Geochemistry and Mineralogy of Ferromanganese Crusts from the Western Cocos-Nazca Spreading Centre, Pacific

Minerals

Kevin McCartney¹  Benjamin Wernette²  Rafał J. Wróbel³  Adam Piestrzyński⁴  Gabriela A. Kozub-Budzyń⁴  Francisco Javier González⁵  Egidio Marino⁵  Iker Blasco⁵  Dominik Zawadzki⁶  Łukasz Maciąg⁶ 

[1] Department of Environmental Science and Sustainability, University of Maine at Presque Isle, Presque Isle, ME 04769, USA;Earth and Ocean Sciences, Duke University, 9 Circuit Drive, Durham, NC 27708, USA;Faculty of Chemical Technology and Engineering, West Pomeranian University of Technology, Pułaskiego 10, 70-322 Szczecin, Poland;Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, 30-059 Kraków, Poland;Geological Survey of Spain (IGME-CSIC), 28003 Madrid, Spain;Institute of Marine and Environmental Sciences, University of Szczecin, Adama Mickiewicza 16, 70-383 Szczecin, Poland;

关键词: Fe-Mn oxyhydroxides;    marine deposits;    ferromanganese crusts;    Cocos-Nazca;    mixed crusts;   

DOI  :  10.3390/min12050538

来源: DOAJ

【 摘 要 】

Late Pleistocene–Holocene rocks from the western part of Cocos-Nazca Spreading Centre (C-NSC) include ferromanganese crusts that elucidate the geochemistry and mineralogy of a deep-sea geological setting. Six representative Fe-Mn crust samples were studied using petrological methods, such as optical transmitted light microscopy, energy dispersive X-ray fluorescence spectrometry, inductively coupled plasma mass spectrometry, bulk X-ray diffraction, scanning electron microscopy and electron probe microanalysis. Geochemical, mineralogical and petrological signatures indicate complex formation influenced by mild hydrothermal processes. These crusts consist mostly of mixed birnessite, todorokite-buserite, and Mn-(Fe) vernadite with traces of diagenetic manganates (asbolane), Fe-oxides and oxyhydroxides or hydrothermally associated and relatively pure Mn-oxyhydroxides (manganite). The average Mn/Fe ratio is 2.7, which suggests predominant mixed hydrogenous-early diagenetic crusts with hydrothermal influences. The mean concentrations of three prospective metals (Ni, Cu and Co) are low: 0.17, 0.08 and 0.025 wt %, respectively. The total content of ΣREY is also low, and ranges from 81 to 741 mg/kg (mean 339 mg/kg). We interpret the complex geochemical and mineralogical data to reflect mixed origin of the crusts, initially related with formation of hydrothermal plume over the region. This process occurred during further interactions with seawater from which additional diagenetic and hydrogenetic elemental signatures were acquired.

【 授权许可】

Unknown