Silicate, Hydrous and Carbonate Metasomatism at Lherz, France: Contemporaneous Derivatives of Silicate Melt-Harzburgite Reaction |
| |
Authors: | BODINIER JEAN-LOUIS; MENZIES MARTIN A; SHIMIZU NOBUMICHI; FREY FREDERICK A; McPHERSON ELAINE |
| |
Institution: | 1 LABORATOIRE DE TECTONOPHYSIQUE, ISTEEM, CASE 49, CNRS ET UNIVERSITÉ DE MONTPELLIER 2, PLACE EUGÈNE BATAILLON, 34095 MONTPELLIER CEDEX 05, FRANCE
2 DEPARTMENT OF GEOLOGY, ROYAL HOLLOWAY, UNIVERSITY OF LONDON, EGHAM HILL, EGHAM TW20 0EX, UK
3 DEPARTMENT OF GEOLOGY AND GEOPHYSICS, WOODS HOLE OCEANOGRAPHIC INSTITUTION, WOODS HOLE, MA 02543, USA
4 DEPARTMENT OF EARTH, ATMOSPHERIC AND PLANETARY SCIENCES, MASSACHUSETTS INSTITUTE OF TECHNOLOGY, CAMBRIDGE, MA 02139, USA |
| |
Abstract: | Complex multi-stage models involving silicate, hydrous and carbonatemelts of distinct provenance have been invoked to explain themetasomatism observed in mantle rocks. In contrast, relativelysimple models requiring polybaric crystallization of alkalinesilicate melts have been proposed to explain the occurrenceof veined mantle rocks. To address the spatial and temporalrelationships between veins and wall-rocks, a sequence of drillcores was obtained from Lherz, France. In outcrop the vein (amphibolegarnetpyroxenite dyke) is spatially associated with hornblendite veinlets(lherzite), and proximal amphibole-bearing and distal apatite-bearingwall-rock peridotite. Considerable elemental and isotopic heterogeneityexists in these wall-rock peridotites, in many instances equivalentto, or greater than, that observed in mantle xenoliths fromworldwide localities. A single stage of reactive porous flowbest explains the elemental and isotopic heterogeneity in thewall-rock. In essence it is proposed that emplacement of thesilicate melt (dyke) was inextricably linked to chromatographicfractionation/reaction of derivatives which led to the coexistence,in space and time, of silicate, hydrous and carbonate melts.This model elegantly and simply describes the formation of complexmetasomatic aureoles around mantle veins and negates the need,in the case of basalt-hosted (and kimberlite-hosted) xenoliths,for complex multi-stage models involving several episodes ofmelt influx with each melt being of different provenance. KEY WORDS: mantle metasomatism; trace-element enrichment; isotopic contamination; wall-rock peridotite; Lherz peridotite |
| |
Keywords: | : mantle metasomatism trace-element enrichment isotopic contamination wall-rock peridotite Lherz peridotite |
本文献已被 Oxford 等数据库收录! |
|