The Phapon gold deposit, located in northern Laos, is a unique large-scale gold deposit in Luang Prabang-Loei metallogenic belt. It is hosted in the Lower Permian limestone and controlled by a NE-trending ductile-brit...The Phapon gold deposit, located in northern Laos, is a unique large-scale gold deposit in Luang Prabang-Loei metallogenic belt. It is hosted in the Lower Permian limestone and controlled by a NE-trending ductile-brittle fault system. There are three types of primary ore including auriferous calcite vein type, disseminated type, and breccia type, and the first two are important in the Phapon gold deposit. Based on fluid inclusion petrography and microthermometry, three types of primary fluid inclusions including type 1 liquid-rich aqueous, type 2 vapor-rich aqueous and type 3 daughter mineralbearing aqueous were identified in hydrothermal calcite grains. The ore-forming fluids are normally homogeneous, as indicated by the widespread type 1 inclusions with identical composition. The coexistence of type 1 and type 2 inclusions, showing similar final homogenization temperature but different compositions, indicate that fluid immiscibility did locally take place in both two types of ores. The results of microthermometry and H-O isotopes geochemistry indicate that there are little differences on ore-fluid geochemistry between the auriferous calcite vein-type and disseminated type ores. The oreforming fluids are characterized by medium-low temperatures(157–268 oC) and low salinity(1.6 wt.%–9.9 wt.% NaCl eq.). It is likely to have a metamorphic-dominant mixed source, which could be associated with dehydration and decarbonisation of Lower Permian limestone and Middle–Upper Triassic sandstones during the dynamic metamorphism. The fluid-wallrock interaction played a major role, and the locally occurred fluid-immiscible processes played a subordinate role in gold precipitation. Combined with the regional and ore deposit geology, and ore-fluid geochemistry, we suggest that the Phapon gold deposit is best considered to be a member of the epizonal orogenic deposit class.展开更多
The macroscopic and microscopic studies (in mineral inclusions, stable isotopes, traceelements, etc.) on the Donchuan-Yimen type copper deposits show that the ore material deriv-ed from host rocks and their underlying...The macroscopic and microscopic studies (in mineral inclusions, stable isotopes, traceelements, etc.) on the Donchuan-Yimen type copper deposits show that the ore material deriv-ed from host rocks and their underlying beds, and Bi, Pb, Zn probably did from deep frac-tures. The ore-forming fluid is hot brine in nature, and the water in it is probably stratumwater in origin. The sulphur derived from bacteria reducing of sulphate in sea water. Thecarbon derived from marine carbonate. The organic carbon plays an important role in themetallogenesis. In the Kangdian Axis, two deep fractures controlled the sedimentation of thecupriferous algal reef carbonate formation. They were ore-, heat-, brine-conducting tectonicsand led to the formation and transformation of many copper ore beds.展开更多
基金financially supported by the China Geological Survey Project (No. 121201010000150013)
文摘The Phapon gold deposit, located in northern Laos, is a unique large-scale gold deposit in Luang Prabang-Loei metallogenic belt. It is hosted in the Lower Permian limestone and controlled by a NE-trending ductile-brittle fault system. There are three types of primary ore including auriferous calcite vein type, disseminated type, and breccia type, and the first two are important in the Phapon gold deposit. Based on fluid inclusion petrography and microthermometry, three types of primary fluid inclusions including type 1 liquid-rich aqueous, type 2 vapor-rich aqueous and type 3 daughter mineralbearing aqueous were identified in hydrothermal calcite grains. The ore-forming fluids are normally homogeneous, as indicated by the widespread type 1 inclusions with identical composition. The coexistence of type 1 and type 2 inclusions, showing similar final homogenization temperature but different compositions, indicate that fluid immiscibility did locally take place in both two types of ores. The results of microthermometry and H-O isotopes geochemistry indicate that there are little differences on ore-fluid geochemistry between the auriferous calcite vein-type and disseminated type ores. The oreforming fluids are characterized by medium-low temperatures(157–268 oC) and low salinity(1.6 wt.%–9.9 wt.% NaCl eq.). It is likely to have a metamorphic-dominant mixed source, which could be associated with dehydration and decarbonisation of Lower Permian limestone and Middle–Upper Triassic sandstones during the dynamic metamorphism. The fluid-wallrock interaction played a major role, and the locally occurred fluid-immiscible processes played a subordinate role in gold precipitation. Combined with the regional and ore deposit geology, and ore-fluid geochemistry, we suggest that the Phapon gold deposit is best considered to be a member of the epizonal orogenic deposit class.
基金the National Natural Science Foundation of China.
文摘The macroscopic and microscopic studies (in mineral inclusions, stable isotopes, traceelements, etc.) on the Donchuan-Yimen type copper deposits show that the ore material deriv-ed from host rocks and their underlying beds, and Bi, Pb, Zn probably did from deep frac-tures. The ore-forming fluid is hot brine in nature, and the water in it is probably stratumwater in origin. The sulphur derived from bacteria reducing of sulphate in sea water. Thecarbon derived from marine carbonate. The organic carbon plays an important role in themetallogenesis. In the Kangdian Axis, two deep fractures controlled the sedimentation of thecupriferous algal reef carbonate formation. They were ore-, heat-, brine-conducting tectonicsand led to the formation and transformation of many copper ore beds.
