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针对改则地区新近系唢呐湖组湖相喷流岩的岩石学研究,认为总体上新近系唢呐湖组喷流岩以硅质岩-碳酸盐岩为组合特征,识别出热液通道、皮壳状构造等热液沉积构造及4种热水矿物。喷流岩7件样品δ~(18)O平均值为-15.2‰,δ~(13)C平均值为-3.79‰,所得喷流岩成岩温度平均值为92.10℃;微量元素中Ba,U,Sr,Zr,Sm的富集,U/Th平均值为19.35,Co/Ni为0.23;稀土元素的总量ΣREE变化在6.90×10~(-6)~19.28×10~(-6)之间,稀土元素的页岩标准化配分形式具有中组稀土富集的特点,中等偏强正铕异常,地球化学特征整体上符合热水沉积岩特征,属于中低温热液沉积成因。根据热水沉积岩结构构造特征,将新近系唢呐湖组喷流岩角砾型喷流岩、脉状充填型喷流岩、喷流口附近盆地沉积型喷流岩和远端区域扩散型喷流岩,并建立其沉积模式。
In view of the petrological study of the lacustrine jet lavas of the Neogene Suona Lake Formation in the Gantang area, it is considered that the jet stream rocks of the Neogene Suonahu Formation generally are characterized by the combination of silicalite-carbonate rock, identifying the hydrothermal channels, Shell structure and other hydrothermal sedimentary structures and four kinds of hot water minerals. The average value of δ ~ (18) O and the δ_ (13) C of 7 samples in the jet stream are -3.79 ‰, and the average diagenetic temperature of the jet stream rocks is 92.10 ℃. Among the trace elements Ba, U , Sr, Zr and Sm, the average U / Th value is 19.35, and the Co / Ni content is 0.23. The total content of REEs changes from 6.90 × 10 -6 to 19.28 × 10 -6 The rare earth element shale normalized distribution pattern has the characteristics of rare earth enrichment in the middle group and moderately strong positive europium anomaly. The geochemical characteristics as a whole accord with the characteristics of hydrothermal sedimentary rocks and belongs to the genesis of medium- and low-temperature hydrothermal sediments. According to the tectonic features of hydrothermal sedimentary rocks, the Neogene Suonahu Formation jet-flow breccia-type jet flow veins, vein-filling jet flow rocks, sedimentary-type jet flow rocks in the vicinity of the jet flow outlet and diffusive jet flow rocks in the distal area , And establish its deposition pattern.