The Effect of Water on the 410-km Discontinuity: An Experimental Study
نویسندگان
چکیده
In order to evaluate the effect of H on the pressure and transition interval of the olivine-wadsleyite transformation, synthesis experiments were carried out in hydrous and anhydrous peridotite compositions at 1400oC. Under hydrous, near-saturated conditions, the pressure of the transition is 1.0 ± 0.5 GPa lower than under anhydrous conditions. In addition, the two-phase interval appears to broaden from about 0.4 GPa (12 km) in the anhydrous system to as much as 1.3 GPa (40 km) in the hydrous system. Under hydrous conditions the spatial distribution of olivine and wadsleyite appears to be controlled by H diffusion. Extrapolating previously measured diffusion coefficients for H in olivine and in liquids, it appears that H diffusion driven by gravitational equilibration may serve to narrow the transition interval between olivine and wadsleyite.
منابع مشابه
Seismic detection of a low-velocity layer atop the 410-km discontinuity: verification of an electromagnetically detected layer of partial-melt atop the 410-km discontinuity beneath SE Arizona
Receiver functions calculated from a ten-station subset of the Earthscope Transportable Array (TA) show a well-defined 45 km thick low-velocity layer atop the 410-km discontinuity (“410”) beneath the Tucson, Arizona, region. This observation is consistent with a previously detected layer of increased electrical conductivity in the same region, from which the existence a 5-30 km thick layer of p...
متن کاملCharacterizing the 410 Km Discontinuity Low-Velocity Layer Beneath the La Ristra Array in the North American Southwest
[1] Receiver functions recorded by the 54‐station 920 km long Program for Array Seismic Studies of the Continental Lithosphere–Incorporated Research Institutions for Seismology Colorado Plateau/Rio Grande Rift Seismic Transect Experiment (LA RISTRA) line array display a pervasive negative polarity P to S conversion (Pds) arrival preceding the positive polarity 410 km discontinuity arrival. Thes...
متن کاملThermal, hydrous, and mechanical states of the mantle transition zone beneath southern Africa
Observations of P-to-S conversions from the seismic discontinuities near 410 and 660 km depth reveal the shoaling of the 410-km discontinuity and the deepening of the 660-km discontinuity beneath the Archaean cratons in southern Africa; consequently, the mantle transition zone is 20 km thicker than beneath post-Archaean regions and the global average. The discontinuity structure, combined with ...
متن کاملAppraising the reliability of converted wavefield imaging: application to USArray imaging of the 410-km discontinuity
S U M M A R Y We develop a generic method to appraise the reliability of wavefield imaging methods and use it to validate some novel observations on the 410-km discontinuity. The core concept of the error appraisal method is to produce a simulated data set that replicates the geometry of the real data. Here we implemented two simulation methods: (1) flat layer primary P to S conversions, and (2...
متن کاملUpper mantle P velocity structure beneath the Midwestern United States derived from triplicated waveforms
[1] Upper mantle seismic velocity structures in both vertical and horizontal directions are key to understanding the structure and mechanics of tectonic plates. Recent deployment of the USArray Transportable Array (TA) in the Midwestern United States provides an extraordinary regional earthquake data set to investigate such velocity structure beneath the stable North American craton. In this pa...
متن کاملUbiquitous Low-Velocity Layer Atop the 410-Km Discontinuity in the Northern Rocky Mountains
S43A-1376.GeochemistryGeophysicsGeosystemsG jasbinsek and dueker: 410-km discontinuity, rockies 10.1029/2007GC001661
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 2002