American Geophysical Union Become an AGU Member
Subscribe to AGU Journals		 AGU Home AGU Publications

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 466219 bytes)

GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L07201, doi:10.1029/2008GL033311, 2008

Non-ideal liquidus curve in the Fe-S system and Mercury's snowing core

Bin Chen

Department of Geology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA


Jie Li

Department of Geology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA


Steven A. Hauck II

Department of Geological Sciences, Case Western Reserve University, Cleveland, Ohio, USA


Abstract

We conducted multi-anvil experiments to investigate the melting behavior of the iron-sulfur system at moderate pressures. Our data reveal a positive departure from ideal solution behavior at 14 GPa, as indicated by the presence of two inflection points on the liquidus curve of iron-rich compositions. In contrast, the shape of the liquidus curve at 10 GPa is consistent with nearly ideal mixing between end-member components. Combined with existing data at lower pressures and above 20 GPa, our results suggest a negative liquidus temperature gradient under conditions found at shallow depths in Mercury's core. At the present time, the core is most likely precipitating solid iron in the form of snow, at a single depth or in two distinct zones. Formation and segregation of iron snow would alter the thermal and chemical state of the core and influence the origin and surface expression of the planet's magnetic field.>

Received 21 January 2008; accepted 5 March 2008; published 3 April 2008.

Keywords: melting behavior; Fe-S; Mercury.

Index Terms: 1060 Geochemistry: Planetary geochemistry (5405, 5410, 5704, 5709, 6005, 6008); 1507 Geomagnetism and Paleomagnetism: Core processes (1213, 8115); 6235 Planetary Sciences: Solar System Objects: Mercury; 3924 Mineral Physics: High-pressure behavior.

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 466219 bytes)

Citation: Chen, B., J. Li, and S. A. Hauck II (2008), Non-ideal liquidus curve in the Fe-S system and Mercury's snowing core, Geophys. Res. Lett., 35, L07201, doi:10.1029/2008GL033311.