Description, geochemistry and growth rate of buried nodules from the Central Indian Basin

Buried nodules from siliceous sediments in the central Indian Basin are morphologically variable and mineralogically consist of d-MnO2 and incipient todorokite. Compositionally they are weakly diagenetic. The sediment coarse fractions (>63 µm) at different depths show variable abundances of micronodules, volcanic glass shards and biodebris. Dissolution of biodebris increases and abundance of micronodules decreases with increasing depth. Enrichment in Mn, Fe, Cu, Ni, Co, together with a decrease in organic carbon in the sediment column, may result from diagenetic metal remobilization. Diagenetically remobilized trace metals might have been utilized for the growth of micronodules over the buried nodules.中央印度洋盆地硅质沉积物中的埋藏结核（buried nodules）形态多样，矿物学组成以δ-二氧化锰（d-MnO2）和初生锰钾矿（incipient todorokite）为主，其成分表现出弱成岩作用特征。 不同深度的沉积物粗粒组分（>63 µm）中，微结核（micronodules）、火山玻璃碎屑与生物碎屑（biodebris）的丰度存在显著差异。随着埋藏深度增加，生物碎屑的溶蚀作用逐渐增强，微结核的丰度则逐步降低。 沉积物柱中锰（Mn）、铁（Fe）、铜（Cu）、镍（Ni）、钴（Co）的富集，以及有机碳含量的下降，可能源于成岩金属迁移作用。经成岩作用迁移的微量金属，或为埋藏结核表面微结核的生长提供了物质来源。