云南腾冲热液发育模式及其对塔里木盆地热液溶蚀改造的启示

通过对云南腾冲热液流体形成机制的研究,探讨了塔里木盆地热液活动的特征。研究表明,腾冲温泉气体中CO_2的δ~(13)C(PDB)位于-6.4‰～-4.7‰之间,~3He/~4He比值位于1.09～3.51之间;温泉热液氢、氧同位素组成在大气降水线附近,但向氧同位素偏重的方向偏移。研究认为,腾冲温泉气体主要来自深部地幔,而温泉热液主要是大气降水下渗并受深部热源加热后再向上循环的产物。根据塔里木盆地构造演化特点,认为在二叠纪末期塔北沙雅-轮台断裂和亚南断裂带附近有娄似于腾冲的地质条件,大气降水下渗相关的热液流体活跃,对下古生界碳酸盐岩形成强烈的溶蚀改造作用;但塔中、巴楚以及塔北隆起南部斜坡区则没有类似的地质条件,热液溶蚀改造作用都相对较弱。

Development pattern of hydrothermal fluids in Tengchong, Yunnan Province and its implications for hydrothermal dissolution in the Tarim Basin

Based on the study of the developmentpattern ofhydrothermal fluids in Tengchong，Yunnan Province，we discuss characteristics ofhydrothermal activities in Tarim Basin.According to the study，theδ 13 C（PDB）vaˉlues of the CO 2 in the hot spring gases in Tengchong are between-6.4‰and-4.7‰，and the 3 He/ 4 He ratios are between1.09and3.51.The compositions of oxygen and hydrogen isotopes in hydrothermal fluids from hot spring are sim ilarwith those in meteoric water，but the oxygen isotopes show a tendency of getting heavier in theirmass.Based on the study，we believe gases from hot spring in Tengchongmainly come from deep mantle，while hydrothermal fluids originate from rainfall，which infiltrates downwards and is heated by deep heat sources and then goes upwards.According to the features of structural evolution ofTarim Basin，we believe the ShayaˉLuntai and the Yanan faulted zones in northern Tarim Basin in Late Perm ian had sim ilar geological conditions with those in Tengchong today.Under these conditions，hydrothermal fluids originating from the downward infilˉtration ofmeteoric waterwere active and strongly dissolved carbonates in the Lower Paleozoic.On the contrary，there were no sim ilar geological conditions in the Tazhong area，the Bachu area and the southern slope zone in the Tabei uplift，and thus hydrothermal dissolution was relativelyweaker.