Nature of mantle source contributions and crystal differentiation in the petrogenesis of the 1.78 Ga mafic dykes in the central North China craton
Nature of mantle source contributions and crystal differentiation in the petrogenesis of the 1.78 Ga mafic dykes in the central North China craton
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DOI：
10.1016/j.gr.2006.10.022
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发表时间：
2007-08
影响因子：
6.1
通讯作者：
P. Peng;M. Zhai;Jing-hui Guo;T. Kusky;T. Zhao
中科院分区：
文献类型：
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作者：
P. Peng;M. Zhai;Jing-hui Guo;T. Kusky;T. Zhao
华北克拉通中部约1.78 Ga的基性岩墙群和一些同时代的火山岩组合构成了一个大火成岩省。第一代岩墙侵入于约1000年。1780 Ma，可划分为3组：LT组为辉长岩，具有低Fe-Ti含量，为母岩浆; NW组为高Fe-Ti含量，具有富铁趋势的粗粒岩; EW组为粗粒岩-安山岩，由残余硅质液体结晶而成，具有富硅趋势。它们具有EM-Ⅰ型源区，记录了完整的岩浆过程。这些包括岩石圈物质的污染和地壳熔体的同化，在岩浆房（LT组）和岩浆通道（NW组）中的分离结晶，甚至与额外的蚀变（EW组）。第二代是稍微年轻（约。1760 Ma），几乎没有分布。其铁、钛含量较高，为DM型和EM-I型混合物源。这些岩墙可能与古地幔柱有关：第一代代表从地幔柱头部产生的下地幔熔体，而第二代记录了由地幔柱尾部夹带的软流圈熔体。
Circa 1.78 Ga mafic dyke swarms and some coeval volcanic associations constitute a Large Igneous Province in the central North China craton. The 1st generation of dykes intruded at ca. 1780 Ma and is chemically delineated into 3 groups: the LT Group is gabbroic and has low-Fe–Ti contents, acting as parental magma; the NW Group is high in Fe–Ti-contents and doleritic with an iron-enriched trend; whereas the EW Group is doleritic to andesitic and crystallized from relict siliceous liquids with a silica-enriched trend. They have an EM-I type source and record integral magmatic processes. These include contamination of lithospheric material and assimilation of crustal melts with in-situ crystallization in a magma chamber (the LT Group) and fractional crystallization in magma channels (the NW Group) and even with additional alteration (the EW Group). The 2nd generation is slightly younger (ca. 1760 Ma) and scarcely distributed. It has high-Fe–Ti contents, originated from a mixing source of DM and EM-I types. The dykes could be associated with a palaeo-plume: the 1st generation represents lower mantle melts generated from the plume head, whereas the 2nd generation records extra melts from asthenosphere entrained by the plume tail.