The Petrological Characteristics And Tectonic Significance Of The Mesozoic Volcanic Rocks In Zhongzhuangpu, Hunyuan, Shanxi Province

Zhongzhuangpu Hunyuan area holds the most complete successions of the Mesozoic volcanic rocks strata known inis northeast Shanxi Province region. By do geological field survey,taked outcrop section measurement,collected fresh wet sample personally, and studying volcanic petrographic characteristics, combined with major elements, trace elements, rare earth elements and other geochemical characteristics, intending to made deep research on characteristics、 sources、forming tectonic environment、dynamic background of magma Mesozoic volcanic rocks in Zhongzhuangpu, Conclusions are drawn as follows:1.The volcanic rocks were formed began in late Middle Jurassic period, and ended before the late Early Cretaceous period, forming four volcanic eruption cycles. In each cycle, with a evolution characteristics of transition from alkaline intermediate-basic series to calc-alkaline acidic series, the eruption and flooding facie of the volcano rocks earlier, and the explosive facie of the pyroclastic rocks later.2. The major elements characteristics shows that the Mesozoic volcanic rocks in Zhongzhuangpu are mainly a series of metaluminous and shoshonite rocks, only some are high-K calc-alkaline series. The more acidic in volcanic rocks, the less alkalinity, showing a transition of alkaline to calc-alkaline serizes.3. By comparing with Tadi and Taibai Mountains of Lingqiu、Jiugaoshan of Zuoyun, I found that the volcanic rocks in different at same time show similarities in major elements、trace elements、rare earth element. Their rare earth elements distribution patterns and trace elements spider diagram type are rightist and nearly parallel, reflecting that the volcanic magma sources and magmatism in different areas are allied. Because of the crustal contamination, in Early Zhangjiakou in Lower Cretaceous, the volcanic rocks in Qiangfengling Member are riched in LILEs like Rb、Ba, while are poor in HFSEs like Nb、Y. However, in Later Zhangj iakou in Lower Cretaceous, because of the separate crystallization of plagioclase in magmatism, the volcanic rocks rare earth elements distribution patterns shows Eu negative anomaly. The basalts in Early Zhangj iakou。 Later Yixian in Zhongzhuangpu and Jiugaoshan Zuoyun, the ratio of characteristic elements such as Th/Ta, Ta/Hf, Nb/Zr reflecting that the Mesozoic volcanic rocks in northeast of Shanxi formed in an intraplate extensional environment.4. The Mesozoic volcanic rocks in Zhongzhuangpu formed the village shop area volcanic rocks controlled by the subduction of paleo-Pacific Plate to Eurasian Plate, crust-mantle contamination can be found in Zhongzhuangpu area in Later Jurassic and Early Cretaceous Later Mesozoic. Rifting occurred in the region of Zhongzhuangpu hunyuan by tensile stress. In Early Middle Jurassic continental gravel pile up in faulted basin rift initially, with the further strengthening of the extension, magma erupted activity along the margin of the basin. Finally, the magma in the formation of four volcanic eruption cycles, which mainly contains alkaline intermediate-basic series magma with flowing facies in early, and mainly contains calc-alkaline acidic series magma with explosive facies in late stage.