Magma mixing induced by particle settling     

Christian J. Renggli  Sebastian Wiesmaier  Cristina P. De Campos  Kai-Uwe Hess  Donald B. Dingwell 《Contributions to Mineralogy and Petrology》2016,171(11):96

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High temperature gas–solid reactions in calc–silicate Cu–Au skarn formation; Ertsberg,Papua Province,Indonesia     

Richard?W.?HenleyEmail authorView author&#;s OrcID profile  Frank?J.?Brink  Penelope?L.?King  Clyde?Leys  Jibamitra?Ganguly  Terrance?Mernagh  Jill?Middleton  Christian?J.?Renggli  Melanie?Sieber  Ulrike?Troitzsch  Michael?Turner 《Contributions to Mineralogy and Petrology》2017,172(11-12):106

The 2.7–3 Ma Ertsberg East Skarn System (Indonesia), adjacent to the giant Grasberg Porphyry Copper deposit, is part of the world’s largest system of Cu–Au skarn deposits. Published fluid inclusion and stable isotope data show that it formed through the flux of magma-derived fluid through contact metamorphosed carbonate rock sequences at temperatures well above 600° C and pressures of less than 50 MPa. Under these conditions, the fluid has very low density and the properties of a gas. Combining a range of micro-analytical techniques, high-resolution QEMSCAN mineral mapping and computer-assisted X-ray micro-tomography, an array of coupled gas–solid reactions may be identified that controlled reactive mass transfer through the ~ 1 km³ hydrothermal skarn system. Vacancy-driven mineral chemisorption reactions are identified as a new type of reactive transport process for high-temperature skarn alteration. These gas–solid reactions are maintained by the interaction of unsatisfied bonds on mineral surfaces and dipolar gas-phase reactants such as SO₂ and HCl that are continuously supplied through open fractures and intergranular diffusion. Principal reactions are (a) incongruent dissolution of almandine-grossular to andradite and anorthite (an alteration mineral not previously recognized at Ertsberg), and (b) sulfation of anorthite to anhydrite. These sulfation reactions also generate reduced sulfur with consequent co-deposition of metal sulfides. Diopside undergoes similar reactions with deposition of Fe-enriched pyroxene in crypto-veins and vein selvedges. The loss of calcium from contact metamorphic garnet to form vein anhydrite necessarily results in Fe-enrichment of wallrock, and does not require Fe-addition from a vein fluid as is commonly assumed.  相似文献   

A quantum chemical investigation of the oxidation and dissolution mechanisms of Galena   总被引：1，自引：0，他引：1  

Andrea R. Gerson  Anthony R. O’Dea 《Geochimica et cosmochimica acta》2003,67(5):813-822

The oxidation and dissolution mechanisms of galena (PbS) remain uncertain with a wide variety of possible mechanisms having been proposed in the literature. In this study, the thermodynamic viability of some possible mechanisms has been tested using semi-empirical quantum chemical calculations applied to a perfect (001) galena surface.The adsorption of O₂ and H₂O has been examined in both the gaseous and aqueous environments. In agreement with previous ab initio quantum chemical calculations, the surface induced dissociation of H₂O in either environment was found to be energetically unfavourable. However, the dissociative adsorption of O₂ was found to be possible and resulted in two O atoms bonded to diagonally adjacent S atoms with the O atoms oriented along the diagonal.The adsorption of H⁺ and possible subsequent dissolution mechanisms have been examined in the aqueous environment. An anaerobic mechanism leading to the dissolution of hydroxylated Pb²⁺ was identified. The mechanism involves the protonation of 3 surface S atoms surrounding a central surface Pb atom followed by substitution of this Pb by a further H⁺. The activation energy of this mechanism was estimated to be ≈100 kJ mol⁻¹. Pb²⁺ dissolution could only occur with vacancy stabilisation by a H⁺. The analogous mechanisms for systems comprising H⁺ adsorbed on either 2 or 4 of the S atoms surrounding a central surface Pb were not found to be energetically viable. Subsequent dissolution of one of the protonated S atoms to form H₂S_(g) was not found to be possible thus indicating the likely formation of a Pb-deficient S-rich surface under acidic anaerobic conditions.Acidic aerobic dissolution has also been examined. Congruent dissolution to form H₂SO₄ and Pb²⁺•6H₂O is energetically viable. The dissolution of one of the protonated S atoms neighbouring the Pb²⁺ vacancy, resulting from the anaerobic dissolution, to form H₂SO₄, is also possible.  相似文献   

Fate of tributyltin in sewage sludge treatment     

Karl Fent  Judith Hunn  Dea Renggli  Hanruedi Siegrist 《Marine environmental research》1991,32(1-4)

We have shown that municipal wastewater and sewage sludge are contaminated by organotins. Here, we investigate the behaviour and fate of tributyltin (TBT) in laboratory-scale sewage sludge treatment at various conditions including both aerobic and anaerobic, and mesophilic and thermophilic. Organotins were determined by capillary GC-FPD. Fresh raw sewage sludge was stored in a tank that was connected to five chemostats maintained at different conditions. Raw sludge contained TBT, dibutyltin (DBT) and monobutyltin (MBT) residues in the range of 0·28 to 0·83 mg/kg (dry weight). The volumetric TBT concentration was 10·5 μg/litre in the influent, and ranged from 7·4 to 8·3 μg/litre in the effluent of the different chemostats. In the anaerobic mesophilic treatment, concentrations of TBT did not decrease with increasing sludge residence time, DBT increased and MBT showed no clear trend. The DBT increase is suggested to be due to leaching from the PVC walls of the chemostats, and not to degradation of TBT alone. The TBT reduction did not show significant differences between the mesophilic and thermophilic anaerobic fermentors. These findings indicate that the degradation of TBT during sludge treatment is only low under all conditions tested.  相似文献