the aqueous alteration of carbon-bearing phases in cr carbonaceous chondrites a dissertation ...

181 Pages·2014·26.19 MB·English

THE AQUEOUS ALTERATION OF CARBON-BEARING PHASES IN CR
CARBONACEOUS CHONDRITES

A DISSERTATION SUBMITTED TO THE GRADUATE DIVISION OF THE
UNIVERSITY OF HAWAI‘I AT MĀNOA IN PARTIAL FULFILLMENT OF THE
REQUIREMENTS FOR THE DEGREE OF

DOCTOR OF PHILOSOPHY

IN

GEOLOGY AND GEOPHYSICS

DECEMBER 2014

By

Patrick J. Gasda

Dissertation Committee:

G. Jeffrey Taylor, Chairperson
Eric Hellebrand
Gary Huss
Shiv Sharma
Michael Mottl
Acknowledgements

First, I would like to thank my great advisor G. Jeffrey Taylor for being generally
amazing, introducing me to geology for the first time, accepting to be my advisor even though he
we have different research interests, and then allowing me to pursue this unique project. Jeff also
helped me by finding funding from many different sources. His encouragement and enthusiasm
for my work also helped to motivate me. I would like to thank Ralf Kaiser, who initially got me
into UH and involved UH NASA Astrobiology Institute. Karen Meech, Stephen Freeland, Shiv
Sharma, Jeff Taylor, Mike Mottl, Leona Anthony, and Allison Houghton then helped me
transition to the Geology and Geophysics department from the Chemistry Department. Thank
you to all my funding and equipment sources both for this and side projects: UHNAI, HIGP and
Peter Mouginis-Mark (Director), SOEST, Geology and Geophysics Department, IfA, NASA
(Cooperative Agreement No. NNA09DA77A (Karen Meech, P.I.), NNX07AM62G (Gary Huss,
P.I.)), NASA MIDP and EPSCoR program grants (Shiv Sharma, P.I.), NASA Solar System
Exploration Research Virtual Institute (via Jeffrey Gillis-Davis Co-I of the Vortices virtual
institute, Ben Bussey, P.I.), and The Meteoritical Society. Thank you to my professors who
helped me learn geology so well, especially my qualifying exam and comprehensive exam
committee members. My dissertation committee members also helped me make my dissertation
perfect. Thank you to the administrative assistants at IfA (Laura Toyama, Diane Tokumura) and
HIGP (Rena Lefevre, Vi Nakahara, Grace Furuya) for being very patient and helpful when I
requested funding for equipment and travel. Thank you to all of my collaborators and coauthors
on projects (in no particular order): Anupam Misra, Tayro Acosta-Maeda, Paul Lucey, Jeffrey
Gillis-Davis, David Bates, Barry Lienert, John Sinton (who provided samples), Ryan Ogliore,
Kazuhide Nagashima, Patricia Fryer, John Bradley, Mark Wood, Eric Pilger (who wrote the code
to run our Raman data on the HIGP Linux cluster), Ethan Kastner (who provided computing
support), Aurelien Thomen, The French Institute of Petroleum (provided SIMS standards),
JoAnn Sinton (mounted Smithsonian electron probe standards), the SOEST Engineering Support
Facility (Mario Williamsen), the Meteorite Curation Facility at Johnson Space Center (loaned
and prepared the meteorite samples), and the Smithsonian Institution and the Museum for
Natural History (provided electron probe standards). Thank you to everyone (not mentioned
previously) who gave me useful comments on papers and proposals: Alexander Krot, Mark
Price, Roger Wiens, Robin Turner, the paper editors at Applied Spectroscopy, and my
anonymous paper reviewers. Lastly, my family and friends. I would not have made it without
your support and encouragement.

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Abstract

By studying carbonaceous chondrites, we can understand the processes that occurred in the
protoplanetary disk, constrain the conditions in the solar nebula, and determine the composition
and evolution of organic chemicals that led up to the origin of life on Earth. The CR chondrites
contain ~ 5 wt% carbon, mainly in the form of macromolecular carbon (MMC). There are
examples of petrologic type 3 (primitive) and type 1 (extensively aqueously altered) CR
chondrites, which makes the CRs particularly interesting for studying the stages of aqueous
alteration. The MMC has been studied using in situ electron probe micro analysis (EPMA),
Raman spectroscopy, and secondary ion mass spectrometry (SIMS). EPMA mapping of the
carbon Kα X-rays reveals that there are three types of carbon materials in these chondrites: high
carbon phases (HCPs), matrix carbon (MC), and calcite. By Raman spectroscopy, we determine
that the MC is MMC, but its spectra are unchanged by aqueous alteration. EPMA X-ray mapping
suggests that the morphology of the HCPs and the spatial distribution of the MMC changes with
extent of aqueous alteration. SIMS measurements have revealed that there is an isotopic
difference between the HCPs and the MC in the GRO 95577 and QUE 99177 samples. HCPs
have δ13C ≈ −25 ‰ and δ15N ≈ 40 ‰, and the MC have δ13C ≈ −35 ‰ and δ15N ≈ 160 ‰,
relative to standard terrestrial isotope ratios. In order to produce the MC isotopic values, there
must be a mix of the +δ15N and +δ13C soluble organic molecules and MMC (both present in the
matrix). Therefore, the ‘true’ values for the MMC must be more enriched in 12C and 15N than the
MC values. Results from the calcite measurements show that the production of calcite
fractionates the carbon due to a combination of calcite crystallization and outgassing of CO on
2
the CR parent body.
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Table of Contents
Acknowledgments............................................................................................................... ii

Abstract .............................................................................................................................. iii

List of Tables ................................................................................................................... viii

List of Figures .................................................................................................................... ix

List of Symbols, Abbreviations, and Acronyms ............................................................... xii

Chapter 1: Introduction ........................................................................................................1

1.1 Raman Fitting Techniques .................................................................................6

Chapter 2: Modeling the Raman Spectrum of Graphitic Material in Rock Samples with
Fluorescence Backgrounds: Accuracy of Fitting and Uncertainty Estimation ....................8

2.1 Abstract ..............................................................................................................9

2.2 Introduction ........................................................................................................9

2.2.1 Goodness of Fit and Uncertainty Estimation ....................................12

2.2.2 The Raman Spectrum of Graphitic Materials ...................................14

2.3 Methodology ....................................................................................................16

2.3.1 Second-Derivative Fit to Remove Background Fluorescence ..........16

2.3.2 Monte Carlo Uncertainty Estimation ................................................17

2.3.3 Explanation of the Matlab Code .......................................................17

2.3.4 Raman Spectroscopic Experiments ...................................................18

2.4 Background Subtraction Techniques ...............................................................19

2.4.1 Background Fitting with an Assumed Function ...............................20

2.4.2 Background Fitting without an Assumed Function ..........................22

2.5 Results and Discussion ....................................................................................27

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2.5.1 Comparison of Data Analyzed by the Standard Method and
SGSD Method ............................................................................................27

2.5.2 Simulation of Real Spectra ...............................................................29

2.6 Conclusions ......................................................................................................34

Chapter 3: Chemical Properties of Carbon Materials in CR Carbonaceous Chondrites: the Effects
of Aqueous Alteration ........................................................................................................37

3.1 Abstract ............................................................................................................38

3.2 Introduction ......................................................................................................38

3.2.1 Raman Spectroscopy of Graphitic Materials ....................................41

3.2.2 Modeling the Raman Spectrum of MMC .........................................43

3.2.3 Comparison with Previous Literature Results ..................................45

3.3 Analytical Methods ..........................................................................................47

3.3.1 Sample Preparation ...........................................................................47

3.3.2 Raman Spectroscopy .........................................................................47

3.3.3 Raman Data Reduction .....................................................................48

3.3.4 EPMA Mapping and Quantitative Analysis .....................................48

3.4 Results and Discussion ....................................................................................49

3.4.1 Description of Samples and Regions Studied ...................................49

3.4.2 Raman Measurements .......................................................................59

3.4.3 Combined Raman and EPMA Carbon X-Ray Imaging ....................62

3.4.4 Quantitative Measurements of the Matrix using EPMA ...................68

3.4.5 Organic Carbon Modeling ................................................................70

3.4.6 Checking the Model ..........................................................................72

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3.4.7 EPMA Results ...................................................................................74

3.4.8 Significance of the Atomic H/C Ratios ............................................78

3.5 Aqueous Alteration of the MMC .....................................................................81

3.6 Summary and Conclusions ..............................................................................84

Chapter 4: Isotopic Investigation of Carbon Phases in CR Chondrites GRO 95577 and QUE
99177..................................................................................................................................85

4.1 Abstract ............................................................................................................86

4.2 Introduction ......................................................................................................86

4.2.1 Carbon and Nitrogen Isotopes and Fractionation Trends .................88

4.3 Methods............................................................................................................93

4.4 Results and Discussion ....................................................................................95

4.4.1 Description of the Sample Areas ......................................................95

4.4.2 Isotopic Analyses ..............................................................................97

4.4.3 Calcite Carbon Isotopic Ratios .......................................................103

4.4.4 Implications.....................................................................................108

4.5 Summary and Conclusions ............................................................................110

Chapter 5: Conclusions ....................................................................................................113

5.1 Aqueous Alteration of Macromolecular Organic Compounds in CR
Chondrites ............................................................................................................114

5.2 Future Directions ...........................................................................................116

5.3 Implications for the Origin of Life .................................................................118

Appendix: Supplementary Materials for Chapter 3 .........................................................119

A.1 Aluminum Coating ........................................................................................120

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A.2 Standards .......................................................................................................121

A.3 EPMA Procedure ..........................................................................................123

A.4 Corrections to the Carbon Concentration (ZAF, phi-rho-z, and MACs) ......130

A.5 Oxide Weight Percent Calculation ................................................................137

A.5.1 Iron Partitioning .............................................................................138

A.5.2 Organic Carbon Modeling .............................................................138

A.6 Significance of the Atomic H/C ratios ..........................................................142

Bibliography ....................................................................................................................150

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List of Tables

Table 2.1: The comparison of results between the linear background subtraction and SGSD
methods ......................................................................................................26

Table 3.1: Literature, endmember, and model values of atomic H/C, O/C, and N/C ratios in
CR Chondrites ............................................................................................73

Table 4.1: The summary of δ13C and δ15N measurements in QUE 99177 and GRO 95577
with 2σ errors ...........................................................................................105

Table A.1: EPMA Measurement settings ..................................................................122

Table A.2: Details for the EPMA standards ..............................................................122

Table A.3: C Kα Intensity (cps) measured during WDS spectra on the different standards and
unknowns .................................................................................................125

Table A.4: Appendix C from EPMA for Windows Manual showing the variation between
MAC values for carbon ............................................................................134

Table A.5: Endmember 1 atomic H/C, O/C, and N/C ratios .....................................139

Table A.6: Model atomic H/C, O/C, and N/C ratios ..................................................140

Table A.7: Revised model atomic H/C, O/C, and N/C ratios ....................................141

Table A.8: Two examples of the weight percent oxide calculation using the revised model
ratios in Table A.7....................................................................................143

Table A.9: The summary of results of the weight percent oxide calculation using the revised
model ratios in Table A.7 .........................................................................145
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List of Figures

Figure 2.1: The idealized Raman spectrum of macromolecular carbon .......................14

Figure 2.2: A comparison of various background subtraction techniques using a spectrum
from the EET 92161 chondrite ..................................................................24

Figure 2.3: Four example spectra are used to compare fits of raw Raman spectra using the
linear background subtraction method with the fits of the Savitzky-Golay
smoothed second-derivative spectra ..........................................................25

Figure 2.4: The effect of increasing the break point (S in Equation 7) on the Raman fit
parameters and uncertainties when using different background subtraction (linear,
cubic, and the small window moving average algorithm), the float line, and the
SGSD methods ...........................................................................................31

Figure 2.5: Examples of simulated spectra used for the simulation of real spectra .....32

Figure 3.1: A typical raw Raman spectrum of the MMC from the CR chondrites and its
SGSD modeled spectrum ...........................................................................44

Figure 3.2: An EPMA BSE image, a false-color (RGB) C-Si-Mg X-ray map, a false-color
(RGB) Mg-Si-Al X-ray map, and a C X-ray map of the QUE 99177 grain mount
....................................................................................................................51

Figure 3.3: High resolution BSE images of a high carbon phase and calcite grains in the QUE
99177 grain mount .....................................................................................52

Figure 3.4: An EPMA BSE image, a false-color (RGB) C-Si-Mg X-ray map, a false-color
(RGB) Mg-Si-Al X-ray map, and a C X-ray map of the polished side of EET
92161..........................................................................................................53

Figure 3.5: An EPMA BSE image, a false-color (RGB) C-Si-Mg X-ray map, a false-color
(RGB) Mg-Si-Al X-ray map, and a C X-ray map of the polished side of GRO
95577..........................................................................................................57

Figure 3.6: High resolution BSE images of a calcite-magnetite assemblages with diffuse high
carbon phases and a BSE image, a false-color (RGB) C-Si-Mg X-ray map, and a
C X-ray map of a matrix area between a chondrule and a calcite-magnetite
assemblage GRO 95577 .............................................................................58

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Figure 3.7: A two-dimensional histogram of Raman fit parameter (I /I vs. D-band full width
D G
at half maximum) map data for GRO 95577 and EET 92161 superimposed on
Raman spot data from the polished and unpolished sides of GRO 95577, EET
92161, and QUE 99177..............................................................................61

Figure 3.8: An array of BSE and false-color (RGB) X-ray map images from GRO 95577 and
EET 92161 regions of interest with overlays of Raman maps ...................64

Figure 3.9: Typical Raman spectra of macromolecular carbon (matrix measurements, high
carbon phases, and diffuse high carbon phases) in GRO 95577 ................65

Figure 3.10: Geochemical plots (Oxide weight percent) summarizing the results of EPMA
quantitative measurements the ‘revised model’ to calculate abundance of organics
of the matrices of the samples ....................................................................76

Figure 3.11: Ternary diagrams (mole fraction) summarizing the results of EPMA quantitative
analysis and the ‘revised model’ to calculate abundance of organics in the
matrices of the samples ..............................................................................77

Figure 3.12: The hypothetical macromolecule that could exist using the revised model atomic
H/C, N/C, and O/C ratios for QUE 99177 .................................................80

Figure 4.1: A compilation of literature δ13C vs. δ15N data for the different meteorite groups,
plus IDPs, CR amino acids, CM and CI individual organics, the Solar Nebula, and
different bodies in the Solar System ..........................................................89

Figure 4.2: Backscatter electron images of QUE 99177 showing the locations of the ion probe
measurements .............................................................................................99

Figure 4.3: Backscatter electron images of GRO 95577 showing the locations of the ion probe
measurements ...........................................................................................100

Figure 4.4: The δ15N and δ13C SIMS results for the matrix and high carbon phases in the
QUE 99177 and GRO 95577 chondrites .................................................101

Figure 4.5: Data from Figure 3.4 superimposed onto data from Figure 3.1 to show the
isotopic results from our study in context of literature data ....................106

Figure 4.6: The δ13C data for all of the sample spots measurements superimposed on a plot
with carbonate literature data for some meteorite groups ........................107

Figure 4.7: An illustration depicting the source of the MMC and HCPs, showing the
alteration steps in the solar nebula and the meteorite parent body ..........111

x