Abstract
Clinopyroxene is a major host mineral for lithophile elements in the mantle lithosphere, and therefore, its origin is vital for constraints on mantle evolution and melt generation. In situ Sr isotopic measurement of clinopyroxene has been available since the recent development of laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) in the 2000s. Therefore, there is an increasing demand for natural clinopyroxene reference materials for Sr isotope microanalysis. In this contribution, we present six natural clinopyroxene reference materials from South Africa (JJG1424) and China (YY09-47, YY09-04, YY09-24, YY12-01, and YY12-02) for Sr isotope microanalysis. The Sr content of these clinopyroxenes ranges from 50 to 340 μg g−1, which covers most natural clinopyroxene compositions. Homogeneity of these potential reference materials were investigated and evaluated in detail over a 2-year period using 193-nm nanosecond and 257-nm femtosecond laser systems coupled to either a Neptune or Neptune Plus MC-ICP-MS. Additionally, the major and trace element of these clinopyroxenes were examined by electron probe microanalyzer (EPMA) as well as solution and laser ICP-MS. The in situ 87Sr/86Sr values obtained for the six natural clinopyroxene reference materials agree well with data obtained using the thermal ionization mass spectrometer (TIMS) method. The Sr isotopic stability and homogeneity of these clinopyroxenes make them potential reference materials for in situ Sr microanalysis to correct instrumental fractionation or as quality control materials for analytical sessions. The new Sr isotope data provided here might be beneficial for microbeam analysis in the geochemical community.
Highlights
We investigated whether the homogeneity of Sr isotopes for six natural clinopyroxene from South Africa (JJG1424) and China (YY09-47, YY09-04, YY09-24, YY1201, and YY12-02), which covers a range of 50–350 μg g−1, corresponds well to the natural distribution, at the micrometer scale, using MC-ICP-MS coupled with nano- and femtosecond laser over a 2-year period
Considering the few, or unavailable, natural clinopyroxene reference materials for Sr microanalysis, we investigated thoroughly the assessment by both laser and solution measurements of the Sr isotopic ratios of six potential natural clinopyroxene reference materials from South Africa and China
The Sr isotopic compositions obtained for these samples are all consistent with values obtained by solution methods [both MC-ICP-MS and isotope dilution thermal ionization mass spectrometer (TIMS) (ID-TIMS)]
Summary
Clinopyroxene (CPX), a common Ca-rich mineral in mantle rock, is a principal host of Sr, and its Sr isotopic composition can reveal geological processes in the mantle lithosphere, such as (1) melt refertilization of the mantle (Tang et al, 2011, 2012; Zou et al, 2014; Liu et al, 2016); (2) degree of partial melting the mantle experienced (Griffin and Brueckner, 1985; Norman, 2001; Liu et al, 2016); and (3) metasomatic agents affecting the mantle (Rudnick et al, 2004; Wu et al, 2006; Sapienza et al, 2008; Touron et al, 2008; Sun et al, 2012; Xu et al, 2013; Tang et al, 2017; Aulbach et al, 2019). In situ Sr isotope measurement via ablation multicollector inductively coupled plasma mass spectrometry (LA-MCICP-MS) for clinopyroxene has been growing rapidly. Sun et al (2012) performed an in situ Sr isotopes for clinopyroxene in mantle xenoliths from Hebi, central North China Craton (NCC), and concluded that the clinopyroxene were crystallized from metasomatic melts. Xu et al (2013) conducted in situ Sr isotopic composition of peridotite xenoliths from Kuandian and investigated Pacific slab subduction-related mantle modification of clinopyroxene beneath the eastern NCC Jackson and Hart (2006) reported in situ Sr isotopes in melt inclusions hosted by olivine phenocrysts and observed melts from high 3He/4He and EM II-type mantle end members, respectively. Sun et al (2012) performed an in situ Sr isotopes for clinopyroxene in mantle xenoliths from Hebi, central North China Craton (NCC), and concluded that the clinopyroxene were crystallized from metasomatic melts. Xu et al (2013) conducted in situ Sr isotopic composition of peridotite xenoliths from Kuandian and investigated Pacific slab subduction-related mantle modification of clinopyroxene beneath the eastern NCC
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