Elemental and isotopic compositions of metalliferous and pelagic sediments from the Galapagos mounds area, data of DSDP Leg 70
Fuente:
PANGAEA
Salvato in:
| Autori principali: | , |
|---|---|
| Natura: | Dataset Open Access |
| Lingua: | en |
| Pubblicazione: |
PANGAEA
1982
|
| Soggetti: | |
| Accesso online: | |
| Tags: |
Aggiungi Tag
Nessun Tag, puoi essere il primo ad aggiungerne!!
|
| _version_ | 1867171356647358464 |
|---|---|
| author | Barrett, T J Friedrichsen, Hans |
| author_facet | Barrett, T J Friedrichsen, Hans |
| collection | Datos científicos de ciencias marinas y ambientales |
| contents | Nontronite, the main metalliferous phase of the Galapagos mounds, occurs at a subsurface depth of ~2–20 m; Mn-oxide material is limited to the upper 2 m of these mounds. The nontronite forms intervals of up to a few metres thickness, consisting essentially of 100% nontronite granules, which alternate with intervals of normal pelagic sediment. The metalliferous phases represent essentially authigenic precipitates, apparently formed in the presence of upwelling basement-derived hydrothermal solutions which dissolved pre-existent pelagic sediment. Electron microprobe analyses of nontronite granules from different core samples indicate that: (1) there is little difference in major-element composition between nontronitic material from varying locations within the mounds; and (2) adjacent granules from a given sample have very similar compositions and are internally homogeneous. This indicates that the granules are composed of a single mineral of essentially constant composition, consistent with relatively uniform conditions of solution Eh and composition during nontronite formation. The Pb-isotopic composition of the nontronite and Mn-oxide sediments indicates that they were formed from solutions which contained variable proportions of basaltic Pb, introduced into pore waters by basement-derived solutions, and of normal-seawater Pb. However, the Sr-isotopic composition of these sediments is essentially indistinguishable from the value for modern seawater. On the basis of 18O/16O ratios, formation temperatures of ~20–30°C have been estimated for the nontronites. By comparison, temperatures of up to 11.5°C at 9 m depth have been directly measured within the mounds and heat flow data suggest present basement-sediment interface temperatures of 15–25°C. |
| format | Dataset Open Access |
| id | pangaea_https___doi_org_10_1594_PANGAEA_695931 |
| institution | PANGAEA |
| language | en |
| publishDate | 1982 |
| publisher | PANGAEA |
| record_format | pangaea |
| spellingShingle | Elemental and isotopic compositions of metalliferous and pelagic sediments from the Galapagos mounds area, data of DSDP Leg 70 Barrett, T J Friedrichsen, Hans 70-506; 70-506B; 70-506C; 70-506G; 70-507B; 70-507D; 70-507F; 70-508B; 70-509B; 70-510; Deep Sea Drilling Project; DRILL; Drilling/drill rig; DSDP; Glomar Challenger; Leg70; NOAA and MMS Marine Minerals Geochemical Database; NOAA-MMS; North Pacific/MOUND; North Pacific Ocean Nontronite, the main metalliferous phase of the Galapagos mounds, occurs at a subsurface depth of ~2–20 m; Mn-oxide material is limited to the upper 2 m of these mounds. The nontronite forms intervals of up to a few metres thickness, consisting essentially of 100% nontronite granules, which alternate with intervals of normal pelagic sediment. The metalliferous phases represent essentially authigenic precipitates, apparently formed in the presence of upwelling basement-derived hydrothermal solutions which dissolved pre-existent pelagic sediment. Electron microprobe analyses of nontronite granules from different core samples indicate that: (1) there is little difference in major-element composition between nontronitic material from varying locations within the mounds; and (2) adjacent granules from a given sample have very similar compositions and are internally homogeneous. This indicates that the granules are composed of a single mineral of essentially constant composition, consistent with relatively uniform conditions of solution Eh and composition during nontronite formation. The Pb-isotopic composition of the nontronite and Mn-oxide sediments indicates that they were formed from solutions which contained variable proportions of basaltic Pb, introduced into pore waters by basement-derived solutions, and of normal-seawater Pb. However, the Sr-isotopic composition of these sediments is essentially indistinguishable from the value for modern seawater. On the basis of 18O/16O ratios, formation temperatures of ~20–30°C have been estimated for the nontronites. By comparison, temperatures of up to 11.5°C at 9 m depth have been directly measured within the mounds and heat flow data suggest present basement-sediment interface temperatures of 15–25°C. |
| title | Elemental and isotopic compositions of metalliferous and pelagic sediments from the Galapagos mounds area, data of DSDP Leg 70 |
| topic | 70-506; 70-506B; 70-506C; 70-506G; 70-507B; 70-507D; 70-507F; 70-508B; 70-509B; 70-510; Deep Sea Drilling Project; DRILL; Drilling/drill rig; DSDP; Glomar Challenger; Leg70; NOAA and MMS Marine Minerals Geochemical Database; NOAA-MMS; North Pacific/MOUND; North Pacific Ocean |
| url | https://doi.org/10.1594/PANGAEA.695931 |