMENT FOR THE AWARD OF MASTER
OF SCIENCE (HYDR0GE0LOGY) DEGREE IN THE DEPARTMENT
OF GEOLOGY, FACULTY OF SCIENCE, AHMADU BELLO
UNIVERSITY, ZARIA, NIGERIA.
Department of GeologyFaculty
of Science
Ahmadu Bello University
Zaria, Nigeria
Keywords
GEOPRESSURED AQUIFERS,, _GEO THERMAL GRADIENT,, CHAD FORMATION,, BORNO STATE,, NIGERIA