【摘要】 松辽盆地徐家围子断陷营城组火山岩中含有粗面质岩石,是深层天然气重要储层之一。岩心、钻井及地震资料研究表明,粗面岩具有高位喷发、低位充填的特征,在火山口附近厚度大,远离火山口厚度小。粗面岩主量、微量及同位素地球化学显示其属于钾玄岩系列,富集稀土元素,强不相容元素Rb、Ba、Th、U质量分数较高。粗面岩的(87Sr/86Sr)i=0.704 321～0.705 395,εNd(t)为正值(3.36～3.83),Pb同位素比值相对集中,(206Pb/204Pb)i、(207Pb/204Pb)i、(208Pb/204Pb)i平均值分别为18.43、15.51和38.23。研究表明,粗面质岩浆由区域年轻地壳组分部分熔融形成,经历了一定程度的分离结晶作用,地壳混染作用不显著。粗面质岩浆多期次喷发后形成粗面岩,热液气体不断聚集发生隐蔽爆破形成角砾,未固结的角砾被岩浆期后热液"胶结",形成隐爆角砾岩,构成了粗面质岩石重要的储层类型。更多还原

【Abstract】 Trachyte is one of the important deep-gases reservoirs among volcanic rocks in Yingcheng Formation of Xujiaweizi fault depression,Songliao basin.Core,drill and seismic data exhibit that trachyte always erupt at higher location and flow to low-lying areas.In general,the thickness increases toward crater.Major element,trace element and isotopic geochemistry studies indicate that the trachyte belongs to shoshonitic series.The trachyte are prominently enriched strongly incompatible elements such as Rb,Ba,Th,U,REE,and have low initial 87Sr/86Sr(0.704321-0.705395) ratios.All εNd(t) values of the trachyte are all positive and have a narrow range(3.36-3.83),but they have an analogical radiogenic Pb.The mean of(206Pb/204Pb)i,(207Pb/204Pb)i,(208Pb/204Pb)i are 18.43,15.51 and 38.23,respectively.The features of geochemical data indicate that the trachyte magma are derived from partial melting juvenile crust following fractional crystallization without crustal contamination.Hydrothermal gases continuously gather into trachyte after many times eruptions.The trachytes would be crypto-explosive when the pressure is not large enough to bear.The crypto-explosive breccias are formed when the autobreccias are cemented by hydrothermal fluids,which can creat many cracks and inter-granular space.更多还原