robert bodnar | Virginia Tech (original) (raw)
Papers by robert bodnar
American Mineralogist, Feb 1, 1982
Nature Communications, Jul 14, 2017
Lunar and Planetary Science Conference, Mar 21, 2016
Lunar and Planetary Science Conference, 2001
Science
Samples of the carbonaceous asteroid Ryugu were brought to Earth by the Hayabusa2 spacecraft. We ... more Samples of the carbonaceous asteroid Ryugu were brought to Earth by the Hayabusa2 spacecraft. We analyzed 17 Ryugu samples measuring 1 to 8 millimeters. Carbon dioxide–bearing water inclusions are present within a pyrrhotite crystal, indicating that Ryugu’s parent asteroid formed in the outer Solar System. The samples contain low abundances of materials that formed at high temperatures, such as chondrules and calcium- and aluminum-rich inclusions. The samples are rich in phyllosilicates and carbonates, which formed through aqueous alteration reactions at low temperature, high pH, and water/rock ratios of <1 (by mass). Less altered fragments contain olivine, pyroxene, amorphous silicates, calcite, and phosphide. Numerical simulations, based on the mineralogical and physical properties of the samples, indicate that Ryugu’s parent body formed ~2 million years after the beginning of Solar System formation.
Lithos, 2019
Abstract We present phase equilibria modeling, combined with fluid inclusion microthermometry and... more Abstract We present phase equilibria modeling, combined with fluid inclusion microthermometry and textural observations, to constrain the composition and relative timing of subduction zone fluid-rock interaction during exhumation of two garnet-bearing blueschists from the northern part of the island of Sifnos, Greece. Water (H2O) from seawater was incorporated into the mafic lithologies by low-temperature water-rock interaction to produce hydrous phases, and was subsequently released during the subduction and exhumation cycle. Coupled phase equilibria modeling and textural observations suggest that fluid release resulted from the breakdown of the hydrous phases epidote and glaucophane, and some of the fluid was trapped as fluid inclusions in quartz. Homogenization temperatures and isochores of fluid inclusions are consistent with petrographic observations that suggest fluid inclusions were trapped during exhumation. Constructed isochores cross the inferred P-T path for Sifnos exhumation at pressures of ~0.3–1.0 GPa (~10–30 km depth) and temperatures of ~440–540 °C, suggesting fluid entrapment during the late stages of exhumation and cooling from peak subduction depths of ~70 km. The fluid inclusions have salinities of ~30–35 wt% NaCl equivalent, likely resulting from a multi-stage process that involves an increase in salinity during formation of hydrous minerals during subduction, leaving high salinity fluids and/or halide salts sequestered in pores. This is followed by the partial release of H2O during subsequent breakdown of high-pressure metamorphic phases, with later incorporation of H2O into newly forming retrograde phases. Portions of this fluid that interacted with earlier-formed saline fluids are now preserved as inclusions trapped in quartz. This interpretation suggests that fluid-rock interaction in the northern part of Sifnos occurred in a closed system, with a low water to rock mass ratio (~0.03 to ~0.05) and little to no infiltration of externally-derived lower salinity fluids. The closed system behavior is consistent with the observation that the blueschist unit is bounded by impermeable marble layers that limited exchange with external fluids during burial and/or exhumation.
Gondwana Research, 2014
Abstract Water (H2O) has been identified during Raman analyses at ~ 150–200 °C of fluid inclusion... more Abstract Water (H2O) has been identified during Raman analyses at ~ 150–200 °C of fluid inclusions from granulites that were previously thought to contain pure CO2. At room temperature, H2O in a CO2-rich fluid inclusion forms an optically unresolvable liquid wetting the inclusion walls. During heating, the H2O phase evaporates into the CO2 phase to produce a homogeneous H2O–CO2 fluid throughout the inclusion volume, and the H2O Raman peak at ~ 3640 cm− 1 is clearly resolvable at elevated temperatures. To test and confirm the method, synthetic H2O–CO2 FI of known composition (87.5 mol% and 95 mol% CO2) were also analyzed. Previously studied granulite samples from the Adirondack Mountains, USA, and from the Kerala Khondalite Belt, Sittampundi Complex and Sevitturangampatti, India were tested for the presence of H2O in CO2-rich fluid inclusions. Traces of H2O were found in CO2-rich fluid inclusions in quartz crystals from the Adirondacks and from the Kerala Khondalite Belt. H2O was not detected in CO2-rich secondary fluid inclusions in garnet from the Sittampundi Complex and from Sevitturangampatti. Rather, hydrogarnet was detected along the walls of inclusions in garnet, as evidenced by a peak at ~ 3661 cm− 1. The hydrogarnet is interpreted to be a “step-daughter” phase that formed by reaction of the H2O in the fluid inclusion with the garnet host during retrogression. These observations confirm the presence of an H2O-bearing, CO2-rich fluid at some time during granulite petrogenesis, but do not resolve the question of whether these CO2-rich fluids were trapped at peak metamorphic conditions or during retrogression, or whether the fluid inclusions have reequilibrated following entrapment.
Economic geology and the bulletin of the Society of Economic Geologists, Mar 1, 2022
Geochemical Journal, 2014
Journal of the American Chemical Society
EGU General Assembly Conference Abstracts, Apr 1, 2018
Geochemical Perspectives, 2014
Thus far, we have emphasised the common features of crustal fluids by discussing them in general ... more Thus far, we have emphasised the common features of crustal fluids by discussing them in general terms, but of course the specific fluid compositions and processes may be quite different in different geological settings. One of the main reasons that we are interested in fluids (other than
American Mineralogist, Feb 1, 1982
Nature Communications, Jul 14, 2017
Lunar and Planetary Science Conference, Mar 21, 2016
Lunar and Planetary Science Conference, 2001
Science
Samples of the carbonaceous asteroid Ryugu were brought to Earth by the Hayabusa2 spacecraft. We ... more Samples of the carbonaceous asteroid Ryugu were brought to Earth by the Hayabusa2 spacecraft. We analyzed 17 Ryugu samples measuring 1 to 8 millimeters. Carbon dioxide–bearing water inclusions are present within a pyrrhotite crystal, indicating that Ryugu’s parent asteroid formed in the outer Solar System. The samples contain low abundances of materials that formed at high temperatures, such as chondrules and calcium- and aluminum-rich inclusions. The samples are rich in phyllosilicates and carbonates, which formed through aqueous alteration reactions at low temperature, high pH, and water/rock ratios of <1 (by mass). Less altered fragments contain olivine, pyroxene, amorphous silicates, calcite, and phosphide. Numerical simulations, based on the mineralogical and physical properties of the samples, indicate that Ryugu’s parent body formed ~2 million years after the beginning of Solar System formation.
Lithos, 2019
Abstract We present phase equilibria modeling, combined with fluid inclusion microthermometry and... more Abstract We present phase equilibria modeling, combined with fluid inclusion microthermometry and textural observations, to constrain the composition and relative timing of subduction zone fluid-rock interaction during exhumation of two garnet-bearing blueschists from the northern part of the island of Sifnos, Greece. Water (H2O) from seawater was incorporated into the mafic lithologies by low-temperature water-rock interaction to produce hydrous phases, and was subsequently released during the subduction and exhumation cycle. Coupled phase equilibria modeling and textural observations suggest that fluid release resulted from the breakdown of the hydrous phases epidote and glaucophane, and some of the fluid was trapped as fluid inclusions in quartz. Homogenization temperatures and isochores of fluid inclusions are consistent with petrographic observations that suggest fluid inclusions were trapped during exhumation. Constructed isochores cross the inferred P-T path for Sifnos exhumation at pressures of ~0.3–1.0 GPa (~10–30 km depth) and temperatures of ~440–540 °C, suggesting fluid entrapment during the late stages of exhumation and cooling from peak subduction depths of ~70 km. The fluid inclusions have salinities of ~30–35 wt% NaCl equivalent, likely resulting from a multi-stage process that involves an increase in salinity during formation of hydrous minerals during subduction, leaving high salinity fluids and/or halide salts sequestered in pores. This is followed by the partial release of H2O during subsequent breakdown of high-pressure metamorphic phases, with later incorporation of H2O into newly forming retrograde phases. Portions of this fluid that interacted with earlier-formed saline fluids are now preserved as inclusions trapped in quartz. This interpretation suggests that fluid-rock interaction in the northern part of Sifnos occurred in a closed system, with a low water to rock mass ratio (~0.03 to ~0.05) and little to no infiltration of externally-derived lower salinity fluids. The closed system behavior is consistent with the observation that the blueschist unit is bounded by impermeable marble layers that limited exchange with external fluids during burial and/or exhumation.
Gondwana Research, 2014
Abstract Water (H2O) has been identified during Raman analyses at ~ 150–200 °C of fluid inclusion... more Abstract Water (H2O) has been identified during Raman analyses at ~ 150–200 °C of fluid inclusions from granulites that were previously thought to contain pure CO2. At room temperature, H2O in a CO2-rich fluid inclusion forms an optically unresolvable liquid wetting the inclusion walls. During heating, the H2O phase evaporates into the CO2 phase to produce a homogeneous H2O–CO2 fluid throughout the inclusion volume, and the H2O Raman peak at ~ 3640 cm− 1 is clearly resolvable at elevated temperatures. To test and confirm the method, synthetic H2O–CO2 FI of known composition (87.5 mol% and 95 mol% CO2) were also analyzed. Previously studied granulite samples from the Adirondack Mountains, USA, and from the Kerala Khondalite Belt, Sittampundi Complex and Sevitturangampatti, India were tested for the presence of H2O in CO2-rich fluid inclusions. Traces of H2O were found in CO2-rich fluid inclusions in quartz crystals from the Adirondacks and from the Kerala Khondalite Belt. H2O was not detected in CO2-rich secondary fluid inclusions in garnet from the Sittampundi Complex and from Sevitturangampatti. Rather, hydrogarnet was detected along the walls of inclusions in garnet, as evidenced by a peak at ~ 3661 cm− 1. The hydrogarnet is interpreted to be a “step-daughter” phase that formed by reaction of the H2O in the fluid inclusion with the garnet host during retrogression. These observations confirm the presence of an H2O-bearing, CO2-rich fluid at some time during granulite petrogenesis, but do not resolve the question of whether these CO2-rich fluids were trapped at peak metamorphic conditions or during retrogression, or whether the fluid inclusions have reequilibrated following entrapment.
Economic geology and the bulletin of the Society of Economic Geologists, Mar 1, 2022
Geochemical Journal, 2014
Journal of the American Chemical Society
EGU General Assembly Conference Abstracts, Apr 1, 2018
Geochemical Perspectives, 2014
Thus far, we have emphasised the common features of crustal fluids by discussing them in general ... more Thus far, we have emphasised the common features of crustal fluids by discussing them in general terms, but of course the specific fluid compositions and processes may be quite different in different geological settings. One of the main reasons that we are interested in fluids (other than