A Tentative Model for the Origin of A-Type Granitoids
A-type granites are typically formed in stable intra-plate, back-arc or postcollisional settings and are characterized by highly ferroan and potassic major element compositions, and by strong enrichment in incompatible trace elements. Unlike I-, S- and M-type granites, where the letters denote the d...
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| Format: | Article |
| Language: | English |
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MDPI AG
2023-02-01
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| Series: | Minerals |
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| Online Access: | https://www.mdpi.com/2075-163X/13/2/236 |
| _version_ | 1797619121455628288 |
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| author | Åke Johansson |
| author_facet | Åke Johansson |
| author_sort | Åke Johansson |
| collection | DOAJ |
| description | A-type granites are typically formed in stable intra-plate, back-arc or postcollisional settings and are characterized by highly ferroan and potassic major element compositions, and by strong enrichment in incompatible trace elements. Unlike I-, S- and M-type granites, where the letters denote the dominant source material (igneous, sedimentary or mantle derived), there is no consensus on the source and processes giving rise to A-type magmas. In this contribution, a conceptual model for the origin of A-type granitoids, using the Bornholm A-type granitoid complex in southern Fennoscandia as an example, is presented. In this model, underplated mantle-derived basaltic magma may develop into intermediate and siliceous A-type magma, which is ferroan, potassic and highly enriched in incompatible trace elements, through a combination of fractional crystallization leading to cumulate formation, and partial melting and crustal assimilation, in a process akin to zone refining in metallurgy. The key factor is a relatively stable tectonic environment (postcollisional, anorogenic, or extensional), where there is little or no replenishment of more primitive basaltic magma to the system, allowing it to attain more evolved, enriched and extreme compositions. The A-type granitoids may then be viewed as a more evolved counterpart of subduction-related I-type granitoids. |
| first_indexed | 2024-03-11T08:22:37Z |
| format | Article |
| id | doaj.art-d9b2766a5db940b4b352b3a8eebb7c50 |
| institution | Directory Open Access Journal |
| issn | 2075-163X |
| language | English |
| last_indexed | 2024-03-11T08:22:37Z |
| publishDate | 2023-02-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Minerals |
| spelling | doaj.art-d9b2766a5db940b4b352b3a8eebb7c502023-11-16T22:18:44ZengMDPI AGMinerals2075-163X2023-02-0113223610.3390/min13020236A Tentative Model for the Origin of A-Type GranitoidsÅke Johansson0Department of Geosciences, Swedish Museum of Natural History, P.O. Box 50 007, SE-104 05 Stockholm, SwedenA-type granites are typically formed in stable intra-plate, back-arc or postcollisional settings and are characterized by highly ferroan and potassic major element compositions, and by strong enrichment in incompatible trace elements. Unlike I-, S- and M-type granites, where the letters denote the dominant source material (igneous, sedimentary or mantle derived), there is no consensus on the source and processes giving rise to A-type magmas. In this contribution, a conceptual model for the origin of A-type granitoids, using the Bornholm A-type granitoid complex in southern Fennoscandia as an example, is presented. In this model, underplated mantle-derived basaltic magma may develop into intermediate and siliceous A-type magma, which is ferroan, potassic and highly enriched in incompatible trace elements, through a combination of fractional crystallization leading to cumulate formation, and partial melting and crustal assimilation, in a process akin to zone refining in metallurgy. The key factor is a relatively stable tectonic environment (postcollisional, anorogenic, or extensional), where there is little or no replenishment of more primitive basaltic magma to the system, allowing it to attain more evolved, enriched and extreme compositions. The A-type granitoids may then be viewed as a more evolved counterpart of subduction-related I-type granitoids.https://www.mdpi.com/2075-163X/13/2/236A-type granitesferroan granitesanorogenic granitespetrogenesiszone refiningBornholm granitoids |
| spellingShingle | Åke Johansson A Tentative Model for the Origin of A-Type Granitoids Minerals A-type granites ferroan granites anorogenic granites petrogenesis zone refining Bornholm granitoids |
| title | A Tentative Model for the Origin of A-Type Granitoids |
| title_full | A Tentative Model for the Origin of A-Type Granitoids |
| title_fullStr | A Tentative Model for the Origin of A-Type Granitoids |
| title_full_unstemmed | A Tentative Model for the Origin of A-Type Granitoids |
| title_short | A Tentative Model for the Origin of A-Type Granitoids |
| title_sort | tentative model for the origin of a type granitoids |
| topic | A-type granites ferroan granites anorogenic granites petrogenesis zone refining Bornholm granitoids |
| url | https://www.mdpi.com/2075-163X/13/2/236 |
| work_keys_str_mv | AT akejohansson atentativemodelfortheoriginofatypegranitoids AT akejohansson tentativemodelfortheoriginofatypegranitoids |