Consequences of variable degrees of crustal contamination on the phase petrology an halogen budget of plume-related Northern Etendeka effusives and dikes, NW Namibia

近年来，人们对白垩纪Etendeka双峰式大陆溢流玄武岩省的镁铁质-玄武岩进行了大量的常量、微量元素和放射性同位素地球化学研究。例如，在一个实施例中，Ewart等人，2004 a，B）。所有这些岩石都由特里斯坦羽流成分和数量不等的地壳污染物组成。在纳米比亚西北部的北方Etendeka地区，沃尔维斯海岭与大陆地壳相接处，暴露出一系列不同的镁铁质和岩浆泛滥火山岩（米勒，2008年）。众多的粗玄岩脉下方或相交的洪水火山岩，最有可能是时间和化学有关的Etendeka岩石。我们计划使用相岩石学、主要元素、微量元素和稳定（O、S、C）同位素地球化学结合F、Cl和Br的测定，对这些火山岩和相关脉岩进行深入研究。讨论的问题有：（a）沃尔维斯海岭与该区喷溢岩浆作用的时间和岩石学联系;（B）基于QUILF分析的结晶条件;（c）地壳混染对岩石多样性和结晶强度参数的影响;（d）在结晶相组合和结晶强度参数方面从近海到近海和从北到南的空间趋势的分辨率;（e）重建熔融制度，特别侧重于卤素收支（全岩和磷灰石中的F、Cl、Br）和稳定同位素地球化学（硫化物和磷灰石中的S、Cpx和Plag中的O、磷灰石中的C）;（f）通过将卤素记录与同位素和微量元素地球化学进行比较，解决污染机制（下地壳或上地壳中的流体或熔体）。

In the recent years, mafic to silicic rocks belonging to the Cretaceous Etendeka bimodal continental flood basalt province have been intensively studied by means of major and trace element as well as radiogenic isotope geochemistry (e. g., Ewart et al., 2004a, b). All of these rocks are composed of a Tristan plume component and variable amounts of crustal contaminants. In the Northern Etendeka area, NW Namibia, where the Walvis ridge meets the continental crust, a series of different mafic and silicic flood volcanics is exposed (Miller, 2008). A multitude of dolerite dikes underly or intersect the flood volcanics and are most probably temporally and chemically related to the Etendeka rocks. We plan a thorough study of these volcanic and associated dike rocks using a combination of phase petrology, major, trace element, and stable (O, S, C) isotope geochemistry combined with the determination of F, Cl and Br. The questions to be addressed are a) the temporal and petrological connection of the Walvis Ridge and effusive magmatism in this area; b) the conditions of crystallization based on QUILF analyses; c) the effect of crustal contamination on rock diversity and intensive crystallization parameters; d) the resolution of spatial trends from offshore to on-shore and from North to South in the phase assemblages and intensive parameters of crystallization; e) the reconstruction of the melting regime with specific focus on the halogen budget (F, Cl, Br, on whole rocks and apatite) and the stable isotope geochemistry (S on sulfides and apatite, O on Cpx and Plag, C on apatite); and f) the resolution of the mechanism of contamination (by fluids or melts, in the lower or upper crust) by comparing the halogen record with isotope and trace element geochemistry.