Petrogenesis of Cogenetic Nepheline and Quartz Syenites and Granites (Northern Damara Orogen, Namibia): Enriched Mantle versus Crustal Contamination
| Autor: | Stephan Hoernes, Stefan Jung, E. Hoffer |
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| Rok vydání: | 2005 |
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| Zdroj: | The Journal of Geology. 113:651-672 |
| ISSN: | 1537-5269 0022-1376 |
| DOI: | 10.1086/467475 |
| Popis: | Geochemical and Nd‐Sr‐O whole rock isotope data and Pb isotope data from leached feldspars for a suite of synorogenic (ca. 540 Ma) syenites and granites from the northern part of the Proterozoic Damara orogen (Namibia) constrain their sources and petrogenesis. Major rock types are mildly potassic nepheline syenites and quartz syenites that were primarily generated by fractional crystallization from a mantle‐derived alkaline magma. Even the most primitive samples show pronounced depletion in Nb, Ti, Sr, and P on a primitive mantle–normalized diagram, indicating the involvement of a recycled crustal component in the source. Extrapolation of the Sr‐Nd‐Pb‐O isotope composition of the syenites back to a hypothetical parental melt with 8 wt%–10 wt% MgO suggests derivation from a moderately enriched lithospheric upper mantle ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{t... |
| Databáze: | OpenAIRE |
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