Crystallography of refractory metal nuggets in carbonaceous chondrites: A transmission Kikuchi diffraction approach
© 2017 Elsevier Ltd.Transmission Kikuchi diffraction (TKD) is a relatively new technique that is currently being developed for geological sample analysis. This technique utilises the transmission capabilities of a scanning electron microscope (SEM) to rapidly and accurately map the crystallographic...
| Main Authors: | , , , , , , , , , , , , , , |
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| Format: | Journal Article |
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Pergamon
2016
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| Online Access: | http://hdl.handle.net/20.500.11937/52071 |
| _version_ | 1848758837908078592 |
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| author | Daly, L. Bland, Phil Dyl, K. Forman, Lucy Saxey, David Reddy, Steven Fougerouse, D. Rickard, William Trimby, P. Moody, S. Yang, L. Liu, H. Ringer, S. Saunders, M. Piazolo, S. |
| author_facet | Daly, L. Bland, Phil Dyl, K. Forman, Lucy Saxey, David Reddy, Steven Fougerouse, D. Rickard, William Trimby, P. Moody, S. Yang, L. Liu, H. Ringer, S. Saunders, M. Piazolo, S. |
| author_sort | Daly, L. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | © 2017 Elsevier Ltd.Transmission Kikuchi diffraction (TKD) is a relatively new technique that is currently being developed for geological sample analysis. This technique utilises the transmission capabilities of a scanning electron microscope (SEM) to rapidly and accurately map the crystallographic and geochemical features of an electron transparent sample. TKD uses a similar methodology to traditional electron backscatter diffraction (EBSD), but is capable of achieving a much higher spatial resolution (5-10. nm) (Trimby, 2012; Trimby et al., 2014). Here we apply TKD to refractory metal nuggets (RMNs) which are micrometre to sub-micrometre metal alloys composed of highly siderophile elements (HSEs) found in primitive carbonaceous chondrite meteorites. TKD allows us to analyse RMNs in situ, enabling the characterisation of nanometre-scale variations in chemistry and crystallography, whilst preserving their spatial and crystallographic context. This provides a complete representation of each RMN, permitting detailed interpretation of their formation history.We present TKD analysis of five transmission electron microscopy (TEM) lamellae containing RMNs coupled with EBSD and TEM analyses. These analyses revealed textures and relationships not previously observed in RMNs. These textures indicate some RMNs experienced annealing, forming twins. Some RMNs also acted as nucleation centres, and formed immiscible metal-silicate fluids. In fact, each RMN analysed in this study had different crystallographic textures. These RMNs also had heterogeneous compositions, even between RMNs contained within the same inclusion, host phase and even separated by only a few nanometres. Some RMNs are also affected by secondary processes at low temperature causing exsolution of molybdenite. However, most RMNs had crystallographic textures indicating that the RMN formed prior to their host inclusion. TKD analyses reveal most RMNs have been affected by processing in the protoplanetary disk. Despite this alteration, RMNs still preserve primary crystallographic textures and heterogeneous chemical signatures. This heterogeneity in crystallographic relationships, which mostly suggest that RMNs pre-date their host, is consistent with the idea that there is not a dominant RMN forming process. Each RMN has experienced a complex history, supporting the suggestion of Daly et al. (this issue), that RMNs may preserve a diverse pre-solar chemical signature inherited from the Giant Molecular Cloud. |
| first_indexed | 2025-11-14T09:50:20Z |
| format | Journal Article |
| id | curtin-20.500.11937-52071 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T09:50:20Z |
| publishDate | 2016 |
| publisher | Pergamon |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-520712019-09-20T01:20:12Z Crystallography of refractory metal nuggets in carbonaceous chondrites: A transmission Kikuchi diffraction approach Daly, L. Bland, Phil Dyl, K. Forman, Lucy Saxey, David Reddy, Steven Fougerouse, D. Rickard, William Trimby, P. Moody, S. Yang, L. Liu, H. Ringer, S. Saunders, M. Piazolo, S. © 2017 Elsevier Ltd.Transmission Kikuchi diffraction (TKD) is a relatively new technique that is currently being developed for geological sample analysis. This technique utilises the transmission capabilities of a scanning electron microscope (SEM) to rapidly and accurately map the crystallographic and geochemical features of an electron transparent sample. TKD uses a similar methodology to traditional electron backscatter diffraction (EBSD), but is capable of achieving a much higher spatial resolution (5-10. nm) (Trimby, 2012; Trimby et al., 2014). Here we apply TKD to refractory metal nuggets (RMNs) which are micrometre to sub-micrometre metal alloys composed of highly siderophile elements (HSEs) found in primitive carbonaceous chondrite meteorites. TKD allows us to analyse RMNs in situ, enabling the characterisation of nanometre-scale variations in chemistry and crystallography, whilst preserving their spatial and crystallographic context. This provides a complete representation of each RMN, permitting detailed interpretation of their formation history.We present TKD analysis of five transmission electron microscopy (TEM) lamellae containing RMNs coupled with EBSD and TEM analyses. These analyses revealed textures and relationships not previously observed in RMNs. These textures indicate some RMNs experienced annealing, forming twins. Some RMNs also acted as nucleation centres, and formed immiscible metal-silicate fluids. In fact, each RMN analysed in this study had different crystallographic textures. These RMNs also had heterogeneous compositions, even between RMNs contained within the same inclusion, host phase and even separated by only a few nanometres. Some RMNs are also affected by secondary processes at low temperature causing exsolution of molybdenite. However, most RMNs had crystallographic textures indicating that the RMN formed prior to their host inclusion. TKD analyses reveal most RMNs have been affected by processing in the protoplanetary disk. Despite this alteration, RMNs still preserve primary crystallographic textures and heterogeneous chemical signatures. This heterogeneity in crystallographic relationships, which mostly suggest that RMNs pre-date their host, is consistent with the idea that there is not a dominant RMN forming process. Each RMN has experienced a complex history, supporting the suggestion of Daly et al. (this issue), that RMNs may preserve a diverse pre-solar chemical signature inherited from the Giant Molecular Cloud. 2016 Journal Article http://hdl.handle.net/20.500.11937/52071 10.1016/j.gca.2017.03.037 Pergamon restricted |
| spellingShingle | Daly, L. Bland, Phil Dyl, K. Forman, Lucy Saxey, David Reddy, Steven Fougerouse, D. Rickard, William Trimby, P. Moody, S. Yang, L. Liu, H. Ringer, S. Saunders, M. Piazolo, S. Crystallography of refractory metal nuggets in carbonaceous chondrites: A transmission Kikuchi diffraction approach |
| title | Crystallography of refractory metal nuggets in carbonaceous chondrites: A transmission Kikuchi diffraction approach |
| title_full | Crystallography of refractory metal nuggets in carbonaceous chondrites: A transmission Kikuchi diffraction approach |
| title_fullStr | Crystallography of refractory metal nuggets in carbonaceous chondrites: A transmission Kikuchi diffraction approach |
| title_full_unstemmed | Crystallography of refractory metal nuggets in carbonaceous chondrites: A transmission Kikuchi diffraction approach |
| title_short | Crystallography of refractory metal nuggets in carbonaceous chondrites: A transmission Kikuchi diffraction approach |
| title_sort | crystallography of refractory metal nuggets in carbonaceous chondrites: a transmission kikuchi diffraction approach |
| url | http://hdl.handle.net/20.500.11937/52071 |