Sedimentology and mineralogy of surface sediments from the Chilean continental margin

The regional patterns of texture and composition of modern continental slope and pelagic sediments off Chile between 25°S and 43°S reflect the latitudinal segmentation of geological, morphological, and climatic features of the continental hinterland. Grain-size characteristics are controlled by the grain-size of source rocks, the weathering regime, and mode of sediment input (eolian off northern Chile vs fluvial further south). Bulk-mineral assemblages reveal a low grade of maturity. Regional variations are governed by the source-rock composition of the different geological terranes and the relative source-rock contribution of the Coastal Range and Andes, as controlled by the continental hydrology. The relative abundance of clay minerals is also predominantly influenced by the source-rock composition and partly by continental smectite neoformation. Latitudinal variations of illite crystallinities along the Chilean continental slope (and west of the Peru-Chile trench) clearly reflect modifications of the weathering regime which correspond to the strong climatic zonation of Chile.智利沿岸南纬25°至43°海域现代大陆坡及远洋沉积物(pelagic sediments)的结构与组成区域分布模式，反映了大陆腹地地质、地貌与气候特征的纬度分异格局。沉积物的粒度特征受控于源岩(source rocks)粒度、风化体系以及沉积物输入方式（智利北部外海为风成输入，南部海域则以河流输入为主）。全矿物组合(bulk-mineral assemblages)显示其矿物成熟度较低。区域差异受控于不同地质地体(geological terranes)的源岩组成，以及海岸山脉与安第斯山脉的相对源岩贡献量，而该调控机制受大陆水文体系支配。黏土矿物(clay minerals)的相对丰度同样主要受源岩组成影响，部分受控于大陆环境中蒙脱石(smectite)的新生作用。智利大陆坡（及秘鲁-智利海沟(Peru-Chile trench)西侧）海域的伊利石结晶度(illite crystallinities)纬度变化，清晰反映了风化体系的改造特征，这与智利显著的气候分带格局高度契合。