渤海湾盆地枣园油田古近系孔店组沸石矿物的岩浆热液成因

Magmatic hydrothermal fluid genesis of zeolite in the Paleogene Kongdian Formation of Zaoyuan oilfield, Bohai Bay Basin, China

通过普通薄片、电子探针、包裹体测温、激光拉曼光谱、激光剥蚀电感耦合等离子体质谱等技术分析手段,对渤海湾盆地枣园油田Z56井古近系孔店组二段(简称孔二段)热液流体活动进行识别,并探讨岩浆热液流体与孔二段沸石矿物的成因联系。实验发现:(1)泥岩裂缝内可见焦沥青与绿泥石、重晶石、黄铜矿、黄铁矿、钠沸石、方沸石等热液特征矿物共生;(2)焦沥青激光拉曼光谱的分峰拟合计算温度为324~354℃,绿泥石地质温度计指示温度为124~166℃,钠沸石原生包裹体均一温度为89~196℃,反映了岩浆热液流体的温度变化较大,但是都高于正常地温;(3)绿泥石和重晶石的铕正异常明显,钠沸石的稀土元素配分曲线与孔店组玄武岩相似,指示其来源于岩浆热液流体。同时,钻井资料显示,Z56井孔二段发育多套玄武岩夹层,具备岩浆热液活动的地质基础。因此,岩浆热液流体与孔二段泥岩之间的水-岩相互作用可能是导致研究区孔二段泥岩富含沸石矿物的原因之一。图9表3参48。

Electronic probe, fluid inclusion homogenization temperature, Raman spectroscopy and laser ablation inductively coupled plasma mass spectrometry were utilized to identify the hydrothermal fluid-rock interactions in the second member of the Paleogene Kongdian Formation of Zaoyuan oilfield in Bohai Bay Basin(Kong 2 Member for short) of Well Z56 to find out the relationship between zeolite and hydrothermal fluid. The experimental results show that:(1) Pyrobitumen coexists with hydrothermal fluid characteristic minerals such as chlorite, barite, chalcopyrite, pyrite, natrolite and analcime in mudstone fractures.(2) The temperatures calculated from laser Raman spectrum of pyrobitumen, from the chlorite geothermometer and from measured homogenization temperature of natrolite inclusions are 324-354 ℃, 124-166 ℃ and 89-196 ℃, respectively;although vary widely, all the temperatures are obviously higher than the normal geothermal temperature.(3) The positive Eu anomaly of chlorite and barite, and the similar distribution pattern in rare earth elements between natrolite and basalt indicate they are from magmatic hydrothermal fluid. Moreover, drilling data shows that the Kong 2 Member in Well Z56 has several sets of basalt interlayers, suggesting there was geologic base of magmatic hydrothermal fluid activity. The magmatic hydrothermal fluid-rock interaction may be one of the reasons for the abnormal enrichment of zeolite in Kong 2 Member of the Cangdong Sag.