One-dimensional physical reference models for the upper mantle and transition zone: Combining seismic and mineral physics constraints

2005 ◽  
Vol 110 (B1) ◽  
Author(s):  
F. Cammarano
Keyword(s):  
Transition Zone ◽  
Upper Mantle ◽  
Mineral Physics ◽  
One Dimensional ◽  
Reference Models

scholarly journals Gravity constraints on structure of the East-West Antarctic lithospheric transition zone

2021 ◽  
Author(s):  
Sam Treweek
Keyword(s):  
Transition Zone ◽  
Upper Mantle ◽  
Geophysical Methods ◽  
East Antarctica ◽  
Gravity Models ◽  
West Antarctica ◽  
Asthenospheric Mantle ◽  
Surface Uplift ◽  
Mantle Viscosity ◽  
Taylor Valley

<p><b>The differing structural evolution of cratonic East Antarctica and younger West Antarctica has resulted in contrasting lithospheric and asthenospheric mantle viscosities between the two regions. Combined with poor constraints on the upper mantle viscosity structure of the continent, estimates of surface uplift in Antarctica predicted from models of glacial isostatic adjustment (GIA) and observed by Global Satellite Navigation System (GNSS) contain large misfits. This thesis presents a gravity study ofthe lithospheric transition zone beneath the Taylor Valley, Antarctica, conducted to constrain the variation in lithological parameters such as viscosity and density of the upper mantle across this region.</b></p> <p>During this study 119 new gravity observations were collected in the ice-free regions of the Taylor Valley and amalgamated with 154 existing land-based gravity observations, analysed alongside aerogravity measurements of southern Victoria Land. Gravity data are used to construct 2D gravity models of the subsurface beneath this region. An eastward gradient in Bouguer anomalies of ~- 1.6 mGal/km is observed within the Taylor Valley. Models reveal thickening of the Moho from 23±5 km beneath the Ross Sea to 35±5 km in the Polar Plateau (dipping at 24.5±7.2°), and lithospheric mantle 100 km thicker in East Antarctica (~200±30 km) than West Antarctica (~90±30 km). </p> <p>Models of predicted surface uplift history are used to estimate an asthenospheric mantle viscosity of 2.1x1020 Pa.s at full surface recovery beneath the Ross Embayment, differing by ~14% from the viscosity at 50% recovery. The temperature contrast between lithospheric and asthenospheric mantle is estimated as ~400°C, equivalent to a viscosity that decreases by a factor of about 30 over the mantle boundary.</p> <p>Results demonstrate that the history of surface uplift in the study area may be complicated, resulting in observations of uplift, or subsidence, at GNSS stations. Future work should incorporate additional geophysical methods, such as seismicity and electrical resistivity, improving constraints on gravity models. A better understanding of the surface uplift (or subsidence) history in the Transantarctic Mountains is critical, with implications in reducing uncertainty in GIA models.</p>

scholarly journals Movement of zinc sulphate in a calcium-saturated soil: cation exchange and precipitation of gypsum.

1987 ◽  
Vol 35 (3) ◽  
pp. 295-313
Author(s):  
K. Harmsen
Keyword(s):  
Ion Exchange ◽  
Transition Zone ◽  
Zinc Sulphate ◽  
Solubility Product ◽  
Mass Conservation ◽  
Saturated Soil ◽  
Adsorption Complex ◽  
Dimensional Model ◽  
One Dimensional ◽  
Leaching Solution

A one-dimensional model for the movement of zinc sulphate through calcium-saturated soil is presented. Processes considered include mass flow, ion exchange, precipitation and dissolution. Precipitation occurs when the solubility product of gypsum is exceeded. In the presence of gypsum, ion exchange takes place at two separate interfaces, which move with different velocities through the soil. At the first interface precipitation of gypsum takes place in conjunction with ion exchange, and at the second interface the gypsum dissolves again and ion exchange proceeds until equilibrium is reached with the leaching solution. The composition of the transition zone between the two interfaces is calculated from the conditions of mass conservation and electroneutrality, the solubility product of gypsum and assuming a linear ion exchange equation. It is shown that the concentration of sulphate in the transition zone is higher than in the leaching solution, due to dissolution of gypsum at the second interface. In the presence of gypsum, zinc penetrates deeper into the soil than in its absence, but the fraction of the adsorption complex saturated with zinc is smaller. (Abstract retrieved from CAB Abstracts by CABI’s permission)

scholarly journals An Overview of the Experimental Studies on the Electrical Conductivity of Major Minerals in the Upper Mantle and Transition Zone

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 408 ◽  
Author(s):  
Lidong Dai ◽  
Haiying Hu ◽  
Jianjun Jiang ◽  
Wenqing Sun ◽  
Heping Li ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Transition Zone ◽  
Oxygen Fugacity ◽  
Upper Mantle ◽  
Activation Enthalpy ◽  
Small Polaron ◽  
Experimental Studies ◽  
Transport Processes ◽  
Structural Water ◽  
Nominally Anhydrous Minerals

In this paper, we present the recent progress in the experimental studies of the electrical conductivity of dominant nominally anhydrous minerals in the upper mantle and mantle transition zone of Earth, namely, olivine, pyroxene, garnet, wadsleyite and ringwoodite. The main influence factors, such as temperature, pressure, water content, oxygen fugacity, and anisotropy are discussed in detail. The dominant conduction mechanisms of Fe-bearing silicate minerals involve the iron-related small polaron with a relatively large activation enthalpy and the hydrogen-related defect with lower activation enthalpy. Specifically, we mainly focus on the variation of oxygen fugacity on the electrical conductivity of anhydrous and hydrous mantle minerals, which exhibit clearly different charge transport processes. In representative temperature and pressure environments, the hydrogen of nominally anhydrous minerals can tremendously enhance the electrical conductivity of the upper mantle and transition zone, and the influence of trace structural water (or hydrogen) is substantial. In combination with the geophysical data of magnetotelluric surveys, the laboratory-based electrical conductivity measurements can provide significant constraints to the water distribution in Earth’s interior.

Phase relations of MgFe2O4at conditions of the deep upper mantle and transition zone

2017 ◽  
Vol 102 (3) ◽  
pp. 632-642 ◽  
Author(s):  
Laura Uenver-Thiele ◽  
Alan B. Woodland ◽  
Tiziana Boffa Ballaran ◽  
Nobuyoshi Miyajima ◽  
Dan J. Frost
Keyword(s):  
Transition Zone ◽  
Upper Mantle ◽  
Phase Relations
Sign in / Sign up

Export Citation Format

Share Document