Grain‐scale permeabilities of faceted polycrystalline aggregates

Porous synthetic quartzites and amphibolites, each with faceted pore walls, were synthesized and evaluated to examine the permeability of pore networks similar to those of the lower crust and mantle. Quartzite with a fluid in equilibrium with an Mg–clinopyroxene contained connected networks of pores with a dihedral angle of 30° bounded by walls that were 10–50% faceted. The relationship of their permeability (k) to porosity (φ) is approximated by the previously determined relationship for relatively nonfaceted synthetic quartzite Amphibolite with an HF fluid contained fluorotremolite and a connected network of pores bounded by walls exhibiting 78–90% faceting. These materials showed much lower k for a given φ, with an apparent permeability threshold at φ_c = 0.04. A curve fit to these data yields The results suggest that moderate faceting has little effect on the transmission of fluids through rocks, but extensive faceting significantly alters permeability. This difference is most likely produced through isolation of the fluid to the grain corners at low φ with extensive faceting. Rocks with pores that tend toward faceting may impede the flow of fluids and melt.     

Islam in and out of politics: The Indonesian case

Accounts of the relationship between Islam and politics in Indonesia often fail to appreciate the contribution that an anthropological perspective can make towards understanding the heterogeneity of Muslim communities in the country. Looking at recent events that have political dimensions in the country, this article shows how paying close attention to the popularity of celebrity preachers can complement a political science approach.