Redefinition of shoshonitic intrusive rocks in the southern part of the Jiangshan-Longyou area, Zhejiang, and its significance for ore finding

Abstract：Late Mesozoic intrusive rocks are widespread in the southern part of the Jiangshan-Longyou area, Zhejiang. They were formerly regarded as rocks of the calc-alkali series. Field geological, petrological and element geochemical studies indicate that quartz monzonite, monzonite, syenite and concomitant granite and granite porphyry belong to the shoshonitic series. This suite of rocks has higher contents of alkalis (Na2O+K2O=7.80％-10.47％) and potassium (K2O/Na2O=0.92-1.91), lower titanium contents (TiO2=0.2％-0.88％) and a higher content and wide range of Al2O3 (11.08％-17.77％) and is enriched in large ion lithophile elements(LILE) and light rare earth element(LREE), with high ratios of Ce/Yb(27.29-85.64), Ta/Yb(0.42-0.73) and Th/Yb(3.44-14.44), showing the geochemical characteristics of shoshonitic series rocks. The area is endowed with rich mineral resources, and most ore deposits are intimately associated with shoshonitic intrusive rocks in terms of both time and space. The shoshonitic intrusive rocks are parent rocks of ores, which are an important petrological indicator for ore finding.