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An Early Holocene primary proto-dolomite layer of abiotic origin in Lake Sayram, Central Asia
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  • Jianru Cheng,
  • Xianqiang Meng,
  • Enlou Zhang,
  • Qingfeng Jiang,
  • Zhenyu Ni,
  • Junfeng Ji
Jianru Cheng
Ministry of Education Key Laboratory of Surficial Geochemistry, School of Earth Sciences and Engineering, Nanjing University
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Xianqiang Meng
Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences

Corresponding Author:[email protected]

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Enlou Zhang
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences
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Qingfeng Jiang
School of Geography Sciences, Nantong University
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Zhenyu Ni
Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences
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Junfeng Ji
Nanjing University
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Abstract

The “dolomite problem” is a long-standing puzzle in sedimentology and mineralogy. Previous studies have shown that some dolostones are formed by microbes or in hydrothermal-burial environments. Here, we provide a different case in which an abiotic and Ca-rich proto-dolomite layer with weak cation ordering precipitated in Lake Sayram, Central Asia, during the Early Holocene. The 12-cm-thick layer, with abundant proto-dolomite (mean 50 wt% and maximum=81 wt%), consists of euhedral and rhombohedral grains. The similarδ18O values of proto-dolomites and ostracods at the same depth demonstrate that the former are authigenic. Morphologic and isotopic features of these proto-dolomites are distinct from those of microbial dolomites, suggesting an abiotic origin. We infer that this proto-dolomite layer is the product of a warming and arid climate, which is supported by regional climatic records. This study provides evidence for previous studies that dolomite can precipitate directly in “dolomite seas” at ambient temperature.
16 Dec 2021Published in Geophysical Research Letters volume 48 issue 23. 10.1029/2021GL096309