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沂沭断裂带内高桥盆地早白垩世火山岩SiO_2含量为51.97%~68.94%,由玄武粗安岩、粗面岩和流纹岩组成,都属于碱性岩。岩石富集Rb、Ba、K等大离子亲石元素和轻稀土元素,相对亏损Nb、Ta、Ti等高场强元素和重稀土元素,并具有富集的Sr-Nd-Pb同位素组成。钾质粗面岩具有高稀土Cr、Ni含量、La/Yb、Sr/Y和Th/U高比值,这类似于华北克拉通东南缘早自垩世富集岩石圈来源的基性岩(如方城玄武岩、沂南辉长岩),其可能主要来源于富集岩石圈地幔部分熔融。与之相比,钠质玄武粗安岩具有低Cr、Ni含量、~(87)Sr/~(86)Sr(t)、Th/U和高ε_(Nd)(t)值,表明它可能由岩石圈地幔熔体与软流圈物质混合而成。沂沭断裂带高桥盆地火山岩形成于岩石圈伸展背景下,沂沭断裂带的活动可能诱使软流圈物质的上涌,导致岩石圈地幔升温发生部分熔融,并为软流圈物质的上升提供了通道。
In the Yishu fault zone, the Early Cretaceous volcanic rocks in the Takahashi Basin contain 51.97% -68.94% SiO 2, which are composed of basaltic rocks, basaltic rocks and rhyolite. The rocks are enriched in large ion lithophile and light rare earth elements, such as Rb, Ba and K, and relatively depleted in high field strength elements such as Nb, Ta and Ti and heavy rare earth elements, and have enriched Sr-Nd-Pb isotopic composition. Potassium-rich facies have high ratios of Cr and Ni, La / Yb, Sr / Y and Th / U, which are similar to those derived from the Early Cretaceous lithosphere derived from the southeastern margin of North China Craton Fangcheng basalt, Yinan gabbro), which may be mainly derived from enrichment lithospheric mantle partial melting. In contrast, Na-basaltic sorbite has low Cr and Ni contents, ~ 87 Sr / 86 Sr, t / U and high ε Nd values, indicating that it may By the lithospheric mantle melt and asthenospheric material mixture. Yishu fault zone Takahashi Basin volcanic rocks formed in the lithospheric extension of the background, the Yishu fault zone activity may induce the asthenospheric upwelling, resulting in lithospheric mantle warming partial melting, and asthenospheric material rise Provided access.