Water in nominally anhydrous minerals: Infrared Spectroscopy of San Carlos olivine

In the upper mantle, the presence of a small amount of water can have a large effect on the mantle's properties and behavior. Below the Earth's crust, anhydrous minerals (those whose stoichiometric formula contains no water or OH groups) dominate; however, several studies have shown that olivine, and several other anhydrous minerals, may be able to store significant amounts (maybe oceans) of water. Although these minerals do not have water in their structure, defects (like ion vacancies) in the crystal lattice can allow OH- to bond to crystal sites. There are different theories about the amount of water that exists in the mantle, where it is stored, by what mechanism it is stored, and how it affects mantle viscosity, seismic wave velocities, and the width of the 410-km discontinuity.

To better understand water in the mantle – how much is stored, by what mechanism it is stored, where it is stored – scientists have attempted to recreate mantle conditions and compositions, and have also analyzed natural samples brought up as xenoliths in magmas and kimberlites. The difficulty with these studies is that all of our olivine samples are, obviously, from the crust, and have been altered during transport from the mantle. The water speciation and concentration in natural olivine xenoliths from the crust are probably different than in mantle olivine.

I will be investigating the changes that olivine crystals undergo during their transport up from the mantle (and thus also their original condition in the mantle) by studying several polished San Carlos olivine grains using IR spectroscopy. Specifically, I will be looking to see if/how the outer part of the crystals have different absorption spectra than the crystal's core. This will hopefully shed light on how the OH- concentration and speciation of olivine grains have been altered, and thus give us a better general picture of water in the upper mantle.

Katherine Allen

Barbara Birkes

Ashland University, OH
Geology Major

I will create strain models of an, as yet undefined, area of complex tectonic activity using the latest actual GPS data as well as some fault and slip data. Using a program written by Bill Holt I will create past, present, and future “snapshots” of a tectonically active area in order to view the distortion and rotation of the plate(s) that is occurring. In the long term, said program and data are expected to be used to test hypotheses about how an area has evolved, and to potentially gain insight about the dynamics of plate boundaries.

This project is related to a tremendous research endeavor known as EarthScope. While there are three separate entities to the earthScope effort, my research is most closely related to the Plate Boundary Observatory (PBO). The PBO seeks to create a three dimensional image or “map” of the tectonically active western portion of the United States using geodectic data from a carefully constructed web of GPS stations. On a broader scale, one of the primary objectives of the EarthScope project is to stimulate new tectonic research into the dynamics and history of the plate boundary zone.

Mapping the Pressure and Temperature Distribution Inside a High Pressure Cell Through In-situ X-ray Diffraction

Minerals inside the Earth are subject to high pressures and temperatures. The study of these minerals under these extreme conditions, gives scientists clues as to what is going on with our planet. The SAM85 press at the National Synchrotron Light Source at Brookhaven National Laboratory simulates these conditions using solid pressure medium cells. Understanding the temperature and pressure distribution inside the cell is critical to better comprehend the data collected and derive meaningful results.

The focus of this project is to investigate two types of cells and map pressure and temperature distributions inside the high pressure cell using in-situ X-ray diffraction.

Pressure and temperature variations will be monitored through the volume change of the standard material (eg. NaCl). X-ray diffraction patterns will be analyzed using the computer program Plot85 to derive the volume of the standard at different pressures and temperatures. Decker's equation of state for NaCl will be used to calculate the pressure or temperature from the volume data. I will also simulate the temperature distribution using a theoretical model. The results of this project should give us the necessary information to understand the pressure and temperature distribution inside the high pressure cell and increase accuracy for experimental studies about Earth's interior.

Jorgji Dhima

Through the analysis of the P-waves (compressional waves) and S-waves (shear waves) transmitted each time an earthquake occurs, geophysical research has shown that the outer core of the earth is liquid, unlike the crust, mantle, and inner core which are all believed to be solid. Recognition of patterns in the behavior of S-waves, as they do not travel through the outer core, provides evidence that the outer core is indeed liquid. Recent studies indicate that there may exist lateral heterogeneity in the outermost and innermost parts of this liquid outer core. Through the analysis of the S, ScS, and SKS phases of seismic waves, we will investigate velocity structure and its lateral variation in the top of the outer core, near the core-mantle boundary.

Using data recorded at seismic stations around the globe from recent earthquake events, we will be generating graphs of the raw seismic data using Seismic Analysis Code and Global Mapping Tool software. Using Generalized Ray Theory, we will calculate synthetic seismograms for various seismic wave velocity models in the outer core. Using these models, we will search for a seismic velocity model whose synthetic seismograms best fit the actual seismic data. Through the analysis and comparison of our outer core models, we hope to study the nature and composition of the outer core, including stratification/ non-stratification and whether or not there exist lateral non-homogeneities in the top portion of the outer core of the earth.

Variation of Calibration Parameters in Energy-Dispersive X-Ray Diffraction Data

When X-rays are incident upon a crystal, they are diffracted at different angles as predicted by Bragg's Law, which says that when X-rays of a known wavelength, l , strike the surface of a crystal with interatomic spacing (d-spacing), d, they will diffract at an angle, q .  If the crystal is well-ordered and has regularly-repeating atomic structures, these diffracted X-rays can constructively interfere at certain locations determined by Bragg's Law.  At the National Synchrotron Light Source at the Brookhaven National Laboratory, a machine called the SAM85 is used to create energy-dispersive X-ray diffraction data for various crystals subject to different temperature and pressure conditions.  The SAM85 uses four detectors with a total of 2048 channels to determine how each incident X-ray is diffracted. The energy corresponding to each diffracted X-ray photon can be modeled as a second order function with respect to the channel number. However, the three corresponding calibration parameters used to model this function tend to “drift,” or change with respect to the time taken to run the experiments and the counting rate of the detectors.
My research consists of determining how these calibration parameters vary with time and, if possible, to determine what may be causing the drift. I will start by organizing the standard calibration parameters determined for several different experiments in an Excel spreadsheet for easy future comparison. Then I will use the Windows-based program Plot85 to plot and analyze the data obtained from the SAM85 to determine the channel number, energy, and d-spacing for any diffraction peak. Using this analysis, I will be able to determine the new calibration parameters and observe any drift that occurs.

Marc Palmeri

Analysis of Perovskite

Until recently, conditions within the interior of the earth's mantle were not able to be studied due to limitations on achievable pressures and temperatures in the lab. Advances have been made, however, that allow researchers to simulate conditions comparable to over 700 km within the earth, the lower part of the mantle. It is believed that this part of the earth is comprised mainly of a combination of perovskite ((Mg,Fe)SiO 2 ) and magnesiowustite. Although it is not possible to form actual samples of perovskite on the surface of the earth, an analog that uses calcium instead of magnesium or iron and titanium instead of silicon can be synthesized. This analog can be used to study how the actual perovskite would act in a laboratory situation. By comparing the behavior of acoustic waves sent through prepared samples of the analog with seismological surveys of the inner earth, it is possible to obtain a better understanding of the composition of the earth.

The main goal of my research will be to examine perovskite analog samples that have already undergone testing at X17B2 beamline at Brookhaven National Lab to look at their density, chemistry, and the velocities of the acoustic waves passing through them. With this data, I will be able to compare the results to previously known data about seismological waves in the earth to see how the two sets of information compare. From such research I will be able to come to an understanding of the composition and structure of the inner mantle. In addition, I may be able to create some polycrystalline analog samples consisting of 75% CaTiO 3 and 25% CaSiO 3 in the High Pressure Lab of Stony Brook SUNY for use in future beamline studies. Lastly, I will also be looking at how the velocities of acoustic waves behave with respect to the pressure and temperature applied to the sample at the time.

Seismic waves are the best large scale probes that science has into the Earth’s interior. By measuring the velocities of these waves and comparing them to velocities measured in labs, one can discern the
materials that the waves are traveling through. In order to have a
working set of material properties, experiments need to be conducted on each material in question (as well as poly-crystalline materials) at a
variety of pressures in temperature. Using an electric circuit embedded
in high-pressure presses, it is relatively easy to determine the
temperature of a sample throughout an experiment but pressure
measurements are more difficult. The current method is to include NaCl, which has well-studied phases, along with the material sample and then to monitor the sodium chloride with x-rays. While this procedure is successful, the inconvenience of acquiring a powerful light source slows progress of these experiments.
The focus of my research will be on an alternative method for measuring pressure in press samples. Included with the sample is a buffering rod which separates the press elements from the sample to be studied. If the acoustic properties of this rod vary indicatively with pressure changes within the press it may be possible to use this as an internal gauge, foregoing the inclusion of NaCl and the need for synchrotron beam time. I will be studying the signals from acoustics moving through this rod and coordinating them with simultaneous pressure measurements from monitoring the NaCl of these samples.