Abstract

The results of mineralogical and geochemical studies of the metaclastic rocks of the Grebnev and Magdagachi sequences of the Chalovskaya Group, one of the key lithostratigraphic units of the Argun continental massif in the eastern part of the Central Asian Fold Belt, as well as the results of the U–Pb dating of detrital zircons from these rocks by the LA-ICP-MS method, are presented. It was found that the age of the youngest zircons is ~478 Ma (Early Ordovician) in the metasandstones of the Grebnev Sequence and ~448 Ma (Late Ordovician), in the metasiltstones of the Magdagachi Sequence. Together with the previously determined age of the metadacites of the Isagachi Sequence (476 ± 8 Ma), this suggests the Ordovician age of the Chalovskaya Group, dated previously as Late Precambrian. The available data indicate that the deposits of the Chalovskaya Group accumulated in a setting of an active continental margin or an island arc against the background of intense magmatic activity. Considering that the Early Paleozoic suprasubduction magmatism is manifested in all continental massifs of the eastern part of the Central Asian Fold Belt (Argun, Mamyn, Bureya, Jiamusi, Khanka), one cannot exclude that these continental massifs have a common geodynamic history.

中文翻译：

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中亚褶皱带东部阿尔贡断层奥陶纪Chalovskaya群的年龄和沉积背景

摘要

Chalovskaya群的Grebnev和Magdagachi序列的超碎屑岩的矿物学和地球化学研究的结果，Chalovskaya群是中亚褶皱带东部Argun大陆断层的主要岩性地层学单位之一，提出了用LA-ICP-MS方法从这些岩石中碎屑锆石的U–Pb定年。在格列布涅夫序列的变砂岩中，最小的锆石的年龄为〜478 Ma（早期奥陶纪），而在Magdagachi序列的变质粉砂岩中，最年轻的锆石的年龄为〜448 Ma（晚期奥陶纪）。加上先前确定的Isagachi序列的后闪石的年龄（476±8 Ma），这表明Chalovskaya组的奥陶纪年龄，以前称为晚前寒武纪。现有数据表明，Chalovskaya群的沉积物在强烈的岩浆活动背景下，在活跃的大陆边缘或岛屿弧形环境中积累。考虑到早古生代超俯冲岩浆作用表现在中亚褶皱带东部的所有陆块（Argun，Mamyn，Bureya，佳木斯，Khanka），因此不能排除这些陆块具有共同的地球动力学历史。