A database of chondrite analyses including platinum group elements, Ni, Co, Au, and Cr: Implications for the identification of chondritic projectiles

Tagle, R.; Berlin, J.

doi:10.1111/j.1945-5100.2008.tb00671.x

Cited by 86 publications

(78 citation statements)

References 125 publications

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“…The Chicxulub projectile was a type CM2 chondrite (Trinquier et al, 2006) having an average Ni/Cr ratio of 4.053 (Tagle and Berlin, 2008). The low Ni/Cr ratio in the ODP 207 K-Pg deposit substantiates the hypothesis that most of the Ni and Cr in the ODP 207 K-Pg bed is not of extraterrestrial origin.…”

Section: Nickel and Chromiumsupporting

confidence: 55%

The Chicxulub ejecta deposit at Demerara Rise (western Atlantic): Dissecting the geochemical anomaly using laser ablation-mass spectrometry

Berndt

Deutsch

Schulte

et al. 2011

Geology

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We analyzed in situ the trace-element distributions in the pristine 2-cm-thick spherule-rich Cretaceous-Paleogene (K-Pg) event bed at Ocean Drilling Program (ODP) Leg 207 Site 1259C (Demerara Rise, western Atlantic) using laser ablation−inductively coupled plasma− mass spectrometry (LA-ICP-MS) with a spot diameter of 235 µm, corresponding to a sample volume of ~8.6 × 10 5 µm 3 . Unparalleled so far, this high resolution pinpoints the fallout of the Chicxulub projectile to the uppermost 2 mm of the K-Pg bed. Most of the Ni is not of extraterrestrial origin, as indicated by low, typical uppercrustal Ni/Cr ratios. Very low Zr/Hf and Nb/Ta ratios are confi ned exclusively to the K-Pg bed, indicating that storms and fl ooding spilled highly fractionated supracrustal material off the Guiana craton to reach the seafl oor contemporaneously with the now-altered glass spherules. Chicxulub ejecta volumetrically dominate the K-Pg bed but contributed only minimally to the trace-element budget, as indicated by the very low rare earth element concentrations. At the top of the ejecta layer, together with the fallout of Pt from the impactor (~0.1 ppm), a pronounced Pb enrichment (up to 1500 ppm) occurs, which is interpreted to derive from the Guiana craton. Both elements obviously were contained in submicrometer-size particles that could only reach the seafl oor attached to larger particles, the sedimentation of which may have occurred up to a year after the Chicxulub impact event. Our high-resolution analysis of the K-Pg event bed allows us, for the fi rst time, to differentiate among the contributing components in detail, as well as assess the settling time frame of this geologically important boundary deposit.

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Section: Nickel and Chromiumsupporting

confidence: 55%

The Chicxulub ejecta deposit at Demerara Rise (western Atlantic): Dissecting the geochemical anomaly using laser ablation-mass spectrometry

Berndt

Deutsch

Schulte

et al. 2011

Geology

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“…1987) also show progressive depletion of the volatile PGE from an unfractionated chondritic parent body. If one considers the CI elemental ratios for PGE as shown in Table 5 (Tagle and Berlin 2008), two nuggets in the present collection show Os/Ir (normalized to CI) close to unity, whereas in AAS‐22‐D3‐P4, the Os/Ir ratio is approximately 1.45 and in AAS‐26‐D1‐Hh the ratio is 0.72. The Os/Ir ratios of the latter two samples do not fall within the chondritic range (Fig.…”

Section: Resultsmentioning

confidence: 73%

“…In the one nanometer nugget where Pd has been reported by Bonte et al. (1987), the Pt/Pd ratio is 3.04, which is much more than the chondritic ratio of 1.70 (Tagle and Berlin 2008); therefore, large percentages of Pd appear to have been volatilized even in this nugget. Moreover, Bonte et al.…”

Section: Resultsmentioning

confidence: 83%

“…In contrast, when we look at the elemental ratios in the nuggets of AAS‐26‐D1‐P8 and AAS‐26‐D1‐Hh where Pt is present, we see Pt/Ir = 0.87 and 0.19, and Pt/Os = 0.97 and 0.27, respectively, which are much below the CI chondritic average of 2.03 and 1.97 (for Pt/Ir and Pt/Os) because of large‐scale depletion of Pt in these nuggets. Furthermore, Pt/Ru and Pt/Rh ratios of CI chondrites are 1.34 and 7.12, respectively (Tagle and Berlin 2008). These ratios when compared with the data show Pt/Ru = 1.01 and 0.32 in two of the nuggets where Pt is present, and Pt/Rh ratios are 9.32 and 4.46 (see Table 5).…”

Section: Resultsmentioning

confidence: 99%

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Micrometer‐ and nanometer‐sized platinum group nuggets in micrometeorites from deep‐sea sediments of the Indian Ocean

Rudraswami

Parashar

Prasad³

2011

Meteorit & Planetary Scien

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Abstract-We examined 378 micrometeorites collected from deep-sea sediments of the Indian Ocean of which 175, 180, and 23 are I-type, S-type, and G-type, respectively. Of the 175 I-type spherules, 13 contained platinum group element nuggets (PGNs). The nuggets occur in two distinct sizes and have distinctly different elemental compositions: micrometer (lm)-sized nuggets that are >3 lm contain dominantly Ir, Os, and Ru (iridium-platinum group element or IPGE) and sub-lm (or nanometer)-sized (<1 lm) nuggets, which contain dominantly Pt, Rh, and Pd (palladium-PGE or PPGE). The lm-sized nuggets are found only one per spherule in the cross section observed and are usually found at the edge of the spherule. By contrast, there are hundreds of nanometer-sized nuggets distributed dominantly in the magnetite phases of the spherules, and rarely in the wu¨stite phases. Both the nugget types are found as separate entities in the same spherule and apparently, nugget formation is a common phenomenon among I-type micrometeorites. However, the lm-sized nuggets are seen in fewer specimens (2.5% of the observed I-type spherules). In all, we analyzed four nuggets of lm size and 213 nanometer-sized nuggets from 13 I-type spherules for platinum group elements. Chemically, the lm-sized PGNs contain chondritic ratios of Os ⁄ Ir, but are depleted in the more volatile PGE (Pt, Rh, and Pd) relative to chondritic ratios. On the other hand, the nanometer-sized nuggets contain dominantly Pt and Rh. Importantly, the refractory PGEs are conspicuous by their absence in these nanometer nuggets. Palladium, the most volatile PGE is highly depleted (<1.1%) with respect to chondritic ratios in the lm-sized PGNs, and is observed in only 17 of 213 nanometer nuggets with concentrations that are just above the detection limit ( ‡0.2%). Distinct fractionation of the PGE into IPGE (Ir, Os, Ru) and PPGE seems to take place during the short span of atmospheric entry. These observations suggest several implications: (1) The observation of fractionated PGE in an Fe-Ni system gives rise to the possibility that Earth's core could contain fractionated PGE. (2) The present data support the processes suggested for the fractionated PGE patterns observed in the ejecta of ancient meteorite impacts. (3) Meteoric metals released in the troposphere could contain fractionated PGNs in large numbers.

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“…[] recently (Figure b). In addition to Fe and Ni, these nuggets contain only Pt, except for the large (>200 nm) ones with Pt contents > ~5%, for which Rh is also detected in proportions consistent with the chondritic Pt:Rh ratio of 7 [ Tagle and Berlin , ].…”

Section: Spherule Descriptionsmentioning

confidence: 99%

Micrometeorite flux on Earth during the last ~50,000 years

2013

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[1] Flux of micrometeorites is estimated by using cosmic spherule counts from a seafloor area of 2.50 m 2 from the Indian Ocean. The spherules are recovered from sediment samples in close-spaced locations from the Indian Ocean after sieving 293 kg of sediment. The terrestrial age of the spherules has a range of 0-~50,000 years. The spherules have a size range of 57-750 μm (average size 265 ± 92 μm). The diameter of the spherules increases from scoriaceous-barred-cryptocrystalline-glassy types. The time-averaged flux of the spherules is 160 t/yr, a sizeable mass (>60%) resides in the >300 μm fraction; the slope of distribution is similar to that of Deep-Sea Spherules but significantly different from other collections which have lower average diameters. It is observed here, a significant population of cosmic dust resides in the larger sizes which can be recovered by sampling large areas in time and space. The spherule textures are similar to that of unbiased collections from the polar regions, indicating that the textural types of cosmic dust that have been raining on the Earth during the last 50 kyr have been constant regardless of size. Major element chemistry of a majority of the spherules show elemental ratios that are close to a CM or CI chondritic parent body; a single spherule (0.2% of the population) suggests an achondritic parent body. Unbiased collections spanning large areas temporally and spatially enlarge the inventory of the Earth-crossing meteoroid complex and provide valuable inputs for models on cosmic dust accretion.

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A database of chondrite analyses including platinum group elements, Ni, Co, Au, and Cr: Implications for the identification of chondritic projectiles

Cited by 86 publications

References 125 publications

The Chicxulub ejecta deposit at Demerara Rise (western Atlantic): Dissecting the geochemical anomaly using laser ablation-mass spectrometry

The Chicxulub ejecta deposit at Demerara Rise (western Atlantic): Dissecting the geochemical anomaly using laser ablation-mass spectrometry

Micrometer‐ and nanometer‐sized platinum group nuggets in micrometeorites from deep‐sea sediments of the Indian Ocean

Micrometeorite flux on Earth during the last ~50,000 years

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