Abstract: The Ediacaran represents a key interval in Earth’s surface evolution. Fibrous dolomite, a well-developed carbonate fabric, offers important insights into contemporaneous seawater and pore-water conditions. This review integrates petrographic, crystallographic and geochemical data to assess the origin, distribution, and paleo-environmental significance of fibrous dolomite in the Yangtze Block and Tarim Basin. Primary fibrous dolomites are typically characterized by fibrous morphologies, well-developed growth zoning, and length-slow optical properties, whereas secondary, replacive fibrous dolomites commonly display botryoidal, acicular habits or square terminations, absent growth zoning, and length-fast optical fabrics. Trace element distributions likely provide further constraints on genesis. Multiple fibrous dolomite types have been identified in the Ediacaran Doushantuo (Member I) and Dengying (Member II and IV) formations of the Yangtze Block, as well as in the upper Qigebulake Formation of the Tarim Basin. These include bladed dolomite, fascicular-fast, radial-fast, fascicular-fast and radial-slow dolomite. The former three types are likely to be of replacive origin, whereas fascicular and radial length-slow dolomite likely represent primary precipitates. The Ediacaran seawater characterized by high Mg/Ca ratios, elevated alkalinity and low sulfate promotes the precipitation of fibrous aragonite and highMg calcite precursors. Intense evaporation further increases Mg/Ca, while sulfatereducing bacteria releases Mg²⁺, leads to the increase of pH and alkalinity values, thereby facilitating the nucleation of primary fibrous dolomite. In summary, the Ediacaran fibrous dolomites generally preserve critical geochemical signatures of paleo-seawater and pore-water, and in some cases reflect hydrothermal fluid influence. Their geochemical archives provide robust constraints on the redox state, provenance, and temporal–spatial evolution of Ediacaran Ocean, offering critical evidence for reconstructing Precambrian Ocean chemistry and assessing its environmental controls on early life evolution.

Key words: Ediacaran, fibrous dolomite, primary dolomite, dolomite formation, paleo-environment