The Abra deposit,a large lead-silver-copper–gold polymetallic deposit in Western Australia,is located at the eastern of the metallogenic belt of the Jillawarra basin in the Bangemall basin.The 4 th to the 6 th rock s...The Abra deposit,a large lead-silver-copper–gold polymetallic deposit in Western Australia,is located at the eastern of the metallogenic belt of the Jillawarra basin in the Bangemall basin.The 4 th to the 6 th rock section of the Irrigully Group of Edmund Series are the principal ore-host strata,composed mainly of sandstone and fine sandstone.The orebody in Abra can be classified into two types as upper layer-like lead-silver and lower veins or netvein copper–gold.The metal minerals are mainly galena,chalcopyrite,and pyrite,while the gangue minerals are mainly quartz,dolomite,and barite.Both ReOs isotopic age of the pyrite(1329.5±98 Ma)with the initial(187Os/188Os)=5.0±3.8 and Pb isotopic compositions(206 Pb/204 Pb=15.914–15.967,207Pb/204Pb=15.425–15.454,208Pb/204Pb=35.584–35.667)suggests that the metal minerals were sourced from the wall-rocks.d DV-SMOWvalues of quartz range from-35%to-17%whereas d18 OV-SMOWvalue range from 12%to 16%which indicates that the ore-forming fluids of Abra were mediumlow temperature and medium–low salinity,and were mainly metamorphic water and secondary atmospheric precipitation.When the medium–low temperature oreforming fluids are mixed with oxidizing reducing fluids carrying a large number of metal substances,a large number of ore-forming substances will be precipitated when the physical and chemical conditions change,thus it can be considered that the Abra deposit is a medium–low temperature hydrothermal polymetallic deposit.展开更多
The succession of an Abra ovata community that had formed at the flooded area in Sulaksky Bay (the Caspian Sea) since the mid-1980s was investigated. The resident species Abra ovata and Cerastoderma glaucum, the pione...The succession of an Abra ovata community that had formed at the flooded area in Sulaksky Bay (the Caspian Sea) since the mid-1980s was investigated. The resident species Abra ovata and Cerastoderma glaucum, the pioneer settlers, were found remaining dominant in the community structure and driving the course of its succession, despite some decrease in settlement density and in the rate of occurrence. It was the tolerance of the Sulaksky pioneer settlers for later colonists (macrophytes, mytilids, crustaceans and other organisms) that determined the development of the first succession stage. The next succession stage in Abra ovata communities of Sulaksky Bay does not quite agree with the pattern typical of solid substrates. On the one hand, the community development supports the tolerance model: the pioneer Abra, in spite of being dominant through all the succession stages, does not oppose the settling of other multiple colonists;on the other hand, it agrees with a facilitation model where the abundance of the original settlers, the grazing species, provokes appearance of sturgeon.展开更多
基金funded by the Joint Fund Projects(U1812402)the National Natural Science Foundation of China(41103024)the“Financial Subsidy for Overseas Mineral Resource Risk Exploration in 2010”project。
文摘The Abra deposit,a large lead-silver-copper–gold polymetallic deposit in Western Australia,is located at the eastern of the metallogenic belt of the Jillawarra basin in the Bangemall basin.The 4 th to the 6 th rock section of the Irrigully Group of Edmund Series are the principal ore-host strata,composed mainly of sandstone and fine sandstone.The orebody in Abra can be classified into two types as upper layer-like lead-silver and lower veins or netvein copper–gold.The metal minerals are mainly galena,chalcopyrite,and pyrite,while the gangue minerals are mainly quartz,dolomite,and barite.Both ReOs isotopic age of the pyrite(1329.5±98 Ma)with the initial(187Os/188Os)=5.0±3.8 and Pb isotopic compositions(206 Pb/204 Pb=15.914–15.967,207Pb/204Pb=15.425–15.454,208Pb/204Pb=35.584–35.667)suggests that the metal minerals were sourced from the wall-rocks.d DV-SMOWvalues of quartz range from-35%to-17%whereas d18 OV-SMOWvalue range from 12%to 16%which indicates that the ore-forming fluids of Abra were mediumlow temperature and medium–low salinity,and were mainly metamorphic water and secondary atmospheric precipitation.When the medium–low temperature oreforming fluids are mixed with oxidizing reducing fluids carrying a large number of metal substances,a large number of ore-forming substances will be precipitated when the physical and chemical conditions change,thus it can be considered that the Abra deposit is a medium–low temperature hydrothermal polymetallic deposit.
文摘The succession of an Abra ovata community that had formed at the flooded area in Sulaksky Bay (the Caspian Sea) since the mid-1980s was investigated. The resident species Abra ovata and Cerastoderma glaucum, the pioneer settlers, were found remaining dominant in the community structure and driving the course of its succession, despite some decrease in settlement density and in the rate of occurrence. It was the tolerance of the Sulaksky pioneer settlers for later colonists (macrophytes, mytilids, crustaceans and other organisms) that determined the development of the first succession stage. The next succession stage in Abra ovata communities of Sulaksky Bay does not quite agree with the pattern typical of solid substrates. On the one hand, the community development supports the tolerance model: the pioneer Abra, in spite of being dominant through all the succession stages, does not oppose the settling of other multiple colonists;on the other hand, it agrees with a facilitation model where the abundance of the original settlers, the grazing species, provokes appearance of sturgeon.
