The research work “Geology and Petrochemistry of Granitic Pegmatites in Jema’a Field” is a systematic study of the pegmatites in relation to the adjoining granitoids (biotite muscovite granite, albite granite and granite aplite) with a view to understanding their geological and geodynamic evolution and subsequent economic potential through the behavior of rare elements. The field work was conducted on a scale of 1:50, 000. 33 rocks and mineral separates extracted from pegmatites were analyzed. The samples were subdivided into two parts; one part was analyzed using X-Ray Fluorescence to generate data on major and minor elements, while Instrumental Neutron Activation Analysis was used to generate data on trace elements. The other part of the samples was made into thin section for petrographic studies. Petrochemical and petrographic interpretations concur on the changes in colour of micas from brown biotite in granitoids to blue muscovite, to purplish green mica to purple mica in the pegmatites corresponding to increase in rare elements (Rb, Cs, Na, Ta, Nb, Ga) and volatiles (P, H2O, F) from the granitoids into the pegmatites. This constitute a fractionation trend. This is also strongly supported by fairly consistent increase in Aluminum Saturation Index (A/CNK), normative corundum, normative albite, Lost on Ignition (LOI), differentiation Index (DI) and corresponding decrease in Ba, Zr and Ti. The pegmatites contains more fluxes and liquidus depressing elements (P, H2O, F) especially phosphorus. The granitoids (biotite muscovite granite, albite granite and granite aplite) are therefore fertile, peraluminous, siliceous and S-type and are parental to the pegmatites. The feldspars display perthitic textures which show incomplete solid solution and lowering of liquidus. The tectonic discrimination of the granitoids and the pegmatites show that they were formed within syncollisional, peraluminous, and active continental margin. The research suggest fractionation as a metallogenetic process. The genetic model presents the granitoids ; biotite muscovite granite, albite granite and granite aplite as products of internal chemical differentiation of a fractionating batholiths where NaO replaces K2O as the system is cooling. This is common to most granite-rare-elements-pegmatites systems all over the world. Fractionation via rare elements accumulations is therefore an exploration tool.
Inhaltsverzeichnis (Table of Contents)
-
Introduction
- General Statement
- Statement of the Problem
- Aims and Objectives of the Present Work
- Scope of the Present Work
-
Literature Review
- Geologic Setting
-
Materials and Methods
- Materials Required
- Exploration Method
- Field Methods
- Sampling
- Laboratory Methods
- Field Analysis
- Sample Preparation
- Sample Analysis
- Conceptual Model Theories
- Past
- The Present
Results
- Petrographic Studies
- Macro and Microscopic Studies
- Granitoids
- Biotite-Muscovite Granite (BMG)
- Albite Granite (AG)
- Granite Aplite (GA)
- Amphibolite (AMP)
- Migmatite (MG)
- Microcline Perthite (group 1)
- Albite Antipethite (group 2)
- Albite (group 3)
- Coarse Muscovite (group 1)
- Muscovite (group 2)
- Recrystallized Medium Muscovite (group 3)
- Tourmaline (group T1)
- Tourmaline (group T2)
- Major and Minor Elements Geochemistry
- Interpretations of CIPW Norm
- Thomton and Turtle, (1960) Differentiation Index
- Interpretation of Niggli Norm
- Classification of Granites after Chappell and White (1974)
- Evidence from Magmatic Experiments
- Petrochemistry of Rare Elements Granitoids and Pegmatites
- Aluminum Saturation Index (A/CNK)
- Variation (wt %) of CaO – NaO – K2O in Granitoids and Pegmatites
- Classification of Granitoids using Q – A – P Diagram
- Variation (ppm) of Rb – Ba – Sr for Differentiation of Granitoids
- Trace Element Geochemistry
- Trace Elements
- Mineral Chemistry
- Feldspars
- Micas
- Muscovites
- Biotitic Material
- Tourmaline
- Tectonic Setting Discrimination of the Research Area
- Fertile Granite in Aluminum Saturation Index Diagram coded by Tectonic Affiliation and Geochemical Signature
- Tectonic Classification based on SiO2 Content and K2O/Na2O ratio
- Rb (ppm) versus Nb + Y (ppm)
- Lithological and Structural Relationships
Discussion of Results
- Granitoids
- Rare Elements as Exploration Tool
- Feldspars
- Muscovites
- Tourmalines
- Petrogenesis
- Petrogenic Model
Conclusions and Recommendation
- Conclusions
- Recommendations
Zielsetzung und Themenschwerpunkte (Objectives and Key Themes)
The main objective of this research is to conduct a systematic geologic study of granitic pegmatites in the Jema'a pegmatite field, Kaduna State, Nigeria, in relation to the adjoining granitoids. This involves understanding the geology and geodynamic evolution of the pegmatites, determining their mineralogical and geochemical characteristics, evaluating their economic mineral potential, and relating them to tectonic regimes and magma generation processes.
- Geochemistry and Petrochemistry of Granitic Pegmatites
- Tectonic Setting and Magma Generation
- Economic Mineral Potential of Pegmatites
- Regional Zonation and Mineral Associations
- Petrogenesis of Rare-Element Pegmatites
Zusammenfassung der Kapitel (Chapter Summaries)
Chapter One: Introduction provides an overview of the research area, the significance of the Jema'a pegmatite field, and outlines the aims and objectives of the study. The chapter also discusses the scope of the work, including the methods employed for data collection and analysis.
Chapter Two: Literature Review presents a comprehensive review of relevant literature on the geological setting of the Nigerian Basement complex, the Pan-African orogeny, and the genesis and exploration of rare-element pegmatites. The chapter provides a foundation for understanding the context of the research and the current state of knowledge in the field.
Chapter Three: Materials and Methods details the materials used and the methods applied in the research. It covers field work, sampling techniques, laboratory procedures for sample preparation and analysis, and the conceptual models used to interpret the data. The chapter provides a clear explanation of the methodologies employed to ensure the reliability and reproducibility of the findings.
Chapter Four: Results presents the findings of the study. The chapter analyzes the petrographic characteristics of the granitoids and pegmatites, including their mineral composition, textures, and structural features. It further examines the geochemical data, including major, minor, and trace elements, to understand the chemical evolution of the pegmatite-forming melts and their relationship to the host rocks. The chapter also discusses the tectonic setting discrimination of the research area and the lithological and structural relationships observed in the field.
Chapter Five: Discussion of Results interprets the findings of the study and discusses their implications. The chapter connects the petrographic and geochemical data to understand the petrogenesis of the rare-element pegmatites. It discusses the role of fractionation, the importance of fluxes, and the influence of the tectonic setting on the formation and evolution of the pegmatites. The chapter also highlights the potential of the research area for rare-element mineralization.
Schlüsselwörter (Keywords)
This study examines the geology and petrochemistry of granitic pegmatites in the Jema'a pegmatite field, Kaduna State, Nigeria. Key terms and concepts include: rare-element pegmatites, fertile granites, aluminum saturation index (A/CNK), fractionation, tectonic setting discrimination, Pan-African orogeny, lithological relationships, and economic mineral potential.
- Quote paper
- Ahmed Isah Haruna (Author), 2012, Geology and Petrochemistry of Granitic Pegmatite in Jema’a Pegmatite Field, Kaduna State, Munich, GRIN Verlag, https://www.grin.com/document/200666
