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大兴安岭北部的漠河盆地广泛发育中生界二十二站组砂岩,其形成时代一直备受争议.首次利用碎屑锆石LA-ICP-MS U-Pb法测年对其形成时代作出较为精确的限定,并结合地球化学特征对其物源区及大地构造背景进行了探讨.研究结果表明,二十二站组砂岩碎屑物磨圆度较低、分选差,表现出源区相对不稳定,快速剥蚀、搬运及沉积的特征.锆石颗粒粗大,具有清晰的震荡环带,Th/U值为0.35~1.07,为典型的岩浆锆石.测年结果显示,90个测点年龄主要分布在3个群落:152~170Ma,峰值年龄约为158Ma,这一年龄区间揭示了二十二站组沉积成岩的下限为晚侏罗世;179~193Ma,峰值年龄约为190Ma;205~214Ma,峰值年龄约为210Ma.3个年龄峰值为蒙古-鄂霍茨克洋演化过程中一系列岩浆活动的地质记录,其中210Ma与190Ma峰值年龄与盆地南缘额尔古纳地块晚三叠世、早侏罗世的岩浆事件相吻合,而158Ma峰值年龄则对应于盆地北缘晚侏罗世的岩浆事件.主、微量元素构造判别图解揭示其物源区具有活动大陆边缘的特征,同时锆石定年数据显示其没有任何前中生代的碎屑物,暗示了该3期岩浆岩均形成于额尔古纳地块北缘的中生代活动大陆边缘环境,并为二十二站组的形成提供了主要碎屑物质.由此说明,二十二站组砂岩形成于晚侏罗世蒙古-鄂霍茨克洋闭合后的造山过程中,漠河盆地南北两侧物源区快速剥蚀、快速搬运与快速沉积的环境.
Sandstone of Mesozoic Twenty-two Stations is widely developed in the Mohe basin in the northern part of the Daxinganling Mountains and its formation has been the subject of controversy for the first time. It is the first time that the detrital zircon LA-ICP-MS U- And the tectonic setting of its provenance and tectonics are discussed in combination with the geochemical characteristics.The results show that the roundness of the sandstone debris in the No. 22 station group is lower and the sorting is poor and the source area is relatively unstable , Rapid erosion, transport and sedimentary characteristics.The zircon grains are coarse and have clear oscillatory ring with Th / U value of 0.35 ~ 1.07, which is a typical magmatic zircon.The dating results show that the age of 90 measuring points is mainly distributed In the three communities: 152 ~ 170Ma, the peak age is about 158Ma. This age interval reveals that the lower limit of sedimentary diagenesis of the Twenty-two stations is Late Jurassic. The peak age is about 179Ma and about 190Ma, The peak age is about 210 Ma. The three age peaks are the geological records of a series of magmatism during the Mongolian-Okhotsk oceanic evolution. The 210 Ma and 190 Ma peak ages coincide with the Late Triassic of the Erguna block in the southern margin of the basin, The Jurassic events coincided with the magmatic events, while the 158Ma peak age was correct The Late Jurassic magmatism events should have occurred in the Late Jurassic in the northern margin of the basin, indicating that the source and source regions of the Late Jurassic are characterized by active continental margins, while zircon zircon dating shows no pre-Mesozoic detritus All of the three magmatic rocks were formed on the continental margins of the Mesozoic anomaly on the northern margin of the Erguna block and provided the major detrital material for the formation of the Y2 2 formation.Therefore, During the late orogeny of the Late-Jurassic Mongolia-Okhotsk Ocean, the source areas of the two sides of the Mohe Basin were rapidly denuded, rapidly transported and rapidly deposited.