GEOLOGY AND STRUCTURAL EVOLUTION OF THE AREA WEST OF MAHUTA PART OF ZURU SCHIST BELT, SHANGA SHEET 73SE NORTHWESTERN NIGERIA
GEOLOGY AND STRUCTURAL EVOLUTION OF THE AREA WEST OF MAHUTA PART OF ZURU SCHIST BELT, SHANGA SHEET 73SE NORTHWESTERN NIGERIA
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Date
2017-11
Authors
MBITSA, KITHA
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Abstract
The study area is located within the northwestern part of Zuru Schist Belt, which is the largest schist belt in northwestern Nigeria. This research involved a detailed analysisof mesoscopic structures and petrographic descriptionof the majorlithological units. The major rocks in the study area are quartz-mica schist, medium grained granite and quartzitewhile the minor rocks arethe mica-schist, quartz veins, pegmatites and aplite dykes that have a dominant NE-SW trend. Both ductile and brittle structures were identified in the study area, with folds,lineations and foliations constituting the ductile structures while the brittle structures are joints and faults. The structures were analyzed through geometric, kinematic and dynamic analysis.These are orientatedin E-W, NW-SE, NE-SW and N-S directions. Rose diagram of lineaments revealed major NW-SE and NNE-SSW trends. The main type of jointthat dominated the study area is an orthogonal joint with a dihedron angle of 90°; and a local stress rotation model is suggested for their formation. Dynamic analysis of normal faults revealed the orientation of the three principal stress asσ1 (87/087), σ2 (02/222) and σ3 (02/312) while their kinematic axes are P-axis (compressional =87/087), T-axis (tensional=02/312) and B-axis (transitional=02/222). The study area was subjected to polyphase deformation. The phases of tectonic deformations have been recognized from the structuresand classified as D1, D2 and D3.The first phase (D1) was associated with the deformationof anS0bedding and development of S1schistosity foliation and low-lying and obliterated minor F1 folds which occurred during the Eburnean. The second phase (D2) involved heterogeneous deformation which gave rise to an S2 crenulation foliation of the earlier S1 cleavage and F2 major tight to isoclinal folds occurred during the early stage of the Pan-African orogeny while the third deformation phase (D3) is associated with the formation of F3 folds and brittle structures such as dextral faults, normal faults and joints which occurred at the late stage of the Pan-African orogeny. Strain analysis confirmed that the study area was affected by heterogeneous deformation as evident from the varying orientations of fry haloes andwide range (1.22-2.90) of average axial ratio.
Description
A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES
AHMADU BELLO UNIVERSITY, ZARIA, IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF MASTER OF SCIENCE
DEGREE IN GEOLOGY
DEPARTMENT OF GEOLOGY
FACULTY OF PHYSICAL SCIENCES
AHMADU BELLO UNIVESITY,
ZARIA, NIGERIA
Keywords
GEOLOGY,, STRUCTURAL EVOLUTION,, AREA WEST,, MAHUTA,, ZURU SCHIST BELT,, SHANGA SHEET 73SE,, NORTHWESTERN NIGERIA