Crustal evolution of the Southern Benin-Nigerian shield : insights from late post-orogenic lithium-cesium-tantalum (LCT) pegmatite mineralization
department or school: Science, Irving K. Barber Faculty of (Okanagan)
department or school: Earth, Environmental and Geographic Sciences, Department of (Okanagan)
data provider: DSpace
degree campus: UBCO
creator: Nweke, Nchekwube Dieudonne
issued: 2025-06-23T22:42:20Z
issued: 2025
related degree: Master of Science - MSc
degree grantor: University of British Columbia
description: Lithium-cesium-tantalum (LCT) pegmatites are a key source of economic lithium. The timing of LCT pegmatite crystallization within the context of an orogenic system (i.e., pre-, syn- and post-orogenic) appears to vary globally and exerts a primary influence on the distribution of lithium mineralization in orogenic belts. The recent advances in in-situ Rb–Sr mica geochronology have enabled the direct dating of lepidolite, a major phase in LCT pegmatites. When combined with in-situ Rb–Sr, Lu-Hf, and U–Pb geochronology on other related major and accessory phases, the timing of LCT pegmatite crystallization can be accurately determined and placed in the context of a region’s magmatic and thermometamorphic history. Here, we present new in-situ Rb–Sr, Lu–Hf, and U–Pb geochronology data and results of petrological modeling from an east to west transect of the Benin-Nigeria shield to constrain the timing of magmatism, metamorphism, and LCT pegmatite crystallization related to the Pan-African orogeny. Crystallization ages of Pan-African granites across our transect range from ca. 625–600 Ma. Magmatism is followed by a thermal metamorphic peak at ca. 550–530 Ma, as recorded by Lu-Hf systematics of post-kinematic garnet and monazite U–Pb. The southwesteern Benin-Nigeria shield cooled through biotite Rb–Sr closure temperatures at ca. 500 Ma. Lepidolite in an LCT pegmatite swarm found in the western part of our transect crystallized at ca. 489 Ma, consistent with post-orogenic pegmatite genesis. In the absence of the wide-scale detachment structures associated with orogenic collapse, we propose that the LCT pegmatites were generated by remelting of highly fractionated Pan-African granite due to post-orogenic thermal maturation of the Benin-Nigeria shield. Garnet-staurolite schists record a static increase in geothermal gradients from ~1040 °C/GPa to ~1160 °C/GPa. The cause of this late thermal pulse is not yet determined but may be associated with lithosphere delamination, the br…
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/91416
note: Crustal Evolution of The Southern Benin-Nigerian Shield: Insights from Late Post-Orogenic Lithium-Cesium-Tantalum (LCT) Pegmatite Mineralization by Nchekwube Dieudonne Nweke B.Sc., Chukwuemeka Odumegwu Ojukwu University, 2019 M.Sc., Chukwuemeka Odumegwu Ojukwu University, 2023 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE COLLEGE OF GRADUATE STUDIES (Earth and Environmental Sciences) THE UNIVERSITY OF BRITISH COLUMBIA (Okanagan) June 2025 © Nchekwube Dieudonne Nweke, 2025 ii The following individuals certify that they have read, and recommend to the College of Graduate Studies for acceptance, a thesis entitled: Crustal Evolution of the Southern Benin-Nigerian Shield: Insights from Late post-orogenic Lithium-Cesium-Tantalum (LCT) Pegmatite Mineralization submitted by Nchekwube Dieudonne Nweke in partial fulfillment of the requirements of the degree of Master of Science in Earth and Environmental Sciences Dr. Brendan Dyck, Irving K. Barber Faculty of Science – Department of EEGS Supervisor Dr. Kyle Larson, Irving K. Barber Faculty of Science – Department of EEGS Supervisory Committee Member Dr. Alessandro Ielpi, Irving K. Barber Faculty of Science – Department of EEGS Supervisory Committee Member Dr. Richard M. Palin, University of Oxford External Examiner iii Abstract Lithium-cesium-tantalum (LCT) pegmatites are a key source of economic lithium. The timing of LCT pegmatite crystallization within the context of an orogenic system (i.e., pre-, syn- and post-orogenic) appears to vary globally and exerts a primary influence on the distribution of lithium mineralization in orogenic belts. The recent advances in in-situ Rb–Sr mica geochronology have enabled the direct dating of lepidolite, a major phase in LCT pegmatites. When combined with in-situ Rb–Sr, Lu-Hf, and U–Pb geochronology on other related major and accessory phases, the timing of LCT pegmatite crystallization can be accurately determined and placed in …
has type: Thesis/Dissertation
date issued: 2025-09
is shown at: 10.14288/1.0449180
language: eng
degree discipline: Earth and Environmental Sciences
provider: Vancouver : University of British Columbia Library
publisher: University of British Columbia
rights: Attribution-NonCommercial-NoDerivatives 4.0 International
rights URI: http://creativecommons.org/licenses/by-nc-nd/4.0/
scholar level: Graduate
contributor: Dyck, Brendan
type: Text
identifier URI: http://hdl.handle.net/2429/91416