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The distribution of cadmium, manganese and selenium between coexisting sphalerite and galena and of cadmium and manganese between wurtzite and galena has been studied experimentally over the temperature range 600ø-800 ø C. The distribution of selenium between galena and chalcopyrite has been investigated between 390 ø and 595 ø C. Cadmium and manganese are strongly fractionated toward sphalerite or wurtzite relative to galena, while the sequence for fractionation of selenium is: galena > chalcopyrite > sphalerite. Cadmium-and manganese-bearing galena and sphalerite solid solutions appear to exhibit Henry's law behavior throughout the concentration ranges normally found in nature. Selenium-bearing galena and sphalerite solid solutions behave as sensibly ideal mixtures over the temperature range studied. Therefore, at concentration levels expected in nature distribution coefficients (K) for these systems are functions of temperature and pressure alone. Log K vs 1/Tøa: plots are linear for each of these systems and their slope and position suggest that they may be used to estimate temperatures of ore formation to a precision of =t=15ø-20 ø C down to temperatures as low as 200 ø C for many deposits. The effect of pressure, as calculated from precise molar volume data, is insignificant. Values of the distribution coefficients should be determined in the range 200o-500 ø C to check our linear extrapolations to low temperatures. Polytyping of natural sphalerites may lead to serious underestimation of temperature if unrecognized.The most serious barrier to the application of these data to ore deposits is the necessity for an accurate paragenetic interpretation coupled with precise sampling. The materials analyzed must represent samples that equilibrated with respect to the partitioned components at the time of deposition and that have preserved their compositions throughout the postdepositional history of the deposit. The common occurrence of growth zones suggests that in many cases it will be necessary to sample contemporaneous and internally homogeneous zones in each of the minerals. A nearly absolute degree of sample purity is required, particularly for the depleted phase. The rapid rates of solid state reaction in galena and chalcopyrite imply that both phases should be considered suspect even i• low temperature environments. Concordant temperature estimates based on the partitioning of two or more elements should provide an excellent test of the degree of approach to, and preservation of, equilibrium compositions. of the distribution coefficient which follows therefore differs in no•tion from that of McIntire (1963).SAlthough we may s•ak of the "manganese content" of sphalerite, we must really consider the component to be MnS not Mn because the •lid •lution is between ZnS and MnS not ZnS and Mn.phases. Substituting (2) into (1) we see: Nhp .•.• g• g• = N• • •o]n (3) nS IMnS •'• mMns' "YMnSMnS' IMnS and the distribution coefficient, K, defined as the ratio of the concentrations of the minor component in any two phase...

The Summitville Au-Ag-Cu deposit is a classic volcanic dome-hosted high-sulfidation deposit. It occurs in the Quartz Latite of South Mountain, a composite volcanic dome that was emplaced along the coincident margins of the Platoro and Summitville calderas at 22.5F0.5 Ma, penecontemporaneous with alteration and mineralization. A penecontemporaneous quartz monzonite porphyry intrusion underlies the district and is cut and overlain by pyrite-quartz stockwork veins with traces of chalcopyrite and molybdenite.Alteration and mineralization proceeded through three hypogene stages and a supergene stage, punctuated by at least three periods of hydrothermal brecciation. Intense acid leaching along fractures in the quartz latite produced irregular pipes and lenticular pods of vuggy silica enclosed sequentially by alteration zones of quartz-alunite, quartz-kaolinite, and clay. The acidsulfate-altered rocks host subsequent covellite + enargite/luzonite + chalcopyrite mineralization accompanied by kaolinite, and later barite-base-metal veins, some containing high Au values and kaolinite.The presence of both liquid-and vapor-rich fluid inclusions indicates the episodic presence of a low-density fluid at all levels of the system. In the mineralized zone, liquid-rich fluid inclusions in healed fractures in quartz phenocrysts and in quartz associated with mineralization homogenize to temperatures between 160 and 390 8C (90% between 190 and 310 8C), consistent with the range (200-250 8C) estimated from the fractionation of sulfur isotopes between coexisting alunite and pyrite. A deep alunite-pyrite pair yielded a sulfur-isotope temperature of 390 8C, marking a transition from hydrostatic to lithostatic pressure at a depth of about 1.5 km.Two salinity populations dominate the liquid-rich fluid inclusions. One has salinities between 0 and 5 wt.% NaCl equivalent; the other has salinities of up to 43 wt.% NaCl equivalent. The occurrence of high-salinity fluid inclusions in vein quartz associated with mineralization, as well as in the deep stockwork veins, suggests that brines originating deep in the system transported the metals. The dD H2O of alunite parent fluids was near À45x and their d 18 O ranged from 7x to À1x, depending on the degree of exchange in the alteration zone at low water-rock ratio, or mixing with unexchanged meteoric water. The low dD values of some alunite samples are interpreted to result from postdepositional exchange with later ore fluids.Fluid exsolved from the magma at depth had dD H2O and d 18O H2O values near À70x and 10x, respectively. During and following migration to the top of the magma chamber, the fluid underwent isotopic exchange with the partially crystallized magma and its solid and cooler, but still plastic, carapace just below the transition from a lithostatic to hydrostatic pressure regime. These evolved magmatic fluids had dD H2O and d18 O H2O values close to À40x and 5x, respectively, prior to release into the superjacent hydrostatically pressured fracture zone, wherein the fluids separ...

Techniques are presented for the separation of alunite [KAl3(SO4)2(OH)