南极底流活动对中印度洋海盆沉积物稀土元素超常富集的制约

The REY-rich deep-sea sediments is a newly discovered potential undersea rare earth resources. But the enrichment mechanism of REY remains elusive, so it is significant to carry out relevant research for its distribution understanding, resource potential evaluation and exploration target delineation. Based on the research results, a scientific hypothesis was presented as following: the Antarctic bottom water is the key factor for the enrichment of REY in REY-rich deep-sea sediments. To confirmed or falsified this hypothesis, the changes of REY-rich phases and Antarctic bottom water of newly discovered REY-rich deep-sea sediments in Central Indian Ocean Basin will be studied through petrography, geochemistry, isotope and geochronology. And this research will determine the relationship between Antarctic bottom water and REY-rich phases, reveal the effects of REY enrichment mechanism and lay the foundation for REY mineralization and exploration in the ocean.

深海富稀土沉积是近几年来发现的一种新型潜在海底稀土资源。目前此类沉积物中稀土元素超常富集的机制尚不清楚。开展深海富稀土沉积的富集机制研究对于认识其分布规律和资源潜力评价及勘探靶区圈定具有重要意义。本项目基于前期的初步研究提出一个科学假设：即南极底流活动是深海富稀土沉积物中稀土元素超常富集的重要因素，其要点包括，富稀土沉积物中稀土元素的富集相和沉积物记录的南极底流强度演化规律。本申请以我国发现的中印度洋海盆富稀土区沉积物为研究对象，拟采用岩相学、地球化学、同位素和年代学等方法开展综合研究，在阐明全岩沉积物稀土元素的富集相随时间的变化规律和南极底流强度演化规律耦合关系的基础上，证实或证伪上述假设，以揭示深海稀土富集机制，为阐明深海富稀土沉积资源成矿规律以及深海找矿勘探提供依据。

针对我国发现的中印度洋海盆富稀土沉积物，通过精细的岩相学、地球化学、同位素和年代学等结果的综合分析，查明了富稀土沉积物中的稀土元素主要是由其内的稀土元素富集相（主要为生物磷灰石，其次微结核）在沉积物-海水界面处从海水中捕获的。刻画了早成岩作用驱动下富稀土沉积物中稀土元素在流体-富集相之间的迁移规律；确定了在于低沉积速率“阈值”的条件，南极底流可通过控制鱼牙磷灰石和微结核含量进一步影响富稀土沉积物的形成。研究结果为深海富稀土沉积的找矿勘探提供依据。