Strontium and Oxygen isotope compositions from DSDP Holes 54-424A, 54-424B and 70-509B


Autoria(s): Clauer, Norbert; O´Neil, JR; Honnorez, Jose J; Buatier, Martine D
Cobertura

MEDIAN LATITUDE: 0.590987 * MEDIAN LONGITUDE: -86.130760 * SOUTH-BOUND LATITUDE: 0.588800 * WEST-BOUND LONGITUDE: -86.132200 * NORTH-BOUND LATITUDE: 0.597000 * EAST-BOUND LONGITUDE: -86.130200 * DATE/TIME START: 1977-05-23T00:00:00 * DATE/TIME END: 1979-11-27T00:00:00

Data(s)

22/08/2011

Resumo

Strontium and O isotope compositions of green clay minerals from sediment cores of three boreholes drilled into (sites 424A and 509B) and close to a hydrothermal mound (site 424B) near the Galapagos Spreading Center (DSDP Legs 54 and 70) were determined. The green clays consist mostly of a transition from Fesmectite (nontronite) to glauconite. 87Sr/86Sr ratios were measured on clay size-fractions after gentle acid leaching and on the recovered leachates from different samples. The 87Sr/86Sr ratios of the clay residues from both the 424A and B sites are well below the modern seawater value, which points consistently to precipitation from hydrothermal fluids that contained variable amounts of seawater, even away from mound. However, most of the clay residues from mound site 509B have 87Sr/86Sr ratios significantly above the seawater value, suggesting the occurrence of a detrital component together with the new authigenic particles. The clay minerals of the hydrothermal mound are mixed with detrital components, and that of the sample taken outside but near the mound as a reference for the surrounding oceanic environment, yields a hydrothermal signature. Crystallization temperatures of the clays range from 32 to 63 °C assuming a d18O value of +2.2 per mil for the mineralizing fluids. Hydrothermal fluids generated in the underlying oceanic crust, mixed in varied proportions with ambient seawater and migrated into beds of the mound in a sequence of recurrent processes that ultimately resulted in the formation of the observed clay minerals. No significant temperature differences were detected for crystallization of the K-rich glauconite and K-depleted nontronite. The 87Sr/86Sr ratios of the Sr leached off the clay particles are near the value of modern seawater, inferring a progressive replacement of the hydrothermal fluids by seawater in the pore space of the mound sediments.

Formato

application/zip, 2 datasets

Identificador

https://doi.pangaea.de/10.1594/PANGAEA.787607

doi:10.1594/PANGAEA.787607

Idioma(s)

en

Publicador

PANGAEA

Direitos

CC-BY: Creative Commons Attribution 3.0 Unported

Access constraints: unrestricted

Fonte

Supplement to: Clauer, Norbert; O´Neil, JR; Honnorez, Jose J; Buatier, Martine D (2011): 87Sr/86Sr and d18O/d16O ratios of clays from a hydrothermal area near the Galapagos rift as records of origin, crystallization temperature and fluid composition. Marine Geology, 288, 32-42, doi:10.1016/j.margeo.2011.07.003

Palavras-Chave #1/Sr; 1/Sr ratio; 1000 lnAlpha(M-H2O) d18O(fluide) = + 2.2 per mil; 1000 lnAlpha(M-H2O) d18O(fluide) = 0 per mil; 1000 lnAlpha(Min-H2O) d18O(fluide) = +0.4 per mil; 1000 lnAlpha(Min-H2O) d18O(fluide) = +2.2 per mil; 87Rb/86Sr; 87Sr/86Sr; 87Sr/86Sr e; d18O; d18OM; d18OMin; d18O recon; Deep Sea Drilling Project; delta 18O; delta 18O, reconstructed; Depth; DEPTH, sediment/rock; DSDP; Event; Isotope ratio mass spectrometry; Label; Lab no; mbsf; Multicollector mass spectrometry; ODP sample designation; Rb; Rb/Sr; Rubidium; Rubidium/Strontium ratio; Rubidium 87/Strontium 86 ratio; Sample, optional label/labor no; Sample code/label; Sample labels (size); Sr; Strontium; Strontium 87/Strontium 86, error; Strontium 87/Strontium 86 ratio; T cal; Temperature, calculated
Tipo

Dataset