New forms of abundant carbonatite–silicate volcanism: recognition criteria and further target locations
| Autor: | Stuart L. Kearns, D. K. Bailey |
|---|---|
| Rok vydání: | 2012 |
| Předmět: |
010504 meteorology & atmospheric sciences
Lava Geochemistry Pyroclastic rock 010502 geochemistry & geophysics 01 natural sciences chemistry.chemical_compound chemistry Geochemistry and Petrology Ultramafic rock Carbonatite Carbonate Phenocryst Mafic Scoria Geology 0105 earth and related environmental sciences |
| Zdroj: | Mineralogical Magazine. 76:271-284 |
| ISSN: | 1471-8022 0026-461X |
| DOI: | 10.1180/minmag.2012.076.2.03 |
| Popis: | In the Calatrava province of central Spain, numerous Quaternary pyroclastic vents have erupted carbonatite magmas carrying silicate melt fragments, mantle debris and megacrysts. Lava flows are rare. Maar and scoria deposits have carbonate matrices and pass into tuff sheets with carbonate contents >50%, which are spread widely away from the eruptive centres and constitute the most abundant form of effusive carbonate. Immense quantities of mantle debris are present in the erupted material. The tuffs have a distinctive fabric, which consists of a pale matrix carrying black silicate glass clasts that contain globules of immiscible carbonate and carbonate phenocrysts. There is evidence of similar volcanism in the Limagne province of central France and in other intra-continental provinces in Europe and Africa. About 500 vents have been identified in France and Spain: all the vents examined to date have erupted carbonatite magma. Such eruptions are not generally recognized in classical volcanology. As pyroclastic carbonatite was not previously recognized in Spain and France, a detailed examination of other mafic and ultramafic alkaline provinces, where research has traditionally concentrated on lava flows, is vital. For any search to be successful, evidence from the pyroclastic rocks will be required. |
| Databáze: | OpenAIRE |
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