碳酸盐化霞石岩岩浆成矿效应的实验研究

Carbonatites and the products of their surface weathering constitute the main source of strategic metals, such as REE and Nb, thus has improtant significance for economy and society. Although most of researchers believe that carbonated nephelinite is the parental magma for mineralized carbonatite, the mechamism by which rare metal elements were highly concentrated is not clear. This study propose to experimentally study the differentiation of carbonated nephelinite, and discuss the phase equilibria in crustal chambers. We will focus on the conditions triggering fractional crystallization versus liquid immiscibility, evolution processes of immiscible emulsion and cumulus minerals, and the effect of other ligands on the partitioning of rare metals between the immiscible carbonatitic and nephelinitic melts. The ultimate aim of this study is to seek the key conditions for the mineralization of strategic metal in carbonatite and understand the formation mechanism, and establish the indicators for such mineralization, and also to provide fundamental information for both theory and mineral exploration.

碳酸岩及其风化产物是全球战略性关键金属，特别是REE与Nb的主要来源，从而具有重要的经济价值和社会意义。虽然大家公认碳酸盐化霞石岩岩浆是成矿碳酸岩的母岩浆，但是导致REE和Nb等稀有金属元素在碳酸岩中超常富集的机理并不清楚。本申请拟通过对碳酸盐化母岩浆的演化过程进行实验岩石学研究，探讨其在地壳岩浆房内的相平衡关系。重点关注分离结晶和液态不混溶各自发生的条件，岩浆房内不混溶乳浊液和堆晶矿物的演化过程，以及其他配体对于稀有金属元素在不混溶硅酸盐-碳酸盐熔体之间分配系数的影响。最终的目的是从本质上找到控制碳酸岩中关键金属成矿的苛刻条件，理解其形成机制，构建找矿标志，为寻找与碳酸岩相关的关键金属提供重要理论基础和直接的找矿信息。

本项目通过对关键科学问题的梳理，为了深入和全面调查碳酸盐化霞石质岩浆在地壳内的相关系以及演化过程。在研究过程中，以传统的地质学为基础，利用实验岩石学为主要手段，结合传统岩石学和地球化学等方法，揭示碳酸岩的母岩浆的产生和演化等过程和物理化学条件及其对矿床的控制机理，并取得了系统性研究进展。项目取得了一系列重要研究成果，其中已发表的成果包括：1）总结了与成矿碳酸岩相关的实验岩石学进展；2）碳酸岩的母岩浆在地壳条件下，岩浆在经历分离结晶的过程中，含PO43-配体的碳酸岩结晶出的方解石可以富集REE，后期的地质作用可以使得REE释放出来并成矿。相关研究成果发表在地学前缘和Scientific Reports专业内知名刊物上。