The gold deposits, occurring in the south subzone of western Qinling, are the onlytypical and important strata-bound gold deposits, which are associated with submarine exhala-tive sedimentation. The god deposits inclu...The gold deposits, occurring in the south subzone of western Qinling, are the onlytypical and important strata-bound gold deposits, which are associated with submarine exhala-tive sedimentation. The god deposits include the La, erma ore deposit, the Qiongmo ore de-posit and the Yaxiang ore occurrence. They are hosted in the Cambrian silicalite formationcomposed of black chert and slate. The presence of typical chert offers important evidence to e-valuate the Possib1e submarine exhalative system and its role in the formation of the gold de-posits, which are closely associated with percolation and diffusion in the horizontal, vertical andaxial directions. Element-assemblage zonation is clearly seen due to differences in element con-centrations in different directions. Such a zonation makes gold, selenium, uranium, copper,stibium, molybdenum, mercury, etc. precipitate in the form of simple 0r composite orebodies.The establishment of the element-assemblage zonation is highly helpful for evaluating directlythe metallogenesis of gold deposits.展开更多
The Upper Permian Xuanwei Formation widely occurs in western Guizhou,unconformably overlying the Emeishan basalts,and mainly consists of black shales.It is～170 m thick at Cuyudong Village,Weining County,West Guizhou,...The Upper Permian Xuanwei Formation widely occurs in western Guizhou,unconformably overlying the Emeishan basalts,and mainly consists of black shales.It is～170 m thick at Cuyudong Village,Weining County,West Guizhou,China,where the samples of black shale and sandy shale were collected and analyzed.The shales mainly contain SiO2,18.9%?44.1%,Al2O3,14.8%?52.8%,Fe2O3,1.0%?41.2%,LOI,3.2%?21.1%,TiO2,1.0%-6.7%,and MgO,0.2%?2.5%.The contents of all other major elements are lower than 1.0%.It is shown that the black shales have higher contents of Fe2O3 and LOI than normal shales.The siderites occurred in the black shales with higher contents of Fe2O3,which may be attributed to hydrothermal activities on seafloor.All analyzed shale samples have extremely high Ga,47.8×10-6-109.9×10-6(70.5×10-6 on average),higher than the industrial mining standard of Ga Resource Industry Standard.The total contents of rare-earth elements(REE) of 9 black shale samples vary from 213×10-6 to 1460×10-6,suggesting that these black shales are enriched in REE.The shale-normalized REE patterns display both positive and negative Ce anomalies(Ce/Ce* from 0.5 to 1.7),revealing that the Xuanwei shales were precipitated under oxic and anoxic conditions.The Rb-Sr chronological diagram of 6 shale samples in the Xuanwei Formation shows an age of 255±12 Ma.Strontium isotopic ratios(87Sr/86Sr)t0 range from 0.70635 to 0.70711,suggesting that these Xuanwei black shales might be derived from chemical weathering of the Emeishan basalts.展开更多
It is beheved that the Shujiaba Formation belongs to a series of thick turbidites. 20 ichnogenera have been found in the formation, of which 14 genera were found in the Devonian System of China for the first time The ...It is beheved that the Shujiaba Formation belongs to a series of thick turbidites. 20 ichnogenera have been found in the formation, of which 14 genera were found in the Devonian System of China for the first time The ichnogenera are mostly of typical deep-water ones and belong to the Nereites ichnofacies A detailed study of morphology and behaviour of the trace fossils indicates that the Shujiaba Formation was deposited in a bathyal-abyssal environment.展开更多
文摘The gold deposits, occurring in the south subzone of western Qinling, are the onlytypical and important strata-bound gold deposits, which are associated with submarine exhala-tive sedimentation. The god deposits include the La, erma ore deposit, the Qiongmo ore de-posit and the Yaxiang ore occurrence. They are hosted in the Cambrian silicalite formationcomposed of black chert and slate. The presence of typical chert offers important evidence to e-valuate the Possib1e submarine exhalative system and its role in the formation of the gold de-posits, which are closely associated with percolation and diffusion in the horizontal, vertical andaxial directions. Element-assemblage zonation is clearly seen due to differences in element con-centrations in different directions. Such a zonation makes gold, selenium, uranium, copper,stibium, molybdenum, mercury, etc. precipitate in the form of simple 0r composite orebodies.The establishment of the element-assemblage zonation is highly helpful for evaluating directlythe metallogenesis of gold deposits.
基金supported by the National Basic Research Program of China (2007CB411401)the National Natural Science Foundation of China (No. 40930425)
文摘The Upper Permian Xuanwei Formation widely occurs in western Guizhou,unconformably overlying the Emeishan basalts,and mainly consists of black shales.It is～170 m thick at Cuyudong Village,Weining County,West Guizhou,China,where the samples of black shale and sandy shale were collected and analyzed.The shales mainly contain SiO2,18.9%?44.1%,Al2O3,14.8%?52.8%,Fe2O3,1.0%?41.2%,LOI,3.2%?21.1%,TiO2,1.0%-6.7%,and MgO,0.2%?2.5%.The contents of all other major elements are lower than 1.0%.It is shown that the black shales have higher contents of Fe2O3 and LOI than normal shales.The siderites occurred in the black shales with higher contents of Fe2O3,which may be attributed to hydrothermal activities on seafloor.All analyzed shale samples have extremely high Ga,47.8×10-6-109.9×10-6(70.5×10-6 on average),higher than the industrial mining standard of Ga Resource Industry Standard.The total contents of rare-earth elements(REE) of 9 black shale samples vary from 213×10-6 to 1460×10-6,suggesting that these black shales are enriched in REE.The shale-normalized REE patterns display both positive and negative Ce anomalies(Ce/Ce* from 0.5 to 1.7),revealing that the Xuanwei shales were precipitated under oxic and anoxic conditions.The Rb-Sr chronological diagram of 6 shale samples in the Xuanwei Formation shows an age of 255±12 Ma.Strontium isotopic ratios(87Sr/86Sr)t0 range from 0.70635 to 0.70711,suggesting that these Xuanwei black shales might be derived from chemical weathering of the Emeishan basalts.
基金Project supported by the National Natural Science Foundation of China.
文摘It is beheved that the Shujiaba Formation belongs to a series of thick turbidites. 20 ichnogenera have been found in the formation, of which 14 genera were found in the Devonian System of China for the first time The ichnogenera are mostly of typical deep-water ones and belong to the Nereites ichnofacies A detailed study of morphology and behaviour of the trace fossils indicates that the Shujiaba Formation was deposited in a bathyal-abyssal environment.
