GENESIS OF TOURMALINIZATION IN DUTSEN DANBAKOSHI AREA, SHEET 56 (MUSAWA S.E) N.W NIGERIA
GENESIS OF TOURMALINIZATION IN DUTSEN DANBAKOSHI AREA, SHEET 56 (MUSAWA S.E) N.W NIGERIA
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Date
2013-03
Authors
GEZAWA, Jamilu Garba
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Abstract
Field mapping in Dutsen Danbakoshi was carried out using topographical map of Musawa SE
sheet 56 on a scale 1: 50, 000 and the quartz-tourmaline ridges were further mapped on a scale
of 1: 10, 000 to study it in a more detail. Petrographic studies were conducted using both
transmitted and reflected light microscope. The geochemical analysis of 21 representative
samples was carried out using X-ray fluorescence, inductively coupled sector field mass
spectrometry and mass spectrometry.
Field mapping reveals that the area is underlain by Older Granite, Metasandstone, and Diorite as
the major rock types. Quartz-tourmaline ridges occur as minor intrusive. These rocks have been
deformed; sheared with the joints trending N-S to NNE-SSW, which coincided with the pattern
of the Pan-African basement structures.
Petrographic studies have shown that the granites are composed of quartz, microcline and biotite
as major minerals; the Diorite is composed of plagioclase, hornblende, quartz and biotite. The
Metasandstone consists mainly of quartz and feldspar. The quartz–tourmaline is principally
composed of tourmaline and quartz.
Geochemical and isotopic analyses results show that SiO2 in granites to be 72.71-67.30 wt%,
diorite 48.38-38.90 wt% and quartz-tourmaline 57.97-35.41 wt% while K2O in granite 6.98-4.43
wt%; diorite 1.08-0.02 wt% and quartz-tourmaline 0.01-0.19 wt%. The trace element
composition shows enrichment of Sr (1200-0.036 ppm), Rb (319-0.038 ppm), Ba (1000-0.04
ppm). The rare earth elements in the samples show enrichment in La (87.9-12 ppm), Nd (64.1-
9.5 ppm), Ce (163-0.11 ppm), Eu (1.66-0.13 ppm), Tb (1.5-0.3 ppm), Ho (1.6-0.3 ppm), Lu
(0.68-0.11 ppm), and boron isotope (σ 11B) in the quartz-tourmaline ranges from -15.84‰ -
17.92‰
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Various discrimination diagrams were used to classify the rock types and their tectonic settings.
The granites plot in syncollisional field. Based on REE distribution pattern and their enrichment
of LREE and depletion of HREE, they are of continental or crustal origin. The negative Eu
anomaly is probably indicating the formation of both the host rocks (granite and diorite) and
quartz-tourmaline in Upper Proterozoic metasedimentary environment. The negative Ce
anomaly is signifying the formation of quartz-tourmaline under oxidizing conditions.
The host rocks (granite and diorite) and quartz-tourmaline are both enriched in LREE and
depleted in HREE with negative Eu anomaly indicating syngenetic relationship.
Boron isotope values (σ 11B) of quartz-tourmaline ranges from (– 15.84‰ to – 17.92‰) thus
signifying continental or crustal origin of the boron enriched residual fluids which led to the
tourmalinization and also indicating possible dual provenance of tourmaline to be high pressure
metamorphic rocks or granite and pegmatite. The boron isotope values also suggest that the
granitoids from which the B enrich residual fluids were generated were probably originated as a
result of the reworking of preexisting basement complex rocks.
Description
A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES,
AHMADU BELLO UNIVERSITY ZARIA,
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD
OF A
THE DEGREE OF MASTER OF SCIENCE IN GEOLOGY
DEPARTMENT OF GEOLOGY,
FACULTY OF SCIENCE
AHMADU BELLO UNIVERSITY, ZARIA
NIGERIA
MARCH, 2013
Keywords
GENESIS,, TOURMALINIZATION,, DUTSEN,, DANBAKOSHI,, NIGERIA