Abstract—

The results of geological, geochemical, Sm–Nd isotopic geochemical studies of metamorphic rocks of the Djagdagle Formation and U–Pb geochronological studies of its zircons are presented. In correlation schemes of geological complexes of the Bureya Terrane, this formation is the oldest (conditionally, Late Archean) amid other formations of the terrane; thus, it is considered its basement. The biotite and two-mica garnet-bearing gneisses of the formation formed owing to transformation of primary sedimentary rocks. The maxima on the relative probability curve of zircon age correspond to 487, 541, 690, 778, and 896 Ma. Thus, the Djagdagle Formation is Paleozoic rather than Early Precambrian, as was considered before. The lower age boundary of the accumulation of the protolith is identified by the age of the youngest zircon population of ~487 Ma. Similar ages of some cores and rims of zircons indicate that the rocks of the protolith underwent structural metamorphic transformations under PT conditions of amphibolite facies. The results of Sm–Nd and Lu–Hf isotopic studies indicate that the geological complexes which originated by means of reworking of the Mesoproterozoic crust could have been the source of primary sedimentary rocks. Taking into account the lack of Mesoproterozoic (and older) rocks in the structure of the Bureya Terrane, it can be suggested that the sources included some amount of ancient recycled material. Similar geological evolution of the Bureya and Jiamusi terranes is suggested on the basis of similar age ranges of metasedimentary rocks of the Djagdagle Formation and Turan Group of the Bureya Terrane and the Kimkan Formation of the Jiamusi Terrane. This is also evident from their synchronous Neoproterozoic magmatism.

中文翻译：

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中亚褶皱带布列亚地层Djagdagle组变质岩的晚古生代时代和原生质岩的性质

摘要—

提出了贾格达格组变质岩的地质，地球化学，Sm-Nd同位素地球化学研究结果及其锆石的U-Pb地球年代学研究结果。在Bureya地层的地质复合体的关联方案中，该地层是该地层其他地层中最古老的（有条件的为晚太古代）。因此，它被认为是其地下室。该地层的黑云母和含二云母石榴石的片麻岩是由于原始沉积岩的转变而形成的。锆石年龄的相对概率曲线上的最大值分别对应于487、541、690、778和896 Ma。因此，Djagdagle地层是古生界而不是早前的寒武纪。原生石堆积的较低年龄边界是由最年轻的锆石种群的年龄〜487 Ma确定的。角闪石相的PT条件。Sm-Nd和Lu-Hf同位素研究的结果表明，通过中元古代地壳的再造而形成的地质复合体可能是原始沉积岩的来源。考虑到Bureya Terrane结构中缺少中元古代（和更老的）岩石，因此可以认为来源包括一定数量的古代回收材料。根据Bureya地貌的Djagdagle组和Turan群和佳木斯地貌的Kimkan组的相似沉积岩的年龄范围，提出了Bureya和佳木斯地貌的相似地质演化。从他们的新元古代同步岩浆作用也可以看出这一点。