scholarly journals Constraints on the ice composition of carbonaceous chondrites from their magnetic mineralogy

2021 ◽  
Author(s):  
Sanjana Sridhar ◽  
James Bryson ◽  
Ashley King ◽  
Richard Harrison
Keyword(s):  
Size Range ◽  
Parent Body ◽  
Carbonaceous Chondrites ◽  
Magnetic Mineralogy ◽  
Aqueous Alteration ◽  
First Order ◽  
Direct Replacement ◽  
History Of ◽  
Bulk Chemical ◽  
Weathering Effects

Carbonaceous chondrites experienced varying degrees of aqueous alteration on their parent asteroids, which influenced their mineralogies, textures, and bulk chemical and isotopic compositions. Although this alteration was a crucial event in the history of these meteorites, their various alteration pathways are not well understood. One phase that formed during this alteration was magnetite, and its morphology and abundance vary between and within chondrite groups, providing a means of investigating chondrite aqueous alteration. We measured bulk magnetic properties and first-order reversal curve (FORC) diagrams of CM, CI, CO, and ungrouped C2 chondrites to identify the morphology and size range of magnetite present in these meteorites. We identify two predominant pathways of aqueous alteration among these meteorites that can be distinguished by the resultant morphology of magnetite. In WIS 91600, Tagish Lake, and CI chondrites, magnetite forms predominantly from Fe-sulfides as framboids and stacked plaquettes. In CM and CO chondrites, <0.1 μm single-domain (SD) magnetite and 0.1–5 μm vortex (V) state magnetite formed predominantly via the direct replacement of metal and Fe-sulfides. After ruling out differences in temperature, water:rock ratios, terrestrial weathering effects, and starting mineralogy, we hypothesise that the primary factor controlling the pathway of aqueous alteration was the composition of the ice accreted into each chondrite group’s parent body. Nebula condensation sequences predict that the most feasible method of appreciably evolving ice concentrations was the condensation of ammonia, which will have formed a more alkaline hydrous fluid upon melting, leading to fundamentally different conditions that may have caused the formation of different magnetite morphologies. As such, we suggest that WIS 91600, Tagish Lake, and the CI chondrites accreted past the ammonia ice line, supporting a more distal or younger accretion of their parent asteroids.

scholarly journals Exogenous copper sulfide in returned asteroid Itokawa regolith grains are likely relicts of prior impacting body

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Katherine D. Burgess ◽  
Rhonda M. Stroud
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Low Temperature ◽  
Copper Sulfide ◽  
Parent Body ◽  
Carbonaceous Chondrites ◽  
Aqueous Alteration ◽  
Thermal Alteration ◽  
Transmission Electron ◽  
Rubble Pile

AbstractSamples from asteroid 25143 Itokawa returned by the Hayabusa mission have been identified as LL4-6 ordinary chondrite materials and have shown it to be a rubble pile that aggregated after break-up of a parent body. Here we investigate particle RB-CV-0038 from the Itokawa regolith using scanning and transmission electron microscopy and energy dispersive spectroscopy. We identify a cubanite-chalcopyrite-troilite-pyrrhotite assemblage, the phases and structure of which are indicative of low-temperature, aqueous alteration. Cubanite is stable only at temperatures below around 250 °C and has thus far only been identified in CI carbonaceous chondrites and the comet 81P/Wild2 sample suite. Chalcopyrite is also very rare in the meteorite record and is found mostly in R chondrites and some CK chondrites. Because the Itokawa parent body experienced significant thermal alteration with little evidence of low-temperature equilibration or aqueous alteration, we propose that the assemblage we identify is most likely exogenous and represents a component of an impacting body.

The magnetism of meteorites and early Solar System magnetic fields

1994 ◽  
Vol 349 (1690) ◽  
pp. 197-207 ◽  
Keyword(s):  
Solar System ◽  
Remanent Magnetization ◽  
Parent Body ◽  
Primary Component ◽  
Carbonaceous Chondrites ◽  
Ordinary Chondrites ◽  
Early Solar System ◽  
History Of ◽  
Magnetizing Field ◽  
Feni Alloy

The characteristics of the remanent magnetization of chondrite, achondrite and shergottite, nakhlite and chassignite (SNC) meteorites are described, and interpretation in terms of magnetizing fields in the ancient Solar System discussed. The magnetism of ordinary chondrites is commonly scattered in direction within samples, implying magnetization of constituent fragments before accumulation. The magnetic history of these meteorites is uncertain because of lack of knowledge of the origin and properties of tetrataenite, an ordered FeNi alloy often carrying the bulk of the magnetization. Achondrites also often possess scattered magnetization, the primary component probably being acquired during cooling after differentiation of the parent body. A magnetizing field of internal origin is possible. Estimates of magnetizing field strength are in the approximate range 5-100 μ T, with carbonaceous chondrites showing the highest values. The SNC meteorites, probably originating on Mars, provide evidence for a weak, ancient Martian magnetic field of the order 1 μ T.

Applications of SEM/EDXA in cement clinker investigation

1990 ◽  
Vol 48 (4) ◽  
pp. 870-871
Author(s):  
Arezki Tagnit-Hamou ◽  
Shondeep L. Sarkar
Keyword(s):  
Mineralogical Composition ◽  
Physicochemical Characteristics ◽  
Cement Clinker ◽  
Accurate Information ◽  
Phase Identification ◽  
History Of ◽  
Bulk Chemical ◽  
Resolution Imaging ◽  
Proven Method ◽  
Instantaneous Chemical

All the desired properties of cement primarily depend on the physicochemical characteristics of clinker from which the cement is produced. The mineralogical composition of the clinker forms the most important parameter influencing these properties.Optical microscopy provides reasonably accurate information pertaining to the thermal history of the clinker, while XRDA still remains the proven method of phase identification, and bulk chemical composition of the clinker can be readily obtained from XRFA. Nevertheless, all these microanalytical techniques are somewhat limited in their applications, and SEM/EDXA combination fills this gap uniquely by virtue of its high resolution imaging capability and possibility of instantaneous chemical analysis of individual phases.Inhomogeneities and impurities in the raw meal, influence of kiln conditions such as sintering and cooling rate being directly related to the microstructure can be effectively determined by SEM/EDXA. In addition, several physical characteristics of cement, such as rhcology, grindability and hydraulicity also depend on the clinker microstructure.

scholarly journals Microstructural and paleomagnetic insight into the cooling history of the IAB parent body

2018 ◽  
Vol 229 ◽  
pp. 1-19 ◽  
Author(s):  
Claire I.O. Nichols ◽  
Robert Krakow ◽  
Julia Herrero-Albillos ◽  
Florian Kronast ◽  
Geraint Northwood-Smith ◽  
...  
Keyword(s):  
Parent Body ◽  
Cooling History ◽  
History Of ◽  
Insight Into

Disorder-Induced Low-Frequency Raman Band Observed in Deposited MoS2 Films

1994 ◽  
Vol 48 (6) ◽  
pp. 733-736 ◽  
Author(s):  
N. T. McDevitt ◽  
J. S. Zabinski ◽  
M. S. Donley ◽  
J. E. Bultman
Keyword(s):  
Crystal Structure ◽  
Thin Films ◽  
Raman Band ◽  
Low Frequency ◽  
Pulsed Laser ◽  
Laser Deposition ◽  
First Order ◽  
Order Spectrum ◽  
History Of ◽  
Frequency Feature

Crystalline disorder in thin films plays an important role in determining their properties. Disorder in the crystal structure of MoS2 films prepared by magnetron sputtering and pulsed laser deposition was evaluated with the use of Raman spectroscopy. The peak positions and bandwidths of the first-order Raman bands, in the region 100 to 500 cm−1, were used as a measure of crystalline order. In addition, a low-frequency feature was observed at 223 cm−1 that is not part of the normal first-order spectrum of a fully crystalline specimen. Data presented here demonstrate that this band is characteristic of crystalline disorder, and its intensity depends on the annealing history of the film. This behavior seems to be analogous to the disorder found in graphite thin films.

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