Application prospect of the single-grain mineral Rb-Sr isotopic isochron dating in metallogenic geochronology

Ore-forming age dating of ore deposits has been one of the key and problematic factors in metallogeny study and is of the fundament for understanding the metallogenic genesis. Due to the lack of suitable minerals for the dating, isotopic equilibrium between different minerals, multi-stage formation of minerals and other factors, the precise dating of ore deposits by isotopic methods still has many technological limits for a long time. Remarkably inconsistent dating results acquired by different researchers or different isotopic systems always seriously hinder intensive studies on metallogenic genesis, which in turn is hard to support the ore exploration. In recent years, the improvements of separation and purification of elements and isotopic measurement with thermal ionization mass spectrometer(TIMS) ensure the accurate measurements of isotopic composition in micro-samples, providing possibility for the isotopic dilution dating of single-grain minerals. After briefly reviewing the applications of the Rb-Sr isotopic isochron dating technique in the metallogenic genesis, this paper emphatically introduced the advantages and difficulties of the Rb-Sr isotopic dating via the isochron method of single-grain minerals. In comparison to traditional Rb-Sr isotopic dating, the Rb-Sr isotopic isochron dating of single-grain minerals can match the fundamental principles of the isochron dating to the hilt, namely:simultaneity, homogeneity, isotopic closure and equilibrium of minerals. Different parent/daughter ratios existing in different grains of the same mineral can reach to the maximum extent, so that it can improve the quality of such isochron and then yield more accurate isochron ages. The Rb-Sr isotopic isochron dating of single-grain minerals can prospectively break through the long-standing "choke point" of the ore deposits dating, offering extensive application in the age-dating of various hydrothermal deposits and contributing intensive studies on the mineralization.