In:
Rapid Communications in Mass Spectrometry, Wiley, Vol. 36, No. 22 ( 2022-11-30)
Abstract:
In situ Pb isotope analyses of tiny melt inclusions using laser ablation–multi‐collector–inductively coupled plasma–mass spectrometry (LA–MC–ICP–MS) are crucial for exploring the origins of mafic lavas. However, quantitative use of this technique with low‐Pb ( 〈 10 ppm) melt inclusions is difficult due to their low 204 Pb content and 204 Hg interference. Methods Pb isotopic ratios of various reference glasses and olivine‐hosted melt inclusions were determined using LA–MC–ICP–MS. Multiple ion counters were used to simultaneously determine signal intensities of all Pb isotopes and 202 Hg. An Hg signal‐removal smoothing device reduced its signal in the gas blank by 〉 80%. Instrumental mass bias was corrected using the standard–sample bracketing method. Results With 24–90 μm diameter laser spots, 2–4 Hz repetition rates, and 2.5–4 J cm −2 energy fluence, the analytical precisions of 20x Pb/ 204 Pb ratios ( x = 6, 7, 8) for standards BHVO‐2G, ML3B‐G, NIST 614, NKT‐1G, T1‐G, GOR132‐G, and StHs6/80‐G were 〈 1.0% (2RSD) when 208 Pb signals 〉 100 000 cps. The Wangjiadashan melt inclusions have 206 Pb/ 204 Pb = 17.14–18.44, 207 Pb/ 204 Pb = 15.28–15.66, and 208 Pb/ 204 Pb = 37.12–38.68. Conclusions The described method improves the precision and accuracy of in situ Pb isotope analysis in low‐Pb melt inclusions using LA–MC–ICP–MS. The Pb isotopic compositions of the Wangjiadashan melt inclusions indicate the coexistence of LoMu and EMII+young HIMU components in the mantle source of weakly alkaline basalts.
Type of Medium:
Online Resource
ISSN:
0951-4198
,
1097-0231
Language:
English
Publisher:
Wiley
Publication Date:
2022
detail.hit.zdb_id:
2002158-6
detail.hit.zdb_id:
58731-X
SSG:
11
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