TY - JOUR
T1 - Major and trace element compositions and resource potential of ferromanganese crust at Takuyo Daigo Seamount, northwestern Pacific Ocean
AU - Nozaki, Tatsuo
AU - Tokumaru, Ayaka
AU - Takaya, Yutaro
AU - Kato, Yasuhiro
AU - Suzuki, Katsuhiko
AU - Urabe, Tetsuro
N1 - Funding Information:
We are grateful to the officers, crews, scientists, and ROV operating team of cruise NT09-02 for their valuable collaborations. We thank Y. Itabashi for assistance with ICP-MS analyses at the University of Tokyo. Constructive review comments by two anonymous reviewers and editor (J.-I. Ishibashi) much improved our manuscript. This study was supported by the Japan Society for the Promotion of Science through Grants-in-Aid Nos. 20109001, 21840069, and 24740360.
PY - 2016
Y1 - 2016
N2 - We report major element and trace element compositions of ferromanganese crusts (Fe-Mn crusts) on Takuyo Daigo Seamount, northwestern Pacific Ocean. Highly enriched elements in these crusts, such as Co (6500 ppm), Ni (4000 ppm), Mo (520 ppm), Te (39 ppm), W (92 ppm), Pt (0.19 ppm), and rare earth elements (REEs; ΣREE = 1700 ppm), exhibit strong positive correlations with either Fe or Mn concentrations. Chemical analyses of the crusts show that the Fe/Mn ratio decreases toward shallower water and older deposits. Thus, deeper or younger crust is more promising as a REE (other than Ce) resource, and shallower or older crust has a greater potential as Co, Ni, Ce, and Pt resources. REE profiles of Fe-Mn crusts with less than 0.5 wt% P, normalized to post-Archean average Australian shale, are flat with positive Ce anomalies whereas samples with more than 0.5 wt% P are enriched in heavy REE, and four samples from deep in the crusts with more than 2.2 wt% P do not exhibit positive Ce anomalies. These differences in REE patterns can be explained by mixing of Fe-Mn oxide and Ca-phosphate minerals (apatite). Assuming that Fe-Mn crusts with 5 cm thickness and 1.29 g/cm3 dry density are homogeneously distributed at water depths from 1000 to 3000 m along the 500 km perimeter of Takuyo Daigo Seamount, the possible reserve represented by Fe-Mn crusts is roughly 65 Mt of ore. Based on the average concentrations obtained here, resource amounts at Takuyo Daigo Seamount are 420 ×103 t Co, 110 ×103 tREO, 2500 t Dy, and 440 t Tb, comparable to the known reserves of major mineral producing nations. Thus, Fe-Mn crusts in the northwestern Pacific Ocean have a notable potential as a source of Co.
AB - We report major element and trace element compositions of ferromanganese crusts (Fe-Mn crusts) on Takuyo Daigo Seamount, northwestern Pacific Ocean. Highly enriched elements in these crusts, such as Co (6500 ppm), Ni (4000 ppm), Mo (520 ppm), Te (39 ppm), W (92 ppm), Pt (0.19 ppm), and rare earth elements (REEs; ΣREE = 1700 ppm), exhibit strong positive correlations with either Fe or Mn concentrations. Chemical analyses of the crusts show that the Fe/Mn ratio decreases toward shallower water and older deposits. Thus, deeper or younger crust is more promising as a REE (other than Ce) resource, and shallower or older crust has a greater potential as Co, Ni, Ce, and Pt resources. REE profiles of Fe-Mn crusts with less than 0.5 wt% P, normalized to post-Archean average Australian shale, are flat with positive Ce anomalies whereas samples with more than 0.5 wt% P are enriched in heavy REE, and four samples from deep in the crusts with more than 2.2 wt% P do not exhibit positive Ce anomalies. These differences in REE patterns can be explained by mixing of Fe-Mn oxide and Ca-phosphate minerals (apatite). Assuming that Fe-Mn crusts with 5 cm thickness and 1.29 g/cm3 dry density are homogeneously distributed at water depths from 1000 to 3000 m along the 500 km perimeter of Takuyo Daigo Seamount, the possible reserve represented by Fe-Mn crusts is roughly 65 Mt of ore. Based on the average concentrations obtained here, resource amounts at Takuyo Daigo Seamount are 420 ×103 t Co, 110 ×103 tREO, 2500 t Dy, and 440 t Tb, comparable to the known reserves of major mineral producing nations. Thus, Fe-Mn crusts in the northwestern Pacific Ocean have a notable potential as a source of Co.
KW - Fe-mn crust
KW - Northwestern pacific ocean
KW - Resource potential evaluation
KW - Takuyo daigo seamount
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U2 - 10.2343/geochemj.2.0430
DO - 10.2343/geochemj.2.0430
M3 - Article
AN - SCOPUS:85007382627
VL - 50
SP - 527
EP - 537
JO - Geochemical Journal
JF - Geochemical Journal
SN - 0016-7002
IS - 6
ER -