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同位素测年数据显示 ,徐宿地区的辉绿岩床是震旦纪早期和震旦纪晚期两次侵入的产物。岩床多呈板状或楔状 ,为超浅成—浅成侵入体 ,其化学成分以高SiO2 、CaO和低Al2 O3、MgO及(K2 O +Na2 O)为特征 ,属大陆拉斑玄武岩系列。稀土元素配分模式为轻稀土富集型 ,但稀土元素分馏并不强烈。Rb、K、La等不相容元素富集 ,而Nb、Sr亏损明显。δ18O值在 6 6 3‰～ 9 93‰之间 ,多数 >8‰。研究表明 ,该区基性岩浆来源于过渡型地幔 ,主要通过部分熔融方式形成 ,在岩浆上侵过程中遭到陆壳或花岗质岩石的混染。
Isotope dating data show that the diabase beds in the Xu area are the result of two intrusions in the early Sinian and Late Sinian. Most of the bedrock is plate-like or wedge-shaped, which is an ultra-shallow into a shallow intrusive body. Its chemical composition is characterized by high SiO2, CaO and low Al2 O3, MgO and (K2 O + Na2 O) and belongs to continental tholei basalt series. Rare earth elements with light rare earth enrichment model, but the rare earth element fractionation is not strong. Rb, K, La and other incompatible elements enrichment, while Nb, Sr loss significantly. δ18O values ranged from 6 6 3 ‰ to 9 93 ‰, with a majority of> 8 ‰. The study shows that the mafic magma originates from the transitional mantle and is mainly formed by partial melting, which is contaminated by continental crust or granitic rocks during the process of magmatic intrusion.