早-晚古生代地幔DUPAL组成演变与特提斯域陆块北向汇聚机制

地球上存在非洲和太平洋两个巨大的地震波低速异常省（LLSVPs），其540Ma内在地球上的位置没有变化。古特提斯洋在晚古生代曾位于非洲LLSVP之上，其软流圈地幔呈现极端高的DUPAL同位素组成特征（称之为DUPAL异常峰），暗示出非洲LLSVP与DUPAL异常、特提斯离散可能的成因联系，但早古生代的原特提斯地幔是否也存在DUPAL仍不清楚。本项目聚焦尚无相关数据的早古生代蛇绿岩，并对比晚古生代-中生代特提斯蛇绿岩，在剔除弧组分或地壳混染基础上，对能反映软流圈地幔成分的MORB型和OIB型基性岩及单矿物采用ΔεHf(P/I)i-ΔεNd(P/I)i同位素共变体系和Δ8/4-7/4Pb同位素体系共同揭示“DUPAL异常峰”的时间范围和演变趋势，阐明DUPAL异常与长期存在的LLSVP内在关联，论证非洲LLSVP深部物质上涌是特提斯域陆块北向汇聚的驱动力，更好地理解地幔对流的工作机制。

Two Large Low Shear Velocity Provinces (LLSVPs) have been existing beneath Africa and the Pacific ocean, which remains nearly stationary from 540Ma within Earth's mantle. Palaeogeographic study indicate the most regions of Paleo-Tethyan ocean occupied above the Africa LLSVP, coincidentally, an extreme DUPAL isotopic compositions (we called the "DUPAL peak") have been found in the Paleo-Tethyan suboceanic mantle, which hints the Africa LLSVP and the Tethyan DUPAL anomaly may have an intimate relationship with Gondwana continental blocks northward aggregation, however, whether the early Paleozoic Proto-Tethyan mantle has DUPAL anomaly is still ambiguous. This project will mainly focus on the early Paleozoic Tethyan ophiolites with not any DUPAL relevant data reported , comparing with the late Paleozoic-Cenozoic Tethyan ophiolites, to analyze the high precision Pb-Hf-Nd isotopic data of whole rock and mineral separates from MORB- and OIB-type mafics in these ophiolites, and avoid the mantle potentially influenced by arc or crustal materials, finally we use the ΔεHf(P/I)i-ΔεNd(P/I)i andΔ8/4-7/4Pb parameter to constrain the DUPAL peak distribution and evolution with the time, aim to reveal the inherent relationship between the DUPAL peak and LLSVPs, which will document the intrinsic relations between the LLSVP and northward aggregation of the continent blocks within Tethyan tectonic domain. This project will lead to better understand evolution and deep processes of the Tethyan mantle system.