三塘湖盆地牛东石炭系火山岩示顶底构造特征、成因及地质意义

三塘湖盆地牛东区块石炭系卡拉岗组火山岩中发育的示顶底构造,类同于碳酸盐岩发育的示顶底构造。该火山岩中的示顶底构造主要发育于火山岩的气孔及自碎缝中,其下部主要为渗滤泥沉积,上部常为结晶的钠沸石或其它自生矿物,二者之间界面平直。同时在火山岩示顶底构造发育部位杏仁体常具溶蚀特征。分析表明,火山岩中示顶底构造的特征及成因与渗流带的淋滤作用有关。示顶底构造发育部位杏仁体溶蚀孔的发育及气孔中未完全充填的剩余孔隙极大地改善了火山岩的储集性能。火山岩中示顶底构造的发现对火山岩岩层的顶底识别、火山岩岩相的划分及油气勘探具有重要的意义。

Features, Origin and Geological Significance of Geopetal Structures in Carboniferous Volcanic Rocks in Niudong Block, Santanghu Basin

Features of geopetal structures in Carboniferous Kalagang volcanic rock that develops at Niudong Block in Santanghu Basin are similar to common structures of carbonate rock.The geopetal structures in the Kalagang volcanic rock commonly develop in vesicles and autoclased fractures.In geopetal structures,the filling of vesicles and autoclased fractures has two parts that the percolating mud is usually under the interface and the crystal natrolite and other authigenic minerals are mostly on the top.The interface between both is parallel.In addition,the dissolution of amygdaloidal is often companied with the geopetal structures.Analysis has shown that the features of geopetal structures and the dissolutions of amygdaloidal nearby geopetal structures are relative in origin with the eluviation of leached zone.The dissolutions of amygdaloidal companying with geopetal structures and the remainder vesicles in which authigenic minerals are not full greatly improve reservoir capability of the volcanic rock.Discover of geopetal structures in the volcanic rock has a great geological significance in identifying the top and the bottom of volcanic formation and the classification of volcanic facies as well as petroleum exploration.