The reaction path in the (Ba, Sr, Ca)SO-4 solid-solution aqueous-solution (SSAS) system was experimentally studied using a batch-reactor method. The effect of the impurities "fluorite" and "iron sulfide...The reaction path in the (Ba, Sr, Ca)SO-4 solid-solution aqueous-solution (SSAS) system was experimentally studied using a batch-reactor method. The effect of the impurities "fluorite" and "iron sulfides" admixed in a natural barite sample on the reaction path was followed by analyzing the aqueous solution continuously. The dissolution and precipitation of the impurity "fluorite" affected strongly the reaction path in the SSAS system, especially the Ca/Sr/Ba ratio in the aqueous solution. This influence became stronger with decreasing CaSO-4 in the solid solution. The dissolution and precipitation of fluorite could hinder the CaSO-4 component from dissolving into water, and reduce the release rate of SO{2-}-4 from the solid solution to the aqueous solution and the removing rate of Ba{2} from the aqueous solution. In the presence of fluorite and sulfides, the aqueous Ba{2} and Sr{2} concentrations were controlled by the dissolution-precipitation of the end-members BaSO-4 and SrSO-4, respectively; the aqueous F-, Ca{2} and SO{2-}-4 concentrations were controlled by the dissolution-precipitation of fluorite. The incongruent dissolution of the (Ba, Sr, Ca)SO-4 solid solution caused the solid phase to become progressively more enriched in the more insoluble component (BaSO-4), while the aqueous composition shifted towards the more soluble end-members (SrSO-4 and CaSO-4) as equilibrium was approached to.展开更多
Gneiss\|distilled water interaction at room temperature was investigated with batch\|reactors to study water\|rock reaction and geochemical evolution of the aqueous phase with time. The ion concentrations in water wer...Gneiss\|distilled water interaction at room temperature was investigated with batch\|reactors to study water\|rock reaction and geochemical evolution of the aqueous phase with time. The ion concentrations in water were controlled not only by the dissolution of primary minerals, but also by the precipitation of secondary minerals. The decreasing fraction sizes of gneiss could favor dissolution and precipitation simultaneously. Ca\+\{2+\} and K\++ were the major cations, and HCO\+-\-3 was the major anion in water. All the ions except Ca\+\{2+\} increased in concentration with time. The Ca\+\{2+\} release from the rock to the aqueous phase was initially much faster than the release of K\++, Na\++ and Mg\+\{2+\}. But after about 5-24 hours, the Ca\+\{2+\} concentrations in water decreased very slowly with time and became relatively stable. During the experiment, the water varied from the Ca\|(K)\|HCO\-3\|type water to the K\|Ca\|HCO\-3\|type water, and then to the K\|(Ca,Na)\|HCO\-3\|type water. The water\|gneiss interaction was dominated by the dissolution of K\|feldspar in the solution. The remaining secondary minerals were mainly kaolinite, illite and K(Mg)\|mica.展开更多
Sagvandite is an enstatite+magnesite rock formed from dunite or harzburgite bodies occurring as tectonically emplaced fragments from the upper mantle in many orogenic belts by interaction with CO2-bearing crustal flui...Sagvandite is an enstatite+magnesite rock formed from dunite or harzburgite bodies occurring as tectonically emplaced fragments from the upper mantle in many orogenic belts by interaction with CO2-bearing crustal fluids at upper amphibolite facies P-T conditions.Sagvandite bodies occur widespread in distinct nappes in the Scandinavian Caledonides in Norway.Common to all of the many sagvandite outcrops is their general structure of radial bundles of very coarse cm-sized enstatite crystals and interstitial magnesite.Often some strongly resorbed primary olivine is preserved,in addition to minor accessory Cr-spinel and chromite.The dunite to sagvandite conversion is governed by three metasomatic reactions:(1)carbonatization of peridotite by CO2-bearing fluids;(2)interaction with external fluids containing dissolved silica;(3)loss of Mg by dissolution of forsterite in NaCl-rich deep fluids.Simultaneous progressξoverall of all three reactions in proportions that conserve the volume of the original dunite can explain the observed structure and mode of sagvandite.The relationship among the progressξof the three reactions suggests that loss of Mg by the ultramafic rock is the dominating process in the iso-volume conversion of dunite to sagvandite.展开更多
文摘The reaction path in the (Ba, Sr, Ca)SO-4 solid-solution aqueous-solution (SSAS) system was experimentally studied using a batch-reactor method. The effect of the impurities "fluorite" and "iron sulfides" admixed in a natural barite sample on the reaction path was followed by analyzing the aqueous solution continuously. The dissolution and precipitation of the impurity "fluorite" affected strongly the reaction path in the SSAS system, especially the Ca/Sr/Ba ratio in the aqueous solution. This influence became stronger with decreasing CaSO-4 in the solid solution. The dissolution and precipitation of fluorite could hinder the CaSO-4 component from dissolving into water, and reduce the release rate of SO{2-}-4 from the solid solution to the aqueous solution and the removing rate of Ba{2} from the aqueous solution. In the presence of fluorite and sulfides, the aqueous Ba{2} and Sr{2} concentrations were controlled by the dissolution-precipitation of the end-members BaSO-4 and SrSO-4, respectively; the aqueous F-, Ca{2} and SO{2-}-4 concentrations were controlled by the dissolution-precipitation of fluorite. The incongruent dissolution of the (Ba, Sr, Ca)SO-4 solid solution caused the solid phase to become progressively more enriched in the more insoluble component (BaSO-4), while the aqueous composition shifted towards the more soluble end-members (SrSO-4 and CaSO-4) as equilibrium was approached to.
文摘Gneiss\|distilled water interaction at room temperature was investigated with batch\|reactors to study water\|rock reaction and geochemical evolution of the aqueous phase with time. The ion concentrations in water were controlled not only by the dissolution of primary minerals, but also by the precipitation of secondary minerals. The decreasing fraction sizes of gneiss could favor dissolution and precipitation simultaneously. Ca\+\{2+\} and K\++ were the major cations, and HCO\+-\-3 was the major anion in water. All the ions except Ca\+\{2+\} increased in concentration with time. The Ca\+\{2+\} release from the rock to the aqueous phase was initially much faster than the release of K\++, Na\++ and Mg\+\{2+\}. But after about 5-24 hours, the Ca\+\{2+\} concentrations in water decreased very slowly with time and became relatively stable. During the experiment, the water varied from the Ca\|(K)\|HCO\-3\|type water to the K\|Ca\|HCO\-3\|type water, and then to the K\|(Ca,Na)\|HCO\-3\|type water. The water\|gneiss interaction was dominated by the dissolution of K\|feldspar in the solution. The remaining secondary minerals were mainly kaolinite, illite and K(Mg)\|mica.
文摘Sagvandite is an enstatite+magnesite rock formed from dunite or harzburgite bodies occurring as tectonically emplaced fragments from the upper mantle in many orogenic belts by interaction with CO2-bearing crustal fluids at upper amphibolite facies P-T conditions.Sagvandite bodies occur widespread in distinct nappes in the Scandinavian Caledonides in Norway.Common to all of the many sagvandite outcrops is their general structure of radial bundles of very coarse cm-sized enstatite crystals and interstitial magnesite.Often some strongly resorbed primary olivine is preserved,in addition to minor accessory Cr-spinel and chromite.The dunite to sagvandite conversion is governed by three metasomatic reactions:(1)carbonatization of peridotite by CO2-bearing fluids;(2)interaction with external fluids containing dissolved silica;(3)loss of Mg by dissolution of forsterite in NaCl-rich deep fluids.Simultaneous progressξoverall of all three reactions in proportions that conserve the volume of the original dunite can explain the observed structure and mode of sagvandite.The relationship among the progressξof the three reactions suggests that loss of Mg by the ultramafic rock is the dominating process in the iso-volume conversion of dunite to sagvandite.
