Comagmatic relation between the Yanqian and Furong granites in northwestern Zhejiang Province and its significance to prospecting fluorite deposits

The Yanshanian intermediate-acidic intrusive rocks are distributed widely in Cambrian carbonate strata in the Bamianshan area, northwestern Zhejiang Province. Yanqian granite is one of the most important fluorite-forming intrusions. The study shows that the Yanqian granite and adjacent Furong granite are monzonitic granite, both of which have similar petrogeochemical features, such as higher F contents(more than 0.36%). The similar chondrite-normalized REE distribution patterns and obvious negative Eu anomalies(δEu=0.01～0.07)suggest that they were the products of cognate magmatic activity. Geophysical survey displays that they are connected in the deep and should be derived from the same intrusion. 2.5D computer interaction inversion calculation by RGIS software shows that the hidden superface depths of the Yanqian and Furong granites range from 900 to 1 200 m. Currently, several large-to medium-sized “Changshan-type” fluorite deposits have been found along the outer contact zones of carbonate strata around the southern Yanqian granite, but there have been no major prospecting discoveries made on the northern side of the Furong granite and the eastern side of the Yanqian granite. The understanding of co-magmatic relation between the Yanqian granite and Furong granite is of important significance to prospecting fluorite deposits in the study area.