The origin process of manganese ores remains unsolved worldwide. Exploring the origins of stromatolites that contain manganese may be a key to deciphering the sedimentary environments and metallogenic processes of these deposits. However, only a few manganese stromatolites have been discovered and described until now. Microbialites are well developed in the manganese deposits, located near the top of the Ediacaran Doushantuo Formation in Chengkou area of Chongqing, northern Yangtze Craton, but has not been explicitly studied; and whether they are true stromatolites or Epiphyton microbialites remains controversial. Based on field and core observations and thin section microscopy, the characteristics of five types of manganese stromatolites and their growth modes are described in detail in this study. The results show that these stromatolites grew in a biostrome in shoal and lagoon environments and were syngenetic with oncolites and oolites on a carbonate ramp behind the shoal. Manganese stromatolites can be categorized into three forms: (1) stratiform; (2) columnar, which includes branched and columnar types; and (3) stratiform-columnar, which is a transitional type. Based on a criterion that the diameter is less than or greater than 1 mm, columnar stromatolites are further divided into micro-columnar (< 1 mm) and columnar (> 1 mm) columns, which display synchronous growth and are similar to Pseudogymnosolenaceae. Their shapes are mainly controlled by water depths and hydrodynamic strengths. The greater the water depth, the more columnar the columns tend to be. Excessively strong hydrodynamic conditions decrease the growth rate of stromatolites, and they even stopped growth due to wave damage. Furthermore, pillared laminar textures (not Epiphyton), which consist of dendritic, micro-branched and micro-columnar stromatolites, are a common feature of the larger stratiform, stratiform-columnar and columnar stromatolites. The alternations of laminae with different internal textures record subtle fluctuations in water depths and hydrodynamic strengths, which indicate that stromatolite growth is controlled by tidal cycles at the lamina level. Therefore, it is possible that the vertical evolution of the stromatolites could reveal the changing characteristics of both local and regional sedimentary environments, i.e., stromatolite shape changes from columnar to stratiform can represent the onset of shallower environments with weak hydrodynamic conditions. In addition, as important reef builders in shallow carbonate ramps, microstromatolites accelerate the development from ramp to platform. Indicators of microbial control on stromatolite shapes and manganese sedimentation processes include the fabric of stromatolite laminae, organic rhodochrosite with a micritic texture that is usually clotted, spherical, tubular, fibrous or dendritic, which suggests that the laminae resulted from microbially induced in situ precipitation.

中文翻译：

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扬子克拉通北部城口埃迪卡拉纪陡山沱组碳酸锰叠层石

锰矿的成因过程在世界范围内仍未解决。探索含锰叠层石的起源可能是破译这些矿床的沉积环境和成矿过程的关键。然而，到目前为止，只有少数锰叠层石被发现和描述。位于扬子克拉通北部重庆城口地区埃迪卡拉纪陡山沱组顶部附近的锰矿床中微生物岩发育良好，但尚未明确研究；它们是真正的叠层石还是附生菌微生物岩仍然存在争议。本研究基于野外和岩心观察以及薄片显微镜观察，详细描述了五种类型的锰叠层石的特征及其生长模式。结果表明，这些叠层石生长在浅滩和泻湖环境中的生物基质中，并与浅滩后面碳酸盐斜坡上的柱状石和鲕粒同生。锰叠层石可分为三种形态：（1）层状；(2)柱状，包括支状和柱状；(3)层状柱状，为过渡型。根据直径小于或大于1mm的标准，柱状叠层石进一步分为微柱状（<1mm）和柱状（>1mm）柱，它们表现出同步生长，类似于Pseudogymnosolenaceae。它们的形状主要受水深和水动力强度控制。水深越大，柱子就越呈柱状。过强的水动力条件会降低叠层石的生长速度，甚至会因波浪破坏而停止生长。此外，由树枝状、微分枝和微柱状叠层石组成的柱状层状结构（不是附生藻）是较大层状、层状柱状和柱状叠层石的共同特征。具有不同内部纹理的薄片的交替记录了水深和水动力强度的细微波动，这表明叠层石的生长受薄片水平的潮汐循环控制。因此，叠层石的垂直演化有可能揭示局部和区域沉积环境的变化特征，即：叠层石形状从柱状变为层状可以代表较浅水动力条件较弱的环境的开始。此外，微叠层石作为浅层碳酸盐斜坡重要的造礁造礁者，加速了斜坡向台地的发育。微生物对叠层石形状和锰沉积过程的控制指标包括叠层石薄片的结构，有机菱锰矿具有泥晶质地，通常为凝块、球形、管状、纤维状或树枝状，这表明薄片是由微生物诱导的原位沉淀形成的。