[PDF] Petrogenesis Metallogenesis Of Granitic Rare Metal Pegmatites Along The Southern Margin Of The Zimbabwe Craton eBook

Author : Ahmed Isah Haruna
Publisher : GRIN Verlag
Page : 221 pages
File Size : 45,8 MB
Release : 2012-09-27
Category : Science
ISBN : 3656280134

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Doctoral Thesis / Dissertation from the year 2012 in the subject Geography / Earth Science - Geology, Mineralogy, Soil Science, grade: "none", Abubakar Tafawa Balewa University (School of Science), course: Economic Geology-Mineral Exploration, language: English, abstract: 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.

Author : V. Janoušek
Publisher : Geological Society of London
Page : 298 pages
File Size : 42,97 MB
Release : 2020-07-02
Category : Science
ISBN : 1786204487

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Granites (sensu lato) represent the dominant rock-type forming the upper–middle continental crust but their origin remains a matter of long-standing controversy. The granites may result from fractionation of mantle-derived basaltic magmas, or partial melting of different crustal protoliths at contrasting P–T conditions, either water-fluxed or fluid-absent. Consequently, many different mechanisms have been proposed to explain the compositional variability of granites ranging from whole igneous suites down to mineral scale. This book presents an overview of the state of the art, and envisages future avenues towards a better understanding of granite petrogenesis. Particular emphasis of this Volume is on the following topics: Compositional variability of granitic rocks generated in contrasting geodynamic settings during Proterozoic to Phanerozoic Periods, Main permissible mechanisms producing subduction-related granites, Crustal anatexis of different protoliths, and the role of water in granite petrogenesis, New theoretical and analytical tools available for modelling whole-rock geochemistry, in order to decipher the sources and evolution of granitic suites.

Author : Kurt Bucher
Publisher : Springer Science & Business Media
Page : 434 pages
File Size : 13,90 MB
Release : 2011-06-27
Category : Science
ISBN : 3540741690

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Petrogenesis of Metamorphic Rocks presents a large number of diagrams showing the stability relations among minerals and groups of minerals found in metamorphic rocks. The diagrams help to determine the pressure and temperature conditions under which a given set of metamorphic rocks may have formed. Other parameters that control metamorphic mineral assemblages are also discussed and pitfalls resulting from simplifications and generalizations are highlighted. The book discusses the most common metamorphic rock types, their nomenclature, structure and graphical representation of their mineral assemblages. Part I defines basic principles of metamorphism, introduces metamorphic processes, geologic thermometry and barometry and defines metamorphic grade. Part II presents in a systematic way mineralogical changes and assemblages found in the most common types of metamorphic rocks. The computation of diagrams is based on recent advances in quantitative petrology and geochemistry. An extensive bibliography, including the key contributions and classic papers in the field, make it an invaluable source book for graduate students and professional geologists.

Author : Eugene Nathan Cameron
Publisher :
Page : pages
File Size : 20,13 MB
Release : 1949
Category : Pegmatites
ISBN : 9781934969977

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Studies of strategic mineral deposits in the major domestic pegmatite districts by the U.S. Geological Survey from 1939-1945 resulted in the clarification of many problems related to the internal structure, mineralogy and origin of granitic pegmatites. This report summarises about 68 man years of work in the pegmatite districts of New England, the Southeastern States, South Dakota, Idaho, Montana, Wyoming, Colorado, and New Mexico.