Chemical composition of DSDP and ODP cherts@en

Rare earth element (REE), major, and trace element abundances and relative fractionations in forty nodular cherts sampled by the Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) indicate that the REE composition of chert records the interplay between terrigenous sources and scavenging from the local seawater. Major and (non-REE) trace element ratios indicate that the aluminosilicate fraction within the chert is similar to NASC (North American Shale Composite), with average Pacific chert including ~7% NASC-like particles, Indian chert ~11% NASC, Atlantic chert ~17% NASC, and southern high latitude (SHL) chert 53% NASC. Using La as a proxy for sum REE, approximations of excessive La (the amount of La in excess of that supplied by the detrital aluminosilicate fraction) indicate that Pacific chert contains the greatest excessive La (85% of total La) and SHL chert the least (38% of total La). As shown by interelement associations, this excessive La is most likely an adsorbed component onto aluminosilicate and phosphatic phases. […]本数据集涵盖深海钻探计划（Deep Sea Drilling Project, DSDP）与大洋钻探计划（Ocean Drilling Program, ODP）采集的40份结核状燧石的稀土元素（Rare earth element, REE）、常量元素与微量元素丰度及相对分馏特征。研究结果表明，燧石的稀土元素组成记录了陆源物质来源与当地海水吸附清除作用之间的相互调控过程。常量元素及（非稀土元素）微量元素比值分析显示，燧石中的铝硅酸盐组分与北美页岩组合（North American Shale Composite, NASC）特征相似；其中太平洋燧石平均包含约7%的类北美页岩组合颗粒，印度洋燧石约含11%的北美页岩组分，大西洋燧石约含17%的北美页岩组分，而南极高纬度（southern high latitude, SHL）燧石的北美页岩组分占比可达53%。以镧（La）作为总稀土元素的替代指标，对过剩镧（即碎屑铝硅酸盐组分供给之外的镧含量）进行估算的结果显示，太平洋燧石的过剩镧占总镧的比例最高（85%），南极高纬度燧石的该比例最低（38%）。正如元素间关联分析所显示的，该过剩镧最可能为吸附于铝硅酸盐与磷酸盐相的吸附组分。[…]