Petrology, geochemistry and age of foidites in SW Germany

德国西南部的岩石学、地球化学和福伊岩年龄

• 批准号: 446059916
• 负责人: Privatdozent Dr. Michael Marks
• 金额: --
• 依托单位: Arbeitsgruppe Geologie und Geodynamik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/446059916?language=en
• 关键词: Petrology; geochemistry; age; foidites; SW

Foidites are mantle-derived and strongly SiO2-undersaturated volcanic rocks, with primitive olivine melilitites possibly representing primary magma compositions. Among the Palaeogene volcanic rocks in SW Germany, foidite occurrences are concentrated in seven areas (Kaiserstuhl, Upper Rhine graben, Bonndorf graben including Vosges, Hegau, Urach, Lower Neckar). Mineralogically, they range between olivine melilitites, nephelinites and haüynites, with clear differences between those areas. However, except for the Kaiserstuhl, their petrology has not been systematically investigated and their ages are not reliably constrained. The proposed study will test the following hypotheses: (i) Mineralogical differences of the melilitite-nephelinite-haüynite series at the locations to be investigated relate to variable degrees and courses of magmatic differentiation of parental olivine melilititic magmas. (ii) The intrusion ages for these rocks relate to transient geodynamic settings that cause distinct melting events in the mantle manifested in distinct ages for the different areas to be studied.To test these hypotheses, detailed petrographic and mineral chemical data (EMPA and LA-ICP-MS on minerals) will be combined with petrological modeling (T-aSiO2-fO2 conditions and differentiation paths), isotope geochemical (Sr-Nd-Pb) and geochronological data (LA-ICP-MS dating). The expected results will enable us to characterize the crystallization conditions and differentiation paths for the foidites at the different localities. Their comparison with each other will help to decipher potential genetic relations between the foidite types of each locality and will show if the courses of differentiation at the different localities are similar or different from each other. Such a comparative study has never been performed so far and the results are expected to have major implications on our understanding on the potential heterogeneity of the mantle domains below SW Germany. The results of this study will be integrated in recent models on the post-Variscan tectonic evolution in SW Germany.

富伊德岩为幔源性强sio2欠饱和火山岩，原始橄榄石千粒岩可能代表原始岩浆成分。在德国西南部的古近系火山岩中，福伊特岩主要赋存于Kaiserstuhl、Upper Rhine地堑、Bonndorf地堑（包括Vosges、Hegau、Urach、Lower Neckar）等7个地区。在矿物学上，它们介于橄榄石千粒岩、钠云母岩和haynite岩之间，在这些区域之间有明显的差异。然而，除了Kaiserstuhl外，它们的岩石学还没有被系统地研究过，它们的年龄也没有可靠的限制。拟议的研究将检验下列假设：(i)待调查地点的千英石-钠云母石-海<s:1>云母岩系列的矿物学差异与母橄榄石千英石岩浆的不同程度和不同过程有关。（ii）这些岩石的侵入年龄与瞬态地球动力学背景有关，这些背景导致不同的地幔熔融事件，在不同的研究区域表现为不同的时代。为了验证这些假设，详细的岩石学和矿物化学数据（矿物的EMPA和LA-ICP-MS）将与岩石学模拟（T-aSiO2-fO2条件和分化路径）、同位素地球化学（Sr-Nd-Pb）和地质年代学数据（LA-ICP-MS测年）相结合。预期的结果将使我们能够表征不同位置的软质岩的结晶条件和分化路径。它们之间的相互比较将有助于破译每个地方的foidite类型之间潜在的遗传关系，并将表明不同地方的分化过程是相似还是不同。到目前为止，还没有进行过这样的比较研究，预计结果将对我们对德国西南部地幔域潜在异质性的理解产生重大影响。该研究结果将被整合到最近的德国西南部后瓦里斯坎构造演化模型中。