Farnella Cruise F7-86-HW, cobalt-rich ferromanganese crust data report for Karin Ridge and Johnston Island, Central Pacific

Hein, James R.; Schwab, William C.; Foot, D.G.; Masuda, Yoshio; Usui, Akira; Davis, Alicé S.; Fleishman, C.L.; Barna, D.L.; Pickthorn, Ledabeth G; Larson, David A.; Ruzzi, Peter; Benninger, L.M.; Gein, L.M.

doi:10.3133/ofr87663

Cited by 7 publications

(7 citation statements)

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“…Minor (<5%) amounts of CFA occur in many more rocks from these regions. A mean P205 content of 5.2% was determined for 9.4 kg of representative homogenized rocks plus associated Fe-Mn crusts recovered in 25 dredges from Karin Ridge and South Johnston Island Ridge (SOJIR) in the Johnston Island area [Hein et al, 1987]. We suggest that these quantities are typical for the central Pacific region in general.…”

mentioning

confidence: 83%

“…The EPSP are localized high grade deposits, but in order to estimate the total amount of phosphorus locked up in them, we took the mean phosphorus content of 9.4 kg of representative homogenized rocks from 25 dredge hauls. This mean content is 5.2% P205 (2.3% P) [Hein et al, 1987] and is used in our first model to calculate the maximum seamount phosphorus sink. In this model, the thickness of the phosphatized rock layer is taken to be 2 m, twice the known thickness of phosphatized rock as determined by dredging [Hein et al, 1985[Hein et al, , 1987[Hein et al, , 1990a Table 7).…”

Section: Abundance Of Phosphorus In Equatorial Paci•c Cretaceous Seammentioning

confidence: 99%

“…This mean content is 5.2% P205 (2.3% P) [Hein et al, 1987] and is used in our first model to calculate the maximum seamount phosphorus sink. In this model, the thickness of the phosphatized rock layer is taken to be 2 m, twice the known thickness of phosphatized rock as determined by dredging [Hein et al, 1985[Hein et al, , 1987[Hein et al, , 1990a Table 7).…”

Section: Abundance Of Phosphorus In Equatorial Paci•c Cretaceous Seammentioning

confidence: 99%

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Two Major Cenozoic Episodes of Phosphogenesis Recorded in Equatorial Pacific Seamount Deposits

Hein¹,

Yeh²,

Gunn³

et al. 1993

Paleoceanography

145

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Sea_mount phosphorites have been recognized since the 1950s, but this is the first study to provide an in depth exploration of the origin and history of these widespread deposits. Representative samples from equatorial Pacific Cretaceous s•mounts were analyzed for chemical, mineralogical, and stable isotope compositions. The phosphorites occur in a wide variety of forms, but most commonly carbonate fluorapatite (CFA) replaced middle Eocene and older carbonate sediment in a deep water environment (>1000 m). Element ratios distinguish seamount phosphorites from continental margin, plateau, and insular phosphorites. Uranium and thorium contents are low and total rare earth element (REE) contents are generally high. REE ratios and shale-normaiized patterns demonstrate that the REEs and host CFA were derived from seawater. Strontium isotopic compositions compared with inferred Cenozoic seawater curves define two major episodes of Cenozoic phosphafization: Late Eocene/early Oligocene (39-34 Ma) and late Oligocene/early Miocene (27-21 Ma); three minor events are also indicated. The major episodes occurred at times of climate transition, the first from a nonglacial to glacial earth and the second from a predominantly glacial to warm earth. The paleoceanographic conditions that existed at those times initiated and sustained development of phosphorite by 1U. S. Geological Survey, Paper number 93PA00320 0883-8305/93/93PA-00320510.00 accumulation of dissolved phosphorus in the deep sea during relatively stable climatic conditions when oceanic circulation was sluggish. Fluctuations in climate, sealevel, and upwelling that accompanied the climate transitions may have driven cycles of enrichment and depletion of the deep-sea phosphorus reservoir. As temperature gradients in the oceans increased, Antarctic glaciafion expanded and oceanic circulation and upwelling intensified. Expansion and intensification of the oxygen minimum zone may have increased the capacity for midwater storage of phosphorus supplied by dynamic upwelling around seamounts; however, the bottom waters never became anoxic during the phosphogenic episodes. Fluctuations in the CCD and lysocline, CO2 fluxes, and changes in bottom water circulation and temperatures may have bathed the seamount carbonates in more corrosive waters which, coupled with increased supplies of dissolved phosphorus, promoted replacement processes. The late Eocene/early Oligocene phosphogenic episode recorded in seamount deposits is not matched by large phosphofite deposits in the geologic record, whereas the late Oligocene/early Miocene episode and middle Miocene event are matched by large deposits distributed globally. The seamount phosphorires are exposed at the surface of the seamounts and have been for most of the Neogene and Oligocene. The phosphorires do not show signs of etching that would indicate substantial undersaturation of seawater phosphate with respect to CFA. Mass balance calculations indicate that about 5.4-19 x 1012 g of P205 are locked up in equatorial Pacific seamount ...

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mentioning

confidence: 83%

Section: Abundance Of Phosphorus In Equatorial Paci•c Cretaceous Seammentioning

confidence: 99%

Section: Abundance Of Phosphorus In Equatorial Paci•c Cretaceous Seammentioning

confidence: 99%

See 1 more Smart Citation

Two Major Cenozoic Episodes of Phosphogenesis Recorded in Equatorial Pacific Seamount Deposits

Hein¹,

Yeh²,

Gunn³

et al. 1993

Paleoceanography

145

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“…However, during the past 10-20 My, the average Fe isotopic composition of central Pacific seawater recorded by CD29-2 and 28DSR9 became largely invariant at δ 56=54 Fe ≈ +0:4 ± 0:1‰ (±2 SD). This switch to relative Fe isotopic homogeneity over the past [10][11][12][13][14][15][16][17][18][19][20] My is roughly coincident with a sharp increase in eolian dust deposition in the central and North Pacific (refs. 61 and 62, Fig.…”

Section: Cd29-2 Latitude (°)mentioning

confidence: 99%

Persistence of deeply sourced iron in the Pacific Ocean

Horner¹,

Williams

Hein

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Biological carbon fixation is limited by the supply of Fe in vast regions of the global ocean. Dissolved Fe in seawater is primarily sourced from continental mineral dust, submarine hydrothermalism, and sediment dissolution along continental margins. However, the relative contributions of these three sources to the Fe budget of the open ocean remains contentious. By exploiting the Fe stable isotopic fingerprints of these sources, it is possible to trace distinct Fe pools through marine environments, and through time using sedimentary records. We present a reconstruction of deep-sea Fe isotopic compositions from a Pacific Fe−Mn crust spanning the past 76 My. We find that there have been large and systematic changes in the Fe isotopic composition of seawater over the Cenozoic that reflect the influence of several, distinct Fe sources to the central Pacific Ocean. Given that deeply sourced Fe from hydrothermalism and marginal sediment dissolution exhibit the largest Fe isotopic variations in modern oceanic settings, the record requires that these deep Fe sources have exerted a major control over the Fe inventory of the Pacific for the past 76 My. The persistence of deeply sourced Fe in the Pacific Ocean illustrates that multiple sources contribute to the total Fe budget of the ocean and highlights the importance of oceanic circulation in determining if deeply sourced Fe is ever ventilated at the surface.

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“…Lastly, the environmental impact of removing sand from the shallow fore reef should be evaluated, especially the effect on incident wave energy and the exchange of sand between the beach and offshore so that beach erosion does not result from the mining. (Hein andothers, 1985, 1987a, b, in press) Metallic deposits of various types and origins occur on the sea floor and are a potential resource for the future. In particular, cobalt-rich ferromanganese crusts (hereafter referred to simply as "crusts") coat the hard substrate on the flanks of volcanic ridges, seamounts, and guyots (Hawaii, Johnston Island, Howland-Baker, Wake, Kingman-Palmyra) in the U.S. EEZ.…”

Section: Future Mapping Needsmentioning

confidence: 99%

Proceedings of the 1989 Exclusive Economic Zone symposium on Mapping and research; Federal-State partners in EEZ mapping

McGregor¹

1990

Circular

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Mapping and ~esearch (JOMAR) and the Association of American State Geologists. Attending the meeting were approximately 220 individuals who represented Federal Government agencies, executive and legislative branches (63 percent); private industry, including consultants (10 percent); State governments (9 percent); academic institutions (8 percent); societies, nonprofit groups, and private citizens (7 percent); and foreign attendees (3 percent). A list of attendees and their affiliations is contained in Appendix 2. The meeting was separated into three sections. The first, or plenary, session dealt with broad programmatic objectives and policy issues, the second involved presentations of 16 case studies of regional mapping projects, and the final session consisted of 6 technical workshops. The following highlights the major points and areas of discussion developed at the symposium. Details are contained in the papers submitted by the individual participants in the main section of the proceedings. In a few cases, written papers were not submitted by the participants; Manuscript approved for publication, June 28, 1990. serve as a guidepost for subsequent activities, products, and research in the EEZ.

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Farnella Cruise F7-86-HW, cobalt-rich ferromanganese crust data report for Karin Ridge and Johnston Island, Central Pacific

Cited by 7 publications

References 1 publication

Two Major Cenozoic Episodes of Phosphogenesis Recorded in Equatorial Pacific Seamount Deposits

Two Major Cenozoic Episodes of Phosphogenesis Recorded in Equatorial Pacific Seamount Deposits

Persistence of deeply sourced iron in the Pacific Ocean

Proceedings of the 1989 Exclusive Economic Zone symposium on Mapping and research; Federal-State partners in EEZ mapping

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