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本文研究了渤海湾黄骅盆地早白垩世基性-中性-酸性火山岩和第三纪基性火山岩的元素和Sr-Nd同位素地球化学特征。早白垩世火山岩以碱性系列为主,不同基性程度的岩石具有一致的富集Sr、Ba、K、Rb等大离子亲石元素,强烈亏损Nb、Ta、Zr等高场强元素,轻重稀土强烈分异,Sr-Nd同位素组成与EMⅠ相似,Sr同位素初始比高于方城玄武岩和汉诺坝基性麻粒岩。主量和微量元素分析表明,酸性火山岩主要来自于地壳重熔,基性火山岩具有板片流体/熔体交代富集的特征,二者的岩浆混合作用可能是中性火山岩的成因,它们共同构成了东北亚晚中生代活动大陆边缘岛弧火山岩的一部分。第三纪基性火山岩以碱性系列为主,弱富集大离子亲石元素和Ti,不亏损Nb、Ta等高场强元素,Zr呈弱亏损,Sr-Nd同位素组成显示呈亏损型,亏损程度低于碱锅玄武岩和汉诺坝玄武岩,但总体与OIB相似,表明岩浆源区为软流圈地幔,并且高热上涌的软流圈对上部带有俯冲带印记的岩石圈地幔的萃取可能是导致弱富集的原因。从早白垩世的岛弧环境到第三纪陆内裂谷盆地,其控制因素可能归咎于东北亚东侧大洋板块的俯冲和相互转换。法拉隆板块于晚中生代向东北亚俯冲,但晚白垩世时被伊佐奈崎与北新几内亚板块取代,后两者之间的洋脊俯冲引起的“板片窗”效应,导致了渤海湾地区裂谷盆地的发育和同期软流圈地幔来源的玄武质火山活动。
In this paper, the elemental and Sr-Nd isotope geochemical characteristics of the Early Cretaceous basic-neutral-acidic volcanic rocks and Tertiary basic volcanic rocks in the Huanghua Basin, Bohai Bay, are studied. Early Cretaceous volcanic rocks are mainly alkaline series. Rocks of different basicity have the same enrichment of large ion lithophile elements such as Sr, Ba, K, Rb, etc., which strongly deplete high field strength elements such as Nb, Ta and Zr, The REEs are highly heterogeneous with Sr-Nd isotopic composition similar to that of EMⅠ, and the initial Sr isotope ratios are higher than those of Fangcheng basalts and Hannuoba basal granulites. The analysis of major and trace elements shows that the acidic volcanic rocks mainly come from the remelting of the crust and the basic volcanic rocks have the characteristics of sheet fluid / melt exchange enrichment. The magmatic mixing of the two may be the origin of the neutral volcanic rocks, which together constitute Part of the arctic volcanic rocks of continental margins in the Mesozoic Late Mesozoic activities in Northeast Asia. The Tertiary basic volcanic rocks mainly consist of alkaline series. They are weakly enriched in large ion lithophile elements and Ti, high loss field elements such as Nb and Ta are not depleted, Zr is weakly depleted, and Sr-Nd isotopic compositions show a depletion pattern. The degree of depletion is lower than that of alkali basalt and Hannoba basalt but generally similar to that of OIB, indicating that the magmatic source area is an asthenospheric mantle, and the asthenospheric upwelling asthenospheric mantle extraction from the upper lithospheric mantle May be the reason leading to weak enrichment. From the Early Cretaceous island arc environment to the Tertiary intracontinental rift basin, the controlling factors may be attributed to the subduction and interconversion of the oceanic plates in the eastern part of Northeast Asia. The Failailong plate subducted northeast Asia in the late Mesozoic, but was replaced by the Izumisaki and Neo-Guinea plates during the Late Cretaceous. The “slab window” effect caused by the subduction of the ridge between the two resulted in the Bohai Bay Regional rift basin development and basaltic volcanic activity from asthenospheric mantle.