Confirmation of A- type volcanics in Baimianshi and Dongkeng Basin,South Jiangxi Province and their geological implication

There occur bimodal volcanic rocks in Dongkeng- Linjiang and Baimianshi- Changpu volcanic- sedimentary basins in southern Jiangxi Province, in which the rhyolites have the geochemical characteristic of high SiO2 (71.35％ in average), high Na2O＋ K2O (6.19％～ 8.36％ ) with K2O Na2O, metaluminous to weakly peraluminous, and highΣ REE. Their trace elements show depletion of Sr, Ba and Ti, and enrichment of Zr and Hf. All of above show the similar feature of A- type granite. Therefore, the rhyolites have been confirmed to be of A- type volcanic rocks. Highe Sr and lowe Nd suggest that the volcanic suite originated from partial remelting of a crustal source.