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Geologische Rundschau

, Volume 69, Issue 3, pp 801–810 | Cite as

Garnet xenocrysts in the Mashhad granite, NE Iran

  • I. R. Plimer
  • Z. Moazez-Lesco
Aufsätze
  • 57 Downloads

Abstract

Garnet-bearing tonalite is present within 300 m of the contact with garnet-rich hornfels. It is suggested that the almandine xenocrysts in the tonalite are of accidental origin and represent residuals from the assimilation of garnet-rich hornfels by tonalite. Contaminated tonalite is enriched in Al2O3 and FeO and depleted in SiO2 and biotite and amphibole from the garnet-bearing tonalite are richer in Fe and Al than from the centre of the pluton. The garnet xenocrysts are unzoned and derived from normally-zoned porphyroblasts in the hornfels. Ca and Mg have partitioned from the tonalite into garnet whereas Fe has partitioned from garnet to biotite and amphibole and Mn has partitioned from garnet to ilmenite.

Keywords

SiO2 Al2O3 Assimilation Almandine Accidental Origin 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Zusammenfassung

Granat-führende Tonalite liegen innerhalb von 300 m zum Kontakt zu Granat-reichen Hornfelsen. Es wird vermutet, daß der Almandin im Tonalit aus Assimilationsresten des Granat-reichen Hornfelses stammt. Der so beeinflußte Tonalit ist mit A12O3 und FeO angereichert und SiO2 entsprechend verdünnt. Die Biotite und Amphibole der Granatführenden Tonalite sind reicher an Fe und Al als die entsprechenden Minerale vom Zentrum des Plutons. Die Granat-Xenocrysten sind nicht zoniert und stammen von normal-zonierten Porphyroblasten des Hornfelses. Ca und Mg sind vom Tonalit in den Granat eingewandert, während Fe aus dem Granat austrat und in Biotit und Amphibol eingebaut wurde. Mn ist vom Granat in Ilmenit gewandert.

Résumé

Des tonalites grenatifères se rencontrent jusqu'à 300 m. du contact avec des cornéennes riches en grenat. On présume que l'almandin de la tonalite résulte de résidus d'assimilation de la cornéenne riche en grenat. La tonalite ainsi influencée est enrichie en Al 203, et de ce fait diluée en SiO 2. La biotite et l'amphibole de la tonalite grenatifère sont plus riches en Fe et Al que ces mÊmes minéraux dans la partie centrale du pluton. Les xénocrystes de grenat ne sont pas zonés et proviennent des porphyroblastes normalement zonés de la cornéenne. Du Ca et du Mg sont passés de la tonalite dans le grenat, tandis que du Fe sortait du grenat et passait dans la biotite et l'amphibole. Du Mn a migré du grenat dans l'ilménite.

кРАткОЕ сОДЕРжАНИЕ

тОНАлИты, ВМЕЩАУЩИЕ г РАНАт, жАлЕгАУт с МОЩН ОстьУ В 300 М НАД кОНтАктОМ с РОгОВИкОМ, БОгАтыМ г РАНАтОМ. пРЕДпОлАгАУ т, ЧтО АльМАНДИН тОНАлИтА О БРАжУЕтсь Иж ОстАткОВ АссИМИлИ РОВАННОгО РОгОВИкА, Б ОгАтОгО гРАНАтАМИ. ЁтОт тОНАлИт ОкАжыВАЕтсь ОБОгАЩЕННыМ ОкИсыУ А лУМИНИь И ДВУхВАлЕНтНОгО жЕлЕжА И ОБЕДНЕННыМ О кИсьУ кРЕМНИь. БИОтИт ы И АМФИБОлы тОНАлИтОВ, сОДЕРжАЩИ Е гРАНАт, ОкАжыВАУтсь О БОгАЩЕННыМИ жЕлЕжОМ И АлУМИНИЕМ пО сРАВНЕНИУ с тЕМИ жЕ МИ НЕРАлАМИ Иж цЕНтРАлы НОИ ЧАстИ плУтОНА. гРАНАтксЕНО кРИсты НЕ пРОьВльУт жОНАльН ОстИ И ОБРАжОВАлИсь И ж НОРМАльНО жОНАльНых пОРФИРОБлАстОВ РОгО ВИкА. кАльцИИ И МАгНИИ ВНЕДРИлИсь Иж тОНАлИтОВ В гРАНАты, В тО ВРЕМь, кА к жЕлЕжО МИгРИРОВАлО Их пОслЕДНИх И ОтлОжИлО сь В БИОтИтАх И АМФИБОлА х. МАРгАНЕц жЕ МИгРИРО ВАл Иж гРАНАтОВ В ИлМЕНИт.

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Copyright information

© Ferdinand Enke Verlag Stuttgart 1980

Authors and Affiliations

  • I. R. Plimer
    • 1
  • Z. Moazez-Lesco
    • 2
  1. 1.North Broken Hills Ltd.MelbourneAustralia
  2. 2.Faculty of SciencesFerdowsi UniversityMashhadIran

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