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Regional Variations in the Mineralogy of Metasomatic Assemblages in Mantle Xenoliths from the West Eifel Volcanic Field, Germany |
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| Authors: | SHAW CLIFF S J; EYZAGUIRRE JIMENA; FRYER BRIAN; GAGNON JOEL |
| Institution: | 1 DEPARTMENT OF GEOLOGY, UNIVERSITY OF NEW BRUNSWICK, 2 BAILEY DRIVE, FREDERICTON, NEW BRUNSWICK, CANADA, E3B 5A3 2 DEPARTMENT OF EARTH SCIENCES, UNIVERSITY OF WESTERN ONTARIO, LONDON, ONTARIO, CANADA, N6A 5B7 3 DEPARTMENT OF EARTH SCIENCES AND THE GREAT LAKES INSTITUTE FOR ENVIRONMENTAL RESEARCH, UNIVERSITY OF WINDSOR, WINDSOR, ONTARIO, CANADA, N9B 3P4 4 DEPARTMENT OF EARTH SCIENCES AND THE GREAT LAKES INSTITUTE FOR ENVIRONMENTAL RESEARCH, UNIVERSITY OF WINDSOR, WINDSOR, ONTARIO, CANADA, N9B 3P4 |
| Abstract: | Xenoliths record two distinct events in the mantle below theQuarternary West Eifel Volcanic Field, Germany. The first, duringthe Hercynian Orogeny, led to widespread formation of secondary,Ti-poor amphibole, clinopyroxene and phlogopite. The signatureof the second event, related to Quaternary volcanism, variesacross the field. At Dreiser Weiher and Meerfelder Maar, thisevent is characterized by amphibole–phlogopite–clinopyroxeneveins, hosted in lherzolite and harzburgite xenoliths broughtto the surface by sodic olivine nephelinite–basanite suitelavas. These veins formed from crystallization of sodic magmathat flowed along fractures in the mantle. At Rockeskyller Kopf,Gees and Baarley, the Quaternary event is characterized by wehrlitexenoliths, many of which have phlogopite–clinopyroxeneveins, that were transported by potassic foid suite lavas. Wehrliteformed by reaction of lherzolite–harzburgite, with a largevolume of potassic magma that flowed along grain boundariesrather than in fractures. During reaction, orthopyroxene wasconsumed and secondary clinopyroxene, olivine and phlogopiteprecipitated. Veins formed in wehrlites only during periodicover-pressure events. The composition of the magmas parentalto the veins is similar to the lavas that carried the xenolithsto surface, indicating that the source of foid and olivine nephelinite–basanitesuite magma is domainal, as was the flow regime and magma flux. KEY WORDS: Eifel; mantle xenoliths; metasomatism; trace elements |
| Keywords: | : Eifel mantle xenoliths metasomatism trace elements |
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