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首页> 外文期刊>Geosciences >New Occurrence of Pyroxenites in the Veria-Naousa Ophiolite (North Greece): Implications on Their Origin and Petrogenetic Evolution
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New Occurrence of Pyroxenites in the Veria-Naousa Ophiolite (North Greece): Implications on Their Origin and Petrogenetic Evolution

机译：Veria-Naousa蛇绿岩（北部希腊）中新出现的辉石岩：对它们的起源和成岩演化的影响

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The Veria-Naousa ophiolite represents a dismembered unit in north Greece, which includes variably serpentinised lherzolite and harzburgite, locally intruded by a sparse network of dykes or thin layers of websterite and olivine-orthopyroxenite composition. The websterite and the olivine-orthopyroxenite show abundant petrographic and geochemical evidence (relic olivines with mantle affinities, Cr-rich spinels, low Al 2 O 3 , depletions in incompatible elements, and concave upwards rare earth element patterns) that they comprise replacive bodies from refractory subarc mantle precursors. The occurrence of these pyroxenites in dykes implies that channelled percolation of melts account for their replacive character. High CaO/Al 2 O 3 , low Zr and crystallisation of diopside suggest that a melt of ankaramitic/carbonatitic composition percolated in lherzolite replacing porphyroclastic olivine and forming the pyroxenes in the websterite. At a shallower level, harburgites were impregnated by boninitic melts (inferred by U-shape rare earth element patterns and very rich in Cr spinels) triggering the replacement of porphyroclastic olivine by orthopyroxene for the formation of olivine-orthopyroxenite. These peritectic replacements of olivine commonly occur in a mantle wedge regime. The peculiar characteristics of the Veria-Naousa pyroxenites with LREE and compatible elements enrichments resemble the subarc pyroxenites of Cabo Ortegal implying a similar environment of formation. Whole-rock and mineralogical (spinel and clinopyroxene) compositions are also in favour of a backarc to arc environment. It is recommended that the evolution of the Veria-Naousa pyroxenites record the evolution of the subarc region and the opening of a backarc basin in a broad SSZ setting in the Axios Zone of eastern Greece.
机译：Veria-Naousa蛇绿岩代表了希腊北部的一个被肢解的单位，其中包括各种蛇纹石化的锂铁矿和harzburgite，它们被稀疏的堤坝网络或薄薄的韦斯特石和橄榄石-正辉石组成侵入。韦氏体和橄榄石-原辉石岩显示出丰富的岩石学和地球化学证据（具有地幔亲和力，富含Cr的尖晶石，Al 2 O 3含量低，不相容元素耗尽和向上凹入的稀土元素图案的遗迹橄榄石），它们由难燃弧下地幔前体。这些辉绿岩在堤坝中的存在暗示着熔体的沟道渗滤作用是其替代性特征。较高的CaO / Al 2 O 3，较低的Zr和透辉石的结晶表明，钙钛矿/碳酸盐组合物的熔体渗透到锂铁矿中，取代了卟啉碎石橄榄石，并在辉石中形成了辉石。在较浅的水平上，钙硼榴石被邦尼体熔体浸渍（由U型稀土元素图案推断出，并且富含Cr尖晶石），触发用邻苯二酚代替卟啉碎石橄榄石以形成橄榄石-正火辉石。这些橄榄岩的包晶层替代通常发生在地幔楔形构造中。具有LREE和相容元素富集的Veria-Naousa热解石的独特特征类似于Cabo Ortegal的亚弧热解石，意味着形成环境类似。全岩石和矿物学（尖晶石和斜茂铁）组成也有利于弧后环境。建议Veria-Naousa辉绿岩的演化记录下亚弧区域的演化以及希腊东部Axios区域内SSZ广阔的背弧盆地的开放。

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