茜素红染色技术应用于川西北中二叠统栖霞组豹斑灰岩流体包裹体测温研究

The Application of Alizarin Red S in the Fluid-inclusion Homogenization Temperature Measurement of Carbonate Rocks from the Middle Permian Qixia Formation,Western Sichuan Basin

碳酸盐岩流体包裹体测温过程中宿主矿物的准确鉴别和包裹体形成期次的确定尤为关键,将包裹体测温与其他技术结合才能更好地解决包裹体的生源和属性。本文以川西北中二叠统栖霞组豹斑灰岩晶洞充填物中鞍形白云石和方解石为研究对象,在岩石学特征研究确定二者形成顺序基础上,借助茜素红染色正确区分流体包裹体的宿主矿物。研究结果表明,染色剂的使用对流体包裹体测温结果无影响,染色前后包裹体的均一化温度测量差值在1℃以内,而染色剂配制比例（尤其是盐酸浓度）、染色时间和染色液清除方式是茜素红染色技术能否成功应用于碳酸盐岩流体包裹体测温的关键。本研究准确获得了鞍形白云石和分布于鞍形白云石晶间和晶内的方解石的包裹体均一化温度,分别集中在110~190℃和70~130℃区间,二者具有40~60℃的温度差。研究认为,方解石的沉淀时间晚于鞍形白云石,鞍形白云石的沉淀可能与峨眉山玄武岩喷发热事件有关,热事件后的温度降低导致鞍形白云石的溶解并伴随方解石的沉淀。

The accurate identification of host mineral and the formation stage of fluid inclusions are critical to temperature measurement,and the combination of inclusion technology and other technologies could be better to figure out the source and properties.Vug fillings in Middle Permian Qixia Formation of western Sichuan Basin are characterized by the intimate intergrowth of saddle dolomite and calcite.In this paper,Alizarin Red S is successfully used to distinguish the host minerals of fluid inclusions on the basis of the recognition of the sequence of diagenetic authigenic minerals.The results show that the Alizarin red staining techniques used in measuring fluid inclusion temperature of carbonates is feasible due to the difference of homogenization temperature of fluid inclusions before and after Alizarin Red staining is within 1℃.Solution proportion（especially the concentration of hydrochloric acid）,dyeing time and the clearing way of staining solution are key parameters to the application of Alizarin red staining technique on the temperature measurement of fluid inclusion.Fluid-inclusion homogenization temperature of saddle dolomite mainly range from 110℃ to 190℃,up close to 270℃,and that of calcite is mainly between 70℃ and 130℃.Formation temperature difference of about 40- 60℃ between saddle dolomite and calcite may be related to the Emeishan basalt eruptions in the late Permian.Fluids with high temperature related to the Emeishan basalt eruptions overcome the dolomite precipitation kinetics barrier and cause saddle dolomite precipitated.Saddle dolomite was dissolved and calcite precipitated in the dissolution space of dolomite and intergranular pores due to the decrease of paleo-temperature after the thermal event.