Radiographic study on the viscosity of the Fe-FeS melts at the pressure of5 to 7 GPa

Stokes' viscometry combined with in situ X-ray radiographic observation, us ing the 6-8 type multi-anvil press and synchrotron radiation, has been appl ied to the viscosity measurement of the Fe-FeS melt up to pressures of 7 GP a. The viscosity is found to be about 2 x 10(-2) Pa-s at 5 to 7 GPa and tem peratures about 1350 K, in marked contrast to previous viscosity measuremen ts, which showed high viscosity, 0.5 to 14 Pa-s, at 2 to 5 GPa (LeBlanc and Secco 1996). Our viscosity data, however, is consistent with all other evi dence, which include 1 atm viscosity data, X-ray structure analysis, and ab initio simulations. Recent viscosity measurements (Dobson et al. 2000) als o showed the viscosity of Fe-FeS melt to be about 10(-2) Pa-s at 2.5 GPa. T hus, we are confident that the viscosity of the Fe-FeS melt is close to a t ypical value (10(-2) Pa-s) of viscosity for liquid metal even at high press ures.