The Heldburg Phonolite, Central Germany: Reactions between phonolite and xenocrysts from the upper mantle and lower crust
The Heldburg Phonolite, Central Germany: Reactions between phonolite and xenocrysts from the upper mantle and lower crust
复制标题
DOI：
10.1016/j.lithos.2013.09.012
复制
发表时间：
2013-12
期刊：
影响因子：
3.5
通讯作者：
Thomas B. Grant;R. Milke;S. Pandey;H. Jahnke
中科院分区：
文献类型：
--
作者：
Thomas B. Grant;R. Milke;S. Pandey;H. Jahnke
德国中部的Heldburg Phonite含有丰富的捕虏体物质碎片，通常被视为单一的橄榄石和斜方辉石包裹体，以及较大的多矿物微捕虏体。捕虏晶和微捕虏体成分指示了两种堆积型烃源岩：一种是含尖晶石的二辉橄榄岩，另一种是富辉石的辉长岩。寄主熔体与包裹体之间的不平衡导致橄榄石上形成金云母-透辉石双缘，斜方辉石上形成角闪石-金云母或角闪石-透辉石双缘。边缘组合和熔体向某些微捕虏体的渗透表明，捕虏体物质是由声岩直接从其源岩中取样的。角闪石和单斜辉石斑晶的温压测定支持了声岩起源于上地幔的观点。因此，反应圈提供了涉及演化的富碱熔体和上地幔和下地壳围岩的交代事件的小规模类似物。边缘内的化学分带和来自宿主的成分特征的遗传表明，边缘生长速度快，成分通过边缘的扩散速度慢。捕虏晶在熔体中的停留时间大约在几个月到一年之间。
The Heldburg Phonolite, Central Germany contains abundant fragments of xenolithic material most commonly seen as single xenocrysts of olivine and orthopyroxene as well as larger poly-mineralic micro-xenoliths. The xenocryst and micro-xenolith compositions indicate two cumulate source rocks; a spinel-bearing lherzolite and a pyroxene rich gabbro-norite. Disequilibrium between the host melt and xenocrysts lead to the formation of phlogopite–diopside double rims on olivine and either amphibole–phlogopite or amphibole–diopside double rims on orthopyroxene. The rim assemblages and infiltration of melt into some micro-xenoliths suggest that the xenolithic material was sampled by the phonolite directly from their source rocks. The idea that the phonolite originated from the upper mantle is supported by thermobarometry of amphibole and clinopyroxene phenocrysts. The reaction rims therefore provide small-scale analogues of a metasomatic event involving an evolved alkali enriched melt and upper mantle and lower crust wall rocks. Chemical zoning within the rims and the inheritance of compositional features from their hosts indicates rapid rim growth rates with slow diffusion rates of components through the rims. Residence times for the xenocrysts in the melt are in the order of several months to a year.