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Mantle and crust interaction in post-collisional setting, a case study of lamprophyric-granitic composite dykes of northern Aigoual pluton, French Massif Central
Thesis (MSc)--Stellenbosch University, 2022.
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2022
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| _version_ | 1867613932520210432 |
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| access_status_str | Open Access |
| author | Werle, Mariana |
| author2 | Stevens, Gary |
| author_browse | Stevens, Gary Werle, Mariana |
| author_facet | Stevens, Gary Werle, Mariana |
| author_sort | Werle, Mariana |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2022. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/124950 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:43:59.926Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2022 |
| publishDateRange | 2022 |
| publishDateSort | 2022 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/124950 Mantle and crust interaction in post-collisional setting, a case study of lamprophyric-granitic composite dykes of northern Aigoual pluton, French Massif Central Werle, Mariana Stevens, Gary Moyen, Jean-Francois Laurent, Oscar Stellenbosch University. Faculty of Science. Dept. of Earth Sciences. Granite -- French Massif Central Lamprophyres -- France Mantle metasomatism Crustal -- Growth Petrogenesis Dykes (Geology) UCTD Thesis (MSc)--Stellenbosch University, 2022. ENGLISH ABSTRACT: Lamprophyre to granite composite dykes in the northern extremity of the post-Variscan Aigoual pluton, French Massif Central (FMC), offer an opportunity to study the complexity of the processes that control crustal growth in post-collisional tectonic settings through mantle and crust interactions. The aim of this thesis is to contribute to an improved understanding of the petrogenesis of the composite dykes and to constrain the mantle contribution to post-collisional magmatism in the FMC. In the field, most dykes are composite and vary gradationally from lamprophyres to granites. The lamprophyres are metaluminous to slightly peraluminous, display moderate to high compatible element contents such as Cr (54 – 572 ppm) and Ni (23 – 148 ppm) and coupled with the relativly high Mg# (up to 60), indicate a mantle-derived source for at least this component of the composite system. However, the lamprophyres display crust-like signatures with enrichment in LILE (K2O, Sr, Rb, Ba, Pb, V) and LREE and in both radiogenic (Sr, Nd and Hf whole-rock and zircon) and stable (O) isotopic systems. These data indicate that the dual geochemical signature is source-related, and that lamprophyres were generated by partial melting within the spinel-lherzolite stability field of an enriched mantle highly metasomatised by sediment-derived melts or fluids introduced to the mantle during subduction preceding Variscan continental collision. The granites from composite dykes are peraluminous, have high K2O with shoshonitic affinity and trace elements and isotopic signatures like the lamprophyres. These similarities and relativly high contents of Cr, Ni, Mg and Fe, related to crust-derived granites in FMC, display a mantle-derived component involved in the petrogenesis of granites from composite dykes. Although completely hidden from both radiogenic and stable isotopes and incompatible element contents, addition of new mantle-material is identified in lamprophyres and granites by the high compatible element contents (such as Cr, Ni, Fe and Mg). Combining geochemical modelling with granites outcrops patterns in the FMC, addition of new-mantle material represents ca. 22 to 28% of the post-collisional magmatic material in the FMC and crustal growth may be significant in post-collisional sites. This work demonstrates the intimate relations (physically, petrologically and geochemically) between lamprophyres and granites in the composite dykes of northern border of Aigoual pluton, and provides constraints on the mantle and crust interactions and contributions of mantle material in post-collisional granitoids from the FMC. RESUMO: Diques compostos por lamprófiros e granitos na extremidade norte do plúton Aigoual pós- Variscano, Maciço Central Francês (MCF), permitem estudar a complexidade dos processos que controlam a formação de crosta em ambiente pós-colisional através de interações entre manto e crosta. O objetivo dessa tese é a petrogênese dos lamprófiros e granitos em um sistema de diques compostos e estabelecer a contribuição mantélica no magmatismo pós-colisional do MCF. Em campo, os diques compostos variam gradacionalmente de lamprófiros a granitos. Os lamprófiros variam de metaluminosos a fracamente peraluminosos, possuem teores moderados a altos de elementos compatíveis como Cr (54 – 572 ppm) e Ni (23 – 148 ppm) e, juntamente com o relativo alto Mg# (maior que 60), indicam uma fonte manto derivada para esse componente do sistema composto. Entretanto, os lamprófiros possuem assinatura crustal com enriquecimento em LILE (K2O, Sr, Rb, Ba, Pb, V) e ETRL e nos sistemas isotópicos radiogênicos (Sr, Nd e Hf rocha total e zircão) e estável (O). Os estudos indicam essa dualidade geoquímica é relacionada à fonte. Os dados indicam fusão parcial no campo de estabilidade do espinélio-lherzolito de um manto fortemente metassomatizado por fluidos ou magmas derivados de sedimentos introduzidos no manto durante a subducção que precede a colisão continental na orogênese Variscana. Os granitos dessa área são peraluminosos, possuem alto K2O com afinidade shoshonítica e possuem conteúdos de elementos traço e assinaturas isotópicas similares aos lamprófiros. Essas similaridades e relativo alto conteúdo de Cr, Ni, Mg e Fe comparados aos granitos derivados da crosta no MCF demonstram que há componente mantélico envolvido na petrogênese da porção granítica dos diques compostos. Apesar de completamente oculto do ponto de vista de isótopos estáveis e radiogênicos, a adição de novo material proveniente do manto é identificada pelo alto teor em elementos compatíveis como Cr, Ni, Mg e Fe. Combinando modelagem geoquímica com o padrão dos afloramentos, a adição de novo material manto derivado representa cerca de 22 – 28% do material magmático no MCF indicando que o crescimento crustal no ambiente pós-colisional é significante. Esse estudo demonstra a relação intrínseca (física, petrológica e química) entre lamprófiros e granitos em um sistema de diques compostos da porção norte do plúton Aigoual e fornece indícios sobre a relação manto e crosta nos granitoides pós-colisionais do MCF. Masters 2022-03-09T17:20:15Z 2022-04-29T09:43:03Z 2022-03-09T17:20:15Z 2022-04-29T09:43:03Z 2022-04 Thesis http://hdl.handle.net/10019.1/124950 en_ZA Stellenbosch University xi, 148 pages : illustrations (some color), maps application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Granite -- French Massif Central Lamprophyres -- France Mantle metasomatism Crustal -- Growth Petrogenesis Dykes (Geology) UCTD Werle, Mariana Mantle and crust interaction in post-collisional setting, a case study of lamprophyric-granitic composite dykes of northern Aigoual pluton, French Massif Central |
| title | Mantle and crust interaction in post-collisional setting, a case study of lamprophyric-granitic composite dykes of northern Aigoual pluton, French Massif Central |
| title_full | Mantle and crust interaction in post-collisional setting, a case study of lamprophyric-granitic composite dykes of northern Aigoual pluton, French Massif Central |
| title_fullStr | Mantle and crust interaction in post-collisional setting, a case study of lamprophyric-granitic composite dykes of northern Aigoual pluton, French Massif Central |
| title_full_unstemmed | Mantle and crust interaction in post-collisional setting, a case study of lamprophyric-granitic composite dykes of northern Aigoual pluton, French Massif Central |
| title_short | Mantle and crust interaction in post-collisional setting, a case study of lamprophyric-granitic composite dykes of northern Aigoual pluton, French Massif Central |
| title_sort | mantle and crust interaction in post collisional setting a case study of lamprophyric granitic composite dykes of northern aigoual pluton french massif central |
| topic | Granite -- French Massif Central Lamprophyres -- France Mantle metasomatism Crustal -- Growth Petrogenesis Dykes (Geology) UCTD |
| url | http://hdl.handle.net/10019.1/124950 |
| work_keys_str_mv | AT werlemariana mantleandcrustinteractioninpostcollisionalsettingacasestudyoflamprophyricgraniticcompositedykesofnorthernaigoualplutonfrenchmassifcentral |