Wendy Bohrson - Academia.edu (original) (raw)

Papers by Wendy Bohrson

Research paper thumbnail of Planetary Felsic Crust Formation at Shallow Depth

arXiv: Earth and Planetary Astrophysics, 2020

Current theories suggest that on Earth and, possibly, on other terrestrial planets early in their... more Current theories suggest that on Earth and, possibly, on other terrestrial planets early in their history, the first continental crust may has been produced by direct melting of hydrated peridotite. However, the conditions, mechanisms and necessary ingredients of such production remain elusive. To fill this gap, we have conducted experiments of serpentinite melting in the presence of variable proportions of basaltic melt, at typical conditions of the shallow lithosphere and asthenosphere. These experiments revealed formation of silica-rich liquids, which are similar to tonalite-trondhjemite-granodiorite magmas (TTG) identified in modern terrestrial oceanic mantle settings. Our results suggest a new mechanism of aqueous fluid-assisted partial melting of peridotite that may have operated on the early Earth and Mars just after the solidification of an ultramafic-mafic magma ocean, leading to the formation of the first embryos of continental crust. The proposed mechanism of the continen...

Research paper thumbnail of Origin of primitive ocean island basalts by crustal gabbro assimilation and multiple recharge of plume‐derived melts

Geochemistry, Geophysics, Geosystems, 2017

Research paper thumbnail of Oxygen isotope heterogeneity of arc magma recorded in plagioclase from the 2010 Merapi eruption (Central Java, Indonesia)

Geochimica et Cosmochimica Acta, 2016

Research paper thumbnail of Oxygen Isotope Composition of Plagioclase from the Steens Basalt, Columbia River Basalt Province, Se Oregon

Research paper thumbnail of Genesis of Evolved Ocean Island Magmas by Deep- and Shallow-Level Basement Recycling, Socorro Island, Mexico: Constraints from Th and other Isotope Signatures

Journal of Petrology, 1998

Research paper thumbnail of Petrogenesis of alkaline basalts from Socorro Island, Mexico: Trace element evidence for contamination of ocean island basalt in the shallow ocean crust

Journal of Geophysical Research: Solid Earth, 1995

Postcaldera mafic volcanism on Socorro Island, Mexico, an island located in the eastern Pacific O... more Postcaldera mafic volcanism on Socorro Island, Mexico, an island located in the eastern Pacific Ocean on a segment of a mid‐ocean ridge spreading center abandoned at ∼3.5 Ma, dominantly comprises alkalic basalt, hawaiite, and mugearite with subordinate mildly alkalic‐transitional basalt. Most major element data are consistent with differentiation of alkalic basalt to hawaiite and mugearite by up to 50% fractionation of plagioclase+clinopyroxene+olivine±Fe−Ti oxides. High‐field strength element abundances are consistent with this interpretation, and the narrow range in Zr/Nb suggests that parental magmas formed by similar degrees of partial melting of a relatively homogeneous mantle source. Sr and Nd isotopic ratios exhibit relatively narrow ranges (0.7031–0.7032, 0.5128–0.5130, respectively). Despite this, a subset of the alkalic basalts has negative Ce anomalies and abundances of P2O5, Ba, Y, and some rare earth elements in excess of those predicted by fractional crystallization mo...

Research paper thumbnail of Prolonged history of silicic peralkaline volcanism in the eastern Pacific Ocean

Journal of Geophysical Research: Solid Earth, 1996

Socorro Island, Mexico, is an alkaline and peralkaline volcanic island located in the eastern Pac... more Socorro Island, Mexico, is an alkaline and peralkaline volcanic island located in the eastern Pacific Ocean on a mid‐ocean ridge spreading center that was abandoned at ∼3.5 Ma. Silicic peralkaline rocks comprise up to 80% of the surface of the island, rendering Socorro virtually unique in the Pacific Ocean. Precise, replicate 40Ar/39Ar ages of 21 peralkaline trachytes and rhyolites reveal a history of episodic volcanic activity from ∼540 to 370 ka that may have culminated with caldera formation; repose periods between these episodes may have had maximum duration of ∼30 kyr. After up to 200 kyr of quiescence, 40Ar/39Ar ages indicate that postcaldera silicic peralkaline activity commenced by 180 ka, forming the Cerro Evermann Formation. Postcaldera mafic alkaline lavas of the Lomas Coloradas Formation erupted dominantly between 70 and 150 ka based upon relative age relations. The dominant lithology of precaldera and syncaldera silicic peralkaline deposits on Socorro is nonfragmental a...

Research paper thumbnail of Shallow-Level Processes in Ocean-island Magmatism: Editorial

Journal of Petrology, 1998

Research paper thumbnail of Editorial: Magma-Rock and Magma-Mush Interactions as Fundamental Processes of Magmatic Differentiation

Frontiers in Earth Science, 2021

Research paper thumbnail of Crustal heating and assimilation by LIP magmas: volatile perspectives from experimental petrology and thermodynamic modeling

Goldschmidt2021 abstracts, 2021

Research paper thumbnail of Diagnosing open-system magmatic processes using the Magma Chamber Simulator (MCS): part I—major elements and phase equilibria

Contributions to Mineralogy and Petrology, 2020

Research paper thumbnail of Rejuvenation of crustal magma mush: A tale of multiply nested processes and timescales

American Journal of Science, 2018

Research paper thumbnail of Dynamics and thermodynamics of magma mixing: Insights from a simple exploratory model

American Mineralogist, 2016

Research paper thumbnail of Thermodynamic Model for Energy-Constrained Open-System Evolution of Crustal Magma Bodies Undergoing Simultaneous Recharge, Assimilation and Crystallization: the Magma Chamber Simulator

Journal of Petrology, 2014

Research paper thumbnail of Chapter 13 Petrogenesis of the Campanian Ignimbrite: implications for crystal-melt separation and open-system processes from major and trace elements and Th isotopic data

Developments in Volcanology, 2006

Research paper thumbnail of Bulk rock composition and geochemistry of olivine-hosted melt inclusions in the Grey Porri Tuff and selected lavas of the Monte dei Porri volcano, Salina, Aeolian Islands, southern Italy

Central European Journal of Geosciences, 2012

The Aeolian Islands are an arcuate chain of submarine seamounts and volcanic islands, lying just ... more The Aeolian Islands are an arcuate chain of submarine seamounts and volcanic islands, lying just north of Sicily in southern Italy. The second largest of the islands, Salina, exhibits a wide range of compositional variation in its erupted products, from basaltic lavas to rhyolitic pumice. The Monte dei Porri eruptions occurred between 60 ka and 30 ka, following a period of approximately 60,000 years of repose. The bulk rock composition of the Monte dei Porri products range from basaltic-andesite scoria to andesitic pumice in the Grey Porri Tuff (GPT), with the Monte dei Porri lavas having basaltic-andesite compositions. The typical mineral assemblage of the GPT is calcic plagioclase, clinopyroxene (augite), olivine (Fo72−84) and orthopyroxene (enstatite) ± amphibole and Ti-Fe oxides. The lava units show a similar mineral assemblage, but contain lower Fo olivines (Fo57−78). The lava units also contain numerous glomerocrysts, including an unusual variety that contains quartz, K-feldsp...

Research paper thumbnail of Open-System Magma Chamber Evolution: an Energy-constrained Geochemical Model Incorporating the Effects of Concurrent Eruption, Recharge, Variable Assimilation and Fractional Crystallization (EC-E'RA FC)

Journal of Petrology, 2004

Research paper thumbnail of Energy-constrained open-system magmatic processes IV: Geochemical, thermal and mass consequences of energy-constrained recharge, assimilation and fractional crystallization (EC-RAFC)

Geochemistry, Geophysics, Geosystems, 2003

Research paper thumbnail of Energy-Constrained Recharge, Assimilation, and Fractional Crystallization (EC-RAχFC): A Visual Basic computer code for calculating trace element and isotope variations of open-system magmatic systems

Geochemistry, Geophysics, Geosystems, 2007

Research paper thumbnail of Open-System Magmatic Processes: Energy-Constrained Recharge, Assimilation and Fractional Crystallization (EC-RAFC)

ABSTRACT Geochemical data for igneous rocks provide conclusive evidence for the occurrence of ope... more ABSTRACT Geochemical data for igneous rocks provide conclusive evidence for the occurrence of open-system processes within magma bodies, the most critical of which are magma recharge (including enclave formation), assimilation of anatectic melt, and formation of cumulates by fractional crystallization. We have previously derived a model that tracks the composition of a magma body undergoing AFC; explicit in this model is accounting of country rock heating and the compositional effects of partial melting. The EC-AFC algorithm is based on solution of a system of differential equations that express conservation of energy (enthalpy), mass and species (trace elements and isotope ratios) (Spera and Bohrson 2001, Bohrson and Spera 2001). Here EC-AFC is extended to incorporate the effects of enthalpy, matter and species transport during magma recharge; this model, EC-RAFC, tracks the trace element and isotopic composition of melt, enclaves and cumulates as thermal equilibration is approached. EC-RAFC is formulated as a set of 3+t+i+s coupled nonlinear ordinary differential equations, where the number of trace elements, radiogenic and stable isotope ratios simultaneously modeled are t, i, and s, respectively. Solution of the EC-RAFC equations provides values for the average temperature of wallrock, mass of melt within the magma body, mass of cumulates and enclaves, mass of wall rock, mass of anatectic melt assimilated, concentration of t trace elements and i+s isotopic ratios in standing melt, cumulates, enclaves and anatectic melt as a function of the local temperature of standing magma. Input parameters include equilibration temperature, initial temperature and composition of magma, recharge magma, and wallrock, distribution coefficients, heat of fusion of wallrock and heats of crystallization of pristine and recharge magma, and isobaric specific heat capacities of all constituents. The magma recharge mass function is specified a priori and defines how recharge magma is added to standing magma (e.g., episodically, continuously). The present EC-RAFC simulator incorporates a weak coupling to major element mass balance and phase relations by means of a set of melt productivity functions based on laboratory experiments or Gibbs Energy minimization simulations (e.g., MELTS, Ghiorso 1997). Melt productivity functions prescribe the relationship between melt mass fraction and temperature. The EC-RAFC model, although a simplification of complex natural systems, is the first to examine systems characterized by magma recharge in a manner that self-consistently conserves energy, mass, and species. EC-RAFC not only provides an essential link between the physical and chemical controls governing complex open-system magma chambers, but also predicts complex geochemical behaviors that have analogues in natural magmatic systems; a number of these are examined in a companion abstract (Bohrson and Spera, this issue).

Research paper thumbnail of Planetary Felsic Crust Formation at Shallow Depth

arXiv: Earth and Planetary Astrophysics, 2020

Current theories suggest that on Earth and, possibly, on other terrestrial planets early in their... more Current theories suggest that on Earth and, possibly, on other terrestrial planets early in their history, the first continental crust may has been produced by direct melting of hydrated peridotite. However, the conditions, mechanisms and necessary ingredients of such production remain elusive. To fill this gap, we have conducted experiments of serpentinite melting in the presence of variable proportions of basaltic melt, at typical conditions of the shallow lithosphere and asthenosphere. These experiments revealed formation of silica-rich liquids, which are similar to tonalite-trondhjemite-granodiorite magmas (TTG) identified in modern terrestrial oceanic mantle settings. Our results suggest a new mechanism of aqueous fluid-assisted partial melting of peridotite that may have operated on the early Earth and Mars just after the solidification of an ultramafic-mafic magma ocean, leading to the formation of the first embryos of continental crust. The proposed mechanism of the continen...

Research paper thumbnail of Origin of primitive ocean island basalts by crustal gabbro assimilation and multiple recharge of plume‐derived melts

Geochemistry, Geophysics, Geosystems, 2017

Research paper thumbnail of Oxygen isotope heterogeneity of arc magma recorded in plagioclase from the 2010 Merapi eruption (Central Java, Indonesia)

Geochimica et Cosmochimica Acta, 2016

Research paper thumbnail of Oxygen Isotope Composition of Plagioclase from the Steens Basalt, Columbia River Basalt Province, Se Oregon

Research paper thumbnail of Genesis of Evolved Ocean Island Magmas by Deep- and Shallow-Level Basement Recycling, Socorro Island, Mexico: Constraints from Th and other Isotope Signatures

Journal of Petrology, 1998

Research paper thumbnail of Petrogenesis of alkaline basalts from Socorro Island, Mexico: Trace element evidence for contamination of ocean island basalt in the shallow ocean crust

Journal of Geophysical Research: Solid Earth, 1995

Postcaldera mafic volcanism on Socorro Island, Mexico, an island located in the eastern Pacific O... more Postcaldera mafic volcanism on Socorro Island, Mexico, an island located in the eastern Pacific Ocean on a segment of a mid‐ocean ridge spreading center abandoned at ∼3.5 Ma, dominantly comprises alkalic basalt, hawaiite, and mugearite with subordinate mildly alkalic‐transitional basalt. Most major element data are consistent with differentiation of alkalic basalt to hawaiite and mugearite by up to 50% fractionation of plagioclase+clinopyroxene+olivine±Fe−Ti oxides. High‐field strength element abundances are consistent with this interpretation, and the narrow range in Zr/Nb suggests that parental magmas formed by similar degrees of partial melting of a relatively homogeneous mantle source. Sr and Nd isotopic ratios exhibit relatively narrow ranges (0.7031–0.7032, 0.5128–0.5130, respectively). Despite this, a subset of the alkalic basalts has negative Ce anomalies and abundances of P2O5, Ba, Y, and some rare earth elements in excess of those predicted by fractional crystallization mo...

Research paper thumbnail of Prolonged history of silicic peralkaline volcanism in the eastern Pacific Ocean

Journal of Geophysical Research: Solid Earth, 1996

Socorro Island, Mexico, is an alkaline and peralkaline volcanic island located in the eastern Pac... more Socorro Island, Mexico, is an alkaline and peralkaline volcanic island located in the eastern Pacific Ocean on a mid‐ocean ridge spreading center that was abandoned at ∼3.5 Ma. Silicic peralkaline rocks comprise up to 80% of the surface of the island, rendering Socorro virtually unique in the Pacific Ocean. Precise, replicate 40Ar/39Ar ages of 21 peralkaline trachytes and rhyolites reveal a history of episodic volcanic activity from ∼540 to 370 ka that may have culminated with caldera formation; repose periods between these episodes may have had maximum duration of ∼30 kyr. After up to 200 kyr of quiescence, 40Ar/39Ar ages indicate that postcaldera silicic peralkaline activity commenced by 180 ka, forming the Cerro Evermann Formation. Postcaldera mafic alkaline lavas of the Lomas Coloradas Formation erupted dominantly between 70 and 150 ka based upon relative age relations. The dominant lithology of precaldera and syncaldera silicic peralkaline deposits on Socorro is nonfragmental a...

Research paper thumbnail of Shallow-Level Processes in Ocean-island Magmatism: Editorial

Journal of Petrology, 1998

Research paper thumbnail of Editorial: Magma-Rock and Magma-Mush Interactions as Fundamental Processes of Magmatic Differentiation

Frontiers in Earth Science, 2021

Research paper thumbnail of Crustal heating and assimilation by LIP magmas: volatile perspectives from experimental petrology and thermodynamic modeling

Goldschmidt2021 abstracts, 2021

Research paper thumbnail of Diagnosing open-system magmatic processes using the Magma Chamber Simulator (MCS): part I—major elements and phase equilibria

Contributions to Mineralogy and Petrology, 2020

Research paper thumbnail of Rejuvenation of crustal magma mush: A tale of multiply nested processes and timescales

American Journal of Science, 2018

Research paper thumbnail of Dynamics and thermodynamics of magma mixing: Insights from a simple exploratory model

American Mineralogist, 2016

Research paper thumbnail of Thermodynamic Model for Energy-Constrained Open-System Evolution of Crustal Magma Bodies Undergoing Simultaneous Recharge, Assimilation and Crystallization: the Magma Chamber Simulator

Journal of Petrology, 2014

Research paper thumbnail of Chapter 13 Petrogenesis of the Campanian Ignimbrite: implications for crystal-melt separation and open-system processes from major and trace elements and Th isotopic data

Developments in Volcanology, 2006

Research paper thumbnail of Bulk rock composition and geochemistry of olivine-hosted melt inclusions in the Grey Porri Tuff and selected lavas of the Monte dei Porri volcano, Salina, Aeolian Islands, southern Italy

Central European Journal of Geosciences, 2012

The Aeolian Islands are an arcuate chain of submarine seamounts and volcanic islands, lying just ... more The Aeolian Islands are an arcuate chain of submarine seamounts and volcanic islands, lying just north of Sicily in southern Italy. The second largest of the islands, Salina, exhibits a wide range of compositional variation in its erupted products, from basaltic lavas to rhyolitic pumice. The Monte dei Porri eruptions occurred between 60 ka and 30 ka, following a period of approximately 60,000 years of repose. The bulk rock composition of the Monte dei Porri products range from basaltic-andesite scoria to andesitic pumice in the Grey Porri Tuff (GPT), with the Monte dei Porri lavas having basaltic-andesite compositions. The typical mineral assemblage of the GPT is calcic plagioclase, clinopyroxene (augite), olivine (Fo72−84) and orthopyroxene (enstatite) ± amphibole and Ti-Fe oxides. The lava units show a similar mineral assemblage, but contain lower Fo olivines (Fo57−78). The lava units also contain numerous glomerocrysts, including an unusual variety that contains quartz, K-feldsp...

Research paper thumbnail of Open-System Magma Chamber Evolution: an Energy-constrained Geochemical Model Incorporating the Effects of Concurrent Eruption, Recharge, Variable Assimilation and Fractional Crystallization (EC-E'RA FC)

Journal of Petrology, 2004

Research paper thumbnail of Energy-constrained open-system magmatic processes IV: Geochemical, thermal and mass consequences of energy-constrained recharge, assimilation and fractional crystallization (EC-RAFC)

Geochemistry, Geophysics, Geosystems, 2003

Research paper thumbnail of Energy-Constrained Recharge, Assimilation, and Fractional Crystallization (EC-RAχFC): A Visual Basic computer code for calculating trace element and isotope variations of open-system magmatic systems

Geochemistry, Geophysics, Geosystems, 2007

Research paper thumbnail of Open-System Magmatic Processes: Energy-Constrained Recharge, Assimilation and Fractional Crystallization (EC-RAFC)

ABSTRACT Geochemical data for igneous rocks provide conclusive evidence for the occurrence of ope... more ABSTRACT Geochemical data for igneous rocks provide conclusive evidence for the occurrence of open-system processes within magma bodies, the most critical of which are magma recharge (including enclave formation), assimilation of anatectic melt, and formation of cumulates by fractional crystallization. We have previously derived a model that tracks the composition of a magma body undergoing AFC; explicit in this model is accounting of country rock heating and the compositional effects of partial melting. The EC-AFC algorithm is based on solution of a system of differential equations that express conservation of energy (enthalpy), mass and species (trace elements and isotope ratios) (Spera and Bohrson 2001, Bohrson and Spera 2001). Here EC-AFC is extended to incorporate the effects of enthalpy, matter and species transport during magma recharge; this model, EC-RAFC, tracks the trace element and isotopic composition of melt, enclaves and cumulates as thermal equilibration is approached. EC-RAFC is formulated as a set of 3+t+i+s coupled nonlinear ordinary differential equations, where the number of trace elements, radiogenic and stable isotope ratios simultaneously modeled are t, i, and s, respectively. Solution of the EC-RAFC equations provides values for the average temperature of wallrock, mass of melt within the magma body, mass of cumulates and enclaves, mass of wall rock, mass of anatectic melt assimilated, concentration of t trace elements and i+s isotopic ratios in standing melt, cumulates, enclaves and anatectic melt as a function of the local temperature of standing magma. Input parameters include equilibration temperature, initial temperature and composition of magma, recharge magma, and wallrock, distribution coefficients, heat of fusion of wallrock and heats of crystallization of pristine and recharge magma, and isobaric specific heat capacities of all constituents. The magma recharge mass function is specified a priori and defines how recharge magma is added to standing magma (e.g., episodically, continuously). The present EC-RAFC simulator incorporates a weak coupling to major element mass balance and phase relations by means of a set of melt productivity functions based on laboratory experiments or Gibbs Energy minimization simulations (e.g., MELTS, Ghiorso 1997). Melt productivity functions prescribe the relationship between melt mass fraction and temperature. The EC-RAFC model, although a simplification of complex natural systems, is the first to examine systems characterized by magma recharge in a manner that self-consistently conserves energy, mass, and species. EC-RAFC not only provides an essential link between the physical and chemical controls governing complex open-system magma chambers, but also predicts complex geochemical behaviors that have analogues in natural magmatic systems; a number of these are examined in a companion abstract (Bohrson and Spera, this issue).