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报道在敦煌地块东巴兔山干沟地区发现形成于中太古代(~3.06 Ga)的片麻岩.岩相学和岩石化学数据表明研究样品为花岗闪长质片麻岩,具有太古宙TTG质岩石特征.LA-ICPMS锆石U-Pb定年结果显示,锆石核部年龄为~3.06 Ga,表明这套片麻岩形成于中太古代,为敦煌地区迄今为止发现的最古老的岩石;锆石边部1.92~1.86 Ga的年龄记录了敦煌地块古元古代末期的构造-热事件.锆石核部Hf同位素结果显示,除2个锆石测点的εHf(t)值为5.6和1.2,对应的锆石Hf两阶段模式年龄为3091 Ma和3356 Ma外,其余26个测点的εHf(t)值均为负值,介于–9.4~–0.5,对应的两阶段模式年龄为4.00~3.45 Ga,峰值为~3.82 Ga,表明该花岗闪长质片麻岩原岩的岩浆源区以古老地壳物质为主,伴有少量新生地壳物质的加入;揭示该地区早期地壳物质最初形成的时间至少在始太古代(3.80~4.00 Ga).结合塔里木地块和华北地块前寒武纪地质已有研究成果,提出敦煌杂岩与米兰杂岩并非同一构造岩石单元;敦煌地块可能曾属于华北克拉通的一部分.
It is reported that gneiss formed in Meso-Archean (~ 3.06 Ga) was discovered in the Dangshan Tugou area, Dongba, Dunhuang massif. The petrographic and petrochemical data show that the study sample is granodiorite gneiss, Zircon TTG zircons. The U-Pb zircon dating from the LA-ICPMS shows that the core of the zircon is ~ 3.06 Ga, indicating that this set of gneisses was formed in the middle Archean and is the oldest discovered in Dunhuang Rock and the tectono-thermal events of the Late Paleoproterozoic in the Dunhuang block from 1.92 to 1.86 Ga on the margin of zircon.The Hf isotopic results of the zircon core show that εHf (t) 5.6 and 1.2, respectively. The corresponding Hf two-stage ages of zircons are 3091 Ma and 3356 Ma, and the εHf (t) values of other 26 sites are all negative, ranging from -9.4 to -0.5. The corresponding two-stage models The ages ranged from 4.00 to 3.45 Ga with a peak value of ~ 3.82 Ga, suggesting that the magmatic source of the granodiorite gneiss was dominated by ancient crustal materials with a small amount of nascent crustal material added to reveal the early crustal material The initial formation time was at least from the Archean (3.80 ~ 4.00 Ga). Combining the Precambrian geology of Tarim block and North China block Research results, presented in Milan Dunhuang Complex Complex structure is not the same rock units; Dunhuang plot may have been part of the North China craton.