Geologische Rundschau

, Volume 62, Issue 3, pp 754–773 | Cite as

Vulkanismus und Graben-Bildung im Roten Meer

  • W. Schneider
  • H. Wachendorf
Aufsätze

Zusammenfassung

Von Vulkanit-Proben derValdivia-Kampagnen 1971/72 werden die Ergebnisse petrographischer und chemischer Untersuchungen dargestellt. Im zentralen Graben des Roten Meeres sind Olivin-Tholeiit-Baselte ohne modalen Pyroxen verbreitet. Außerhalb des zentralen Grabens treten neben vorwiegend holokristallinen Pyroxen-führenden Olivin-Tholeiit-Basalten Alkali-Basalte sowie basaltische Tuffe und Hyaloklastite auf. Vergleichsweise wurden Basalte und deren saure Differentiate aus dem Hinterland von Djibouti untersucht. Kristallisations- und Differentiationsgrad der Gesteine sind Abbild eines diapirartig aufgestiegenen Asthenolithen. Die Aufwölbung der Asthenosphäre wird durch die Einsenkung eines Scheitelgrabens kompensiert. Eine Trennung der kontinentalen Kruste betrifft nur den Bereich des zentralen Grabens.

Abstract

During theValdivia cruise 1971/72 volcanic fragments were raised from the bottom of the Red Sea, especially from the axial through. Data on petrography and chemistry are represented. The axial trough is floored with olivine-tholeiitic basalts without modal pyroxene. According to the rapid ascent from relatively shallow depth olivinetholeiitic magma reached the sea-floor before any substantial differentiation took place. Beyond the axial trough alkali-basalts, basaltic tuffs, hyaloklastites are distributed as well as olivine-tholeiitic basalts with modal pyroxene. For comparison basalts and their acid differentiates from the hinterland of Djibouti have been analyzed and discussed. The grade of crystallisation and fractionation of the melt is in a direct connection with the diapiric upwelling of the asthenosphere. The upwarped asthenosphere is compensated by normal faulting and rifting of the axial trough. The attenuation and separation of the continental crust is restricted to the axial trough.

Résumé

Pendant les campagnes de laValdivia en 1971/72, des échantillons de volcanites ont été prélevés au fond de la Mer Rouge, à des fins d'analyses pétrographiques et chimiques. Dans le fossé central il y a des basaltes tholéiitiques à olivine sans pyroxène modal. En dehors du fossé central apparaissent des basaltes alcalins, des tufs basaltiques et des hyaloclastites ainsi que des basaltes tholéiitiques à olivine et pyroxène modal prédominemment holocristallins. A titre de comparaison, des basaltes et leurs différenciats acides, prélevés dans le hinterland de Djibouti, ont été analysés. Le degré de cristallisation et de différenciation des roches est en relation avec l'asténolite monté par voie diapirique. Le bombement de l'asténosphère est compensé par l'enfoncement du fossé. La séparation de la croûte continentale est restreinte au fossé axial.

Краткое содержание

Приведены результат ы петрографических и химических исследований проб вулканита, отобранны х во время рейса судна Вальдивиа в 1971/1972 гг. В центральной части гр абена распространен ы оливино-толеиитовые базальты без модального пирок сена. Вне центральног о грабена встречаются, наряду с преимущественно гол окристаллическими п ироксеновыми оливино-толеиитовым и базальтами, щелочные базальты, а также база льтовые туфы и гиалокластиты. Для сравнения подвер гались исследованию также базальты и их кислые д ифференциаты из тыловой области Дж ибути. Степень криста ллизации и дифференциации горны хпород отражен а диапироподобным по днявшимся астенолитом. Поднятие свода астен осферы компенсирует ся погружением грабена до максимальной глубины. Отделение ма териковой коры имеет место только в центральной части.

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Copyright information

© Ferdinand Enke Verlag Stuttgart 1973

Authors and Affiliations

  • W. Schneider
    • 1
  • H. Wachendorf
    • 1
  1. 1.Institut für Geologae und Paläontologie der Technischen Universität33 Braunschweig

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