A series of experimental geochemical studies have been done to confirm the organic metallogenic mechanism of weathering crust RE deposits. It has been concluded that: (1) Rich REbearing weathering crusts contain abund...A series of experimental geochemical studies have been done to confirm the organic metallogenic mechanism of weathering crust RE deposits. It has been concluded that: (1) Rich REbearing weathering crusts contain abundant organisms such as monoacids, diacids and nonacid compounds. Varieties and quantities of the organisms decrease from the upper to the lower of the profile. Humic acids are mainly fulvic acids, which are characterized by containing conjugated π system, carboxylic group, hydroxyl group and only a few nitrogenous groups. No obvious benzene ring has been found. (2) The upper part of the weathering crust contains a great deal of microorganisms, of which the varieties and quantities decrease from the upper to the lower of the profile. No microorganism has been found in the deep part of the profile. The microorganisms and their metabolites such as aminoacids, shortchain acids and organic compounds with small molecular weights can form water soluble RE complexes, which accelerate the RE transportation from original rocks and precipitation states to watersoluble states and thus provide prerequisites for retransportation and reaccumulation of RE. (3) Medium and longchain acids can form REnAm(OH)x(H2O)y type mixedligand polynuclear RE complexes, which devoted to the RE accumulation, whereas shortchain acids and aminoacids can form not only mixedligand complexes with RE, but also water soluble complex ions, which also devoted to the transport and accumulation of RE. (4) The fulvic acids are very soluble in water. They are apt to be mobile in the weathering crust and are able to form soluble complex ions and insoluble mixedligand polynuclear complexes with RE at normal temperature and atmospheric pressure and pH4～6. The composition of these complexes varies with different conditions of the weathering crust. (5) All the organic acids, fulvic acids and microorgaisms have contributed to keeping constant pH condition of the weathering crust. (6) Complexes consisting of clays, RE(Al, Fe……) and fulvic acids have been found in the weathering crust and a bonding pattern has been preliminarily studied. As a conclusion, the dissolution, transport and accumulaiton of REE during weathering is a organic and inorganic interacted process.展开更多
文摘A series of experimental geochemical studies have been done to confirm the organic metallogenic mechanism of weathering crust RE deposits. It has been concluded that: (1) Rich REbearing weathering crusts contain abundant organisms such as monoacids, diacids and nonacid compounds. Varieties and quantities of the organisms decrease from the upper to the lower of the profile. Humic acids are mainly fulvic acids, which are characterized by containing conjugated π system, carboxylic group, hydroxyl group and only a few nitrogenous groups. No obvious benzene ring has been found. (2) The upper part of the weathering crust contains a great deal of microorganisms, of which the varieties and quantities decrease from the upper to the lower of the profile. No microorganism has been found in the deep part of the profile. The microorganisms and their metabolites such as aminoacids, shortchain acids and organic compounds with small molecular weights can form water soluble RE complexes, which accelerate the RE transportation from original rocks and precipitation states to watersoluble states and thus provide prerequisites for retransportation and reaccumulation of RE. (3) Medium and longchain acids can form REnAm(OH)x(H2O)y type mixedligand polynuclear RE complexes, which devoted to the RE accumulation, whereas shortchain acids and aminoacids can form not only mixedligand complexes with RE, but also water soluble complex ions, which also devoted to the transport and accumulation of RE. (4) The fulvic acids are very soluble in water. They are apt to be mobile in the weathering crust and are able to form soluble complex ions and insoluble mixedligand polynuclear complexes with RE at normal temperature and atmospheric pressure and pH4～6. The composition of these complexes varies with different conditions of the weathering crust. (5) All the organic acids, fulvic acids and microorgaisms have contributed to keeping constant pH condition of the weathering crust. (6) Complexes consisting of clays, RE(Al, Fe……) and fulvic acids have been found in the weathering crust and a bonding pattern has been preliminarily studied. As a conclusion, the dissolution, transport and accumulaiton of REE during weathering is a organic and inorganic interacted process.
