There are two main methods to determine boron isotopic composition.One is the solution method,in which boron is purified after the samples are dissolved in solution and the boron isotope ratios are determined by therm...There are two main methods to determine boron isotopic composition.One is the solution method,in which boron is purified after the samples are dissolved in solution and the boron isotope ratios are determined by thermal ionization mass spectrometry(P-TIMS and N-TIMS) or multicollector inductively coupled plasma mass spectrometry(MC-ICP-MS).The other is an in-situ analysis method,in which the in-situ boron isotopic ratios in minerals are analyzed directly using secondary ion mass spectrometry(SIMS) or laser ablation multicollector inductively coupled plasma mass spectrometry(LA-MC-ICP-MS).In the in-situ analysis method for boron isotopes,the multifarious chemical purification and separation processes of the solution method are avoided,with increased work efficiency.In addition,the microzones and microbeddings of minerals can be analyzed in-situ to reveal the fine processes and conditions of mineral formation.In this study,using the standard-sample-bracketing(SSB) method,mass bias of the instrument and the fractionation of isotopes were calibrated,and the in-situ determination method of LA-MC-ICP-MS for boron isotopes was established.Through detailed analyses on a series of boron isotope standards and samples,a matrix effect was assessed but not detected,and the analysis results were in accordance with the formerly reported values or P-TIMS determined values,within the error range.The analytical results for IAEA B4 and IMR RB1 with relatively high boron contents were δ 11B =-(8.36±0.58)‰(2σ,n=50) and δ 11B =-(12.96±0.97)‰(2σ,n=57),respectively;the analytical result for IAEA B6 with rela-tively low boron content was δ 11B =-(3.29±1.12)‰(2σ,n=35).In-situ measurements for B isotopes were performed on geo-logical samples such as tourmaline,ulexite,ludwigite,inyoite and ascharite,with the results consistent with those determined by P-TIMS,within the error range.展开更多
The Laocheng granitoid pluton is located in the South Qinling tectonic domain of the Qinling orogenic belt,southern Shaanxi Province,and consists chiefly of quartz diorite,granodiorite and monzogranite.A LA-ICP-MS zir...The Laocheng granitoid pluton is located in the South Qinling tectonic domain of the Qinling orogenic belt,southern Shaanxi Province,and consists chiefly of quartz diorite,granodiorite and monzogranite.A LA-ICP-MS zircon U-Pb isotopic dating,in conjunction with cathodoluminescence images,reveals that the quartz diorite and granodiorite were emplaced from 220 Ma to 216 Ma,while the monzogranite was emplaced at～210 Ma.In-situ zircon Hf isotopic analyses show that theε_（Hf）（t） values of the quartz diorite and granodiorite range from-8.1 to ＋1.3,and single-stage Hf model ages from 809 Ma to 1171 Ma,while theε_（Hf）（t）values of the monzogranite are-14.5 to ＋16.7 and single-stage Hf model ages from 189 Ma to 1424 Ma.These Hf isotopic features reveal that the quartz diorite, granodiorite and monzogranite were formed from the mixing of the magmas derived from partial melting of the depleted mantle and the lower continent crustal materials,and there were two stages of continental crust growth during the Neoproterozoic（～800 Ma）and Indosinian（～210 Ma）eras, respectively,in the south Qinling tectonic domain of the Qinling orogrnic belt,Central China.展开更多
基金supported by the National Special Research Program for Non-Profit Trades (Sponsored by MLR, 200911043-20 and 200811114)
文摘There are two main methods to determine boron isotopic composition.One is the solution method,in which boron is purified after the samples are dissolved in solution and the boron isotope ratios are determined by thermal ionization mass spectrometry(P-TIMS and N-TIMS) or multicollector inductively coupled plasma mass spectrometry(MC-ICP-MS).The other is an in-situ analysis method,in which the in-situ boron isotopic ratios in minerals are analyzed directly using secondary ion mass spectrometry(SIMS) or laser ablation multicollector inductively coupled plasma mass spectrometry(LA-MC-ICP-MS).In the in-situ analysis method for boron isotopes,the multifarious chemical purification and separation processes of the solution method are avoided,with increased work efficiency.In addition,the microzones and microbeddings of minerals can be analyzed in-situ to reveal the fine processes and conditions of mineral formation.In this study,using the standard-sample-bracketing(SSB) method,mass bias of the instrument and the fractionation of isotopes were calibrated,and the in-situ determination method of LA-MC-ICP-MS for boron isotopes was established.Through detailed analyses on a series of boron isotope standards and samples,a matrix effect was assessed but not detected,and the analysis results were in accordance with the formerly reported values or P-TIMS determined values,within the error range.The analytical results for IAEA B4 and IMR RB1 with relatively high boron contents were δ 11B =-(8.36±0.58)‰(2σ,n=50) and δ 11B =-(12.96±0.97)‰(2σ,n=57),respectively;the analytical result for IAEA B6 with rela-tively low boron content was δ 11B =-(3.29±1.12)‰(2σ,n=35).In-situ measurements for B isotopes were performed on geo-logical samples such as tourmaline,ulexite,ludwigite,inyoite and ascharite,with the results consistent with those determined by P-TIMS,within the error range.
基金financially supported by the National Project of Scientific and Technological Support(Grant No:2006BAB01A11)
文摘The Laocheng granitoid pluton is located in the South Qinling tectonic domain of the Qinling orogenic belt,southern Shaanxi Province,and consists chiefly of quartz diorite,granodiorite and monzogranite.A LA-ICP-MS zircon U-Pb isotopic dating,in conjunction with cathodoluminescence images,reveals that the quartz diorite and granodiorite were emplaced from 220 Ma to 216 Ma,while the monzogranite was emplaced at～210 Ma.In-situ zircon Hf isotopic analyses show that theε_（Hf）（t） values of the quartz diorite and granodiorite range from-8.1 to ＋1.3,and single-stage Hf model ages from 809 Ma to 1171 Ma,while theε_（Hf）（t）values of the monzogranite are-14.5 to ＋16.7 and single-stage Hf model ages from 189 Ma to 1424 Ma.These Hf isotopic features reveal that the quartz diorite, granodiorite and monzogranite were formed from the mixing of the magmas derived from partial melting of the depleted mantle and the lower continent crustal materials,and there were two stages of continental crust growth during the Neoproterozoic（～800 Ma）and Indosinian（～210 Ma）eras, respectively,in the south Qinling tectonic domain of the Qinling orogrnic belt,Central China.
