Geochemical composition of sediments from ODP Site 164-997, Blake Ridge@en

Twenty-two trace elements in 355 sediment samples from Site 997 on the Blake Ridge were examined by inductively coupled plasma-optical emission spectrometry and inductively coupled plasma-mass spectrometry, for respective fractions of acid-soluble and insoluble compositions. Downhole profiles of these elements exhibit complicated fluctuations throughout late Miocene to Pleistocene, principally due to the variations in the acid-soluble fraction. Noncarbonate composition is given from the acid-insoluble residues, which permits us to recognize secular feature of selected element variance for four intervals. These intervals (I: 0-183 mbsf; II: 183- 440 mbsf; III: 440-618 mbsf; and IV: 618-750 mbsf) are interpreted to have originated from changes in the suite of sediments of particular sources and chemical composition, sedimentation rate, dilution of biogenic carbonate abundance, and possibly the current system that controlled deposition and reworking of the terrigenous materials.本研究采用电感耦合等离子体光发射光谱法（inductively coupled plasma-optical emission spectrometry）与电感耦合等离子体质谱法（inductively coupled plasma-mass spectrometry），对布雷克海岭（Blake Ridge）997站位（Site 997）的355件沉积物样品中的22种微量元素进行检测分析，分别针对酸溶组分与酸不溶组分开展对应测试；上述微量元素的钻孔剖面在晚中新世至更新世期间呈现出复杂的波动特征，其主导成因在于酸溶组分的含量变化。通过酸不溶残余物可获取非碳酸盐组分的相关数据，借此我们能够识别四个层段内目标元素变异的长期演化特征；本次研究划定的四个层段为I：0~183 mbsf（meters below sea floor，海底以下米数）、II：183~440 mbsf、III：440~618 mbsf、IV：618~750 mbsf，其形成被认为与特定物源及化学组成的沉积物组合演变、沉积速率变化、生物碳酸盐丰度的稀释效应，以及可能调控陆源物质沉积与再改造的水动力系统变动密切相关。