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首页> 外文期刊>Contributions to Mineralogy and Petrology >Characteristics of the lithospheric mantle beneath East Serbia inferred from ultramafic xenoliths in Palaeogene basanites
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Characteristics of the lithospheric mantle beneath East Serbia inferred from ultramafic xenoliths in Palaeogene basanites

机译：从古生代玄武岩中的超镁铁质异质岩推断东塞尔维亚下方的岩石圈地幔特征

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Mantle xenoliths from Paleogene basanites of East Serbia were studied using EMP and LA-ICP-MS techniques in order to better understand mantle characteristics in this region. Five different mantle lithologies have been distinguished: a dunite/harzburgite/lherzolite (D/HZ/L) group, clinopyroxene-rich lherzolites (Cpx-L), clinopyroxene megacrysts (Cpx-M), spinel-rich olivine websterites (OWB1) and spinel-poor olivine websterites (OWB2). D/HZ/L xenoliths are the most common and represent ‘normal’ mantle composed of typical anhydrous spinel peridotites with well equilibrated, unzoned silicates characterized by high Mg# s. Negative correlations between Mg# and TiO2, Al2O3 and CaO wt% in clinopyroxenes (cpx) and orthopyroxenes (opx) and the Cr–Al trend in spinel (sp) suggest depletion via extraction of basaltic melts. The modal composition of D/HZ/L xenoliths and unusual low-Al opx suggest that the lithospheric mantle underneath East Serbia is more depleted than normal European lithosphere. D/HZ/L xenoliths contain numerous pockets and veins filled by Cr-rich cpx, Ti-rich spinel, altered glass, apatite and rare ilmenite and phlogopite. Petrographic observations, supported by major element contents in sp and cpx, and modelling using trace element contents in cpx, indicate that the pockets and veins formed from infiltration of alkaline melts and reaction with peridotite wall-rock causing opx and spinel replacement. The same alkaline melt-related metasomatism gave rise to the Cpx-L and OWB1 mantle xenoliths and Cpx-M xenocrysts. Trace element contents of cpx in these xenoliths show a distinctively concave downwards REE pattern with a HFSE depletion, very similar to cpx megacrysts from the Pannonian Basin and to vein cpx from Eifel. In contrast, the OWB2 xenoliths show evidence of precipitation from subduction-related mafic to ultramafic melts, as inferred from their opx-rich lithology and unusual Cr-rich spinels. They are probably related to subduction magmatism during the Late Cretaceous.
机译：为了更好地了解该地区的地幔特征，使用EMP和LA-ICP-MS技术对东塞尔维亚古近纪玄武岩的地幔异岩进行了研究。区分出了五种不同的地幔岩性：榴辉岩/哈茨伯格岩/锂铁矿（D / HZ / L）组，富含斜辉石的斜铁矿（Cpx-L），斜辉石大晶（Cpx-M），尖晶石的橄榄石韦氏体（OWB1 ）和贫尖晶石橄榄石韦斯特岩（OWB2 ）。 D / HZ / L异种岩是最常见的，代表“正常”地幔，由典型的无水尖晶石橄榄岩和平衡良好的，未分区的硅酸盐组成，其特征是高Mg＃s。斜py（cpx）和邻and（opx）中Mg＃与TiO2 ，Al2 O3 和CaO的重量百分比呈负相关，而尖晶石（sp）中的Cr–Al趋势表明通过提取玄武岩熔体。 D / HZ / L异岩的模态组成和不寻常的低铝opx表明，东塞尔维亚下的岩石圈地幔比正常的欧洲岩石圈更枯竭。 D / HZ / L异岩含有大量的袋和脉，由富含Cr的cpx，富含Ti的尖晶石，蚀变玻璃，磷灰石和稀有的钛铁矿和金云母填充。岩石学观测得到sp和cpx中主要元素含量的支持，并使用cpx中微量元素含量进行建模，结果表明，由于碱性熔体的渗入以及与橄榄岩壁岩的反应而形成的矿脉和尖晶石置换，形成了矿穴和矿脉。相同的与碱熔体相关的交代作用导致了Cpx-L和OWB1 地幔异种岩和Cpx-M异种晶。这些异质岩中cpx的痕量元素含量显示出一个向下凹的REE模式，具有HFSE耗尽，与Pannonian盆地的cpx大型晶体和Eifel的脉状cpx非常相似。相比之下，OWB2 异质岩显示出从俯冲相关的铁镁质熔体到超镁铁质熔体的沉淀证据，这是从富含opx的岩性和不常见的富含Cr的尖晶石推断出来的。它们可能与白垩纪晚期的俯冲岩浆作用有关。

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