THE GEOCHEMICAL FEATURE OF AURIFEROUS VOLCANIC ROCK SERIES IN CENTRAL JILIN

The auriferous volcanic rocks in central Jilin may be divided into Early Carboniferous Yufutun stage and Late Triassic Nanloushan stage with RbSr ages of 301Ma and 222Ma respectively.Yufutun formation consists of spilite, spilitic porphyrite, keratophyre and quartz keratophyre.Nanloushan formation consists of andesite, dacite, rhyolite, basaltic andesite and latite.They both petrochemically belong to calcitealkaline volcanic rock series of subalkaline system. Yufutun formation is of sodium type;and Nanloushan formation, potassium type.The Σ REE content(111×10^-9~256×10^-9) is enriched in LREE, with a right sloping distribution pattern and negative Eu anomaly(WEu0.93~0.75).In the above two rock associations, the mean content of Au are 28×10^-9 and 72×10^-9 respectively, the initial volume of Sr are 0.70492 and 0.70533 respectively.The study shows that Yufutun stage volcanic rock formed in a tensional environment, that is MiddleLate Palaeozoic riftdepression syncline, and Nanloushan stage volcanic rock was the products of active continental margin beginning from Late Triassic.