低温相变过程对石英矿物中盐水包裹体再平衡作用的影响

Effect of low-temperature phase change on the re-equilibration of brine inclusions hosted in quartz minerals

刘可禹 张书林 杨鹏

LIU Keyu ZHANG Shulin YANG Peng

中国石油大学(华东) 地球科学与技术学院, 山东 青岛 266580 深层油气全国重点实验室 中国石油大学(华东), 山东 青岛 266580 崂山实验室, 山东 青岛 266071

School of Geosciences, China University of Petroleum (East China), Qingdao, Shandong 266580, China National Key Laboratory of Deep Oil and Gas, China University of Petroleum (East China), Qingdao, Shandong 266580, China The Laoshan Laboratory, Qingdao, Shandong 266071, China

流体包裹体显微测温分析应当遵循先开展均一温度测定、后进行冰点测定的分析流程，但在实际操作过程中该测试流程并未严格执行，不少研究者在测完冰点温度(Tm)后继续重复测试该样品的均一温度(Th)，从而导致测试结果可能存在诸多不确定性。为了揭示低温相变过程对盐水包裹体再平衡作用的影响，引起广大研究人员对流体包裹体显微测温流程的重视，在盐水包裹体岩相学观察以及显微激光拉曼分析的基础上，开展流体包裹体显微测温分析，结合流体包裹体PVTx数值模拟以及前人研究结果，定量对比不同测温顺序得到的显微测温数据的差异。结果表明：冰点测试之前，盐水包裹体均一温度可以被多次重复测试；在低温相变测温过程中盐水包裹体可能会发生拉伸甚至泄露，其均一温度值会有一定程度的上升，但其冰点温度值基本不变，因此低温相变测温可能会造成其记录的原始信息发生重置；相较于方解石矿物，石英内部的盐水包裹体具有更强的抵抗再平衡作用影响的能力；较高的气体充填度以及高盐度可以在一定程度上减缓再平衡作用对盐水包裹体的影响；在低温相变测温过程中，由于水结冰产生的体积膨胀作用，盐水包裹体发生拉伸甚至泄露等再平衡现象普遍存在，导致盐水包裹体的均一温度值普遍升高。

Microthermometric measurement of fluid inclusions should follow the sequence of measuring homogenization temperature (Th) first, followed by the measurement of final freezing point temperature (Tm). However, in practice, this measurement sequence has not always been strictly followed. Many researchers may repeatedly measure the homogenization temperature of fluid inclusions even after the measurement of the final freezing point temperature. This may result in erroneous microthermometric data being obtained. In order to highlight this issue and to emphasize the importance of following the correct microthermometric measurement sequence, this study carried out repeated microthermometric measurements of brine inclusions and quantitatively compared the differences in the microthermomitric data obtained from different microthermomitric measurement sequences. The measurement exercise was aided by petrographic observation of brine inclusions and microscopic laser Raman analysis and fluid inclusion PVTx modelling. The results indicate that prior to the measurement of the final freezing point temperature, the homogenization temperature of brine inclusions can be repeatedly measured with the Th data showing no obvious deviation. During the measurement of the final freezing point temperature, the brine inclusion may undergo stretching or even leakage, and any subsequent Th measurements may yield elevated values, but Tm value remains largely unchanged. Therefore, low-temperature (freezing) phase-change measurement may cause resetting of the original PVTx information recorded. Compared to calcite minerals, brine inclusions hosted in quartz have stronger resistance to the influence of re-equilibration, and higher vapor filling degree and high salinity can offset the influence of brine inclusion re-equilibration to a certain extent. In the process of low-temperature phase change temperature measurement, due to the inflation caused by water freezing, it is common for brine inclusions to undergo stretching or even leakage, leading to a general increase in the homogenization temperature of brine inclusions.

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https://doi.org/10.11781/sysydz202305882