地球学报
地毬學報
지구학보
Acta Geoscientia Sinica
2015年
5期
647-658
,共12页
田辉%张健%李怀坤%苏文博%周红英%杨立公%相振群%耿建珍%刘欢%朱士兴%许振清
田輝%張健%李懷坤%囌文博%週紅英%楊立公%相振群%耿建珍%劉歡%硃士興%許振清
전휘%장건%리부곤%소문박%주홍영%양립공%상진군%경건진%류환%주사흥%허진청
凝灰岩%高于庄组%LA-MC-ICPMS U-Pb测年%盖层系%蓟县%华北克拉通
凝灰巖%高于莊組%LA-MC-ICPMS U-Pb測年%蓋層繫%薊縣%華北剋拉通
응회암%고우장조%LA-MC-ICPMS U-Pb측년%개층계%계현%화북극랍통
tuff bed%Gaoyuzhuang Formation%LA-MC-ICPMS U-Pb dating%Calymmian System%Jixian%North China Craton
最近在天津蓟县东水厂村附近中元古代高于庄组三段(即张家峪亚组)下部白云岩中发现了一层15 cm厚的凝灰岩夹层,测得其锆石LA-MC-ICPMS U-Pb年龄为(1577±12) Ma。这一进展不仅使得蓟县地区高于庄组沉积时代第一次获得了精确可靠的年代学约束,也为华北克拉通北缘整个燕山地区中元古界的精确对比提供了新的标尺。与此同时,由于在其紧邻的上覆层位还发现了与标准剖面早年所发现的以光面拟丘阿尔藻(Parachuaria glabra Sun)为代表的同类的宏观藻类,因此本测年结果实际也同时标定了这一宏观藻类群的生存时代。结合笔者等早先获得的北京延庆地区高于庄组三段上部凝灰岩的锆石 U-Pb 年龄((1560±5) Ma)可以确认,整个燕山地区高于庄组三段主体的沉积时限应为1580~1560 Ma,同时可以更为精确地将高于庄组与下伏大红峪组的界线年龄限定为1600 Ma左右,相当于目前通用的国际中元古界盖层系(Calymmian System)的底界。
最近在天津薊縣東水廠村附近中元古代高于莊組三段(即張傢峪亞組)下部白雲巖中髮現瞭一層15 cm厚的凝灰巖夾層,測得其鋯石LA-MC-ICPMS U-Pb年齡為(1577±12) Ma。這一進展不僅使得薊縣地區高于莊組沉積時代第一次穫得瞭精確可靠的年代學約束,也為華北剋拉通北緣整箇燕山地區中元古界的精確對比提供瞭新的標呎。與此同時,由于在其緊鄰的上覆層位還髮現瞭與標準剖麵早年所髮現的以光麵擬丘阿爾藻(Parachuaria glabra Sun)為代錶的同類的宏觀藻類,因此本測年結果實際也同時標定瞭這一宏觀藻類群的生存時代。結閤筆者等早先穫得的北京延慶地區高于莊組三段上部凝灰巖的鋯石 U-Pb 年齡((1560±5) Ma)可以確認,整箇燕山地區高于莊組三段主體的沉積時限應為1580~1560 Ma,同時可以更為精確地將高于莊組與下伏大紅峪組的界線年齡限定為1600 Ma左右,相噹于目前通用的國際中元古界蓋層繫(Calymmian System)的底界。
최근재천진계현동수엄촌부근중원고대고우장조삼단(즉장가욕아조)하부백운암중발현료일층15 cm후적응회암협층,측득기고석LA-MC-ICPMS U-Pb년령위(1577±12) Ma。저일진전불부사득계현지구고우장조침적시대제일차획득료정학가고적년대학약속,야위화북극랍통북연정개연산지구중원고계적정학대비제공료신적표척。여차동시,유우재기긴린적상복층위환발현료여표준부면조년소발현적이광면의구아이조(Parachuaria glabra Sun)위대표적동류적굉관조류,인차본측년결과실제야동시표정료저일굉관조류군적생존시대。결합필자등조선획득적북경연경지구고우장조삼단상부응회암적고석 U-Pb 년령((1560±5) Ma)가이학인,정개연산지구고우장조삼단주체적침적시한응위1580~1560 Ma,동시가이경위정학지장고우장조여하복대홍욕조적계선년령한정위1600 Ma좌우,상당우목전통용적국제중원고계개층계(Calymmian System)적저계。
A 15 cm thick tuff intercalation in dolomite was recently discovered in the lower horizon of the third member (the Zhangjiayu Subformaiton) of the Gaoyuzhuang Formation in the Mesoproterozoic Jixian System at the Dongshuichang Village, Jixian County. A zircon U-Pb age of (1577±12) Ma for the tuff was obtained by means of LA-MC-ICPMS method, consequently for the first time providing precise and reliable chronological constraint on the depositional age of the Gaoyuzhuang Formation in the Jixian area and a new correlation marker for Mesoproterozoic strata in the whole Yanshan area of the northern North China Craton. At the same time, abundant macro-alga fossils represented byParachuaria glabra Sun, the same as those discovered previously in the Mesoproterozoic Standard Section in the Dahongyu Valley, were also found in the dolomite beds directly overlying the newly-discovered tuff beds. Therefore, the newly-obtained tuff age can further provide constraint on the living time of the macro-algaParachuaria glabra Sun in the Gaoyuzhuang Formation. Combined with the zircon U-Pb age (1560±5) Ma obtained previously for the tuff bed in the top horizon of the third member of the Gaoyuzhuang Formation in Yanqing County, northwestern Beijing, it can be concluded that the depositional age of the third member of the Gaoyuzhuang Formation is in the time span of 1580~1560 Ma, and the boundary between the Gaoyuzhuang Formation and the underlying Dahongyu Formation can be quite confidently placed at 1600 Ma that is equivalent to the lower boundary of the International Mesoproterozoic Calymmian System.
