REE and Sr-Nd isotope geochemistry for Yixian fluorite deposit, western Liaoning Province, China, and its geological implications

Abstract

Up to now, there were no systematic studies of geochemistry and isotopic age for the Yixian (义县) fluorite deposit, western Liaoning (辽宁) Province, China. Based on the analysis of metallogenic geological setting, we studied the REE, Rb-Sr and Sm-Nd isotopes. The chondrite-normalized REE patterns of fluorite are characterized by moderate LREE depletion (LREE/HREE=0.95–3.57, (La/Yb)N=0.08–2.84) and enrichment of Sr (146×10−6-596×10−6) and moderately positive Eu anomalies (δEu=1.10–1.34), which are similar to those of the host Mesoproterozoic carbonate rocks. The fluorite display (87Sr/86Sr) t =−0.708 5, (143Nd/144Nd) t =−0.511 785, and e Nd(t)=−12.8, which are similar to those of the host Mesoproterozoic carbonate rocks and volcanic rocks of Middle Jurassic Lanqi (蓝旗) Formation. The REE and Sr-Nd isotope geochemistry suggest that the source of the ore-forming material may be the volcanic rocks of Lanqi Formation and host carbonate rocks. The Sm-Nd isochron age of 154±14 Ma (MSWD=0.23) indicates that the Yixian fluorite mineralization nearly corresponds to the period of Lanqi Formation. Based on the integrated geological and geochemical studies, coupled with previous studies, we suggest that Yixian fluorite deposit formed in the extension setting of postcollisional stage and may be attributed to the partial melting of ancient basaltic rocks in the lower crust induced by underplating of basic magma and to the reaction between the F-rich ore-forming fluids and the host carbonate rocks.