Archive · collection · 1996
Description and 238U, 234U, 232Th and 230Th measurements of the manganese nodule analysed from station SO79_63KG, R/V SONNE
Listed in PANGAEA
Thorium and uranium isotopes were measured in a diagenetic manganese nodule from the Peru basin applying alpha- and thermal ionization mass spectrometry (TIMS).
Description
Alpha-counting of 62 samples was carried out with a depth resolution of 0.4 mm to gain a high-resolution Th-230(excess) profile. In addition, 17 samples were measured with TIMS to obtain precise isotope concentrations and isotope ratios.
We got values of 0.06-0.59 ppb (Th-230), 0.43-1.40 ppm (Th-232), 0.09-0.49 ppb (U-234) and 1.66-8.24 ppm (U-238). The uranium activity ratio in the uppermost samples (1-6 mm) and in two further sections in the nodule at 12.5+/-1.0 mm and 27.3-33.5 mm comes close to the present ocean wa ter value of 1.144+/-0.004. In two other sections of the nodule, this ratio is significantly higher, probably reflecting incorporation of diagenetic uranium.
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The upper 25 mm section of the Mn nodule shows a relatively smooth exponential decrease in the Th-230(excess) concentration (TIMS). The slope of the best fit yields a growth rate of 110 mm/Ma up to 24.5 mm depth. The section from 25 to 30.3 mm depth shows constant Th-230(excess) concentrations probably due to growth rates even faster than those in the top section of the nodule.
From 33 to 50 mm depth, the growth rate is approximately 60 mm/Ma. Two layers in the nodule with distinct laminations (11-15 and 28-33 mm depth) probably formed during the transition from isotopic stage 8 to 7 and in stage 5e, respectively. The Mn/Fe ratio shows higher values during interglacials 5 and 7, and lower ones during glacials 4 and 6.
A comparison of our data with data from adjacent sediment cores suggests (a) a variable sb supply of hydrothermal Mn to sediments and Mn nodules of the Peru basin or (b) suboxic conditions at the water sediment interface during periods with lower Mn/Fe ratios.
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Where it is published
- DOI doi.org/10.1594/pangaea.855848 ↗
DOI / persistent id · from PANGAEA
Catalogue records · 1
- OAI-PMH record ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=oai_dc&identifier=o… ↗
metadata API · from PANGAEA
Topics
- From keywords
- Earth & Environmental Science
- Inferred from text
- Mass spectrometry 75%
Provenance · 1 source records, 8 field assertions
| Source | Key | Last seen | Raw |
|---|---|---|---|
| PANGAEA | oai:pangaea.de:doi:10.1594/PANGAEA.855848 | 11 d ago | JSON v1 |
| Field | Assertion | Extractor | Evidence |
|---|---|---|---|
| access_level | source · PANGAEA | connector:pangaea@1.0.0 | |
| concepts[field].local:field:earth-environmental | mapping · PANGAEA | connector:pangaea@1.0.0 | |
| concepts[modality].local:modality:mass-spectrometry | enrichment · PANGAEA | keyword-concept-rules@1.0.0 | title+description (75%) |
| description | source · PANGAEA | connector:pangaea@1.0.0 | /metadata/dc/description |
| license | source · PANGAEA | connector:pangaea@1.0.0 | /metadata/dc/rights |
| publication_date | source · PANGAEA | connector:pangaea@1.0.0 | |
| spatial | source · PANGAEA | connector:pangaea@1.0.0 | |
| title | source · PANGAEA | connector:pangaea@1.0.0 | /metadata/dc/title |