The trace metal content of modern and ancient peritidal and shallow subtidal dolomites: significance and systematics by Daniel Alejandro Petrash A thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Earth and Atmospheric Sciences University of Alberta © Daniel Alejandro Petrash, 2016 ABSTRACT Dolomitization has traditionally been regarded as being related to the interaction of thermally active Mg-rich fluids with poorly ordered carbonate precursors of elusive origin. Our ideas on how such precursors form have evolved rapidly since the late 1990s, and microbes are now considered key players — i.e., by providing nucleation sites and due to their capacity to regulate pore water alkalinity. Outstanding questions include what triggers the low-temperature reactions conducive to dolomite stabilization and whether or not subsurface chemolithotrophs participate in the catalysis of these reactions. Here these aspects are evaluated throughout three independent but complementary textural and spectroscopic examinations of shallow marine dolomites. First, fine-scale analyses of modern carbonate cements point to biologically mediated manganese and sulfur co-recycling as a necessary control for dolomite stabilization. Second, similar analyses of mid-Cretaceous dolomitic marlstones suggest that in the Aptian-Albian epicontinental sea of northern South America, dolomite precipitation was linked to the utilization of metals and sulfur for organic matter respiration. Reactants were transported to the extended shallow marine setting in association with episodic orbital perturbations, which also triggered high organic matter productivity and burial, and ultimately led to interstitial organogenic dolomite formation. Third, stromatolitic rocks from the Paleoproterozoic Gunflint Formation (Ontario, Canada) were interrogated in order to interpret the variable redox states of pore waters at the time of stromatolite accretion and diagenetic mineral stabilization. This study shows that diagenetic shifts associated with exogenous water mixing, together with variable burial and exhumation histories, led to the development of the temporarily and spatially restricted reaction fronts responsible for the pervasive replacement of early formed - ii - carbonate cements. Such diagenetic complexity adds difficulty to the interpretation of paleomarine geochemical conditions. Overall, this work reveals that the trace metal content of shallow marine dolomite provides information useful for the evaluation of redox conditions that govern mineral authigenesis. However, autocycles and their effect on the activity of subsurface microbes, and thus over the saturation state of minerals in coastal sediments should be carefully considered prior to regional scale paleoceanographic interpretations. - iii - PREFACE This thesis is an original work by Daniel A. Petrash. The research conducted for this doctoral dissertation was supervised by Dr. Kurt O. Konhauser at the University of Alberta. Chapter 2 of this thesis has been published as: Petrash, D.A., Lalonde, S.V., González-Arismendi, G., Gordon, R. A., Méndez, J.A., Gingras, M.K., and Konhauser, K. O., 2015. “Can Mn-S redox cycling drive sedimentary dolomite formation? A hypothesis”. Chemical Geology 404: 27-40. Dr. S. Lalonde, J.A. Mendez-Dot, and I were responsible for sample collection and in situ microelectrode and physcochemical measurements. G. Gonzalez-Arismendi assisted with statistical analyses and geochemical modeling. Dr. R. Gordon was the beamline scientist at the Advanced Light Source. I was responsible for manuscript composition. Dr. M.K Gingras supervised the sedimentological aspects. Dr. S. Lalonde and Dr. K.O. Konhauser contributed to manuscript edits. Chapter 3 of this thesis has been submitted to the American Journal of Science as: “Black shale deposition and early diagenetic dolomite cementation during Oceanic Anoxic Event 1: The mid- Cretaceous Maracaibo Platform, north-western South America” by D.A. Petrash, N. Gueneli, J.J. Brocks, J.A. Mendez-Dot, G. Gonzalez-Arismendi, S.W. Poulton, and K.O. Konhauser. J.A. Mendez-Dot and I were reponsible for core sampling and transmitted light petrographic analyses. G. Gonzalez-Arismendi provided assistance with isotopic analyses. N. Guineli conducted biomarker and Fe-speciation analyses. I conducted high-resolution petrographic and geochemical analyses. N. Guineli and I were responsible for manuscript composition. Dr. K.O Konhauser, Dr. S.W. Poulton, and Dr. J. J. Brocks contributed to manuscript edits. Chapter 4 of this thesis has been submitted to Precambrian Research as: “Chemical and textural overprinting of ancient stromatolites: timing, processes, and implications for their use as paleoenvironmental proxies”. I conducted data collection and analysis and was responsible for manuscript composition. L.J. Robbins, Drs. S. Mojzsis, R. Shapiro, and K.O Konhauser contributed to manuscript edits. The literature review in chapter 1 and concluding analysis in chapter 5 are my original work. This research benefited from the expert advice of reviewers who have taken the time to read and comment on one or more of the chapters. - iv - DEDICATION To Gabriela del Pilar All models are wrong, but some models are useful. George P. E. Box (1919-2013) - v - ACKNOWLEDGEMENTS I express sincere thanks to my supervisor Dr. Kurt Konhauser for his guidance, support, patience, and friendship. My gratitude also extends to Dr. Karlis Muehlenbachs, who also played a major role in my scientific development. Professors Dr. Brian Jones and Dr. Murray Gingras are thankfully acknowledged for their constructive comments and guidance over the last five years. Thanks to my friends from the Geomicrobiology Research Group, especially to Rasmus Haugaard, Leslie Robbins, Dr. Aleksandra Mloszewska, and Dr. Stefan Lalonde for offering me their help and willingness to discuss, review, and improve my manuscripts. Nur Gueneli and Dr. Jochen Brocks (The Australian National University) conducted biomarkers analyses (Chapter III). Dr. Simon Poulton (University of Leeds) performed iron speciation analyses (also in Chapter III). I cannot be grateful enough to them for their timely contribution to this work. Samples from the Frustration Bay locality were made available by Dr. Stanley Awramik (University of California) thanks to the intercession of Dr. Steve Mojzsis (Univeristy of Colourado). I am also grateful to the Support Staff at the Department of Earth And Atmospheric Sciences: Dr. Nathan Gerein, Diane Caird, Dr. Guangcheng Chen, Dr. Andrew Locock, Mark Labbe, Martin Von Dollen, and Igor Jakab. I also thank Dr. Lachlan McLean and Dr. Ferenc Borondics (and team members of the mid-IR (beamline 01B1-1) at the Canadian Light Source) for technical advice and support. The expertise of Dr. Robert Gordon (CLS@APS) was critical for successful analyses at beamline 20ID at the Advanced Photon Source (APS). Use of the APS, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357. Last but certainly not least, I want to express sincere thanks to my mother and my beloved Gabriela del Pilar Gonzalez-Arismendi for inspiration. Their emotional support and enthusiasm for my work made the process of acquiring this degree a rewarding experience. - vi - TABLE OF CONTENTS CHAPTER I General Introduction ................................................................................................................ - 1 - 1.1. Dolomite precipitation in modern shallow marine settings. What do we know? ................ - 4 - 1.1.1. Low-T dolomite formation: a problem of kinetics? .................................................. - 5 - 1.2 Minor and trace element concentrations of dolomite ........................................................... - 7 - 1.3. Objectives of this thesis ....................................................................................................... - 9 - 1.3.1 Specific objectives ................................................................................................... - 11 - 1.4. Overview of manuscripts ................................................................................................... - 11 - 1.5. References .......................................................................................................................... - 19 - CHAPTER II Can Mn-S redox cycling drive sedimentary dolomite formation? A hypothesis .............. - 29 - 2.1. Introduction ........................................................................................................................ - 29 - 2.2. Study site ............................................................................................................................ - 31 - 2.3. Methods ............................................................................................................................. - 32 - 2.3.1. Sample collection .................................................................................................... - 32 - 2.3.2. Bulk mineralogical analysis .................................................................................... - 33 - 2.3.3. Electron microscopy ............................................................................................... - 33 - 2.3.4. Solid phase geochemistry ......................................................................................