Generation and modification of large-scale post-tectonic batholiths (Donkerhuk granite; Namibia): Incremental growth vs in-situ differentiation

研究了纳米比亚大面积未变形后构造花岗岩的主微量元素和放射性成因同位素（Sr、Nd、Pb，后者由酸浸Kfs获得）组成；Donkerhuk花岗岩现有数据不完整，但已发表的主要元素和微量元素变化表明，花岗岩的不同亚型可能起源于不同的来源，并经过不同的过程演化。另一方面，不同的亚型也可能是较大的孤立岩浆批次在地分异的结果。新的结果将限制邻近的南、中部达马拉造山带下地壳结构可能的非均质性，并可用于区分二级过程（例如，有或没有分离结晶的地壳污染，岩浆混合？）和一级过程（例如，不同地壳源的部分熔融，壳幔耦合演化）。该项目旨在了解在原有大陆地壳重组和再加工的时候复杂的地壳过程。这些火成岩过程是各种地壳源的动态熔融的指纹，因此非常适合于增加一般的地壳动力学知识。

The proposed project deals with the major and trace element and radiogenic isotope (Sr, Nd, Pb; the latter obtained on acid-leached Kfs) composition of a large-scale apparently undeformed post-tectonic granite in Namibia; the Donkerhuk granite. Available data are incomplete but published major and trace element variations suggest that the various subtypes of granite may have originated from distinct sources and evolved through different processes. On the other hand, the possibility exists that the various subtypes resulted from in-situ differentiation of larger isolated magma batches. The new results will place constraints on possible heterogeneities of the crustal structure beneath the adjacent southern and central Damara orogen and can be used to distinguish second-order processes (e.g., crustal contamination with or without fractional crystallization, magma mixing?) from first-order processes (e.g., partial melting of diverse crustal sources, coupled crust-mantle evolution). The project aims at understanding complex crustal processes at a time where pre-existing continental crust is re-organized and re-processed. These igneous processes are fingerprints of the dynamic melting of diverese crustal sources and is therefore ideally suited to add knowledge on crustal dynamics in general.