Polymetamorphism in the Geological Development of the South Altai Metamorphic Belt, Central Asian Foldbelt

IF 1 4区地球科学 Q3 GEOLOGY Stratigraphy and Geological Correlation Pub Date : 2023-12-01 DOI:10.1134/s0869593824010040

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Abstract

The crystalline complexes of the Hercynian South Altai Metamorphic Belt (SAMB), which is a part of the Central Asian Foldbelt more than 1500 km long. They compose different-scale tectonic plates, the level of metamorphism in which at the early stages reached the conditions of high-temperature amphibolite subfacies and, in places, granulite facies. In terms of tectonics, the band of their outcrops is confined to the margin of the North Asian Caledonian continent, stretching from southeast to northwest along the southern slope of the Gobi, Mongolian, and Chinese Altai to Eastern Kazakhstan, where they are represented in the Irtysh shear zone. The SAMB includes poly- and monometamorphic complexes. The age of granitoids formed at the late episode of metamorphism was determined for the Tsel tectonic plate of the Gobi Altai in the southeastern part of the SAMB: from 374 ± 2 to 360 ± 5 Ma. These and previously obtained results show that the early stage of low-pressure metamorphism and the late stage of high-pressure metamorphism occurred in the age intervals of ~390–385 and 375–360 Ma, respectively, almost throughout this belt. A short-term stage of stabilization was between these stages. These processes occurred during the closure of the basin with the Tethys-type oceanic crust of the South Mongolian Ocean (paleo-Tethys I). The spatial position of the SAMB is determined by the asymmetric structure of the basin, in which the active continental margin is represented along its northern part, and the passive one is represented along the southern one (in modern coordinates).

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中亚褶皱带南阿尔泰变质岩带地质发展中的多变质作用

摘要海西南阿尔泰变质带（SAMB）是中亚褶皱带的一部分，全长超过 1500 公里。它们组成了不同规模的构造板块，其变质程度在早期阶段达到了高温闪长岩亚相的条件，在某些地方还出现了花岗岩面。从构造上看，它们的出露带仅限于北亚加里东大陆边缘，从东南向西北沿戈壁南坡、蒙古和中国阿尔泰一直延伸到哈萨克斯坦东部，在那里以额尔齐斯剪切带为代表。SAMB包括多变质和单变质复合体。根据测定，在萨马拉盆地东南部戈壁阿尔泰的策勒构造板块变质作用晚期形成的花岗岩的年龄为：374 ± 2 至 360 ± 5 Ma。这些结果和之前获得的结果表明，低压变质的早期阶段和高压变质的晚期阶段分别发生在 ~390-385 Ma 和 375-360 Ma 的年龄段，几乎遍及整个带。在这两个阶段之间有一个短期的稳定阶段。这些过程发生在盆地与南蒙古洋（古特提斯I期）特提斯型洋壳闭合期间。SAMB的空间位置是由盆地的非对称结构决定的，其中活跃的大陆边缘位于盆地北部，而被动的大陆边缘位于盆地南部（按现代坐标）。

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来源期刊

Stratigraphy and Geological Correlation 地学-地质学

CiteScore

1.80

自引率

30.00%

发文量

审稿时长

>12 weeks

期刊介绍： Stratigraphy and Geological Correlation is the only journal that provides comprehensive coverage of the fundamental and applied aspects of stratigraphy and the correlation of geologic events and processes in time and space. Articles are based on the results of multidisciplinary studies and are for researchers, university professors, students, and geologists interested in stratigraphy and the chronological features of the world’s geological record.