Mineralogical control of selenium, tellurium and highly siderophile elements in the Earth’s mantle: Evidence from mineral separates of ultra-depleted mantle residues
Mineralogical control of selenium, tellurium and highly siderophile elements in the Earth’s mantle: Evidence from mineral separates of ultra-depleted mantle residues
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地幔中硒、碲和高亲铁元素的矿物学控制：来自超贫化地幔残渣矿物分离物的证据
DOI：
10.1016/j.chemgeo.2014.12.015
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发表时间：
2015
期刊：
影响因子：
3.9
通讯作者：
Luguet A
中科院分区：
文献类型：
--
作者：
König S;Lorand JP;Lissner M;Bragagni A ;Luguet A
采用同位素稀释氢化物生成ICPMS法，通过矿物分离、高压酸消化和化学提纯，测定了一种超难熔硬锰矿中主要硅酸盐和氧化物矿物分离物（橄榄石、正辉石、斜辉石、尖晶石）中Se-Te等高亲铁元素（HSEs）的收支状况和粒间细组分。此外，为了约束和说明硫化物和/或合金在其完整的块状碳化物基体中的原始位置、分布和尺寸，还进行了x射线计算机微断层扫描（micro-CT）。结果表明，经过高度部分熔融（F≈23%）后，不含贱金属硫化物（BMS）的地幔残余物的全岩Se-Te收支几乎完全由含橄榄石的微包裹体和铂族矿物（PGMs）的粒间组分控制。三维显微ct显示辉石矿中颗粒间PGM的稀缺性和非均质性，晶粒尺寸一般为3 ~ 5 μm，而橄榄石中的PGM包裹体尺寸小于2.5 μm。这些微相的非均质分布以及块状哈尔茨辉石中Se-Te含量的范围使分离体对整个岩石Se-Te收支的单个贡献的量化复杂化。然而，橄榄石中的PGM微包裹体具有残余型CI球粒陨石归一化HSE模式，超球粒Se/Te比值在30 ~ 218之间（Se/TeCI球粒陨石= 9），占岩石整体Se的近100%。颗粒尺寸在125 μm以下的间隙细组分可能只贡献了少量的Se，但高达50%的Te，显示出亚球粒体Se/Te比值约为4，类似于交代PGM特征。随着间隙型和交代型PGMs与橄榄石型残余PGMs比例的增加，岩石整体Te含量增加，Se/Te比值降低。在一个哈尔茨基岩样品的矿物分离物中所见的系统特征与迄今已发表的所有橄榄岩组和宿主相的Se-Te特征的整个光谱相似。结果与Se在共价单硫化物中的相容性相比，Te更倾向于硫化物熔体。这与Mss耗尽后残余PGMs的稳定以及富s - cu挥发性硫化物熔体中交代PGMs的形成进一步一致。总的来说，这调和了部分地幔熔融过程中Te对Se的高度不相容，随后从高度部分地幔熔融中产生的富cu - ni硫化物分异去除Te对Se的影响，并解释了与全球观测到的橄榄岩相比，morb中Te的丰度相似，但Se的丰度更高。
The budget of Se–Te and other highly siderophile elements (HSEs) in major silicate and oxide mineral separates (olivine, orthopyroxene, clinopyroxene, spinel), and intergranular fine components of an ultra-refractory harzburgite have been determined via isotope dilution hydride generation ICPMS after mineral separation, high-pressure acid digestion and chemical purification. In addition, x-ray computed micro-tomography (micro-CT) has been performed in order to constrain and illustrate the original location, distribution and size of sulfides and/or alloys inside their intact, bulk harzburgite matrix. The results show that the whole-rock Se–Te budget of mantle residues, that are devoid of base metal sulfides (BMS) after high degrees of partial melting (F≈ 23%), is almost completely controlled by olivine-hosted micro-inclusions and intergranular fractions of platinum group minerals (PGMs). The scarcity and heterogeneous distribution of intergranular PGMs generally sized 3–5 μm in the harzburgite are revealed by 3D micro-CT, while PGM inclusions in olivine are smaller than 2.5 μm. The heterogeneous distribution of these microphases as well as the range of Se–Te contents in the bulk harzburgite complicate a quantification of individual contributions of separates to the whole-rock Se–Te budget. However, PGM micro-inclusions in olivine with residual-type CI chondrite-normalized HSE patterns and suprachondritic Se/Te ratios between 30 and 218 (Se/TeCI chondrite = 9) host close to 100% of the bulk rock Se. Interstitial fine components up to 125 μm grain size may contribute only minor amounts of Se, but up to 50% of Te to the bulk harzburgite and show subchondritic Se/Te ratios of ca. 4, resembling metasomatic PGM signatures. In dependence on increasing proportions of interstitial and metasomatic PGMs vs. olivine-hosted residual PGMs, the bulk rock Te contents may increase and the Se/Te ratios decrease. The systematics seen in mineral separates of one harzburgitic sample resembles the entire spectrum of Se–Te signatures of all suites of peridotites and host phases so far published. The results are consistent with a higher compatibility of Se in covalent monosulfides compared to Te that prefers sulfide melts. It is further consistent with the stabilization of residual PGMs after Mss exhaustion as well as with formation of metasomatic PGMs in a S-Cu-volatile-rich sulfide melt. Altogether this reconciles a higher incompatibility of Te over Se during partial mantle melting, subsequent removal of Te over Se with Cu-Ni-rich sulfide fractionation from high-degree partial mantle melts, and explains the similar Te but higher Se abundances in MORBs compared to peridotites that is globally observed.
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DOI：
--
发表时间：
1991
期刊：
影响因子：
--
作者：
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作者：
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作者：
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通讯作者：
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影响因子：
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作者：
M. Lissner;S. König;A. Luguet;P. Roux;S. Schuth;A. Heuser;A. L. Roex
通讯作者：
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影响因子：
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作者：
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通讯作者：
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