THE ADAKITE OF LATE TRIASSIC NANLOUSHAN FORMATION AND GUANMA GOLD DEPOSIT IN CENTRAL JILIN PROVINCE

The Late Triassic Nanloushan formation, with a Rb Sr age of 222±10 Ma, belongs to an acid intermediate volcanic rock series. The contents of SiO₂ and A₁₂O₃ in most of the Nanloushan rocks are more than 57% and 15% respectively, with MgO less than 6%. The amount of the rocks that are enriched in Na₂O with Na₂O/K₂O > 2 make up half of the total. The content of Yb in the rocks is 1.74 μg/g and (La/Yb)_n=14.2. The rocks are rich in LREE, with slight negative Eu anomaly (δEu 0.80-0.92). The content of Sr is highly enriched with 405 to 1128 μg/g, Sr/Y ranging from 44.5 to 48.9, and the initial volume of Sr (SrⅠ) 0.70746 and 0.70533 respectively.The Nanloushan volcanic rock series show the characteristics of adakite rock. The Guanma gold deposit occurs in the inner and outer contact zone of the crytoexplosive volcanic breccia and the wallrock of Nanloushan volcanic rock series. The volcanic magma of Nanloushan stage is the source of both heat and material for ore forming. The Guanma gold deposit is of the volcanogene hydrothermal type.