摘要
The volcanic rocks of Jiezha group in Zharigen area, Qinghai Province, are characterized by lower silicon and alkalis but high titanium and calcium for intermediate-basic rocks, low silicon and middle content of alkalis, titanium and calcium for intermediate rocks and high silicon and alkalis, middle titanium and low calcium for acid rocks. The TFeO/MgO—TiO2,diagram shows that the volcanic rocks are mainly plotted in the island arc area. Trace elements characteristics (Th/Nb=0.9>0.11, Nb/Zr>0.04) illustrate that the volcanic rocks may be formed in a tectonic setting of island arc as a result of continent-continent collision. The apparent ages of volcanic rocks by Rb-Sr isotope isochronism are (231±28) Ma and (225±8) Ma, which means that the volcanic rocks belongs Late Triassic.