(Table 3) Li concentrations and isotopic compositions in foraminiferal shells, carbonate sediments, and associated pore waters from ODP Sites 131-806 and 138-851

An improved procedure for lithium isotope analysis using Li3PO4 as the ion source has been investigated for application to geological samples. The 7Li/6Li ratio is measured using double rhenium filament thermal ionization mass spectrometry in which isotopic fractionation is minimized at high temperatures. The method produces a stable, high intensity Li+ ion beam that allows measurement of nanogram quantities of lithium. This results in a reduction in sample size of up to 1000 times relative to that required for the established Li2BO2+ method while maintaining a comparable precision of better than 1‰ (1 sigma). Replicate analyses of the NBS L-SVEC Li2CO3 standard yielded a mean value of 12.1047+/-0.0043 (n=21), which is close to the reported absolute value of 12.02+/-0.03. Intercalibration with a wide range of geological samples shows excellent agreement between the Li3PO4 and Li2BO2+ techniques. Replicate analyses of seawater and a fresh submarine basalt display high precision results that agree with previous measurements. […]

本研究针对地质样本，探讨了一种以Li3PO4为离子源（ion source）的改进型锂同位素分析（lithium isotope analysis）方法。7Li/6Li比值通过双铼灯丝热电离质谱法（double rhenium filament thermal ionization mass spectrometry）测定，该方法在高温条件下可最大限度抑制同位素分馏（isotopic fractionation）。该方法能产生稳定且高强度的Li+离子束（Li+ ion beam），可实现纳克级锂样品的检测。与传统Li2BO2+法相比，其所需样品量减少了多达1000倍，同时仍保持优于1‰（1σ）的相当精度。对NBS L-SVEC碳酸锂（Li2CO3）标准物质的重复分析（replicate analyses）结果显示，平均值为12.1047±0.0043（n=21），与已报道的绝对数值12.02±0.03相近。通过对多种地质样本的交叉校准（intercalibration），Li3PO4法与Li2BO2+法的分析结果具有高度一致性。对海水及新鲜海底玄武岩（submarine basalt）的重复分析结果精度较高，且与先前测定值相符。[...]