Mass spectrometric determination of the dissociation energy of Mn2F6(g)

The gaseous Mn2F6 molecule has been identified for the first time in the vapor produced by MnF3 vaporization and the MnF3(g) dimerization equilibrium studied by the Knudsen cell mass spectrometry technique in the 884–1015 K temperature range. The experimental vapor pressure data were treated by the second- and third-law procedures, and the enthalpy of Mn2F6(g) dissociation has been determined as: equation image. Thermodynamic functions of gaseous MnF3 were calculated from geometrical and vibrational parameters taken from the literature. For gaseous Mn2F6, they were evaluated by comparison with molecular parameters of Co2F6(g). Copyright © 2002 John Wiley & Sons, Ltd

Hydrothermal Controls on Metal Distribution in Porphyry Cu (-Mo-Au) Systems

Extensive research during the 20th century on porphyry Cu (-Mo-Au) deposits has revealed the following major geodynamic, petrological, mineralogical, and geochemical features that characterize these deposits: (1) these systems commonly occur in continental and oceanic magmatic arcs or in collisional orogenic belts; (2) they have spatial and genetic relationships to basaltic-to-felsic magmas emplaced in the upper 10 km of the crust; (3) lateral and vertical alteration-mineralization zoning consists of a Cu (± Mo ± Au) ore shell in the shallow portion of a potassic alteration zone, produced by magmatic fluids; this can be overprinted by phyllic alteration, also largely magmatic in signature, that in turn may be overprinted by argillic alteration, with a dominantly meteoric signature; (4) associated deposits such as skarns, Cordilleran vein, and high and intermediate sulfidation epithermal deposits may occur above or adjacent to porphyry orebodies; (5) porphyry systems form from S- and metal-rich, single-phase aqueous fluid of moderate salinity (2–10 wt % NaCl equiv) exsolved from magmas; during its ascent toward the surface this fluid undergoes a variety of processes that can cause metal precipitation, including decompression, phase separation, cooling, interaction with host rocks, and mixing. In the last 20 years, novel microanalytical techniques for in situ characterization of individual fluid inclusions have provided direct evidence for the chemical and phase composition plus metal content of ore-forming fluids in porphyry systems. In this contribution, we compile a large dataset of published fluid inclusion compositions from more than 30 deposits of the porphyry-skarn-epithermal suite