华南西南段基性火成岩Sr-Nd-Hf-Os同位素研究及其对加里东运动构造属性的约束

Controversies about the Caledonian orogenic affinity in the South China Block (SCB) mainly concentrate on the intracontinental orogeny and subduction-collisional orogeny. However, there is an intimate relationship between the orogenic mechanisms and deep mantle geodynamics. The Early Paleozoic mantle-derived igneous rocks will provide constraints on the Caledonian orogenic affinity from the deep mantle dynamic mechanism. This project will focus on Early Paleozoic mafic rocks from the southeastern-northern part of the Guangxi Province, southwestern SCB. We plan to present major and trace elements and Sr-Nd-Hf-Os isotope compositions of whole-rock and mineral separates in mafic rocks to constrain the mantle source attributes. Moreover, these information combined with the detailed geochronology will aim at 1) to identify the magmatism derived from asthenosphere mantle during Early Paleozoic in the SCB; 2) to constrain the time difference between the mafic rocks derived from asthenospheric and lithospheric mantle (or crust-derived granites), which in turn provide stringent constrains on the Caledonian orogenic affinity through the comparison between these two kinds of mantle-derived mafic rocks. This project will lead a better understanding of the Caledonian orogenic affinity of the SCB as well as the background of deep mantle geodynamics in Early Paleozoic.

华南加里东运动构造属性存在陆内造山和俯冲-碰撞造山的争议，然而不同的造山机制与深部地幔动力学过程具有成因联系，华南早古生代幔源火成岩为从深部地幔动力学机制方面理解加里东运动构造属性提供了制约。本项目拟选择华南西南段桂东南-桂北基性火成岩，对其进行全岩和单矿物主微量元素及Sr-Nd-Hf-Os同位素研究，识别基性岩地幔源区属性，结合基性岩精细年代学研究，本项目试图揭示:(1)华南早古生代是否存在软流圈地幔来源岩浆作用；(2)在时间尺度上识别软流圈地幔来源与岩石圈地幔来源基性岩(或壳源花岗岩)是否存在时代差异，其对比研究是约束加里东构造属性的关键所在。本项目将为理解华南加里东运动构造属性和早古生代深部地球动力学背景提供重要的科学依据。

华南加里东运动构造属性存在陆内造山和俯冲-碰撞造山的争议，然而不同的造山机制与深部地幔动力学过程具有成因联系，华南早古生代幔源火成岩为从深部地幔动力学机制方面理解加里东运动构造属性提供了制约。本项目选择了华南西南段桂东南-桂北基性火成岩，对其进行了全岩和单矿物主微量元素及Sr-Nd-Hf同位素研究，识别了基性岩地幔源区属性，结合基性岩的精细年代学研究，本项目揭示了华南早古生代是否存在软流圈地幔来源岩浆作用；在时间尺度上识别软流圈地幔来源与岩石圈地幔来源基性岩(或壳源花岗岩)是否存在时代差异，为理解华南加里东运动构造属性和早古生代深部地球动力学背景提供了重要的科学依据。此外，本项目在前人对华南西南段地球化学和同位素年代学研究的基础上，重点选择了华南西南段桂东南和桂北中生代幔源基性岩和花岗岩为研究对象，在对基性-酸性火成岩进行全面野外地质调查的基础上，开展了细致的岩石学、年代学、地球化学和Sr-Nd-Hf多元同位素体系的系统性研究，为整个华南中生代构造属性提供了新的思路。