Abstract

The U and Pb contents and C, O, and Pb isotopic compositions are determined for dolomites of the Billyakh Group (6 and 15 samples of the Kotuikan and Yusmastakh formations, respectively), which composes the upper part of the Riphean section of the Anabar Uplift of North Siberia. The δ¹³С and δ¹⁸O values of dolomites vary from –3.0 to +0.8‰ PDB and from 23.7 to 27.3‰ SMOW, respectively, and are in agreement with those of carbonate sediments 1600–1400 Ma in age. On the ²⁰⁶Pb/²⁰⁴Pb–²⁰⁷Pb/²⁰⁴Pb plot, 18 data points of all samples of both formations occur along a straight line which corresponds to the age of 1513 ± 35 Ma. The Pb–Pb age of dolomites is a first direct geochronological characteristic of sedimentary rocks of the Anabar uplift cover and, along with the previously published Rb–Sr age of glauconite of the underlying Ust’-Il’ya Formation, allows us to ascribe the entire sedimentary sequence of the Billyakh Group to the Lower Riphean. These results indicate relatively fast (~10 m.y.) terrigenous-carbonate sedimentation of this group prior to intrusion of dolerites of the Kotui complex and origination of the Mesoproterozoic Kuonamka igneous province on the Siberian Craton. New data close a discussion on the age position of Riphean sediments of the Anabar Uplift.

中文翻译：

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西伯利亚北部Anabar隆升的早期Rhephean Billyakh群：白云岩的C–O同位素地球化学和Pb–Pb年龄

摘要

确定了Billyakh组白云岩的U和Pb含量以及C，O和Pb同位素组成（分别构成了Anabar隆升的Riphean段上部的Billyakh组白云岩（分别为6个和15个Kotuikan组和Yusmastakh组样品）。西伯利亚北部。的δ ¹³ С和δ ^18个白云石的O值分别改变从-3.0到+ 0.8‰PDB和从23.7到27.3‰SMOW，并且与那些碳酸盐沉积物1600年至一四零零年在马年龄协议。在²⁰⁶ Pb / ²⁰⁴ Pb– ²⁰⁷ Pb / ^204上铅图，这两个地层的所有样品的18个数据点沿一条直线出现，该直线对应于1513±35 Ma的年龄。白云岩的Pb–Pb年龄是Anabar隆升覆盖层沉积岩石的第一个直接地质年代学特征，再加上先前公布的底层Ust'-Il'ya层的辉绿岩的Rb–Sr年龄，使我们能够将其归因于比利耶克群到下里菲安的整个沉积序列。这些结果表明，该组的陆源碳酸盐岩沉积相对较快（约10 my），这是在Kotui复合体的白云石侵入和西伯利亚克拉通中元古生代库纳姆卡火成岩省起源之前。新数据结束了有关Anabar隆升的Rhephean沉积物年龄位置的讨论。