Happening @ Michigan https://events.umich.edu/list/rss RSS Feed for Happening @ Michigan Events at the University of Michigan. Smith Lecture: Mineral Exploration and Discovery in Africa, and their Benefits to African Geoscientists - the Ivanhoe Perspective (January 12, 2018 3:30pm) https://events.umich.edu/event/46202 46202-10418365@events.umich.edu Event Begins: Friday, January 12, 2018 3:30pm
Location: 1100 North University Building
Organized By: Earth and Environmental Sciences

Ivanhoe Mines and its predecessor companies (e.g. Ivanplats) have been active in Africa for over 20 years, primarily in the well-known geological provinces of the Central African Copperbelt (DRC, Zambia) and the Bushveld Complex (South Africa). Discoveries of world-class deposits at Kamoa (Cu) in 2008, Flatreef (PGE–Ni–Cu) in 2010, and Kakula (Cu) in 2016, as well as acquisition of the formerly producing Kipushi mine (Cu-Zn) in 2012, have transformed the company from a small, private junior explorer to a prominent, publically traded mining and development company. Ivanhoe’s discoveries came in areas dismissed as geologically un-prospective, and have had fundamental impacts on geological understanding and mineralization models in the Copperbelt and Bushveld. They have also brought substantial benefits and employment to local economies and people, including geoscientists. Ivanhoe is proud to sponsor a wide range of community and sustainability projects, education and technical training, and undergraduate to graduate level studies and research projects.

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Lecture / Discussion Mon, 08 Jan 2018 09:10:47 -0500 2018-01-12T15:30:00-05:00 2018-01-12T16:30:00-05:00 1100 North University Building Earth and Environmental Sciences Lecture / Discussion 1100 North University Building
Smith Lecture: Paleoenvironmental Insights from the Structure and Function of Extinct Plants (January 19, 2018 3:30pm) https://events.umich.edu/event/46203 46203-10418366@events.umich.edu Event Begins: Friday, January 19, 2018 3:30pm
Location: 1100 North University Building
Organized By: Earth and Environmental Sciences

Plants are unique among multicellular organisms because much of their physiology is biophysical, rather than behavioral, and the anatomy that defines these biophysical capabilities is preserved in the fossil record. Mathematical models, when applied to fossilized plant organs—particularly leaves and stems—can provide quantitative insight into the physiology and ecology of plants that have been extinct for hundreds of millions of years. Comparing the physiology of extinct plants with strategies that are currently employed by living plants sheds light on ecophysiological trajectories in plant evolutionary history and the history of plant-environment coevolution.

In this presentation, I will describe the history of water transport in land plants and focus on key plants from the Euramerican Carboniferous tropical forests, including Medullosa, a morphologically diverse genus of Carboniferous plants that evolved fronds and stems capable of high rates of transpiration. Each of these plants contains anatomical features that result in novel physiologies, and together they represent the early evolution of physiological complexity—and the capability to influence regional climates and biogeochemical cycles—in terrestrial ecosystems.

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Lecture / Discussion Fri, 22 Dec 2017 12:44:40 -0500 2018-01-19T15:30:00-05:00 2018-01-19T16:30:00-05:00 1100 North University Building Earth and Environmental Sciences Lecture / Discussion 1100 North University Building
Smith Lecture: Deep Crustal Structure of the Rocky Mountain Region from Seismic Observations, Xenoliths, and Local Studies of Exhumed Terranes (January 26, 2018 3:30pm) https://events.umich.edu/event/46204 46204-10418367@events.umich.edu Event Begins: Friday, January 26, 2018 3:30pm
Location: 1100 North University Building
Organized By: Earth and Environmental Sciences

Geophysical studies, xenoliths, magmatic records, and rare exposures of once deep rocks provide different perspectives with which to investigate the structure, composition, and properties of deep continental crust. Each has its own inherent biases and/or limitations, making integrated approaches particularly valuable in furthering our understanding of lithospheric evolution. We are comparing the structural, metamorphic, geochronological, and petrophysical records from xenoliths and exhumed crustal terranes from a range of localities across the Rocky Mountain region to seismic observations from EarthScope’s USArray and other regional experiments. This presentation will focus on two aspects that offer complimentary perspectives on North American evolution. First, we use seismic results from EarthScope experiments, compilations of active source studies, and selected xenolith studies to attempt to map the distribution of high-velocity lower crust across the continental U.S. and assess its relationship to emplacement and destruction-related mechanisms such as under-and intraplating, collision, extension, heating, cooling, hydration, and delamination. One major emphasis is on the geodynamic influence of garnet-producing and -consuming reactions on the density and velocity structure of the crust. The second aspect emphasizes seismic anisotropy as an important tool for mapping crustal-scale deformation patterns at depth. One preliminary conclusion from this work is that anisotropy in the central Rocky Mountain region apparently reflects competing signals from broadly distributed Paleoproterozoic fabric domains and late-stage localized shear zones. Important points to consider are the geometric and scale biases of seismic detection methods, as well as the physical and chemical processes involved in anisotropy development during deformation.

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Lecture / Discussion Thu, 11 Jan 2018 13:45:08 -0500 2018-01-26T15:30:00-05:00 2018-01-26T16:30:00-05:00 1100 North University Building Earth and Environmental Sciences Lecture / Discussion 1100 North University Building
Smith Lecture: Mountain Building, Strike-slip Faulting, and Landscape Evolution in New Zealand's Marlborough Fault System (February 2, 2018 3:30pm) https://events.umich.edu/event/46205 46205-10418368@events.umich.edu Event Begins: Friday, February 2, 2018 3:30pm
Location: 1100 North University Building
Organized By: Earth and Environmental Sciences

The ~150 km wide dextral Marlborough Fault System and adjacent Kaikoura Mountains accommodate oblique convergence at the NE end of the South Island, New Zealand. Low-temperature thermochronology from this region, which was also the site of the 2016 Mw7.8 Kaikoura earthquake, places new limits on the timing and style of mountain building and the relationship between the mountains and adjacent faults. We sampled rocks for (U-Th/He) and fission track dating from a range of elevations spanning ~2 km within the Kaikoura Mountains, which stand high above active strike-slip faults. The data reveal two phases of exhumation: Miocene cooling localized to hanging wall rocks followed by regional and rapid cooling reflected in all samples starting at ~4-5 Ma. These results suggest that, despite the presence of active mountain front faults, much of the topographic relief in this region predates the onset of strike-slip faulting when portions of the Marlborough Faults were thrust faults during the early development of the transpressive plate boundary. After 5 Ma, the main Marlborough faults transitioned to accommodating primarily strike-slip motion, and regional exhumation likely reflected increased proximity to the migrating Pacific plate subduction zone and the buoyant Chatham Rise. The 2016 earthquake, which lifted and/or laterally shifted the surface along multiple subsidiary Marlborough fault strands, both onshore and off, fits well with evidence from the long-term record of a broad, complex and evolving oblique collision zone.

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Lecture / Discussion Mon, 18 Dec 2017 09:50:28 -0500 2018-02-02T15:30:00-05:00 2018-02-02T16:30:00-05:00 1100 North University Building Earth and Environmental Sciences Lecture / Discussion 1100 North University Building
Smith Lecture: The Meandering Path from River Dynamics to Valley Form (February 9, 2018 3:30pm) https://events.umich.edu/event/46206 46206-10418369@events.umich.edu Event Begins: Friday, February 9, 2018 3:30pm
Location: 1100 North University Building
Organized By: Earth and Environmental Sciences

River channels are central features of many landscapes. In uplands, rivers carve valleys by migrating laterally and cutting downward into the landscape. Viewed in cross-section, valleys often show a textbook “V” shape. In other valleys, the path from the valley top to valley floor descends in discrete steps as river terraces, or in one steep drop into a river gorge. A longstanding question is whether these steps in valley topography record step changes in the history of river incision—driven, for example, by a pulse of tectonic uplift or a change in climate—or instead form by river erosion under steady forcing. Distinguishing these scenarios is central to reconstructing tectonic history and predicting landscape response to contemporary climate change. Numerical models provide a tool for predicting how rivers imprint the landscape, but face significant complications for treating bedrock valleys and common river shapes, including meandering and braiding.

I will present results from a new numerical modeling approach that fingerprints a background process of erosion by meandering rivers using surface ages and geometries. I will then apply this framework to test the likelihood of valley evolution driven by climate change for several North American river valleys. Finally, I will discuss an ongoing physical experiment to test how braided rivers shift across landscapes over geologic timescales. These case studies illuminate key challenges and opportunities for using river dynamics to interpret planetary landscapes and the geologic record.

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Lecture / Discussion Mon, 11 Dec 2017 13:45:43 -0500 2018-02-09T15:30:00-05:00 2018-02-09T16:30:00-05:00 1100 North University Building Earth and Environmental Sciences Lecture / Discussion 1100 North University Building
Smith Lecture: Liquefaction Hazard in the Built Environment: Numerical and Experimental Investigations into the Effectiveness of Liquefaction Mitigation Techniques (February 16, 2018 3:30pm) https://events.umich.edu/event/46207 46207-10418370@events.umich.edu Event Begins: Friday, February 16, 2018 3:30pm
Location: 1100 North University Building
Organized By: Earth and Environmental Sciences

Soil liquefaction continues to cause devastating damage to the built environment during earthquakes. In recent years, earthquakes in Christchurch-New Zealand (2010-2011), Tohoku-Japan (2011), Muisne-Ecuador (2016), have caused widespread liquefaction resulting in unacceptable settlement, tilt and deformation of buildings, especially those on shallow foundations. Field observations from such events provide valuable information about the behavior of soil and the response of structures, but a scarcity of instrumentation means that detailed recordings of the soil and structure responses from the time of the earthquake are lacking. Data is especially sparse regarding the performance and effectiveness of liquefaction mitigation strategies. Numerical and experimental studies have been performed at the University of Colorado Boulder to generate new case histories under controlled conditions. This presentation will summarize trends from both physical and numerical models, focusing on how structural performance is affected by some common liquefaction mitigation approaches

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Lecture / Discussion Mon, 11 Dec 2017 13:03:24 -0500 2018-02-16T15:30:00-05:00 2018-02-16T16:30:00-05:00 1100 North University Building Earth and Environmental Sciences Lecture / Discussion 1100 North University Building
Smith Lecture: What Does the Chemistry of Shallow-water Carbonate Sediments Tell Us About the Global Carbon Cycle Over Earth History? (February 23, 2018 3:30pm) https://events.umich.edu/event/46208 46208-10418371@events.umich.edu Event Begins: Friday, February 23, 2018 3:30pm
Location: 1100 North University Building
Organized By: Earth and Environmental Sciences

Shallow-water carbonate sediments are one of the most extensive and well-studied records of the chemistry and temperature of ancient oceans (Kasting et al., 2006; Veizer et al., 1999; Veizer and Hoefs, 1976). One of the major limitations in the utilization of this archive is the potential for changes in the chemical composition of the sediments at any time after they were initially precipitated. Using a large data set of Ca and Mg isotope measurements in Neogene shallow-water carbonate sediments and associated pore-fluids from the platform to the slope in the Bahamas we have shown that stratigraphic variability in these isotopic systems is due to variations in both mineralogy and style of diagenetic alteration (fluid-buffered vs. sediment-buffered). This interpretation is rather counterintuitive given that these elements, and Ca in particular, are major components of the carbonate sediment and should be relatively robust – almost as robust as C – to diagenetic alteration.

The observation that sediment δ44Ca values in Neogene shallow-water carbonate sediments from the platform top, margin, and slope are largely controlled by mineralogy and the extent of fluid-buffered early marine diagenesis and that temporal variations in fluid-buffered diagenesis can generate stratigraphically coherent co-variation between many carbonate-bound geochemical proxies (δ13C, δ18O, Sr/Ca, etc.) has significant implications for the interpretation of both the major and trace element chemistry of shallow-water carbonate sediments in the geologic record. In particular, it suggests that stratigraphic co-variation between carbonate-bound geochemical proxies need not reflect changes in the global geochemical cycles of these elements but rather changes in the composition of bank-top waters and/or the extent of fluid-buffered vs. sediment-buffered early marine diagenesis. Thus, records of secular change and extreme variability in shallow-water carbonate sediments might be better interpreted as records of the effects of global environmental change and evolution on shallow-water carbonate-producing environments and not archives of global geochemical fluxes (e.g. the relative rates of organic carbon and carbonate burial from the δ13C of CaCO3).

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Lecture / Discussion Mon, 12 Feb 2018 11:47:18 -0500 2018-02-23T15:30:00-05:00 2018-02-23T16:30:00-05:00 1100 North University Building Earth and Environmental Sciences Lecture / Discussion 1100 North University Building
Smith Lecture: Chemically-stratified Midwestern Lakes are Relevant to Precambrian AND Modern Global Biogeochemistry (March 9, 2018 3:30pm) https://events.umich.edu/event/46209 46209-10418372@events.umich.edu Event Begins: Friday, March 9, 2018 3:30pm
Location: 1100 North University Building
Organized By: Earth and Environmental Sciences

The physical, chemical, and biological structure of permanently stratified lakes have analogy to the Earth’s Precambrian oceans. Both have deep waters devoid of oxygen, have lower sulfur contents than the modern ocean, and have biogeochemical cycles predominantly driven by microbes. Through two stratified and iron-rich lakes in Minnesota and Michigan, my group is studying the significance of iron-based photosynthesis in primary productivity and its potential biosignatures, methane production, consumption and export in iron-rich (i.e. ferruginous) waters, as well as primary and diagenetic mineral and isotopic signatures of these systems that are recorded in sediments. While our findings are relevant to Precambrian biogeochemistry, I will present evidence that these small, stratified ferruginous lakes might be fairly common in the Midwest, and perhaps are becoming more so. Therefore, our findings from monitoring these two lakes are also relevant to trends in our region’s water quality, and the contribution of similar lakes to global greenhouse gas, nutrient, and metal cycles.

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Lecture / Discussion Mon, 15 Jan 2018 15:29:44 -0500 2018-03-09T15:30:00-05:00 2018-03-09T16:30:00-05:00 1100 North University Building Earth and Environmental Sciences Lecture / Discussion 1100 North University Building
Smith Lecture: Seismic Investigation of the Magma System beneath Laguna del Maule, Chile (March 16, 2018 3:30pm) https://events.umich.edu/event/46210 46210-10418373@events.umich.edu Event Begins: Friday, March 16, 2018 3:30pm
Location: 1100 North University Building
Organized By: Earth and Environmental Sciences

The Laguna del Maule volcanic field, straddling the Chile-Argentina border at 36° S, is currently the subject of a multi-disciplinary collaborative investigation supported primarily by the U.S. National Science Foundation Integrated Earth Systems program and the Observatorio Volcanológico de Los Andes del Sur (OVDAS) of SERNAGEOMIN. At least 50 post-glacial (younger than 20 ka) eruptions from more than two dozen vents encircling the 25x17 km lake basin have produced rhyodacitic-to-rhyolitic lava flows and ash deposits totaling > 30 km3, suggesting that a large, active, silicic magma reservoir fuels this system. Since 2007, GPS and InSAR geodesy reveal that Laguna del Maule has been experiencing rapid uplift at 20 to 25 cm/year centered within the ring of silicic vents. Moreover, a deformed paleo-shoreline that has been 36Cl-dated implies magma-driven surface uplift of > 60 m and that growth of this large shallow reservoir has occurred over at least the past 9,400 years. UW-Madison, Cornell, and OVDAS have deployed a seismic array covering ~450 km2 that surrounds the lake basin. The array consisted of 18 broadband stations in 2015, and was enlarged to 47 stations in 2016 (37 broadband, 10 short-period). The full array will remain in place until late March 2018. A variety of seismic studies are planned for the seismic array data, including body-wave tomography, surface-wave tomography, attenuation tomography, teleseismic tomography, receiver function analysis, seismic interferometry, and focal mechanism and moment tensor determination. The main goals are to detect the magma chamber underlying Laguna del Maule, characterize its dimensions and properties, and assess the state of stress of the system.

I will report on results from surface-wave tomography, and compare them to the results from other geophysical techniques. Due to the small array aperture (~30 km) and the limited frequency range of usable ambient noise, we combined three types of data for the surface-wave tomography: standard noise correlation analysis using pairs of stations within the array, correlation of earthquake coda at pairs of array stations, and differential dispersion for ambient noise for pairs of array stations correlated with remote stations. Somewhat unexpectedly, the Vs image shows evidence of a strong upper crustal low velocity anomaly along the southwest side of the lake, which does not extend under the entire lake basin. Depending on how the boundaries of the low-Vs anomaly are defined, we obtain estimates of ~25 to ~400 km3, and melt percentages of 5% to 8%. The position of the anomalous body is very close to the estimated source area for the uplift measured by InSAR and GPS. A Bouguer gravity low, interpreted to reflect the magma reservoir, is observed in the same area. In contrast, magnetotelluric results image a large low-resistivity zone near the north side of the lake and much smaller anomalies elsewhere.

Recent fluid dynamic models of bubble migration and accumulation have shown that volatiles can provide a mechanism whereby basaltic magma recharge could catalyze the eruption of rhyolite without imparting a substantial thermal or physical signature on the erupted lavas. This leads to the idea that during the Holocene, rhyolitic magma batches have been repeatedly extracted from a broad spatial footprint beneath the lake basin, but the magma batches that have fed the individual eruptions were likely of relatively modest volume, comparable to the geophysical results.

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Lecture / Discussion Mon, 15 Jan 2018 09:41:43 -0500 2018-03-16T15:30:00-04:00 2018-03-16T16:30:00-04:00 1100 North University Building Earth and Environmental Sciences Lecture / Discussion 1100 North University Building
Smith Lecture: Tidal Tomography: What an Often-neglected Phenomenon Known as Earth Tides Can Tell Us About Buoyancy in the Deepest Part of the Mantle (March 23, 2018 3:30pm) https://events.umich.edu/event/46211 46211-10418374@events.umich.edu Event Begins: Friday, March 23, 2018 3:30pm
Location: 1100 North University Building
Organized By: Earth and Environmental Sciences

Earth’s mantle is a key component of the Earth system: its circulation drives plate tectonics, the long-term recycling of Earth’s volatiles, and as such, holds fundamental implications for the Earth’s surface environment. In order to understand this evolution, a key parameter of the mantle must be known, namely its buoyancy. In this talk, I will discuss how Earth’s body tide can provide fresh and independent constraints on deep mantle buoyancy through a newly developed technique called Tidal Tomography. This comes at a time when other interesting and exciting data sets sensitive to deep mantle buoyancy, e.g., Stoneley modes, have been brought to bear, and we will explore our conclusions in the context of other recent finds.

In particular, we will focus on two regions of the deep mantle known as the Large Low Shear Velocity Provinces (LLSVPs), the buoyancy of which has attracted much debate over the past few decades. Using a global GPS data set of high precision measurements of the Earth’s body tide, we perform a tomographic inversion to constrain the integrated buoyancy of these LLSVPs at the base of the mantle. As a consequence of the long-wavelength and low frequency nature of the Earth’s body tide, these observations are particularly sensitivity to LLSVP buoyancy. Using a probabilistic approach we find that the data are best fit when the bottom two thirds (~700 km) of the LLSVPs have an integrated excess density of ~0.60%.
The detailed distribution of this buoyancy, for example whether it primarily resides in a thin layer at the base of the mantle, will require further testing and the augmentation of the inversions to include independent data sets (e.g., seismic observations). Nevertheless, our inference of excess density requires the preservation of chemical heterogeneity associated with the enrichment of high-density chemical components, possibly linked to subducted oceanic plates and/or primordial material, in the deep mantle. This conclusion has important implications for the stability of these structures and, in turn, the history and ongoing evolution of the Earth system.

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Lecture / Discussion Thu, 18 Jan 2018 11:18:39 -0500 2018-03-23T15:30:00-04:00 2018-03-23T16:30:00-04:00 1100 North University Building Earth and Environmental Sciences Lecture / Discussion 1100 North University Building
Smith Lecture: Surprises in Iron Cycling at the Peru Margin (March 30, 2018 3:30pm) https://events.umich.edu/event/46213 46213-10418375@events.umich.edu Event Begins: Friday, March 30, 2018 3:30pm
Location: 1100 North University Building
Organized By: Earth and Environmental Sciences

Iron is the most important micronutrient in the ocean, yet its sources and sinks to and from the ocean are poorly constrained. The GP16 Eastern Pacific Zonal Transect cruise from Peru to Tahiti in 2013 along 12-15°S crossed the large eastern tropical South Pacific oxygen deficient zone (ODZ) in the eastern half of the transect and the East Pacific Rise (EPR) hydrothermal plume in the western half. Both features were expected to be important sources of dissolved iron into the ocean interior. The EPR hydrothermal iron plume was found to extend for several thousands of kilometers around 2500 m, greatly exceeding prior expectations. In contrast, there was no significant iron plume in the heart of the ODZ around 300 m that extended beyond the coastal margin, despite the ODZ penetrating several thousand of kilometers into the interior. Surprisingly, a deep coastal iron plume in oxygenated waters centered around 2000 m was observed to penetrate >1000 km into the interior. In this talk, I’ll examine the reasons behind the unexpected high Fe from the oxygenated deep slope relative to the more reducing ODZ above.

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Lecture / Discussion Thu, 18 Jan 2018 11:17:51 -0500 2018-03-30T15:30:00-04:00 2018-03-30T16:30:00-04:00 1100 North University Building Earth and Environmental Sciences Lecture / Discussion 1100 North University Building
Smith Lecture: Chemical Insights into Earth’s Microbiomes (April 6, 2018 3:30pm) https://events.umich.edu/event/46214 46214-10418376@events.umich.edu Event Begins: Friday, April 6, 2018 3:30pm
Location: 1100 North University Building
Organized By: Earth and Environmental Sciences

The Planet Earth is a microbial world, and the health of its inhabitants rests on the proverbial backs of microscopic organisms within oceans, rivers, soils and air. The oceans, in particular, are fundamental to the life-sustaining capabilities of Planet Earth, enabling all organisms from microbes to humans to persist and thrive. Within the oceans, microbes have an essential role, making the oxygen we breathe, removing greenhouse gas carbon dioxide from the atmosphere, anchoring the marine food web, fueling life within coral reefs, and promoting the health of fisheries and marine mammals. Detailed studies of microbial metabolism, therefore, provide fundamental knowledge about the life-sustaining processes on Earth. Recent work in this field has focused on the first order question of “who is there?” but second-order questions such as “what are they doing” and “how” are equally critical to assessing the role of microbial reactions in the global carbon cycle. Metabolomics, or the study of biochemical molecules, is one lens through which the chemical capacity of microbes can be viewed. In this presentation, I offer two case studies in which we use metabolomics to understand the chemical interplay of microbes. First, I will present work showing the role of microbes in particle remineralization in the open ocean, with implications for global carbon cycling. Second, I will present work showing the role of human and earth microbiomes in the chemistry of human sewage. These case studies are linked by the over-arching theme of microbial metabolism and its sentinel roles in understanding critical processes on our planet and will highlight the continuing role of analytical chemistry in elucidating fundamental earth system functions.

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Lecture / Discussion Mon, 26 Mar 2018 09:32:03 -0400 2018-04-06T15:30:00-04:00 2018-04-06T16:30:00-04:00 1100 North University Building Earth and Environmental Sciences Lecture / Discussion 1100 North University Building
Smith Lecture: Fluids of the Lower Crust and Upper Mantle: Deep is Different (April 13, 2018 3:30pm) https://events.umich.edu/event/46215 46215-10418378@events.umich.edu Event Begins: Friday, April 13, 2018 3:30pm
Location: 1100 North University Building
Organized By: Earth and Environmental Sciences

Deep fluids are important for the evolution and properties of the lower crust and upper mantle in tectonically active settings. Uncertainty about their chemistry has led past workers to use upper crustal fluids as analogues. However, recent results show that fluids at >15 km differ fundamentally from shallow fluids and help explain high-pressure metasomatism and resistivity patterns. Deep fluids are comprised of four components: H2O, non-polar gases (chiefly CO2), salts (mostly alkali chlorides), and rock-derived solutes (dominated by aluminosilicates and related components). The first three generally define the solvent properties of the fluid, and models must account for observations that H2O activity may be quite low. The contrasting behavior of H2O-gas and H2O-salt mixtures yields immiscibility in the ternary system, which can lead to separation of two phases with fundamentally different chemical and transport properties. Thermodynamic modeling of equilibrium between rocks and H2O using simple ionic species known from shallow-crustal systems yields solutions possessing total dissolved solids and ionic strength that are too low to be consistent with experiments and resistivity surveys. Addition of CO2 further lowers bulk solubility and conductivity. Therefore, additional species must be present in H2O, and H2O-salt solutions likely explain much of the evidence for fluid action in high-P settings. At low salinity, H2O-rich fluids are powerful solvents for aluminosilicate rock components that are dissolved as previously unrecognized polymerized clusters. Experiments show that, near H2O-saturated melting, Al-Si polymers comprise >80% of solutes. The stability of these species facilitates critical critical mixing in rock-H2O systems. Addition of salt (e.g., NaCl) changes solubility patterns, but aluminosilicate contents remain high. Thermodynamic models indicate that the ionic strength of fluids with Xsalt = 0.05 to 0.4 and equilibrated with model crustal rocks have predicted bulk conductivities of 10-1.5 to 100 S/m at porosity of 0.001. Such fluids are thus consistent with conductivity anomalies commonly observed in the lower crust (e.g., the “G” anomaly), and are capable of the mass transfer commonly seen in metamorphic rocks exhumed from the lower crust and subduction zones.

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Lecture / Discussion Fri, 19 Jan 2018 08:20:48 -0500 2018-04-13T15:30:00-04:00 2018-04-13T16:30:00-04:00 1100 North University Building Earth and Environmental Sciences Lecture / Discussion 1100 North University Building