Crystallography of refractory metal nuggets in carbonaceous chondrites: a transmission Kikuchi diffraction approach

Luke Daly, Phil A. Bland, Kathryn A. Dyl, Lucy V. Forman, David W. Saxey, Steven M. Reddy, Denis Fougerouse, William D.A. Rickard, Patrick W. Trimby, Steve Moody, Limei Yang, Hongwei Liu, Simon P. Ringer, Martin Saunders, Sandra Piazolo

Research output: Contribution to journalArticleResearchpeer-review

Abstract

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. (2017), that RMNs may preserve a diverse pre-solar chemical signature inherited from the Giant Molecular Cloud.

LanguageEnglish
Pages42-60
Number of pages19
JournalGeochimica et Cosmochimica Acta
Volume216
DOIs
Publication statusPublished - 1 Nov 2017

Fingerprint

crystallography
Refractory metals
Crystallography
carbonaceous chondrite
Wave transmission
diffraction
Diffraction
metal
Textures
texture
electron
Electron diffraction
backscatter
transmission electron microscopy
Metals
Meteorites
Transmission electron microscopy
Silicates

Keywords

  • Refractory metal nuggets
  • Solar nebula
  • Solar System
  • Origin
  • Meteorites
  • Carbonaceous chondrites
  • Crystallography
  • Crystallisation
  • Transmission Kikuchi diffraction

Cite this

Daly, Luke ; Bland, Phil A. ; Dyl, Kathryn A. ; Forman, Lucy V. ; Saxey, David W. ; Reddy, Steven M. ; Fougerouse, Denis ; Rickard, William D.A. ; Trimby, Patrick W. ; Moody, Steve ; Yang, Limei ; Liu, Hongwei ; Ringer, Simon P. ; Saunders, Martin ; Piazolo, Sandra. / Crystallography of refractory metal nuggets in carbonaceous chondrites : a transmission Kikuchi diffraction approach. In: Geochimica et Cosmochimica Acta. 2017 ; Vol. 216. pp. 42-60.
@article{43914a286ae04bda968bac2b56901c11,
title = "Crystallography of refractory metal nuggets in carbonaceous chondrites: a transmission Kikuchi diffraction approach",
abstract = "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. (2017), that RMNs may preserve a diverse pre-solar chemical signature inherited from the Giant Molecular Cloud.",
keywords = "Refractory metal nuggets, Solar nebula, Solar System, Origin, Meteorites, Carbonaceous chondrites, Crystallography, Crystallisation, Transmission Kikuchi diffraction",
author = "Luke Daly and Bland, {Phil A.} and Dyl, {Kathryn A.} and Forman, {Lucy V.} and Saxey, {David W.} and Reddy, {Steven M.} and Denis Fougerouse and Rickard, {William D.A.} and Trimby, {Patrick W.} and Steve Moody and Limei Yang and Hongwei Liu and Ringer, {Simon P.} and Martin Saunders and Sandra Piazolo",
year = "2017",
month = "11",
day = "1",
doi = "10.1016/j.gca.2017.03.037",
language = "English",
volume = "216",
pages = "42--60",
journal = "Geochimica et Cosmochimica Acta",
issn = "0016-7037",
publisher = "Elsevier",

}

Daly, L, Bland, PA, Dyl, KA, Forman, LV, Saxey, DW, Reddy, SM, Fougerouse, D, Rickard, WDA, Trimby, PW, Moody, S, Yang, L, Liu, H, Ringer, SP, Saunders, M & Piazolo, S 2017, 'Crystallography of refractory metal nuggets in carbonaceous chondrites: a transmission Kikuchi diffraction approach', Geochimica et Cosmochimica Acta, vol. 216, pp. 42-60. https://doi.org/10.1016/j.gca.2017.03.037

Crystallography of refractory metal nuggets in carbonaceous chondrites : a transmission Kikuchi diffraction approach. / Daly, Luke; Bland, Phil A.; Dyl, Kathryn A.; Forman, Lucy V.; Saxey, David W.; Reddy, Steven M.; Fougerouse, Denis; Rickard, William D.A.; Trimby, Patrick W.; Moody, Steve; Yang, Limei; Liu, Hongwei; Ringer, Simon P.; Saunders, Martin; Piazolo, Sandra.

In: Geochimica et Cosmochimica Acta, Vol. 216, 01.11.2017, p. 42-60.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Crystallography of refractory metal nuggets in carbonaceous chondrites

T2 - Geochimica et Cosmochimica Acta

AU - Daly, Luke

AU - Bland, Phil A.

AU - Dyl, Kathryn A.

AU - Forman, Lucy V.

AU - Saxey, David W.

AU - Reddy, Steven M.

AU - Fougerouse, Denis

AU - Rickard, William D.A.

AU - Trimby, Patrick W.

AU - Moody, Steve

AU - Yang, Limei

AU - Liu, Hongwei

AU - Ringer, Simon P.

AU - Saunders, Martin

AU - Piazolo, Sandra

PY - 2017/11/1

Y1 - 2017/11/1

N2 - 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. (2017), that RMNs may preserve a diverse pre-solar chemical signature inherited from the Giant Molecular Cloud.

AB - 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. (2017), that RMNs may preserve a diverse pre-solar chemical signature inherited from the Giant Molecular Cloud.

KW - Refractory metal nuggets

KW - Solar nebula

KW - Solar System

KW - Origin

KW - Meteorites

KW - Carbonaceous chondrites

KW - Crystallography

KW - Crystallisation

KW - Transmission Kikuchi diffraction

UR - http://www.scopus.com/inward/record.url?scp=85017440186&partnerID=8YFLogxK

U2 - 10.1016/j.gca.2017.03.037

DO - 10.1016/j.gca.2017.03.037

M3 - Article

VL - 216

SP - 42

EP - 60

JO - Geochimica et Cosmochimica Acta

JF - Geochimica et Cosmochimica Acta

SN - 0016-7037

ER -