Petrogenesis of the Late Yanshanian mantle-derived intrusions in southeastern China: Response to the geodynamics of paleo-Pacific plate subduction
Petrogenesis of the Late Yanshanian mantle-derived intrusions in southeastern China: Response to the geodynamics of paleo-Pacific plate subduction
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DOI：
10.1016/j.chemgeo.2011.09.014
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发表时间：
2012-10
期刊：
影响因子：
3.9
通讯作者：
Zhenyu He;Xi‐sheng Xu
中科院分区：
文献类型：
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作者：
Zhenyu He;Xi‐sheng Xu
通过对中国东南沿海地区几个燕山晚期正长岩和辉长岩的锆石U-Pb年龄、Hf同位素组成、全岩元素和Sr-Nd同位素组成的研究，确定了它们的源区和构造环境。系统的LA-ICP-MS锆石U-Pb定年结果表明，它们可分为两个主要阶段：早期阶段（141- 118 Ma）和晚期阶段（98- 86 Ma），分别对应于区域上、下火山岩系。早期的正长岩和辉长岩中夹有大量的流纹质和英安质火山岩和少量的花岗岩。它们的母岩浆来源于俯冲沉积物质交代的富集地幔。晚期正长岩主要以破火山口中心侵入体的形式产出，其时代与伴生的火山岩接近，形成与破火山口有关的火山-侵入环杂岩。它们是由亏损的软流圈熔体和与俯冲有关的富集地幔熔体之间的岩浆混合产生的。研究表明，燕山晚期中国东南地区构造环境由挤压环境向拉张环境转变，对应于110 Ma左右古太平洋板块由前向俯冲向后向俯冲的转变。
Several Late Yanshanian syenitic and gabbroic rocks from the coastal area of southeastern (SE) China have been studied to determine zircon U–Pb ages and Hf isotopic compositions as well as whole-rock elemental and Sr–Nd isotopic compositions to constrain their sources and tectonic settings. The systematic LA-ICP-MS zircon U–Pb dating results indicate that they can be divided into two main stages: the early stage (141–118Ma) and the late stage (98–86Ma), which temporally correspond to the regional lower and upper volcanic series, respectively. The early stage syenitic and gabbroic rocks are accompanied by vast rhyolitic and dacitic volcanic rocks with minor granites. Their parental magma was derived from an enriched mantle metasomatized by subducted sedimentary materials. The late stage syenitic rocks mainly occur as the central intrusion of the caldera with ages close to the accompanied volcanics, forming a caldera-related volcanic-intrusive ring complex. They were produced by magma mixing between depleted asthenosphere melts and subduction-related enriched mantle melts. It is suggested that the Late Yanshanian tectonic settings of SE China transformed from a compressional environment to an extensional environment, corresponding to the transformation from forward to rollback subduction of the paleo-Pacific plate at approximately 110Ma.