Trace elemental associations and Sr-Nd isotopic compositions are of important to recognition of biogenic material from mixed marine sediments. The foraminifera shell from the Okinawa Trough strongly enriches Sr,P,Mn a...Trace elemental associations and Sr-Nd isotopic compositions are of important to recognition of biogenic material from mixed marine sediments. The foraminifera shell from the Okinawa Trough strongly enriches Sr,P,Mn and Ba, enriches Li,U,Th,Sc,Co,Cu,Pb,Zn,Cr,Rb,Y,Sb and light rare earth elements,slightly enriches V,Ga,Zr,Nb,Cd and middle rare earth elements,is short of Mo,In,Sn,Cs,Hf,Ta,W,Ti,Bi and heavy rare earth elements. The mechanism of elemental enrichment in forminifera is the concentrations of trace elements in sea water and selective absorption of trace elements during foraminifera living, as well as the geochemical affinity between major elements and trace elements.The REE (rare earth elements)partition pattern of foraminifera shell of the Okinawa Trough shows enrichment of middle rare earth elements with slightly negative Ce anomaly,which are different from those of foraminifera of the Pacific Ocean.The Sr,Nd isotopic ratios of the Okinawa Trough foraminifera are 0 709 769 and 0 512 162,respectively, which are different not only from those of oceanic water, but also from those of river water of China's Mainland, the former is slightly higher than those of oceanic water,but much lower than those of river water;the latter is slightly lower than those of oceanic water,but higher than those of river water,demonstrating that the Okinawa Trough sea water has been influenced by river water of China's Mainland.展开更多
The Lajimiao norite-gabbro complex, as a part of the ophiolites on the southern side of the North Qinling belt, consists of gabbro and norite-gabbro. They were derived from different magma series: the gabbro was deriv...The Lajimiao norite-gabbro complex, as a part of the ophiolites on the southern side of the North Qinling belt, consists of gabbro and norite-gabbro. They were derived from different magma series: the gabbro was derived from tholeiitic magma series with higher TiO2, REE abundance and Fe3+/Fe2+ ratio ; norite-gabbro was derived from calc-alkali magma series with lower TiO2, Fe3+/Fe2+ ratio and REE abundance and much lower HREE abundance, which suggests that the source of the norite-gabbro magma was deeper and controlled by eclogite facies. Geochemical characteristics of both plutonic rocks are similar to those of island-arc basalts, such as relatively high contents of Ba, Pb and Sr and relatively low contents of Nb, Zr and N j.The Sr, Nd isotopic characteristics of the Lajimiao norite-gabbro complex are similar to those of ophiolites. Its εNd values are constant, about+2; whereas εst values have wide variation from - 6.4 to +31.2 and positively correlate with Na2O, H2O+ and CO2 contents and the Fe3+/Fe2+ ratio. The εNd- Nd/Th, εNd- La/Nb and εNd-Ba/Nb diagrams clearly show that there were significant components of terrigenous sediments in the mantle source of the Lajimiao norite-gabbro complex. It suggests that large amount of sediments had been carried into the mantle by the subducted ancient Qinling sea plate during the Palaeozoic.展开更多
Many carbonate-hosted talc mineralization,which are widespread in South China,exclusively developed in Carboniferous dolomitic limestone with many siliceous bands and nodules,and cherts.One of those typical deposits i...Many carbonate-hosted talc mineralization,which are widespread in South China,exclusively developed in Carboniferous dolomitic limestone with many siliceous bands and nodules,and cherts.One of those typical deposits is the Guling talc deposit in Mashan County,central Guangxi province,with a talc reserve of1.51 million tons.Mineral associations in the deposit are sample,mainly including talc and calcite.In this paper,Sm-Nd isotopic system and rare earth elements and yttrium(REE + Y) for the hydrothermal calcite intergrown with talc are used to constrain the age and origin of the talc mineralization.The hydrothermal calcite samples from the deposit display Sm and Nd concentrations ranging from 0.18 to 0.85 and 0.85 to 4.56 ppm,respectively,and variable Sm/Nd ratios of 0.21-0.24.These calcites further yield an Sm-Nd isochron age of 232 ±19 Ma(2a)(MSWD = 0.47) with an concordant initial ^(143)Nd-^(144)Nd ratios of 0.511967 ± 0.000017,which should be interpreted as the mineralization age of the Guling talc deposit.In addition,the calcite samples are enriched in REE with the variable SREE contents ranging from 4.82 to21.50 ppm and display relatively consistent chondritenormalized REE + Y patterns with the LREE enrichment(LREE/HREE=2.00-3.60)and the obvious negative Eu(δEu=0.52-0.68)and Ce(δCe=0.16-0.33)anomalies.The Y/Ho ratios of seven calcites varies from 43.30 to59.34,with a mean value of 49.73.The available mineral associations and REE parameters(i.e.,REE patterns and Y/Ho ratios) of those calcites indicate that the ore-forming fluids of the talc mineralization be probably derived from the meteoric waters,in particular evolved ones in the Karst areas and the ore-forming materials(e.g.,Si and Mg) are likely to be originated from the ore-bearing dolostone in the Yanguan Formation(C_1y) and underlying siliceous rocks in the Liujiang Formation(D_3l).Furthermore,the talc mineralization could take place within a hydrothermal system with relative oxidizing environment and middle temperature,due to the obvious negative Eu and Ce anomalies in the calcites in the Guling deposit.展开更多
Rb -Sr isotopic isochron dating of the volcanic rock samples from the Upper Cretaceous Half Three Point Formation on the King George Island is 71. 33±0. 3 Ma. Correlative study of εND(T)-147Sm/144Nd, 143Nd/144Nd...Rb -Sr isotopic isochron dating of the volcanic rock samples from the Upper Cretaceous Half Three Point Formation on the King George Island is 71. 33±0. 3 Ma. Correlative study of εND(T)-147Sm/144Nd, 143Nd/144Nd-87Sr/86Sr, 87Sr/86Sr-Sr and 87Sr/86Sr-K2O/(K2O+Na2O) indicated that the volcanic rocks were chiefly derived from the depleted mantle source and generally were not mixed crust materials. Of the samples 6 were given the mean Sm -Nd model age (TDM) of 443. 3±20. 6 Ma possibly indicating the age of chemical variation event in the magma source of the study area. Features of the trace elements indicated that the rocks from the Half Three Point Formation are of typical calc-alkaline volcanic suite and similar to those from the Tertiary volcanic rocks of the Fildes Peninsula, being the same products of the island-arc volcanic activity.展开更多
文摘Trace elemental associations and Sr-Nd isotopic compositions are of important to recognition of biogenic material from mixed marine sediments. The foraminifera shell from the Okinawa Trough strongly enriches Sr,P,Mn and Ba, enriches Li,U,Th,Sc,Co,Cu,Pb,Zn,Cr,Rb,Y,Sb and light rare earth elements,slightly enriches V,Ga,Zr,Nb,Cd and middle rare earth elements,is short of Mo,In,Sn,Cs,Hf,Ta,W,Ti,Bi and heavy rare earth elements. The mechanism of elemental enrichment in forminifera is the concentrations of trace elements in sea water and selective absorption of trace elements during foraminifera living, as well as the geochemical affinity between major elements and trace elements.The REE (rare earth elements)partition pattern of foraminifera shell of the Okinawa Trough shows enrichment of middle rare earth elements with slightly negative Ce anomaly,which are different from those of foraminifera of the Pacific Ocean.The Sr,Nd isotopic ratios of the Okinawa Trough foraminifera are 0 709 769 and 0 512 162,respectively, which are different not only from those of oceanic water, but also from those of river water of China's Mainland, the former is slightly higher than those of oceanic water,but much lower than those of river water;the latter is slightly lower than those of oceanic water,but higher than those of river water,demonstrating that the Okinawa Trough sea water has been influenced by river water of China's Mainland.
基金Aproject supported by the National Natural Science Foundation of China (No.49070165)
文摘The Lajimiao norite-gabbro complex, as a part of the ophiolites on the southern side of the North Qinling belt, consists of gabbro and norite-gabbro. They were derived from different magma series: the gabbro was derived from tholeiitic magma series with higher TiO2, REE abundance and Fe3+/Fe2+ ratio ; norite-gabbro was derived from calc-alkali magma series with lower TiO2, Fe3+/Fe2+ ratio and REE abundance and much lower HREE abundance, which suggests that the source of the norite-gabbro magma was deeper and controlled by eclogite facies. Geochemical characteristics of both plutonic rocks are similar to those of island-arc basalts, such as relatively high contents of Ba, Pb and Sr and relatively low contents of Nb, Zr and N j.The Sr, Nd isotopic characteristics of the Lajimiao norite-gabbro complex are similar to those of ophiolites. Its εNd values are constant, about+2; whereas εst values have wide variation from - 6.4 to +31.2 and positively correlate with Na2O, H2O+ and CO2 contents and the Fe3+/Fe2+ ratio. The εNd- Nd/Th, εNd- La/Nb and εNd-Ba/Nb diagrams clearly show that there were significant components of terrigenous sediments in the mantle source of the Lajimiao norite-gabbro complex. It suggests that large amount of sediments had been carried into the mantle by the subducted ancient Qinling sea plate during the Palaeozoic.
基金funded by The 12th Five Year Plan project of State Key Laboratory of Ore-deposit Geochemistry,Chinese Academy of Sciences(SKLODG-ZY125-04)China Natural Science Foundation(41372105)
文摘Many carbonate-hosted talc mineralization,which are widespread in South China,exclusively developed in Carboniferous dolomitic limestone with many siliceous bands and nodules,and cherts.One of those typical deposits is the Guling talc deposit in Mashan County,central Guangxi province,with a talc reserve of1.51 million tons.Mineral associations in the deposit are sample,mainly including talc and calcite.In this paper,Sm-Nd isotopic system and rare earth elements and yttrium(REE + Y) for the hydrothermal calcite intergrown with talc are used to constrain the age and origin of the talc mineralization.The hydrothermal calcite samples from the deposit display Sm and Nd concentrations ranging from 0.18 to 0.85 and 0.85 to 4.56 ppm,respectively,and variable Sm/Nd ratios of 0.21-0.24.These calcites further yield an Sm-Nd isochron age of 232 ±19 Ma(2a)(MSWD = 0.47) with an concordant initial ^(143)Nd-^(144)Nd ratios of 0.511967 ± 0.000017,which should be interpreted as the mineralization age of the Guling talc deposit.In addition,the calcite samples are enriched in REE with the variable SREE contents ranging from 4.82 to21.50 ppm and display relatively consistent chondritenormalized REE + Y patterns with the LREE enrichment(LREE/HREE=2.00-3.60)and the obvious negative Eu(δEu=0.52-0.68)and Ce(δCe=0.16-0.33)anomalies.The Y/Ho ratios of seven calcites varies from 43.30 to59.34,with a mean value of 49.73.The available mineral associations and REE parameters(i.e.,REE patterns and Y/Ho ratios) of those calcites indicate that the ore-forming fluids of the talc mineralization be probably derived from the meteoric waters,in particular evolved ones in the Karst areas and the ore-forming materials(e.g.,Si and Mg) are likely to be originated from the ore-bearing dolostone in the Yanguan Formation(C_1y) and underlying siliceous rocks in the Liujiang Formation(D_3l).Furthermore,the talc mineralization could take place within a hydrothermal system with relative oxidizing environment and middle temperature,due to the obvious negative Eu and Ce anomalies in the calcites in the Guling deposit.
基金The project supported by the State Antarctic Committeethe National Natural Science Foundation of China
文摘Rb -Sr isotopic isochron dating of the volcanic rock samples from the Upper Cretaceous Half Three Point Formation on the King George Island is 71. 33±0. 3 Ma. Correlative study of εND(T)-147Sm/144Nd, 143Nd/144Nd-87Sr/86Sr, 87Sr/86Sr-Sr and 87Sr/86Sr-K2O/(K2O+Na2O) indicated that the volcanic rocks were chiefly derived from the depleted mantle source and generally were not mixed crust materials. Of the samples 6 were given the mean Sm -Nd model age (TDM) of 443. 3±20. 6 Ma possibly indicating the age of chemical variation event in the magma source of the study area. Features of the trace elements indicated that the rocks from the Half Three Point Formation are of typical calc-alkaline volcanic suite and similar to those from the Tertiary volcanic rocks of the Fildes Peninsula, being the same products of the island-arc volcanic activity.
