Refractory metal nuggets in different types of cosmic spherules

Rudraswami, N. G.; Prasad, M.M.; Plane, J. M. C.; Berg, T.; Feng, Wuhu; Balgar, S.

doi:10.1016/j.gca.2014.01.026

Cited by 34 publications

(52 citation statements)

References 46 publications

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“…As the tolerance is raised from 5 − 15 at% , the number of RMNs consistent with Some RMNs have been demonstrably attributed to crystallisation processes, where an RMN has crystallised from a melt; either in experimental studies (Schwander et al, 2015), or observed in cosmic spherules (Rudraswami et al, 2014). When these RMNs are superimposed over RMNs analysed in this study and the literature (Figure 9), crystallisation RMNs fall along the Fe mixing line and the high PGE region of the Ni mixing line.…”

Section: Condensation As a Rmn Forming Processsupporting

confidence: 69%

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In situ analysis of Refractory Metal Nuggets in carbonaceous chondrites

Daly

Bland

Dyl

et al. 2017

Geochimica et Cosmochimica Acta

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Micrometre to sub-micrometre scale alloys of platinum group elements (PGEs) know as refractory metal nuggets (RMNs) have been observed in primitive meteorites. The Australian Synchrotron X-ray Fluorescence (XRF) beamline, in tandem with the Maia detector, allows rapid detection of PGEs in concentrations as low as 50-100 ppm at 2 µm resolution. Corroborating this analysis with traditional electron microscopy techniques, RMNs can be rapidly identified in situ within carbonaceous chondrites. These results dispute the assumption of previous studies: that RMNs are unique to Ca-Al-rich inclusions (CAIs). We find that RMNs (Schwander et al., 2015), host phase and host meteorite. This reveals only weak correlations between parent body processes (sulphidation) and nebular processes (condensation and crystallisation) with RMN compositions. It appears that none of these processes acting in isolation or in tandem can explain the diversity we observe in the RMN population. Our interpretation is that the Solar Nebula inherited an initially compositionally diverse population of RMNs from the giant molecular cloud; that a variety of Solar System processes have acted on that population; but none have completely homogenised it. Most RMNs have experienced disk and asteroidal processing, but some may have retained a primordial composition.RMNs have been identified in pre-solar graphite (Croat et al., 2013) grains. We anticipate that pre-solar RMNs will be present elsewhere in primitive meteorites.

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Section: Condensation As a Rmn Forming Processsupporting

confidence: 69%

“…We also include compositions of RMNs thought to be derived from crystallisation processes (Schwander et al, 2015;Rudraswami et al, 2014). These analyses were plotted alongside observed RMN compositions from this study.…”

Section: Condensation Model and Crystallisation Proxymentioning

confidence: 99%

In situ analysis of Refractory Metal Nuggets in carbonaceous chondrites

Daly

Bland

Dyl

et al. 2017

Geochimica et Cosmochimica Acta

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“…The Antarctica micrometeorites (AMM) were collected from the South Pole Water Well (SPWW), which has a diameter of ∼24 m at a depth of ∼100 m below the snow surface, with a total water volume of ∼5000 m 3 (Taylor et al 1998(Taylor et al , 2000. The cosmic spherules from deep sea sediments (CS-DSS) were collected at water depths of ∼5200 m using an Okean grab sampler with a seafloor penetration depth of ∼15 cm (Rudraswami et al 2012(Rudraswami et al , 2014(Rudraswami et al , 2015aPrasad et al 2013). The AMM and CS-DSS have been dated at ∼900 years BP and 0-50,000 years BP, respectively (Taylor et al 1998(Taylor et al , 2007Prasad et al 2013).…”

Section: Sample Collection and Electron Microscopymentioning

confidence: 99%

“…The composition of minor elements present in the relict mineral helps narrow down the precursor with greater precision than the bulk chemical composition (Steele et al 1985a(Steele et al , 1985b1992), particularly because Mg-rich olivine can be compared with Mg-rich olivine in chondritic components. In contrast, the bulk chemical composition of a particle may alter depending on the heating experienced during atmospheric entry, and is typically close to CI composition (Kurat et al 1994;Brownlee et al 1997;Taylor et al 2000;Rudraswami et al 2012Rudraswami et al , 2014. Earlier studies were limited by statistics due to the small number of relict grains analyzed (Steele et al 1985a(Steele et al , 1985b1992).…”

Section: Introductionmentioning

confidence: 99%

Relict Olivines in Micrometeorites: Precursors and Interactions in the Earth’s Atmosphere

Rudraswami

Prasad

Dey

et al. 2016

ApJ

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Antarctica micrometeorites (∼1200) and cosmic spherules (∼5000) from deep sea sediments are studied using electron microscopy to identify Mg-rich olivine grains in order to determine the nature of the particle precursors. Mg-rich olivine (FeO<5wt%) in micrometeorites suffers insignificant chemical modification during its history and is a well-preserved phase. We examine 420forsterite grains enclosed in 162 micrometeorites of different types -unmelted, scoriaceous, and porphyritic-in this study. Forsterites in micrometeorites of different types are crystallized during their formation in solar nebula; their closest analogues are chondrule components of CV-type chondrites or volatile rich CM chondrites. The forsteritic olivines are suggested to have originated from a cluster of closely related carbonaceous asteroids that have Mg-rich olivines in the narrow range of CaO (0.1-0.3wt%), Al 2 O 3 (0.0-0.3wt%), MnO (0.0-0.3wt%), and Cr 2 O 3 (0.1-0.7wt%). Numerical simulations carried out with the Chemical Ablation Model (CABMOD) enable us to define the physical conditions of atmospheric entry that preserve the original compositions of the Mg-rich olivines in these particles. The chemical compositions of relict olivines affirm the role of heating at peak temperatures and the cooling rates of the micrometeorites. This modeling approach provides a foundation for understanding the ablation of the particles and the circumstances in which the relict grains tend to survive.

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“…Micrometeorites are the largest contributors of extra-terrestrial material; this material is recovered from the Earthʼs surface using different collection techniques that target the stratosphere, Antarctica, and deep-sea sediments (Love & Brownlee 1993;Taylor et al 1998;Peucker-Ehrenbrink & Ravizza 2000;Plane 2012;Prasad et al 2013). The micrometeorites found on the Earthʼs surface have distinct chemical compositions that show similarities and differences with respect to the precursors they originate from; however, in general, a large number of micrometeorites are related to carbonaceous chondrites (e.g., Kurat et al 1994;Brownlee et al 1997;Taylor et al 2000Taylor et al , 2012Yada et al 2005;Rudraswami et al 2011Rudraswami et al , 2012Rudraswami et al , 2014Rudraswami et al , 2015aRudraswami et al , 2015bRudraswami et al , 2016a. The deviations in the chemical compositions from the precursors are caused by modification that occurs during melting and vaporization that take place as these particles enter into the Earthʼs atmosphere.…”

Section: Introductionmentioning

confidence: 99%

Ablation and Chemical Alteration of Cosmic Dust Particles During Entry Into the Earth’s Atmosphere

Rudraswami

Prasad

Dey

et al. 2016

ApJS

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Most dust-sized cosmic particles undergo ablation and chemical alteration during atmospheric entry, which alters their original properties. A comprehensive understanding of this process is essential in order to decipher their preentry characteristics. The purpose of the study is to illustrate the process of vaporization of different elements for various entry parameters. The numerical results for particles of various sizes and various zenith angles are treated in order to understand the changes in chemical composition that the particles undergo as they enter the atmosphere. Particles with large sizes (> few hundred μm) and high entry velocities (>16 km s −1 ) experience less time at peak temperatures compared to those that have lower velocities. Model calculations suggest that particles can survive with an entry velocity of 11 km s −1 and zenith angles (ZA) of 30°-90°, which accounts for ∼66% of the region where particles retain their identities. Our results suggest that the changes in chemical composition of MgO, SiO 2 , and FeO are not significant for an entry velocity of 11 km s −1 and sizes <300 μm, but the changes in these compositions become significant beyond this size, where FeO is lost to a major extent. However, at 16 km s −1 the changes in MgO, SiO 2 , and FeO are very intense, which is also reflected in Mg/Si, Fe/Si, Ca/Si, and Al/Si ratios, even for particles with a size of 100 μm. Beyond 400 μm particle sizes at 16 km s −1 , most of the major elements are vaporized, leaving the refractory elements, Al and Ca, suspended in the troposphere.

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Refractory metal nuggets in different types of cosmic spherules

Cited by 34 publications

References 46 publications

In situ analysis of Refractory Metal Nuggets in carbonaceous chondrites

In situ analysis of Refractory Metal Nuggets in carbonaceous chondrites

Relict Olivines in Micrometeorites: Precursors and Interactions in the Earth’s Atmosphere

Ablation and Chemical Alteration of Cosmic Dust Particles During Entry Into the Earth’s Atmosphere

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