Genesis of late Early Cretaceous high-silica rhyolites in eastern Zhejiang Province, southeast China: A crystal mush origin with mantle input
Genesis of late Early Cretaceous high-silica rhyolites in eastern Zhejiang Province, southeast China: A crystal mush origin with mantle input
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DOI：
10.1016/j.lithos.2017.11.026
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发表时间：
2018
期刊：
影响因子：
3.5
通讯作者：
Ji-Heng Zhang;Jin-Hui Yang;Jing-Yuan Chen;Fu-Yuan Wu;S. Wilde
中科院分区：
文献类型：
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作者：
Ji-Heng Zhang;Jin-Hui Yang;Jing-Yuan Chen;Fu-Yuan Wu;S. Wilde
中国东南部大量中生代长英质火山岩和花岗岩为研究地壳岩浆活动在华夏地块东部地壳演化和改造中的作用提供了独特的机会。研究了浙东上火山层序高硅流纹岩的成因及其与同生花岗岩的关系。天台盆地、永康盆地和柳城盆地的流纹岩年龄为早白垩世晚期（111 ~ 106 Ma）。这些岩石含有大量约130 Ma的继承锆石，与该地区下部火山层序的年龄相对应。然而，不同年龄的锆石具有相似的氧和Hf同位素范围，这意味着它们产生的岩浆具有相似性。上层序流纹岩的地球化学特征与下层序流纹岩相似。结论认为，前者是早期岩浆期形成的岩浆浆液经过长石和锆石等副矿物分馏后的再加工而成。分馏发生在岩浆晶体糊状物中，通过间隙熔体的萃取和残余矿物相的积累，以及同时期玄武岩岩浆在地壳底部的侵位。总体而言，中国东南地区火山岩地球化学特征表明，幕式岩浆活动和结晶糊状的改造是推动该地区火成岩演化和地壳结构的重要机制。
Voluminous Mesozoic felsic volcanic rocks and granites in southeastern China provide a unique opportunity for studying the role of crustal magmatism in the evolution and modification of the crust in the eastern Cathaysia Block. The high-silica rhyolites of the upper volcanic sequence in eastern Zhejiang Province were investigated, focusing on their genesis and their relationship with contemporaneous granites. Rhyolites in the Tiantai, Yongkang and Liucheng basins were dated as late Early Cretaceous (from 111 Ma to 106 Ma in age). These rocks contain a large proportion of inherited zircons of ca. 130 Ma, corresponding to the age of the lower volcanic sequence in the area. However, the zircons of different ages have similar ranges of oxygen and Hf isotopes, implying similarities in the magmas from which they were generated. The rhyolites of the upper sequence also resemble those of the lower sequence in terms of their geochemistry. It is concluded that the former were derived by reworking of magma mush formed during the earlier magmatic episode via fractionation of feldspars and accessory minerals, e.g., zircon. Fractionation took place within the magma crystal mush by extraction of interstitial melts and accumulation of residual mineral phases, aided by the emplacement of contemporaneous basaltic magmas at the base of the crust. Overall, the geochemical features of the volcanic rocks in southeastern China indicate that episodic magmatism and reworking of crystal mush were essential mechanisms that drove the evolution of the igneous rocks and the hence crustal architecture in this area.