漠河盆地二十二站组砂岩形成时代及物源区构造环境判别

发布时间：2018-04-17 15:34

本文选题：漠河盆地 + 二十二站组　；参考：《地球科学》2017年01期

【摘要】：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.
[Abstract]:The Mohe basin in the northern part of Daxinganling has been widely developed in the Mesozoic 22 formation sandstone, and its formation time has been controversial.For the first time, the LA-ICP-MS U-Pb dating of detrital zircon is used to define the age of its formation, and its provenance and tectonic background are discussed in the light of geochemical characteristics.The results show that the sandstones of 22 station have low grinding roundness and poor sorting, showing the characteristics of relatively unstable source area, rapid denudation, transport and deposition.The zircon grain is coarse, and the Th-P U value of the zigzag is 0.35 ~ 1.07, which is a typical magmatic zircon.The dating results show that the age of 90 sites is mainly distributed in 3 communities at 1522 ~ 170 Ma, and the peak age is about 158 Ma. This age range reveals that the lower limit of sedimentary diagenesis in the 22 station formation is late Jurassic ~ (179) ~ (19) Ma, the peak age is about 190 Ma ~ (205) ~ (21) Ma, and the peak age is about 210Ma.3.The peak age is a geological record of a series of magmatic activities during the evolution of the Mongolia-Okhotsk Ocean.The peak ages of 210Ma and 190Ma are consistent with the late Triassic and early Jurassic magmatic events of the Erguna block in the southern margin of the basin, while the 158Ma peak age corresponds to the late Jurassic magmatic events in the northern margin of the basin.The tectonic discriminant diagram of main and trace elements reveals that the provenance region has the characteristics of active continental margin, and the zircon dating data show that there is no pre-Mesozoic clastic material.It is suggested that the magmatic rocks of the three periods were formed in the Mesozoic active continental margin environment of the northern margin of the Erguna block and provided the main clastic material for the formation of the 22 station formation.It is concluded that the sandstones of formation 22 were formed in the late Jurassic Mongolia-Okhotsk ocean closed orogenic process, Mohe basin north and south two sides of the source areas rapid denudation, rapid transport and rapid deposition environment.
【作者单位】：吉林大学地球科学学院;山东科技大学地球科学与工程学院;武警黄金第一支队;
【基金】：中国地质调查局项目(No.1212011085485) 国家自然科学基金项目(No.41272093)
【分类号】：P588.212.3

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