Investigating potential rare earth element (REE) resources and exploring feasible deposits have facing significant challenges.

As well known, fish teeth as potential proxies from deep-sea sediments are the most REE-rich materials in the world. However, the REE enrichment mechanism and the reliability of this tracer are unclear.

Under the guidance of Prof. GUO Qingjun at the Institute of Geographic Sciences and Natural Resources Research of Chinese Academy of Sciences, Dr. DENG Yinan found two distinctive REE took place in the seafloor and deeper subsurface sediments respectively.

“The difference of benthic flux to the REE between the shallow marine realm and deep-sea is significant. REE-rich fish teeth are resulted from the diagenetic REE-uptake from the porewater”, said Dr. DENG.

Analyzing high-resolution geochemical data the team presented that fish teeth in marine contained a great deal of worthy information. They reconstructed REE enrichment mechanism based on deep-sea REE cycling.

This study revealed that fish teeth exposed to pore water had higher adsorptive capacity. It is mainly from the root part from the surrounding pore water absorbed abundant REE during early diagenesis.

“The REE geochemistry of fish teeth has been traditionally regarded as a robust proxy for reconstructing ancient seawater chemistry”, Prof. GUO said.

“However, by analyzing high-resolution of the rare earth elements and yttrium (REY) data of pore water, bottom water and fish teeth, we found that the depth distribution of REEs in pore water is opposite to that of fish teeth. REE patterns and Nd isotopic compositions are not uniformly distributed within fish teeth”, he added.

The study indicated alteration of REEs and Nd isotopic compositions during early diagenesis. Moreover they concluded that REEs from fish teeth are not robust recorders in the deep marine environment throughout Earth’s history. This work was published in Science Advances on June 22.

The study was conducted in collaboration with Guangzhou Marine Geological Survey, Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Yunnan University, Tianjin University and Sun Yat-sen University.