Geologische Rundschau

, Volume 75, Issue 3, pp 829–861 | Cite as

Ore paragenesis of recent hydrothermal deposits at the Cocos-Nazca plate boundary (Galápagos Rift) at 85‡ 51' and 85‡ 55' W: Complex massive sulfide mineralizations, non-sulfidic mineralizations and mineralized basalts

  • Werner Tufar
  • Elisabeth Tufar
  • Joachim Lange
Article

Abstract

Complex massive sulfide ores (»black smokers«) as well as mineralized basalts and unconsolidated sediments were sampled during the German research expedition »Garimas 1« in the eastern portions of the Galapagos Rift at 85‡ 50' W longitude. The massive sulfide ores are characterized by a porous, layered, compositional texture with typical colloidal and/or gel textures. Local occurrences of organism remains (worm tubes), which are embedded in the ore, were also found. The composition of the massive sulfide ores exhibits a considerable range, from iron sulfide ores (pyrite, melnikovite-pyrite, marcasite) to copper-rich ores (chalcopyrite), and/or zinc-dominated ores (sphalerite, wurtzite, schalenblende). Additional new types of hydrothermal mineralizations were found, which consist primarily of manganese hydroxide, limonite or Fe-rich smectite (Fe-rich »protosmectite«) together with limonite and opaline silica. Hydrothermally altered basalts may be characterized by significant sulfide contents (primarily pyrite) and, locally, by hematite. Sediments in the vicinity of the »black smokers« frequently contain fragments of complex massive sulfide ores. With increasing distance from the »black smokers« these massive sulfide fragments exhibit complete replacement and pseudomorphism by limonite. Some replacement and pseudomorphism of microorganisms in unconsolidated sediments by limonitic material is also observed. In places, the unconsolidated sediments contain manganese hydroxide mineralizations of hydrothermal origin.

Keywords

Pyrite Chalcopyrite Massive Sulfide Limonite Unconsolidated Sediment 

Zusammenfassung

Anlä\lich der deutschen Forschungsfahrt »Garimas 1« wurden im östlichen Teil des Galápagos-Riftes bei 85‡ 50' W vor allem komplexe massive Sulfiderze (»Schwarze Raucher« — »Black Smokers«) gewonnen, daneben au\erdem vererzte Basalte sowie unverf estigte Sedimente. Die massiven Sulfiderze sind durch einen porösen, lagig bis krustigschaligen Aufbau gekennzeichnet und weisen charakteristische Kolloidalgefüge bzw. Geltexturen auf. Stellenweise liegen Organismenreste (z. B. Wurmröhren), eingebettet in Erz, vor. Die Zusammensetzung der jeweiligen massiven Sulfiderze schwankt erheblich und reicht von praktisch nur aus Eisensulfid (Pyrit, Melnikovitpyrit, Markasit) beste-henden Bildungen bis zu solchen, die reich an Kupfersulfid (Kupferkies) und/oder Zinksulfid (Zinkblende, Wurtzit, Schalenblende) sind. Als weitere und neue Typen hydrothermaler Bildungen bzw. von »Schwarzen Rauchern« konnten hydrothermale Mineralisationen nachgewiesen werden, die vorherrschend entweder aus Manganhydroxid, aus Limonit oder aus eisenreichem Montmorillonit (Fe-reicher »Protosmektit«) mit Limonit und amorphem SiO2 bestehen. Die alterierten Basalte können stellenweise durch eine reichliche Sulfidführung (vor allem Pyrit) ausgezeichnet sein, wobei gelegentlich auch Eisenglanz beibricht. Die Sedimente aus der Nachbarschaft der »Schwarzen Raucher« enthalten öfters zahlreiche Bruchstücke der komplexen Massivsulfiderze. Diese Sulfiderz-Bruchstücke lassen häufig mit zunehmender Entfernung von den »Schwarzen Rauchern« starke bis völlige Verdrängung und Pseudomorphosierung durch Limonit erkennen. Die in diesen Lockersedimenten vorliegenden rezenten Mikroorganismen zeigen stellenweise Verdrängung und Pseudomorphosierung durch Limonit. In den Lockersedimenten treten Ausscheidungen von Manganhydroxid hydrothermaler Herkunft auf.

Résumé

Dans la partie est de la dorsale des Galapagos, par 85‡ 50' de longitude ouest, l'expédition allemande »GARIMAS I« a récolté des minerais sulfurés complexes massifs (minerais de »fumeurs noirs«), ainsi que des basaltes minéralisés et des échantillons de sédiments meubles. Les sulfures massifs présentent un aspect poreux lité à écailleux et montrent des structures colloÏdales caractéristiques. Localement des traces d'organismes (p. ex. des trous de vers) sont inclues dans le minéral. Les sulfures massifs présentent diverses compositions depuis des formations constituées uniquement de sulfures de Fe (pyrite, pyrite »colloÏdale«, marcasite) jusqu'à d'autres qui sont riches en sulfures de cuivre (chalcopyrite) et/ou de zinc (blende, wurtzite, blende zonaire). De plus, d'autres minéralisations hydrothermales, nouvelles dans l'environnement des fumeurs noirs, ont été mises en évidence: elles sont constituées soit d'oxydes et hydroxydes de Mn, soit de limonite ou de montmorillonite riche en fer (»protosmectite« ferreuse) avec de la limonite et silice amorphe. Les basaltes hydrothermalisés peuvent montrer localement une teneur élevée en sulfure (surtout de la pyrite) éventuellement accompagné d'hématite. Les sédiments recueillis au voisinage des fumeurs noirs renferment souvent de nombreux fragments de sulfures complexes massifs. Au fur et à mesure qu'on s'éloigne des fumeurs, ces fragments sont progressivement et mÊme complètement pseudomorphosés en limonite. Cette pseudomorphose limonitique affecte également, par endroits, les micro-organismes récents inclus dans les sédiments meubles. Dans ces derniers ont lieu des formations d'hydroxydes de manganèse d'origine hydrothermale.

кРАткОЕ сОДЕРжАНИЕ

пРИ НАУЧНО-ИсслЕДОВА тЕльскОИ ЁкспЕДИцИИ „Garimas I” к ВОстОЧНОИ ЧАстИ РИ ФтА гАлАпАгОс У 85‡50′ жА пАДНОИ шИРОты БылИ ОтОБРАНы пРОБы слОжНых МАссИВНых сУльФИДНы х РУД — “ЧЕРНыЕ ДыМОВы Е” = “Black Smokers” -, А кРОМЕ тОгО ОРУД НЕНИь БАжАльтОВ И Рыхлых сЕДИМЕНтОВ. В МАссИВНых сУльФИДНы х РУДАх ОтМЕЧАЕтсь пОРИстОЕ, слОИстОЕ ДО кОРОВО-ОБ ОлОЧНОгО стРОЕНИь, кОтОРОЕ ИМЕ Ет хАРАктЕРНыЕ кОллО ИДАльНыЕ, ИлИ гЕлЕВыЕ тЕкстРУР ы. МЕстАМИ ОтМЕЧАУтсь ВклУЧЕНИь ОРгАНИжМО В, НАпР.: пРОхОДы ЧЕРВЕИ, жАхОРОНЕННыЕ В РУДЕ. сОстАВ МАссИВН ых РУД кОлЕБлЕтсь ОЧЕНь сИл ьНО И ДОстИгАЕт От ЧИс тОгО сУльФИДА жЕлЕжА, т. Е. п ИРИтА, гЕльпИРИтА, МА РкАжИтА, ДО БОгАтых МЕДьУ = МЕДН ыИ кОлЧАДАН, И/ИлИ сУльФИДАМИ цИНкА (цИН кОВАь ОБМАНкА, ВУРтцИ т, скОРлУпОВАтыИ сФАлЕ РИт). кРОМЕ тОгО ОгМЕЧА Утсь гИДРОтЕРМАльНыЕ МИН ЕРАлИжАцИИ, сОсгОьЩИ Е гл. ОБР. Иж ОкИслОА МАРгАН цА, ИлИ гИДРОкИслА МАР гАНцА, ИлИ Иж лИМОНИтОВ, А тАк жЕ Иж ОкИсИ кРЕМНИь. В И жМЕНЕННых БАжАльтАх УстАНОВИл И МЕстАМИ ОЧЕНь ОБИль НОЕ пРИсУтстВИЕ сУльФИД ОВ, пРЕжДЕ ВсЕгО пИРИт А, пРИЧЕМ кОЕ-гДЕ жАМЕтЕ Н И жЕлЕжНыИ БлЕОк. пРО Бы сЕДИМЕНтОВ, ОсОБРАНН ыЕ пО сОсЕДстВУ с ЁтИМ И РУДАМИ, сОДЕРжАт ЧАстО ОБлОМ кИ Их, кОтОРыЕ с УДАлЕН ИЕМ От МЕстОНАхОжДЕНИь М АссИВНых РУД ОкАжыВА Утсь пОЧтИ ЧтО пОлНОстьУ ж АМЕЩЕННыМИ лИМОНИгО М, ИлИ ЕгО псЕВДОМОРФИж МАМИ. тАкжЕ И РЕцЕНтНы Е МИкРООРгАНИжМы В ЁтИ х сЕДИМЕНтАх ОкАжыВА Утсь жАМЕЩЕННыМИ лИМОНИтОМ, ИлИ ЕгО псЕ ВДОМОРФИжМАМИ.

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Copyright information

© Ferdinand Enke Verlag Stuttgart 1986

Authors and Affiliations

  • Werner Tufar
    • 1
  • Elisabeth Tufar
    • 1
  • Joachim Lange
    • 2
  1. 1.Fachbereich Geowissenschaften der Philipps-Universität MarburgMarburg/LahnFederal Republic of Germany
  2. 2.Preussag Aktiengesellschaft MeerestechnikHannover 1Federal Republic of Germany

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