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邹平盆地中生代火山岩可分为三个亚组:中、下亚组具有相似的岩石组合,岩性主要为玄武岩—粗面玄武岩—玄武质粗面安山岩—粗面安山岩;上亚组岩性主要为粗面安山岩。火山岩由早期基性向晚期中偏碱性方向演化,与正常岩浆房酸度增高的岩浆分异趋势相同。具有 Rb、Ba、Sr 等大离子亲石元素(LILE)和轻稀土元素(LREE)富集,Nb、Ta、Ti 等高场强元素(HFSE)相对亏损,类似于岛弧火山岩的地球化学特征。Nb/La、Hf/Sm 比值随 MgO 的降低而升高或基本不变,说明高场强元素亏损是岩浆的原始特征。各亚组火山岩相似的稀土配分模式和微量元素蛛网图,表明它们具有共同的岩浆源区和密切的成因联系,分离结晶起了关键性作用。La/Nb、La/Ta、Ba/Nb 比值较高,说明成岩物质可能主要来自岩石圈地幔。拆沉的大陆中、下地壳部分熔融形成的熔体与古生代岩石圈地幔(亏损的地幔橄榄岩)的相互作用是岩石圈地幔富集的重要方式,随之该富集地幔在陆内岩石圈伸展和区域热异常的双重作用下发生减压部分熔融而形成具有岛弧特征的邹平盆地火山岩。
The Mesozoic volcanic rocks in the Zouping basin can be divided into three subgroups: the middle and lower subgroups have similar rock assemblages, and the lithologies are mainly basalt-rough basalt-basaltic anagrasite-coarse andesite; the lithologies of the Upper Sub-group are mainly Rough andesite. The volcanic rocks evolve from the early basic to the late alkaline, and have the same differentiation trend with the magmatic chamber with increasing acidity in the normal magmatic chamber. (LILE) and LREE enrichment of Rb, Ba and Sr, relative depletion of high field strength elements (HFSE) such as Nb, Ta and Ti, similar to the geochemical characteristics of island arc volcanic rocks . The ratio of Nb / La and Hf / Sm increases with the decrease of MgO or does not change, indicating that the loss of high field strength elements is the original feature of magma. The similar patterns of REE and trace element cobweb in each sub-group of volcanic rocks show that they share a common magmatic source and are closely related to each other. Separation crystallization plays a key role. La / Nb, La / Ta, Ba / Nb ratio is higher, indicating that diagenetic material may be mainly from the lithospheric mantle. The interaction between the melt formed by the partial melting of the lower crust and the Paleozoic lithospheric mantle (depleted mantle peridotite) in the de-sinking continent is an important means of enrichment of the lithospheric mantle, followed by enrichment of the mantle in the intracontinental lithosphere Under the dual action of extension and regional thermal anomalies, the depressurization partially melts to form the Zouping basin volcanic rocks with island arc characteristics.