塔中奥陶系碳酸盐岩流体包裹体特征及其对成岩作用和深部流体作用的指示意义

Ordovician Carbonate Rock Inclusion Features and Its Indicative Significance to Diagenesis and Deep Fluids Action in Tazhong Area,Tarim Basin

塔中地区奥陶系碳酸盐岩经历了多期构造运动,具有复杂的埋藏史和地热史,且受深部流体作用改造,成岩作用比较复杂。本文通过对塔中地区6口井奥陶系碳酸盐岩样品开展详细的显微镜岩矿鉴定、流体包裹体岩相学研究及包裹体均一温度和盐度的测定,结合塔中地区构造、地层埋藏史及热演化史等资料,对塔中地区奥陶系成岩作用及深部流体作用进行了探讨。塔中地区奥陶系包裹体大致可以分为4期:第1期包裹体形成于晚加里东-早海西期早成岩期的同生-准同生或表生暴露阶段,温度接近地表温度,包裹体均一温度<60℃;第2期形成于晚海西期浅埋藏阶段,包裹体均一温度为90～105℃;第3期包裹体形成于波动埋藏-深埋藏阶段,包裹体均一温度变化范围较大,为120～186℃;第4期包裹体均一温度较高,多分布在192～235℃之间,这期高温流体包裹体的形成应该与岩浆-火山或深部热流体作用有关。另外,包裹体的盐度随均一温度升高而发生变化,这可能反映了塔中地区奥陶系在后期受深部热流体影响。

Ordovician carbonate rocks in Tazhong area, Tarim Basin have a complicate burial and thermal history. They were experienced multistage tectogenesis and reconstructed by deep fluids, so their diagenesis was complicated. According to rock-mineral identification, fluid inclusion petrography, homogenisation temperature and salinity meas- urement of Ordovician carbonate rock samples of 6 well, and combining with tectonic evolutional, burial and thermal history data, diagenesis and deep hydrothermal fluids of Ordovician carbonate rocks from the Tazhong area are re- searched in this paper. Fluid inclusions of Ordovician carbonate rocks can be divided into four groups. The first group was formed at contemporaneous - penecontemporaneous or epidiagenetic stage of early diagenesis period from late Caledonian to early Hercynian, its homogenization temperature is less than 50 -60 °C. The second group was formed at shallow burial diagenesis period of late Hercynian, its homogenization temperature is in the range from 90°C to 105°C. The third group was formed at the period from wave burial to deep burial diagenesis, its homogeniza- tion temperature is in the range from 90 ~C to 105 ~C. The homogenization temperature of the forth group is higher and concentrates in the range from 192°C to 235°C. The formation of the forth group of high temperature fluid inclu- sions is most likely related with magmatism or deep hydrothermal fluids. Besides, the phenomenon that salinity varies with the increase of homogenization temperature shows that the Ordovician carbonate rocks in Tazhong area were influ- enced by deep hydrothermal fluids.