Incompatible trace elements are important tracers in igneous petrogenesis for determining processes acting: (i) prior to partial melting on magma sources; (ii) during partial melting, fractional crystallization or contamination of magmas, and (iii) after emplacement of lavas or intrusive rocks close to Earth's surface. Of particular interest are the high field strength elements (HFSE: Ti, Zr, Nb, Hf, Ta) which are incompatible elements with high valence states that are also relatively immobile in aqueous fluids. Abundances of Ti, Ta, and Nb (TITAN) in ocean island basalts (OIB) have been suggested to reflect recycled oceanic crust in mantle source regions, due to retention of these elements in subducted eclogitic rutile. Some of these elements have also been used to determine ‘canonical’ trace element ratios, such as Nb/U and Ta/U, that are considered invariant during petrogenetic processes. In this contribution, we present an extensive set of in situ trace element data for olivine, clinopyroxene, oxide minerals and groundmass for a suite of well-studied ocean island basalt (OIB) lavas from the Canary Islands, Azores, Samoa, Tubuai and La Réunion. The data were obtained using laser-ablation inductively coupled plasma mass spectrometry, and we also report a new open-source reduction routine for abundance determination using this method. Mineral-groundmass partitioning behavior is determined for olivine, clinopyroxene and oxides, showing that these are consistent with published partition coefficients for clinopyroxene and olivine, but are more variable for oxide phases. This variability is due to the wide variety of oxide phases possible in OIB (e.g., Cr-spinel, ilmenite, titanomagnetite) and their formation within the crystallization sequence. The new data shows that Nb and Ta budgets are dominated by fine-grained groundmass, as are most other incompatible trace elements, while the Ti budget is divided between clinopyroxene, oxide and groundmass. Modally reconstructed TITAN anomalies closely reproduce bulk rock compositions in samples with >40 % groundmass. Olivine and clinopyroxene fractional crystallization have negligible effects on TITAN anomalies, while oxide fractionation has more marked effects, with Ti anomalies being most affected. Variability in the HFSE in OIB and their association with other elements (e.g., Nb/U and Ta/U) can reflect source characteristics, although careful screening for petrogenetic effects should be done prior to ascribing significance to TITAN anomalies or canonical trace element ratios.

中文翻译：

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海岛玄武岩矿物相和基质中的微量元素丰度


不相容的微量元素是火成岩中重要的示踪剂，用于确定作用的过程：（i）在岩浆源部分熔化之前； (ii) 在岩浆部分熔化、分步结晶或污染期间，以及 (iii) 在接近地球表面的熔岩或侵入岩就位之后。特别令人感兴趣的是高场强元素（HFSE：Ti、Zr、Nb、Hf、Ta），它们是具有高价态的不相容元素，在水性流体中也相对固定。由于俯冲榴辉岩金红石中保留了这些元素，洋岛玄武岩（OIB）中的钛、钽和铌（TITAN）丰度被认为反映了地幔源区的再循环洋壳。其中一些元素还被用来确定“规范”微量元素比率，例如 Nb/U 和 Ta/U，这些元素在成岩过程中被认为是不变的。在这篇文章中，我们提供了一组广泛的原位微量元素数据，包括橄榄石、单斜辉石、氧化物矿物和来自加那利群岛、亚速尔群岛、萨摩亚、图布艾和拉加那利群岛的一组经过充分研究的洋岛玄武岩 (OIB) 熔岩的基质。团圆。这些数据是使用激光烧蚀电感耦合等离子体质谱法获得的，我们还报告了一种新的开源还原例程，用于使用该方法测定丰度。确定了橄榄石、单斜辉石和氧化物的矿物-基质分配行为，表明这些与已公布的单斜辉石和橄榄石的分配系数一致，但对于氧化物相来说变化更大。这种变化是由于 OIB 中可能存在多种氧化物相（例如铬尖晶石、钛铁矿、钛磁铁矿）及其在结晶过程中的形成。 新数据显示，Nb 和 Ta 预算以细粒基质为主，大多数其他不相容的微量元素也是如此，而 Ti 预算则分为单斜辉石、氧化物和基质。模态重建的 TITAN 异常紧密地再现了具有 >40 % 基质的样品中的块体岩石成分。橄榄石和单斜辉石分异结晶对TITAN异常的影响可以忽略不计，而氧化物分异结晶的影响则更为显着，其中Ti异常影响最大。 OIB 中 HFSE 的变异性及其与其他元素（例如 Nb/U 和 Ta/U）的关联可以反映源特征，尽管在赋予 TITAN 异常或典型微量元素比率的重要性之前应仔细筛选岩石成因效应。