Objective With the development of analytic technologies, in-situ dating on U-bearing oxide minerals （e.g., cassiterite, rutile and baddeleyite） has been widely used in geological chronological researches and has at...Objective With the development of analytic technologies, in-situ dating on U-bearing oxide minerals （e.g., cassiterite, rutile and baddeleyite） has been widely used in geological chronological researches and has attracted remarkable attention to explore evolution of the earth and obtain age information of various geological processes. Matrix effect related studies are especially important during in-situ U- Pb dating based on Laser Ablation Multiple Collector Inductively Coupled Plasma Mass Spectrometry （LA-MC- ICPMS）. However, to our knowledge, only few thorough and systematical matrix effect study of U-bearing oxide minerals has been reported. In this study, we systematically analyzed the matrix effect of U-bearing oxide minerals in order to take place the standards which are difficult to prepare with available standards.展开更多
The poorly studied Douling Complex is a crystalline basement that developed in the Neoproterozoic-Paleozoic weakly metamorphosed to non-metamorphosed strata at the South Qinling tectonic belt.Five banded dioritic-gran...The poorly studied Douling Complex is a crystalline basement that developed in the Neoproterozoic-Paleozoic weakly metamorphosed to non-metamorphosed strata at the South Qinling tectonic belt.Five banded dioritic-granitic gneiss samples from the Douling Complex were chosen for LA-MC-ICPMS U-Pb zircon dating,which yielded protolith emplacement ages of 2469±22Ma,2479±12 Ma,2497±21 Ma,2501±17 Ma and 2509±14 Ma,respectively.An important peak age of^2.48 Ga was also obtained for a metasedimentary rock in the same region.These discoveries suggest the occurrence of magmatic activity of2.51–2.47 Ga at the northern margin of the Yangtze craton.The age-correctedεHf(t)values obtained from in situ zircon Hf isotopic analysis are mainly between 5.5 and+0.3,and the two-stage zircon Hf model ages range from 3.30 to 2.95 Ga.Considering two important periods of^3.3–3.2 Ga and^2.95–2.90 Ga for the continental crustal growth in the Yangtze craton,we infer that the dioritic-granitic gneisses from the Douling Complex are the products of reworking of Paleo-to Mesoarchean crust at the northern margin of the Yangtze craton at^2.5 Ga.In addition,metamorphic ages of 837±8 Ma and 818±10 Ma were obtained for zircon overgrowth rims from a dioritic gneiss and a metasedimentary rock,indicating that the main phase amphibolite facies metamorphism of the Doulng Complex occurred during the Neoproterozoic,although its geological meaning remains ambiguous.展开更多
基金financially supported by the National Natural Science Foundation of China(grants No.41503052 and 41373053)the National Science and Technology Infrastructure(grant No.DDK14-39)
文摘Objective With the development of analytic technologies, in-situ dating on U-bearing oxide minerals （e.g., cassiterite, rutile and baddeleyite） has been widely used in geological chronological researches and has attracted remarkable attention to explore evolution of the earth and obtain age information of various geological processes. Matrix effect related studies are especially important during in-situ U- Pb dating based on Laser Ablation Multiple Collector Inductively Coupled Plasma Mass Spectrometry （LA-MC- ICPMS）. However, to our knowledge, only few thorough and systematical matrix effect study of U-bearing oxide minerals has been reported. In this study, we systematically analyzed the matrix effect of U-bearing oxide minerals in order to take place the standards which are difficult to prepare with available standards.
基金supported by the National Basic Research Program of China(2009CB825006)
文摘The poorly studied Douling Complex is a crystalline basement that developed in the Neoproterozoic-Paleozoic weakly metamorphosed to non-metamorphosed strata at the South Qinling tectonic belt.Five banded dioritic-granitic gneiss samples from the Douling Complex were chosen for LA-MC-ICPMS U-Pb zircon dating,which yielded protolith emplacement ages of 2469±22Ma,2479±12 Ma,2497±21 Ma,2501±17 Ma and 2509±14 Ma,respectively.An important peak age of^2.48 Ga was also obtained for a metasedimentary rock in the same region.These discoveries suggest the occurrence of magmatic activity of2.51–2.47 Ga at the northern margin of the Yangtze craton.The age-correctedεHf(t)values obtained from in situ zircon Hf isotopic analysis are mainly between 5.5 and+0.3,and the two-stage zircon Hf model ages range from 3.30 to 2.95 Ga.Considering two important periods of^3.3–3.2 Ga and^2.95–2.90 Ga for the continental crustal growth in the Yangtze craton,we infer that the dioritic-granitic gneisses from the Douling Complex are the products of reworking of Paleo-to Mesoarchean crust at the northern margin of the Yangtze craton at^2.5 Ga.In addition,metamorphic ages of 837±8 Ma and 818±10 Ma were obtained for zircon overgrowth rims from a dioritic gneiss and a metasedimentary rock,indicating that the main phase amphibolite facies metamorphism of the Doulng Complex occurred during the Neoproterozoic,although its geological meaning remains ambiguous.
