The role of mantle-crust interaction in the early phases of passive margin development: the case of the Voring Plateau, NE Atlantic

建议对东北大西洋外沃林高原104大洋钻井项目642E孔的岩心进行重新取样和研究。这些岩心记录了东北大西洋早期裂谷期的岩浆活动。孔的底部部分由“下系列”组成，由玄武岩安山岩、过铝堇青石英安岩、流纹岩火成岩和互层火山碎屑单元组成。这个下系列位于一个厚的过渡型中洋脊拉斑岩的“上系列”之下。下系列组合清楚地表明了地幔熔融与地壳物质的相互作用和/或底板的显著地壳熔融作用。该剖面特别适合研究地幔岩浆与地壳的污染，因为地壳成分的化学和同位素特征可以明确地定义。迄今为止，对642E孔火山的研究相当有限。此外，自最初的研究以来，在岩石成因概念和同位素和微量元素分析设备方面也有了一些新的发展。新的研究旨在更好地确定这些地下喷发火山的喷发方式和沉积环境，以揭示喷发和岩浆动力学。将利用ICP-MS研究大量新样品的微量元素组成，利用TIMS和多捕收剂ICP-MS研究Sr，Nd,Hf， pb同位素组成，以确定地幔-地壳相互作用的程度和过程。反过来，这将允许更好地约束（原）冰岛地幔柱中产生的地幔熔体在空间和时间上的内在地球化学异质性。

It is proposed to resample and reinvestigate the drill cores from Hole 642E, Ocean Drilling Program Leg 104, Outer Voring Plateau, NE Atlantic. These cores keep a record of magmatic events dating back to the early rifting phases of the NE Atlantic ocean. The bottom section of the hole is made up of a "Lower Series" consisting of basic dykes and flows of basaltic andesites, peraluminous cordierite-bearing dacites, rhyolitic ignimbrites, and interbedded volcaniclastic units. This Lower Series underlies a thick "Upper Series" of transitional-type mid-ocean ridge tholeiites. The Lower Series assemblage is clearly indicative of interaction of mantle melts with crustal material and/or of significant crustal melting by underplating. The section is particulary suited to study contamination of mantle magmas with crust, because the chemical and isotopic character of the crustal component can be unambiguously defined. The research devoted thus far to the Hole 642E volcanics has been rather limited. Moreover, since the original studies, there have been several new developments in petrogenetic concepts and in analytical facilities for isotopic and trace element analysis. The new studies aim to better define the eruption modes and depositional environment of these subaerially erupted volcanics, in order to shed light on eruption and magma dynamics. A substantial amount of new samples will be studied for trace element composition by ICP-MS and Sr,Nd,Hf,Pb-isotopic composition by TIMS and multi-collector ICP-MS with a view to establish the extent and processes of mantle-crust interaction. This will in turn allow to better constrain the intrinsic geochemical heterogeneity - in space and time - of the mantle melts produced in the (proto-) Iceland mantle plume.