Geochemical characteristics of volcanic rocks of the laochang Ag polymetallic deposit, lancang, Yannan Province, China

摘要

In terms of major element, trace element and REE geochemical characteristics of volcanic rocks in the area studied and by making use of the TiO_2-K_2O-P_2O_5, Th-Hf-Ta and Zr- Nb-Y trianglar diagrarms and the environmental discrimination diagrams of incompatible ele- Ment distribution patterns, the authors have drawn some conclusions that are different from Those by previous workers. It is concluded that volcanic rocks in theLaochang Ag polymertallic Deposit at Lancang, Yunnan belong to continental within-plate alkali basalts, and that their Geotectonic setting seems to be at the northeastern margin of East Gondwana Land.