CAJ | 학술논문

太湖冲击成因说由来已久.但始终未成定论.近几年在太湖及周边湖泊的淤泥层中发现了许多形态各异的奇石,经多种方法测试研究,确定为太湖冲击坑的溅射物.根据成份,溅射物分为两大类.一类富铁质,以菱铁矿及其胶结的碎屑为主,包括微小球粒、棍状及各种形态的块状和片状体;另一类贫铁质,以方解石及其胶结的长英质碎屑为主,碎屑为锐角状的石英晶屑及少量粘土和长英质岩屑.溅射物的大小从厘米级块体到毫米级球粒,再至微米级尘粉都有.溅射物外形多具有旋转扭曲形态及熔壳特征,显示了熔融、塑性-半塑性特征.这些特征显示其成因经历了冲击震碎、熔融、挖掘抛射、空中飞行,最后溅落在冲击坑及其周围.溅射物的成分反映了太湖靶岩基岩岩性特征.太湖冲击坑溅射物的发现是继太湖诸岛石英砂岩中石英晶体的冲击变质微结构发现之后,又一重大突破.综合其它特征,可以确定太湖为一冲击坑.
태호충격성인설유래이구.단시종미성정론.근궤년재태호급주변호박적어니층중발현료허다형태각이적기석,경다충방법측시연구,학정위태호충격갱적천사물.근거성빈,천사물분위량대류.일류부철질,이릉철광급기효결적쇄설위주,포괄미소구립、곤상급각충형태적괴상화편상체;령일류빈철질,이방해석급기효결적장영질쇄설위주,쇄설위예각상적석영정설급소량점토화장영질암설.천사물적대소종전미급괴체도호미급구립,재지미미급진분도유.천사물외형다구유선전뉴곡형태급용각특정,현시료용융、소성-반소성특정.저사특정현시기성인경력료충격진쇄、용융、알굴포사、공중비행,최후천락재충격갱급기주위.천사물적성분반영료태호파암기암암성특정.태호충격갱천사물적발현시계태호제도석영사암중석영정체적충격변질미결구발현지후,우일중대돌파.종합기타특정,가이학정태호위일충격갱.
The hypothesis of impact origin of the Taihu Lake was proposed about twenty years ago, but never confirmed. Recently some weird-shaped concretions were found embedded in the mud layer in the vicinity of the Taihu Lake.which might be impact ejecta from the Taihu impact crater .These new samples comprise two categories. One is rich in iron with fine siderite as concretion matrix,including abundant small spheroid concretions, stick-shaped concretions, and irregular shaped concretions.The other one is poor in iron with calcite as concretion matrix. including twisted-shaped concretions.The fragments embedded in matrix mainly consist of angular-sharp-edged quartz grains,and minor fragments of clay and plagioclase minerals. The sizes of the ejected materials range from centimeters of massive rocks to millimeters even to micrometers of the spheroids.Most hand samples show abundant semi-plastic features, such as twisted shape and molten crust,which might be caused by their flying in the air in the molten or semi-molten status.All these features suggest that these new samples once experienced a series of the impact cratering processes,such as the shock-induced fragmentation, shock-induced melting, ejection into the air,flying in the air,and falling in and around the impact crater. The components of the ejected materials are consistent with the target rocks in the Taihu Lake area. The confirmation of impact ejecta is another important discovery after the discovery of the shock-induced microfeatures in deformed quartz in the sandstone of islands in the Taihu Lake.The discovery of the ejection materials,combining with other features,COnfirmed the impact origin of the Taihu Lake.