Geochemistry of Nazca plate surface sediments: An evaluation of hydrothermal, biogenic, detrital, and hydrogenous sources
Geochemistry of Nazca plate surface sediments: An evaluation of hydrothermal, biogenic, detrital, and hydrogenous sources
复制标题
DOI：
10.1130/mem154-p133
复制
发表时间：
1981
期刊：
影响因子：
--
通讯作者：
J. Dymond
中科院分区：
文献类型：
--
作者：
J. Dymond
纳斯卡板块沉积物中强烈的成分梯度是由于不同地理区域沉积物来源的差异造成的。在板块的西缘，与东太平洋海隆有关的热液来源的沉淀物占主导地位的沉积物预算。在板块的北方部分，反映沿赤道沿着的高生产力的生物试验是重要的。靠近大陆的沉积物主要是碎屑状的铝硅酸盐。位于板块中部的盆地中过渡金属的富集程度很高，其来源要么是热液沉淀物，要么是正常海水中的自生铁锰沉积。本研究开发并应用了一个规范的组合物模型，该模型将大量化学成分数据转换为五种不同组分的重量百分比的定量估计：（1）热液沉淀物，（2）生物测试，（3）碎屑铝硅酸盐，（4）氢铁锰沉淀物，和（5）生物体的不溶性残留物。该模型假设每种组分在板上的任何地方都具有恒定的组成，并使用线性规划来获得最适合任何样品的测量组成的组分混合物。利用规范模型对425个样品的化学成分进行了测定和分析。从上升峰100公里内的样品一般有> 80%的热液成分。热液组分的地理分布表明，北部约30 S的底流运输热液沉淀物向西，而南部的30 S的底流进行热液沉淀物向东进入Roggeveen盆地。沉积物的生物含量从赤道附近的约80%降低到20 S纬度以南的小于10%的值。在南美洲大陆1，000 km以内的区域，碎屑丰度一般> 80%;然而，在20 - 25 S之间，碎屑组分异常高的浓度从大陆延伸到Yupanqui盆地。这些数据表明，在板块的这一部分底部云状层运输的重要性。位于东太平洋海隆以东的深盆具有最高的含氢组分含量，这可能是由于铁锰物质不断沉积到一个其他来源贡献很小的区域。在该模型中，生物源物质溶解后剩余的元素被称为”溶解残留物”。该成分在以下盆地中达到最大丰度：
Strong compositional gradients in Nazca plate sediments result from variability in the sedimentary sources in different geographic regions. At the western margin of the plate, precipitates from hydrothermal sources associated with the East Pacific Rise dominate the sediment budget. In the northern part of the plate, biogenic tests that reflect the high productivity along the equator are important. Near the continent the sediments are largely detrital aluminosilicates. The basins, which lie in the central portions of the plate, have strong enrichments in the transition metals whose source is either hydrothermal precipitates or authigenic ferromanganese deposition from normal sea water. This study develops and applies a normative composition model that converts bulk chemical composition data into quantitative estimates of the weight percent of five distinct components:(1) hydrothermal precipitates,(2) biogenic tests,(3) detrital aluminosilicates,(4) hydrogenous ferromanganese precipitates, and (5) the insoluble residue of organisms. The model assumes that each component has a constant composition anywhere on the plate and uses linear programming to arrive at a mixture of components that best accounts for the measured composition of any sample. The chemical compositions of 425 samples were determined and analyzed using the normative model. Samples from within 100 km of the rise crest generally have> 80% hydrothermal components. The geographic distribution of the hydrothermal components indicates that north of approximately 30 S bottom currents transport hydrothermal precipitates to the west, whereas south of 30 S bottom currents carry the hydrothermal precipitates eastward into the Roggeveen Basin. The biogenic contents of the sediments decrease latitudinally from approximately 80% near the equator to values less than 10% south of 20 S latitude. The detrital abundance is generally> 80% in regions within 1,000 km of the South American Continent; however, between 20 and 25 S unusually high concentrations of the detrital component extend away from the continent and into the Yupanqui Basin. These data suggest the importance of bottom nepheloid-layer transport in this part of the plate. The deep basins lying east of the East Pacific Rise have the highest contents of hydrogenous component, presumably caused by a constant deposition of ferromanganese material into a region with small contributions from other sources. Elements remaining after the dissolution of biogenic matter are termed" dissolution residue" in the model. This component reaches a maximum abundance in the basins on