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Econ. Environ. Geol. 2023; 56(1): 55-63

Published online February 28, 2023

https://doi.org/10.9719/EEG.2023.56.1.55

© THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY

Revealing the Paleo-ocean Environment of OSM-XX in the Western Pacific Magellan Seamount with Mineralogical and Geochemical Properties of Ferromanganese Crust

Jinsub Park1, Kiho Yang1,2,*

1Department of Oceanography, College of Natural Sciences, Pusan National University, Busan 46241, Republic of Korea
2Marine Research Institute, Pusan National University, Busan 46241, Republic of Korea

Correspondence to : *kyang@pusan.ac.kr

Received: January 2, 2023; Revised: February 12, 2023; Accepted: February 13, 2023

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided original work is properly cited.

Abstract

Variations in geochemical and mineralogical properties of the ferromanganese(Fe-Mn) crust reflect environmental changes. In the present study, geochemical and mineralogical analyses, including micro X-ray fluorescence and X-ray diffraction, were utilized to reconstruct the paleo-ocean environment of western Pacific Magellan seamount cluster. Samples of the Fe-Mn crust were collected using an epibenthic sledge from the open seamount XX (151° 51.12′ 7.2″ E and 16° 8.16′ 9.6″ N, 1557 meters below sea level) in the Western Pacific Magellan Seamount. According to the structure and phosphating status, the Fe-Mn crust of the OSM-XX can be divided into the following: phosphatizated (L4-L5), massive non-phosphatizated (L3), and porous non-phosphatizated (L1-L2) portions. All ferromanganese layers contain vernadite, and owing to the presence of carbonate fluorapatite (CFA), the phosphatizated portion (L4-L5) is rich in Ca and P. The massive non-phosphatizated section (L3) contains high Mn, Ni, and Co, whereas the porous non-phosphatizated portion (L1-L2), which comprises detrital quartz and feldspar, is rich in Fe. Variations in properties of the Fe-Mn crust from the OSM-XX reflect changes in the nearby marine environment. The formation of this crust started at approximately 51.87 Ma, and precipitation of the CFA during the global phosphatization event that occurred at approximately 36–32 Ma highlights an elevated sea level and low temperature during the associated period. The high Mn, Ni, and Co concentrations and elevated Mn/Fe ratios of samples from the massive phosphatizated portion indicate that the oxygen minimum zone (OMZ) was enhanced, and reducing conditions prevailed during the crust formation. The high Fe and low Mn/Fe ratios in the porous portion indicate a weak OMZ and dominantly oxidizing conditions. These data reflect environmental changes following the end of the Mi-1 glacial period in the Miocene-Oligocene boundary. Subsequently, Mn/Fe and Co/Mn ratios increased slightly in the outermost part of Fe-Mn crust because of the enhanced bottom current and OMZ associated with the continued cooling from approximately 9 Ma. However, the reduced carbonate dissolution rate in the Pacific Ocean from approximately 6 Ma decreased the growth rate of the Fe-Mn crust.

Keywords ferromanganese crust, paleo-oceanography, redox condition, paleo productivity, western Pacific Magellan seamount

서태평양 마젤란해산군 OSM-XX 해저산 망간각의 광물학적, 지화학적 특성과 고해양 고환경 복원 연구

박진섭1 · 양기호1,2,*

1부산대학교 자연과학대학 해양학과
2부산대학교 해양연구소

요 약

망간각의 지화학적, 광물학적 특성의 변화는 인근 환경 변화를 반영한다. 따라서 서태평양 마젤란해산군 OSM-XX의 망간각에 대한 특성 파악과 고해양 복원 연구를 위하여 지화학적, 광물학적 분석을 각각 micro X-ray fluorescence (μ-XRF) 과 X-ray diffraction (XRD)를 이용하여 실시하였다. OSM-XX의 망간각은 인산염화 여부 및 구조에 의해 인산염화 작용을 받은 부분(L4-L5), 인산염화 작용을 받지 않은 치밀한 부분(L3), 인산염화 작용을 받지 않은 다공성 부분(L1-L2)의 세 부분으로 구분되었다. 철망간 산화광물 층에서는 모두 버나다이트 피크가 확인되었으며, 인산염화 작용을 받은 부분은 carbonate fluorapatite(CFA)의 존재와 높은 Ca, P의 특성을 나타내었다. 인산염화 작용을 받지 않은 치밀한 부분은 높은 Mn, Ni, Co를 나타내었고, 인산염화작용을 받지 않은 다공성 부분은 높은 Fe값과 detritus quartz, feldspar가 확인되었다. OSM-XX의 망간각이 성장하는동안 나타난 특성의 변화는 인근 해양환경의 변화를 반영하였다. 약 51.87 Ma의 연대를 나타내는 망간각의 인산염 퇴적체는 약 36-32 Ma의 전지구적 인산염화 작용에 의해 형성된 것으로 보이며, 이는 당시의 상승된 해수면 높이와 낮은 해수온을 지시한다. 또한, 치밀한 구조에서의 높은 Mn, Ni, Co, Mn/Fe 비는 강화된 산소최소층과 환원환경을 지시하며, 다공성 구조에서의 높은 Fe와 낮은 Mn/Fe 비는 약화된 산소최소층과 산화환경을 지시한다. 이는 마이오세-올리고세 경계의 Mi-1 빙하기가 끝난 후 환경변화를 반영하였다. 9 Ma부터 이어진 한랭화의 결과로 인한 저층류와 산소최소층의 강화에 의해 망간각 최외각의 Mn/Fe 비와 Co/Mn 비가 미세하게 증가하였지만, 6 Ma부터 태평양에 발생한 탄산염 용해율의 감소로 성장속도의 감소를 야기하였다.

주요어 망간각, 고해양 복원, 산화환원환경, 고생산성, 서태평양 마젤란 해산군

Article

Research Paper

Econ. Environ. Geol. 2023; 56(1): 55-63

Published online February 28, 2023 https://doi.org/10.9719/EEG.2023.56.1.55

Copyright © THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY.

Revealing the Paleo-ocean Environment of OSM-XX in the Western Pacific Magellan Seamount with Mineralogical and Geochemical Properties of Ferromanganese Crust

Jinsub Park1, Kiho Yang1,2,*

1Department of Oceanography, College of Natural Sciences, Pusan National University, Busan 46241, Republic of Korea
2Marine Research Institute, Pusan National University, Busan 46241, Republic of Korea

Correspondence to:*kyang@pusan.ac.kr

Received: January 2, 2023; Revised: February 12, 2023; Accepted: February 13, 2023

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided original work is properly cited.

Abstract

Variations in geochemical and mineralogical properties of the ferromanganese(Fe-Mn) crust reflect environmental changes. In the present study, geochemical and mineralogical analyses, including micro X-ray fluorescence and X-ray diffraction, were utilized to reconstruct the paleo-ocean environment of western Pacific Magellan seamount cluster. Samples of the Fe-Mn crust were collected using an epibenthic sledge from the open seamount XX (151° 51.12′ 7.2″ E and 16° 8.16′ 9.6″ N, 1557 meters below sea level) in the Western Pacific Magellan Seamount. According to the structure and phosphating status, the Fe-Mn crust of the OSM-XX can be divided into the following: phosphatizated (L4-L5), massive non-phosphatizated (L3), and porous non-phosphatizated (L1-L2) portions. All ferromanganese layers contain vernadite, and owing to the presence of carbonate fluorapatite (CFA), the phosphatizated portion (L4-L5) is rich in Ca and P. The massive non-phosphatizated section (L3) contains high Mn, Ni, and Co, whereas the porous non-phosphatizated portion (L1-L2), which comprises detrital quartz and feldspar, is rich in Fe. Variations in properties of the Fe-Mn crust from the OSM-XX reflect changes in the nearby marine environment. The formation of this crust started at approximately 51.87 Ma, and precipitation of the CFA during the global phosphatization event that occurred at approximately 36–32 Ma highlights an elevated sea level and low temperature during the associated period. The high Mn, Ni, and Co concentrations and elevated Mn/Fe ratios of samples from the massive phosphatizated portion indicate that the oxygen minimum zone (OMZ) was enhanced, and reducing conditions prevailed during the crust formation. The high Fe and low Mn/Fe ratios in the porous portion indicate a weak OMZ and dominantly oxidizing conditions. These data reflect environmental changes following the end of the Mi-1 glacial period in the Miocene-Oligocene boundary. Subsequently, Mn/Fe and Co/Mn ratios increased slightly in the outermost part of Fe-Mn crust because of the enhanced bottom current and OMZ associated with the continued cooling from approximately 9 Ma. However, the reduced carbonate dissolution rate in the Pacific Ocean from approximately 6 Ma decreased the growth rate of the Fe-Mn crust.

Keywords ferromanganese crust, paleo-oceanography, redox condition, paleo productivity, western Pacific Magellan seamount

서태평양 마젤란해산군 OSM-XX 해저산 망간각의 광물학적, 지화학적 특성과 고해양 고환경 복원 연구

박진섭1 · 양기호1,2,*

1부산대학교 자연과학대학 해양학과
2부산대학교 해양연구소

Received: January 2, 2023; Revised: February 12, 2023; Accepted: February 13, 2023

요 약

망간각의 지화학적, 광물학적 특성의 변화는 인근 환경 변화를 반영한다. 따라서 서태평양 마젤란해산군 OSM-XX의 망간각에 대한 특성 파악과 고해양 복원 연구를 위하여 지화학적, 광물학적 분석을 각각 micro X-ray fluorescence (μ-XRF) 과 X-ray diffraction (XRD)를 이용하여 실시하였다. OSM-XX의 망간각은 인산염화 여부 및 구조에 의해 인산염화 작용을 받은 부분(L4-L5), 인산염화 작용을 받지 않은 치밀한 부분(L3), 인산염화 작용을 받지 않은 다공성 부분(L1-L2)의 세 부분으로 구분되었다. 철망간 산화광물 층에서는 모두 버나다이트 피크가 확인되었으며, 인산염화 작용을 받은 부분은 carbonate fluorapatite(CFA)의 존재와 높은 Ca, P의 특성을 나타내었다. 인산염화 작용을 받지 않은 치밀한 부분은 높은 Mn, Ni, Co를 나타내었고, 인산염화작용을 받지 않은 다공성 부분은 높은 Fe값과 detritus quartz, feldspar가 확인되었다. OSM-XX의 망간각이 성장하는동안 나타난 특성의 변화는 인근 해양환경의 변화를 반영하였다. 약 51.87 Ma의 연대를 나타내는 망간각의 인산염 퇴적체는 약 36-32 Ma의 전지구적 인산염화 작용에 의해 형성된 것으로 보이며, 이는 당시의 상승된 해수면 높이와 낮은 해수온을 지시한다. 또한, 치밀한 구조에서의 높은 Mn, Ni, Co, Mn/Fe 비는 강화된 산소최소층과 환원환경을 지시하며, 다공성 구조에서의 높은 Fe와 낮은 Mn/Fe 비는 약화된 산소최소층과 산화환경을 지시한다. 이는 마이오세-올리고세 경계의 Mi-1 빙하기가 끝난 후 환경변화를 반영하였다. 9 Ma부터 이어진 한랭화의 결과로 인한 저층류와 산소최소층의 강화에 의해 망간각 최외각의 Mn/Fe 비와 Co/Mn 비가 미세하게 증가하였지만, 6 Ma부터 태평양에 발생한 탄산염 용해율의 감소로 성장속도의 감소를 야기하였다.

주요어 망간각, 고해양 복원, 산화환원환경, 고생산성, 서태평양 마젤란 해산군

    Fig 1.

    Figure 1.Bathymetry map of the Magellan Seamount Cluster. Black dotted square is open seamount (OSM) XX where ferromanganese crust collected. Upper right map is three-dimensional bathymetry of OSM-XX and Yellow Square indicates epibenthic sledge site.
    Economic and Environmental Geology 2023; 56: 55-63https://doi.org/10.9719/EEG.2023.56.1.55

    Fig 2.

    Figure 2.Photographs of ferromanganese crust(OSM-XX_EBS04_20). Orange dotted square is μ-XRF element mapping analysis area and red box area indicates μ-XRF quantitative analysis area. White dotted layer is XRD analysis area.
    Economic and Environmental Geology 2023; 56: 55-63https://doi.org/10.9719/EEG.2023.56.1.55

    Fig 3.

    Figure 3.μ-XRF mapping of Ferromanganese crust collected from western Pacific Magellan Seamounts. Color intensity indicates elemental intensity.
    Economic and Environmental Geology 2023; 56: 55-63https://doi.org/10.9719/EEG.2023.56.1.55

    Fig 4.

    Figure 4.Vertical profiles of chemical composition in wt.% obtained with μ-XRF quantitative analysis of ferromanganese crust from western Pacific Magellan Seamount.
    Economic and Environmental Geology 2023; 56: 55-63https://doi.org/10.9719/EEG.2023.56.1.55

    Fig 5.

    Figure 5.Vertical profiles of Co/Mn ratio and Mn/Fe ratio along a transect across Fe-Mn crust from western Pacific Magellan Seamounts.
    Economic and Environmental Geology 2023; 56: 55-63https://doi.org/10.9719/EEG.2023.56.1.55

    Fig 6.

    Figure 6.Representative X-ray diffraction patterns of Fe-Mn crust from western Pacific Magellan Seamount. Vernatide(V), Quartz(Q), Feldspar(F), Smectite(S) and Carbonate fluorapatite(CFA) were consisted in Fe-Mn crust.
    Economic and Environmental Geology 2023; 56: 55-63https://doi.org/10.9719/EEG.2023.56.1.55

    Fig 7.

    Figure 7.Age-quantitative analysis point plots derived from Co chronology.
    Economic and Environmental Geology 2023; 56: 55-63https://doi.org/10.9719/EEG.2023.56.1.55
    KSEEG
    Apr 30, 2024 Vol.57 No.2, pp. 107~280

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