Analysis of Mn deposits from Galicia Bank Leg 47@en

This report deals with results of the first stage of a complex study of the predominantly Lower Cretaceous sediments cored at Site 398 at depths from 945 to 1740 meters. The section studied is overlain by 35 meters of Cenomanian sediments, which are similar lithologically to the underlying sequence. In the upper part (Unit 3) a major rock-forming carbonate mineral is present in much of the section as calcite, often with distinct structural features indicative of a biogenic origin (nannofossils, skeletal detritus) and diagenetic recrystallization. Unit 3 is characterized by abundant authigenic minerals represented mainly by siderite and manganese-bearing carbonate minerals.本报告阐述了对398站位（Site 398）945至1740米深度段取心获得的以早白垩世沉积物为主的综合研究第一阶段成果。该地层段之上覆有35米厚的塞诺曼阶（Cenomanian）沉积物，其岩性与下伏地层序列高度相似。在上部层位（单元3）中，研究段大部分区域的主要造岩碳酸盐矿物为方解石（calcite），常呈现显著结构特征，指示其为生物成因（钙质超微化石（nannofossils）、骨骼碎屑）及成岩重结晶作用。单元3以发育大量自生矿物为特征，此类矿物主要由菱铁矿（siderite）以及含锰碳酸盐矿物构成。