摘要
报道了黑龙江省东部小兴安岭东风山群亮子河组和红林组锆石的U-Pb定年结果,并讨论了东风山群的所属时代和构造属性。采自该群的大多数锆石呈自形—半自形晶,显示出典型的岩浆生长环带或条痕状吸收,暗示其岩浆成因,极少数的锆石具有经变质作用形成的暗色增生边。定年结果表明:采自东风山铁矿附近的亮子河组二云母片岩中锆石U-Pb定年结果产生了821 Ma、1 286 Ma、1 396 Ma、1 504～1 595Ma、1.8Ga和2.5Ga年龄众数;采自亮子河组标准剖面的黑云母石英片岩和变质粉砂岩中锆石U-Pb定年结果分别产生了425Ma、453Ma、485Ma、506Ma和288Ma、452Ma、486Ma、699Ma、801Ma、900Ma年龄众数;东风山群上部红林组含炭质粉砂质板岩中锆石U-Pb定年结果产生了275Ma、760Ma、781Ma年龄众数,而红林组中的花岗质片麻岩(原岩为花岗岩,侵入到含炭质粉砂质板岩中)锆石U-Pb定年结果为271Ma。根据上述定年结果,结合区域岩浆事件,可以判定:位于东风山铁矿处的亮子河组沉积于新元古代晚期,这是区域上首次发现具有准确同位素年龄的前寒武纪地层;东风山群亮子河组标准剖面处的黑云母石英片岩和变质粉砂岩应形成于早古生代晚期和晚古生代;而东风山群红林组的形成时代应为晚古生代晚期(275～271Ma)。上述结果揭示,小兴安岭东风山群是由不同时代沉积岩和变形的火成岩所构成,主体形成于古生代,部分地层为新元古代晚期沉积;这些地层的物源主要来源于周边的古生代地质体和少量的前寒武纪基底残片。
LA- ICP- MS U- Pb dating of zircons from the Liangzihe Formation and Honglin Formation of the Dongfengshan Group in the Lesser Xing~ an Mountains, eastern Heilongjiang Province, are presented in order to constrain their forming age and tectonic attribution. Most of zircons from the Dongfengshan Group are euhedral and subhedral in shape and display striped absorption or oscillatory zoning in CL images, implying their magmatic origin. The others show dark accretionary rim, implying their metamorphic origin. The dating results indicate that zircons from two-mica schist in the Liangzihe Formation near the Dongfengshan iron ore deposit yielded age populations of 821 Ma, 1 286 Ma, 1 396 Ma, 1 504- 1 595 Ma, 1 800 Ma, and 2 500 Ma~ zircons from biotite quartz schist and metamorphic siltstone in the standard profile of the Liangzihe Formation yielded age populations of 425 Ma, 453 Ma, 485 Ma, 506 Ma and 288 Ma, 452 Ma, 486 Ma, 699 Ma, 801 Ma, 900 Ma, respectively~ and zircons from carbon-bearing silty slate in the Honglin Formation yielded age populations of 275 Ma, 760 Ma, and 781 Ma; whereas zircons from granitic gneiss （a granitic intrusion intruding into carbon-bearing silty slate） in the Honglin Formation yielded age of 271 Ma. Based on isotopic dating results above and the regional magmatic events, we conclude that the sedimentary processes of the Liangzihe Formation near the Dongfengshan iron ore deposit could take place during the Late Neoproterozoic period, and it is the firstly discovered Precambrian terrane in the region; the biotite quartz schist and metamorphic siltstone near the standard profile of the Liangzihe Formation formed in late stage of Early Paleozoic and Late Paleozoic, respectively; and the sedimentary process of the Honglin Formation in the Dongfengshan Group should take place in the Late Palaeozoic period （275 -271 Ma）. The research results in the paper imply that the Dongfengshan Group in the Lesser Xing^an Range is composed of sedimentary rocks and metamorphic igneous rocks with diff
出处
《吉林大学学报（地球科学版）》
EI
CAS
CSCD
北大核心
2013年第2期440-456,共17页
Journal of Jilin University：Earth Science Edition
基金
国家自然科学基金项目(41072038)
中国地质调查局地质大调查项目(1212010070301)
关键词
小兴安岭
东风山群
锆石U-PB年代学
物源
同位素
the Lesser Xing＇ an Mountains
Dongfengshan Group
zircon U - Pb dating
materialsource
isotope
