Abstract

The Sangilen and Khan-Khuhei blocks in the southwestern part of the Tuva-Mongolian terrane (TMT) combine into a composite structure, formed in the course of the Early Paleozoic (ca. 505–495 Ma) regional low- to moderate-pressure metamorphism. Manifestations of an earlier higher pressure metamorphism are known in both blocks. The upper age limit for the Sangilen block is defined by granites with an age of 536 ± 6 Ma. The early metamorphic rocks in both blocks are intruded by the granitoids of the Orto-Adyr complex with ages of 516 ± 5 and 513 ± 4 Ma, respectively. The emplacement of this complex preceded the Early Paleozoic (505–495 Ma) low- to moderate-pressure metamorphism. The high-temperature metamorphic rocks of the Sangilen and Khan-Khuhei blocks of TMT can be considered as the fragments of the Late Ediacaran higher pressure metamorphic belt, accreted to the TMT margin at ca. 510–505 Ma and reworked in the interval of 505–495 Ma under conditions of a regional low- to moderate-pressure metamorphism. The emplacement of the granitoids of the Orto-Adyr complex marks the conversion of the passive margin of the Neoproterozoic TMT block, covered by the Ediacaran carbonate platform, into an active margin. The geochronological studies of detrital zircons from the metaterrigenous rocks of the Sangilen block demonstrated that the source rocks of these zircons were mostly the Early Neoproterozoic magmatic rocks.

中文翻译：

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中亚褶皱带图瓦-蒙古地体西南部变质杂岩年代学和地球动力学背景

摘要

图瓦-蒙古地体（TMT）西南部的Sangilen和Khan-Khuhei地块组合成复合构造，形成于早古生代（约505-495 Ma）区域性中低压变质作用过程中. 在两个区块中都知道早期高压变质作用的表现形式。Sangilen 地块的年龄上限由年龄为 536 ± 6 Ma 的花岗岩定义。两个地块的早期变质岩均被 Orto-Adyr 杂岩体的花岗岩侵入，年龄分别为 516±5 和 513±4 Ma。该杂岩体的就位发生在早古生代（505-495 Ma）低至中压变质作用之前。TMT 的 Sangilen 和 Khan-Khuhei 地块的高温变质岩可以认为是晚埃迪卡拉纪高压变质带的碎片，增加到大约 TMT 利润率。510～505 Ma，505～495 Ma 区间在区域性中低压变质作用条件下改造。Orto-Adyr 杂岩体花岗岩的就位标志着被埃迪卡拉纪碳酸盐台地覆盖的新元古代 TMT 地块的被动边缘转变为活动边缘。桑吉伦地块准陆源岩碎屑锆石年代学研究表明，这些锆石的烃源岩多为早新元古代岩浆岩。Orto-Adyr 杂岩体花岗岩的就位标志着被埃迪卡拉纪碳酸盐台地覆盖的新元古代 TMT 地块的被动边缘转变为活动边缘。桑吉伦地块准陆源岩碎屑锆石年代学研究表明，这些锆石的烃源岩多为早新元古代岩浆岩。Orto-Adyr 杂岩体花岗岩的就位标志着被埃迪卡拉纪碳酸盐台地覆盖的新元古代 TMT 地块的被动边缘转变为活动边缘。桑吉伦地块准陆源岩碎屑锆石年代学研究表明，这些锆石的烃源岩多为早新元古代岩浆岩。