IU Indianapolis ScholarWorks :: Browsing by Author "Macris, Catherine A."

Browsing by Author "Macris, Catherine A."

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Diopside, enstatite and forsterite solubilities in H2O and H2O-NaCl solutions at lower crustal and upper mantle conditions
(Elsevier, 2020-06) Macris, Catherine A.; Newton, Robert C.; Wykes, Jeremy; Pan, Ruiguang; Manning, Craig E.; Earth Sciences, School of Science
The interaction of fluids with rock-forming minerals plays an important role in the chemical evolution of mafic and ultramafic rocks in the lower crust and upper mantle. Recent work highlights the importance of salt-rich fluids in element transport in settings such as the mantle wedge above subduction zones and high-grade granulite facies metamorphism. Forsterite (Mg2SiO4), enstatite (MgSiO3) and diopside (CaMgSi2O6) are key rock-forming minerals in these settings in the system CaO-MgO-SiO2. We determined experimentally the solubilities of diopside, enstatite and forsterite in H2O-NaCl fluids at a range of pressures and temperatures. Forsterite solubility was determined at 1 GPa, 800 and 900 °C, in pure H2O and in H2O-NaCl solutions. Forsterite dissolved congruently at nearly all conditions. Its solubility in pure H2O is low, but increases greatly with rising NaCl concentration in the fluid. Enstatite solubility was investigated in H2O-NaCl solutions at 1 GPa, 800 and 900 °C. Enstatite dissolved incongruently to yield forsterite at all conditions. Addition of excess silica led to suppression of forsterite and showed that fluids in equilibrium with enstatite with or without forsterite are strongly enriched in Si relative to Mg, though Mg solubility is significant at high salinity. Diopside solubility was determined in pure H2O at 650–900 °C and 0.7–1.5 GPa, and in H2O-NaCl solutions at 800 °C and 1 GPa, with NaCl concentrations approaching halite saturation. Diopside dissolves incongruently yielding residual forsterite at all conditions investigated. The solubility of diopside in pure H2O increases with increasing pressure, temperature and salinity. Diopside dissolution in H2O-NaCl solutions displays a dependence on fluid salinity similar to that of forsterite and wollastonite. The results of forsterite solubility experiments in H2O-NaCl solutions were used to calculate the compositions of fluid coexisting with enstatite or diopside where forsterite was present. The concentration of solutes coexisting with enstatite decreases with rising NaCl, similar to quartz. In contrast, bulk solutes coexisting with diopside increase with NaCl, similar to wollastonite and forsterite. These patterns imply complexing among rock-forming components and fluid components, that Ca-chloride species are substantially more stable than Mg-chloride species, and that hydrous Na-silicate complexes are important components of deep H2O-NaCl fluids. The results show that salt-bearing brines have substantial metasomatic power and may exert significant control on the chemical evolution of lower crustal and upper mantle mafic and ultramafic rocks.
The Dynamics of the Late Neogene Antarctic Ice Sheets in the Central Ross Sea using a Multianalytical Approach
(2022-06) Mallery, Christopher Wallace; Licht, Kathy J.; Macris, Catherine A.; Gilhooly, William P. III
With the goal of determining ice sheet history in the central Ross Sea since the late Miocene, the provenance of glacial till from IODP expedition 374 site U1522 was assessed using a suite of three analyses. A total of 3,869 zircons, between 250-63 microns in size, from sixteen different cores were measured for U-Pb isotopes via LA-ICP-MS. Zircon data was compared to neodymium isotope and clast lithology datasets from collaborators. Site U1522 shows three distinct provenance shifts from the late Miocene to the Pleistocene, two of which are coincident with Ross Sea Unconformities three and two. Late Miocene samples have abundant Cretaceous zircon populations, radiogenic neodymium values, and clasts interpreted as having a West Antarctic provenance. In latest Miocene samples, zircons are mostly Ross Orogeny age (c. 470 615 Ma) and Cretaceous zircon grains are almost absent, neodymium values are relatively un radiogenic, and dolerite clasts are present signaling a shift to East Antarctic derived ice. Above Ross Sea Unconformity 3, early to mid Pliocene samples show a shift back to West Antarctic provenance with abundant Cretaceous zircons and more radiogenic neodymium values. Late Pliocene to Pleistocene samples, deposited above Ross Sea Unconformity 2, reflect dominant East Antarctic provenance with few Cretaceous zircon dates, relatively un radiogenic neodymium values, and the presence of dolerite clasts. These data are broadly in agreement with ice sheet interpretations suggested by clast analysis from ANDRILL site AND-1B. Permo-Triassic zircon dates suggest the presence of unexposed bedrock of this age beneath the West Antarctic Ice Sheet based on their association with Cretaceous dates that have not been reported from East Antarctica. The zircon dataset also reveals two late Miocene intervals with a previously undocumented Eocene Oligocene magmatic event ~30 40 Ma. The coexistence of Cretaceous dates in these intervals suggests a likely West Antarctic source. The absence of Eocene Oligocene zircons in subsequent Plio Pleistocene sediments may be explained by substantial erosion and offshore deposition of the West Antarctic interior, including volcanic edifices following the Middle Miocene Climatic Transition.
Equilibrium Fractionation of Non-traditional Stable Isotopes: an Experimental Perspective
(MSA, 2017-01) Shahar, Anat; Elardo, Stephen M.; Macris, Catherine A.; Earth Sciences, School of Science
Evaporating Planetesimals: A Modelling Approach
(2021-10) Hogan, Arielle Ann; Macris, Catherine A.; Barth, Andrew P.; Druschel, Gregory K.
This thesis is a comprehensive investigation into the mechanics of evaporation experienced by planetesimals during accretion, a planet-building process. The evaporation events that these rocky bodies experience govern their chemical evolution, impacting the chemistry of the final body – a planet. Studying these planet-building processes is notoriously difficult (e.g., Sossi et al., 2019). There are still many unknowns surrounding what controls the degree of evaporation these bodies experience, and the resulting chemical signatures. The current study was designed to attempt to define some important parameters that govern silicate melt evaporation. Here, we isolate and evaluate the effects of (1) pressure, (2) oxygen fugacity and (3) the activity coefficient of MgO on evaporating planetesimals through a series of computational models. The model introduced in this study, the ƒO2 Modified KNFCMAS Model, uses a robust stepwise routine for calculating evaporative fluxes from a shrinking sphere. The modelling results are then compared to data from partial evaporation experiments of synthetic chondrite spheres to demonstrate the validity of this model, and to expose unknowns about the physicochemical conditions of high temperature silicate melts experiencing evaporation (in this case, the effective pressure, and the activity coefficient of MgO). Major element-oxide and isotope data from the models yielded two main conclusions concerning planetesimals: (1) the rate of evaporation is controlled by pressure and oxygen fugacity and (2) the chemical composition of the residual melt is controlled by oxygen fugacity and the activity coefficient of MgO. Results from computational modelling and evaporation experiments were used to determine an approximation for the activity coefficient of MgO in a simplified chondritic composition, as well as the effective pressure experienced by the evaporating spheres during the partial evaporation experiments. This study outlines the controls on planetesimal chemistry during evaporation and provides a more accessible means of studying these complex processes.
Evaporation-induced copper isotope fractionation: Insights from laser levitation experiments
(Elsevier, 2021-04) Ni, Peng; Macris, Catherine A.; Darling, Emilee A.; Shahar, Anat; Health Sciences, School of Health and Human Sciences
As a transition metal that is moderately volatile at high temperatures, copper shows limited isotopic fractionation in terrestrial mantle-derived rocks but significant enrichment in its heavier isotope (up to 12.5‰ for 65Cu/63Cu) in objects that experienced volatile loss during formation, such as tektites, trinitite glasses, and lunar rocks. Previous efforts to model the Cu isotope fractionation trend from measurements of δ65Cu in tektites found that the trend cannot be explained by the theoretical isotope fractionation factor (α) for free evaporation of Cu, making it necessary to experimentally study Cu isotope fractionation under conditions similar to tektite formation. Here we present new experimental data of elemental (Na, K, Cu) and isotopic (Cu) fractionation during evaporation. Our experiments, conducted by laser-heating an aerodynamically levitated glass sphere to 1750, 2000, and 2150 °C, show rapid loss of Na, K, and Cu from the molten glass. In particular, > 99.99% of Cu was lost within 60 seconds. The evaporation induced loss of Cu is accompanied by progressive enrichment in its heavier isotope in the residue glass, with a maximum fractionation in δ65Cu of ∼18‰ relative to the synthesized initial sample. The empirical fractionation factor (α) calculated from our laser levitation data is 0.9960 ± 0.0002. Compared to similar experiments conducted for Zn, Cu appears to be significantly more volatile and show higher degrees of Cu isotope fractionation, consistent with observations in natural tektites. Comparing isotopic fractionation in a range of moderately volatile elements among laser levitation experiments, tektites, trinitites, and the bulk silicate Moon suggest that they experienced evaporation under various degrees of effective vapor saturation (∼74%, 93%, ∼99%, ∼99%), which depart significantly from free-evaporation (0%).
Exploring Competing Theories of Viscous Emulsion and Fractional Crystallization of the Impact Melt that Formed the Sudbury Igneous Complex
(2023-01) Horman, Alexandra Rose; Macris, Catherine A.; Barth, Andrew P.; Gilhooly, William P., III.
The Sudbury Igneous Complex (SIC) in Sudbury, Canada is a remnant geologic structure from a meteor impact that occurred ~1.85 Ga. The impact produced ~30,000 km3 of superheated melt which reached >2200 °C. The existing SIC is composed of three compositionally distinct layers, norite, quartz gabbro, and granophyre, which stretch the entire lateral distance of the complex. The presentation of layers in the SIC is unusual for impact melts, and the crystallization path has been debated by scientists. The SIC differs from more common layered mafic complexes because of its intermediate composition, crustal isotopic signature, and large volume of granophyre. This thesis is an investigation of some of the main theories surrounding the SIC and how it crystallized to form such distinct layers. There are two main theories of how the SIC formed its compositionally distinct layers: (1) fractional crystallization and (2) separation by viscous emulsion. The viscous emulsion theory involves isolated droplets of melt separating from the surrounding melt body due to differences in viscosity and density, similar to an emulsion of oil and water. In this study, viscous emulsion theory was investigated experimentally by heating samples of rock from the SIC to the extreme temperatures associated with the Sudbury impact, and then analyzing the cooled experimental products using electron microscopy to determine if there was evidence of textures that would be consistent with expectations for a viscous emulsion. Fractional crystallization was investigated by modeling using the vii software EasyMELTS to evaluate compositions from the SIC to estimate how they would crystallize according to the temperature, pressure, and other properties of the melt. There was no textural evidence of a viscous emulsion found in the experimental products. The models produced compositions similar to what is seen in the SIC but had limited application to fractional crystallization theory.
Fluid evolution during burial and exhumation of the Tso Morari UHP complex, NW India: Constraints from mineralogy, geochemistry, and thermodynamic modeling
(Springer, 2022-12-25) Pan, Ruiguang; Macris, Catherine A.; Menold, Carrie A.; Earth and Environmental Sciences, School of Science
The Tso Morari terrane within the Himalayan orogenic belt underwent ultrahigh-pressure (UHP) coesite-eclogite metamorphism due to northward subduction of the Indian continent under the Eurasian continent during the early Eocene. The Tso Morari UHP terrane has been intensely studied petrologically, mineralogically, and geochemically over the past several decades. However, the fluid history (e.g., phases and pressure–temperature conditions, fluid compositions and sources, and processes of fluid–rock interactions) and thermal structure during exhumation remain unresolved. To address these issues, we sampled a traverse from the center of an eclogite boudin out into the host orthogneiss. Three major fluid evolution stages (FESs) were identified and characterized using petrography, mineral and bulk-rock chemistry, and thermodynamic modeling. FES 1 constrained mineral dehydration and hydration reactions during prograde metamorphism before reaching peak pressure at 29.0 ± 0.8 kbar and 591 ± 9 °C by modeling garnet growth in the eclogites. FES 2 constrained mineral reactions in the eclogite matrix due to destabilization of internal hydrous minerals. This FES caused the formation of epidote at 22.8 ± 0.6 kbar, amphibole core domains (glaucophane) at 19.0 ± 0.4 kbar, amphibole rim domains (barroisite) at 14.5 ± 1.0 kbar, and symplectite at 9.0 ± 1.0 kbar, during isothermal decompression (600–650 °C). FES 3 caused amphibolization of eclogite at the boudin rim at 625 ± 50 °C and 9.0–14.0 kbar. Metasomatism resulted in increased K2O, CO2, and bulk-rock Fe3+/ΣFe in the amphibolized eclogites. Large ion lithophile elements (LILE) (e.g., K, Rb, Cs, Sr, Ba) and trace element ratios of Ba/Rb and Cs/Rb are also elevated relative to the eclogite core. The fluid most likely originated from dehydrating host orthogneiss and/or metasediments. Thermodynamic modeling also predicts that the Tso Morari complex was exhumed through a low-temperature (< 650 ± 50 °C) regime in the subduction channel
Isotope velocimetry: Experimental and theoretical demonstration of the potential importance of gas flow for isotope fractionation during evaporation of protoplanetary material
(Elsevier, 2022-07-01) Young, Edward D.; Macris, Catherine A.; Tang, Haolan; Hogan, Arielle A.; Shollenberger, Quinn R.; Earth and Environmental Sciences, School of Science
We use new experiments and a theoretical analysis of the results to show that the isotopic fractionation associated with laser-heating aerodynamic levitation experiments is consistent with the velocity of flowing gas as the primary control on the fractionation. The new Fe and Mg isotope data are well explained where the gas is treated as a low-viscosity fluid that flows around the molten spheres with high Reynolds numbers and minimal drag. A relationship between the ratio of headwind velocity to thermal velocity and saturation is obtained on the basis of this analysis. The recognition that it is the ratio of flow velocity to thermal velocity that controls fractionation allows for extrapolation to other environments in which molten rock encounters gas with appreciable headwinds. In this way, in some circumstances, the degree of isotope fractionation attending evaporation is as much a velocimeter as it is a barometer.
Metamorphic P-T Path and Multiple Fluid Events During Burial and Exhumation of the Tso Morari UHP Terrane, NW Himalaya
(2021-11) Pan, Ruiguang; Macris, Catherine A.; Barth, Andrew P.; Gilhooly, William P. III; Moreno, Max Jacobo; Menold, Carrie A.
The Tso Morari terrane within the Himalayan orogenic belt underwent ultrahigh-pressure (UHP) coesite-eclogite metamorphism due to northward subduction of the Indian continent under the Eurasian continent during the early Eocene. In this study we optimized a best protocol for thermodynamically modelling pressure-temperature (P-T) paths of high-grade metabasites using the Tso Morari eclogite as a case study through evaluating the effects of employing commonly used thermodynamic modeling techniques (e.g., programs, thermodynamic datasets, a-X relations). A “fishhook” shaped clockwise P-T path was obtained with a peak pressure of ~28.5 kbar at ~563 °C, followed by a peak temperature of ~613 °C at ~24.5 kbar. The peak pressures predicted by modelling protocols are consistent with the conventional thermobarometry results and petrographic observations from the Tso Morari eclogites. Secondly, thermodynamic modelling using P-M(H2O) pseudosections on Tso Morari UHP rocks indicates three distinct fluid events during the prograde and retrograde metamorphism. Fluid Event 1 caused the fluid-assisted homogenization of prograde garnet cores in eclogite at ~18.5 kbar and ~555 °C; Fluid Event 2 is evidenced by the formation of poikiloblastic epidote (~23.5 kbar and ~610 °C, at the expense of lawsonite) and amphibole (from ~19.0 to ~14.5 kbar at ~610 °C, at the expense of omphacite and talc), and symplectite association (~8.7 kbar and ~625 °C) in the eclogite matrix without external fluid supply. Fluid Event 3 was determined through modelling the amphibolitization of eclogites with external fluid infiltration at ~9.0–12.5 kbar and ~608 °C. This fluid phase most likely derived from the mixing of dehydrated host orthogneiss and/or metasediments during exhumation through the amphibolite-facies zone in the subduction channel. This study demonstrates the need for using careful petrographic observations in parallel with thermodynamic modelling to achieve realistic results.
Origin of β-cristobalite in Libyan Desert Glass: The hottest naturally occurring silica polymorph?
(GSW, 2022-07-01) Cavosie, Aaron J.; Rickard, William D. A.; Evans, Noreen J.; Rankenburg , Kai; Roberts, Malcolm; Macris, Catherine A.; Koeberl, Christian; Earth and Environmental Sciences, School of Science
Identifying and determining the origin of β-cristobalite, a high-temperature silica polymorph, in natural samples is challenging as it is rarely, if ever, preserved due to polymorphic transformation to α-cristobalite at low temperature. Formation mechanisms for β-cristobalite in high-silica rocks are difficult to discern, as superheating, supercooling, bulk composition, and trace element abundance all influence whether cristobalite crystallizes from melt or by devitrification. Here we report a study of α-cristobalite in Libyan Desert Glass (LDG), a nearly pure silica natural glass of impact origin found in western Egypt, using electron microprobe analysis (EMPA), laser ablation inductively coupled mass spectrometry (LA-ICP-MS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). The studied grains are mostly 250 μm in diameter and consist of ~150 μm wide cores surrounded by ~50 μm wide dendritic rims. Compositional layering in LDG continues across cristobalite grains and mostly corresponds to variations in Al content. However, layering is disrupted in cores of cristobalite grains, where Al distribution records oscillatory growth zoning, whereas in rims the high Al occurs along grain boundaries. Cristobalite cores thus nucleated within layered LDG at conditions that allowed mobility of Al into crystallographically controlled growth zones, whereas rims grew when Al was less mobile. Analysis of 37 elements indicates little evidence of preferential partitioning; both LDG and cristobalite are variably depleted relative to the upper continental crust, and abundance variations correlate to layering in LDG. Orientation analysis of {112} twin systematics in cristobalite by EBSD confirms that cores were formerly single β-cristobalite crystals. Combined with published experimental data, these results provide evidence for high-temperature (>1350 °C) magmatic crystallization of oscillatory zoned β-cristobalite in LDG. Dendritic rims suggest growth across the glass transition by devitrification, driven by undercooling, with transformation to α-cristobalite at low temperature. This result represents the highest formation temperature estimate for naturally occurring cristobalite, which is attributed to the near pure silica composition of LDG and anomalously high temperatures generated during melting by meteorite impact processes.

Browsing by Author "Macris, Catherine A."

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