Reconstructing the marine 187Os/188Os record and the particulate flux of meteoritic osmium during the late Cretaceous

Search for the proverbial mantle osmium sources to the oceans: Hydrothermal alteration of mid-ocean ridge basalt

“…This suggests that the total amount of cosmic dust plus meteorite derived Os accreted annually to the Earth ranges from (263-515) ± 51 mol yr À1 . An assessment of Os deposited on the ocean floor could be obtained by analyzing the marine sediments (Peucker-Ehrenbrink and Ravizza, 2000;Sharma et al, 2000;Dalai and Ravizza, 2006;Ravizza, 2007). The 187 Os/ 188 Os ratio of recently deposited clay from the Domes Site C = 0.79 (Esser and Turekian, 1988) and suggests $436 mol yr À1 of Os comes from meteorites (Sharma et al, 2000) and appears consistent with the above assessment.…”

“…As the Os/Ir ratio of meteorites is $1 both of these estimates appear to be in good agreement. That there is a possible temporal variation in the amount of ET Os accreted to Earth is demonstrated by a recent study (Ravizza, 2007), which suggests that between 65.5 and 78 Ma the Os flux was between 13 and 52 mol yr À1 , much less than that estimated for the Cenozoic. Using the above observations we estimate that the ET Os accretion rate close to the present-day could be between 38 and 320 mol yr À1 .…”

Os‐isotope insights into major environmental changes of the Arctic Ocean during the Cenozoic

“…Osmium isotopes were measured by NTIMS [ Creaser et al , 1991] on a VG Sector 54; DTM Os‐standard isotopic composition was repeatedly measured on a Channeltron at 0.1739 ± 0.0005 (n = 6, 50 pg‐loads) during the course of this study. Leach experiments following Ravizza 's [2007] protocol (dilute H 2 O 2 + HNO 3 ) are also reported (0.45 pg Os‐blank per ml of leach solution, coming from the hydrogen peroxide, n = 2). Rhenium isotope dilution measurements were obtained on a MC‐ICP‐MS (Micromass IsoProbe), using tungsten as internal standard to monitor mass bias, and an Aridus desolvating membrane.…”

Os isotope chemostratigraphy applied to organic‐rich marine sediments from the Eocene‐Oligocene transition on the West African margin (ODP Site 959)

“…Os was analyzed by directly sparging Os into an Element2 magnetic sector inductively coupled plasma‐mass spectrometry (ICP‐MS) [ Hassler et al , 2000] from the nitric acid/peroxide solutions. This has been done previously using unheated solutions and less aggressive reagent mixtures [ Dalai et al , 2006; Ravizza , 2007]. Re was purified from the remaining solution after sparging using anion exchange resin (Biorad AG1‐X8) and was analyzed using an Element2 ICPMS.…”