Gongchangling high-grade magnetite ores,which constitute one of the major rich from deposits in China,occur in the BIF .of the Anshan-Group in Precambrian metamorphic rocks.But its origin has long been a controversial...Gongchangling high-grade magnetite ores,which constitute one of the major rich from deposits in China,occur in the BIF .of the Anshan-Group in Precambrian metamorphic rocks.But its origin has long been a controversial problem,although most researchers are in favour of the eoncept that it is genetically related to hydrothermal process connected with migmatite.On the basis of field observation,this problem has been dealt with in this paper in the light of fluid inclusion studies.The results show that hydrothermal activity,was widespread in this region,which can be divided into two stages.The late stage hydrothermal activity was intensively developed around rich iron dposits.The formation temperature of the late stage hydrbthermal fluids is in the range of 487- 505℃,and they are slightly alkaline with a salinity of 13.2-28.1 wt%,consisting mainly of Na^+,Ca^++,Cl^-,So4^-,etc.As revetled by temperature measurements,the formation temperatures of fluid inclusions are quite uniform from,place to place within the vast areas in this region,and the comparason of these temperatures between rich ores and migmatite and wall rocks indieates that the late hydrothermal fluids are of metamorphie origin.The authors suggest that the rich magnetite ores in the Gongchangling Range seem to be the result of the reworking process(alteration)by metamorphie hydrothermal fluids in response to regional metamorphism on some sedimentary ore deposits that were originally relatively rich in iron.展开更多
A huge gypsum miarolitic cavity has been found locatedin an antimony mineralized layer. It is an interformational bleb. Four crystallization steps are recognized for mineral crystals in the miarolitic cavity. Gypsum c...A huge gypsum miarolitic cavity has been found locatedin an antimony mineralized layer. It is an interformational bleb. Four crystallization steps are recognized for mineral crystals in the miarolitic cavity. Gypsum crystals seem to have been formed through two forms of crystallization. The data on fluid inclusions and hydrogen isotopes.show that this cavity is the product of hypergenic process, the orebeariug solution is derived from meteorie water, and the compositional material comes from the oxidized ore zone. During the formation of the miarolitic cayity, the pH-value was within the range of 4--5, i.e., weakly acidic solution, and the formation temperature less than 50℃. It can be clearly seen from the crystallization behaviour of gypsum cyrstals and mineral association that there have taken place significant changes in the pH-value of mineralization solution.展开更多
文摘Gongchangling high-grade magnetite ores,which constitute one of the major rich from deposits in China,occur in the BIF .of the Anshan-Group in Precambrian metamorphic rocks.But its origin has long been a controversial problem,although most researchers are in favour of the eoncept that it is genetically related to hydrothermal process connected with migmatite.On the basis of field observation,this problem has been dealt with in this paper in the light of fluid inclusion studies.The results show that hydrothermal activity,was widespread in this region,which can be divided into two stages.The late stage hydrothermal activity was intensively developed around rich iron dposits.The formation temperature of the late stage hydrbthermal fluids is in the range of 487- 505℃,and they are slightly alkaline with a salinity of 13.2-28.1 wt%,consisting mainly of Na^+,Ca^++,Cl^-,So4^-,etc.As revetled by temperature measurements,the formation temperatures of fluid inclusions are quite uniform from,place to place within the vast areas in this region,and the comparason of these temperatures between rich ores and migmatite and wall rocks indieates that the late hydrothermal fluids are of metamorphie origin.The authors suggest that the rich magnetite ores in the Gongchangling Range seem to be the result of the reworking process(alteration)by metamorphie hydrothermal fluids in response to regional metamorphism on some sedimentary ore deposits that were originally relatively rich in iron.
文摘A huge gypsum miarolitic cavity has been found locatedin an antimony mineralized layer. It is an interformational bleb. Four crystallization steps are recognized for mineral crystals in the miarolitic cavity. Gypsum crystals seem to have been formed through two forms of crystallization. The data on fluid inclusions and hydrogen isotopes.show that this cavity is the product of hypergenic process, the orebeariug solution is derived from meteorie water, and the compositional material comes from the oxidized ore zone. During the formation of the miarolitic cayity, the pH-value was within the range of 4--5, i.e., weakly acidic solution, and the formation temperature less than 50℃. It can be clearly seen from the crystallization behaviour of gypsum cyrstals and mineral association that there have taken place significant changes in the pH-value of mineralization solution.
