中国石油勘探 ›› 2025, Vol. 30 ›› Issue (5): 111-125.DOI: 10.3969/j.issn.1672-7703.2025.05.009

• 石油地质 • 上一篇    下一篇

中国埃迪卡拉纪纤维状白云石研究进展

张洪   

  1. 中国石化集团国际石油勘探开发有限公司
  • 出版日期:2025-09-15 发布日期:2025-09-14
  • 作者简介:张洪(1972-),男,湖北洪湖人,博士,2011年毕业于中国矿业大学(北京),高级工程师,现主要从事油气勘探方面的工作。地址:北京市朝阳区惠新东街甲6号,邮政编码:100029。
  • 基金资助:
    国家自然科学基金面上项目“陆相页岩层系润湿非均质性的微观形成机制研究(42272191)”;国家科技重大专项“深层白云岩储层形成的主控因素与规模分布”(2017ZX05008)。

The research progress of the Ediacaran fibrous dolomite in China

Zhang Hong   

  1. Sinopec International Petroleum Exploration and Production Corporation
  • Online:2025-09-15 Published:2025-09-14

摘要: 埃迪卡拉纪是古海洋与古气候演化的关键时期,其广泛分布的纤维状白云石为重建该阶段海洋化学特征提供了重要证据。为此,本文综述了纤维状白云石的成因类型和判别依据,重点探讨了埃迪卡拉纪纤维状白云石在中国的分布、成因机制及其古环境意义。岩石学特征、晶体光学性质及地球化学组成等多维属性可作为识别其成因的重要依据。原生成因纤维状白云石多呈纤维状结构,具正延性光学特征,常发育清晰的生长环带;而次生交代成因则表现为针状、葡萄状形态或方形终端,具负延性光学特征,且生长环带欠发育。此外,微量元素含量在判别白云石成因类型中具有一定的潜力。中国扬子板块埃迪卡拉系底部(陡一段)和顶部(灯二段和灯四段)及塔里木盆地奇格布拉克组顶部发育多种类型的纤维状白云石,包括板状白云石、束状- 负延性白云石、放射状- 负延性白云石、束状-正延性白云石与放射状- 正延性白云石。前三类白云石主要为次生交代文石或高镁方解石后的产物,而束状- 正延性与放射状-正延性白云石则更可能为自古海水或海相孔隙水中直接沉淀形成的原生白云石。埃迪卡拉纪海水具有高Mg/Ca比值、高碱度和低硫酸根浓度的特征,促使文石与高镁方解石母质类纤维状矿物沉淀。蒸发作用进一步提升Mg/Ca比值,缺氧环境下硫酸盐还原菌的代谢活动则释放Mg2+、提高pH 与碱度,有效克服沉淀障碍,促进原生纤维状白云石的形成。中国埃迪卡拉纪纤维状白云石普遍记录了同期海水或海相孔隙水的地球化学特征,部分样品亦显示热液流体的介入。其地球化学信号能够有效揭示古海洋氧化还原状态、流体来源及其时空演化过程,为重建前寒武纪海洋化学体系及评估其对早期生命演化的环境约束机制,提供了重要的地质证据。

关键词: 埃迪卡拉纪, 纤维状白云石, 原生白云石, 白云石成因, 古环境

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

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