Review of Rare Earths and Fluid-Rock Interaction
摘要
As demonstrated by a great amount of geologic and experimental evidences, RE of rock systems may be mobilized during fluid-rock interaction when solutions are rich in F-, Cl-, CO32-, HCO3-, CO2, HPO42-, HS-, S2-, SO42-, though little has been known about the mobilizing mechanism of these anions or ligands. The fractionation of RE resulted from hydrothermal alterations, i. e., fluid-rock interactions, are distinctive. One set of field data implies the preferential mobility of the LRE, while another set of field observations demonstrates the dominant mobilization of the HRE, and some theoretical prediction is not consistent with the field evidence. The Eu anomalies caused by fluid-rock interaction are complex and compelling explanation is not available due to inadequate experimental approaches. To know the exact behavior of RE during fluid-rock interaction and to solve the contradiction between some theoretical predictions and field observations, the following works remain to be done: (1) experimental investigations of RE mobility and fractionation as a function of fluid chemistry, e.g., the activity of F-, Cl-, CO32-, HCO3-, CO2, HPO42-, HS-, S2-, SO42-, etc.; (2) experimental determination of RE mobility and fractionation as a function of T, P, pH, Eh and water/rock ratios; (3) investigation of the mechanism and the controlling factors of RE partitioning between hydrothermal minerals and fluids. It was demonstrated that RE mobility is a potentially useful method for exploration.