The eastern part of the Souss Basin (Morocco) contains several Mn deposits in the Tasdremt district. Three Mn orebodies occur within the Cenomanian-Turonian dolostones and the Senonian (Coniacian to Maastrichtian) detrital series, the main orebody being located at the boundary between them. The Mn ores consist of coronadite group minerals, mostly coronadite and hollandite, in a karstified dolostone. New field observations, petrographic analyses, and geochemical data define the Tasdremt deposits as a karst-hosted accumulation (11–60 wt.% Mn), particularly enriched in Ba (1.5–8.2 wt.%) and Pb (1.0–5.0 wt.%) with poor contaminations in Al, Fe, and P. This study shows that the ore-forming process is similar to that occurring in the Imini C3 level, located ~ 100 km to the north-east. Such similarities with the high-grade pyrolusite-bearing ore suggest that the Tasdremt deposit is a lateral equivalent of the Imini deposits. However, the scarcity of pyrolusite in Tasdremt results in lower Mn grades, the Tasdremt ores being considered an aborted/incomplete system in comparison with the Imini deposits. 40Ar/39Ar geochronology of K-bearing Mn oxides yields late Cretaceous ages, defining three phases at ~ 91.5 Ma, ~ 77.5–82 Ma, and ~ 65–67 Ma. Although the source of metals remains hypothetical, mineralizing fluids were carried by O2-free groundwater that mixed with O2-rich shallow meteoric waters at the Tasdremt depositional site. The dissolution of the host dolostones and the karst environment have provided suitable conditions for the precipitation of Mn oxides, causing the coeval increase of pH and Eh, respectively. The Early Atlasic deformation during the Late Cretaceous is associated with mineralization events and was responsible for creation of low stand reliefs from Tasdremt to Imini. This period enabled karstification and mineralization. Connecting the Tasdremt deposits to other African Mn deposits is difficult since the latter consist of laterite resting above Paleoproterozoic Mn protores, and consequently formed under different conditions from karst-hosted deposits. It is likely that other Mn occurrences formed along the Atlas belt in similar settings.

中文翻译：

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晚白垩世含锰岩溶的 Tasdremt 矿床的多阶段成因（High Atlas，摩洛哥）

苏斯盆地的东部（摩洛哥）在 Tasdremt 地区包含几个锰矿床。三个锰矿体出现在 Cenomanian-Turonian 白云岩和 Senonian (Coniacian to Maastrichtian) 碎屑系列中，主要矿体位于它们之间的边界处。锰矿石由岩溶白云岩中的冠辉石族矿物组成，主要是冠辉石和荷兰石。新的实地观察、岩相分析和地球化学数据将 Tasdremt 矿床定义为岩溶沉积物（11-60 wt.% Mn），特别富含 Ba（1.5-8.2 wt.%）和 Pb（1.0-5.0 wt.%）。 %)，Al、Fe 和 P 的污染较差。这项研究表明，成矿过程与位于东北约 100 公里处的 Imini C3 层发生的过程相似。与含高品位软锰矿的矿石的这种相似性表明 Tasdremt 矿床是 Imini 矿床的横向等价物。然而，Tasdremt 中软锰矿的稀缺导致锰品位较低，与 Imini 矿床相比，Tasdremt 矿石被认为是一个中止/不完整的系统。含钾锰氧化物的 40Ar/39Ar 年代学产生晚白垩世时代，在 ~ 91.5 Ma、~ 77.5-82 Ma 和 ~ 65-67 Ma 定义三个阶段。虽然金属的来源仍然是假设的，但矿化流体是由不含 O2 的地下水携带的，这些地下水与 Tasdremt 沉积地点的富含 O2 的浅层大气水混合。宿主白云岩的溶解和岩溶环境为Mn氧化物的沉淀提供了合适的条件，分别导致pH和Eh同时升高。晚白垩世早期阿特拉斯纪的变形与矿化事件有关，并导致从 Tasdremt 到 Imini 形成低矮的地势起伏。这一时期促成了岩溶和矿化。将 Tasdremt 矿床与其他非洲锰矿床连接起来很困难，因为后者由位于古元古代锰原体上方的红土组成，因此形成于与岩溶赋存矿床不同的条件下。其他锰矿很可能在类似的环境中沿着阿特拉斯带形成。将 Tasdremt 矿床与其他非洲锰矿床连接起来很困难，因为后者由位于古元古代锰原体上方的红土组成，因此形成于与岩溶赋存矿床不同的条件下。其他锰矿很可能在类似的环境中沿着阿特拉斯带形成。将 Tasdremt 矿床与其他非洲锰矿床连接起来很困难，因为后者由位于古元古代锰原体上方的红土组成，因此形成于与岩溶赋存矿床不同的条件下。其他锰矿很可能在类似的环境中沿着阿特拉斯带形成。