扬子地块南缘元古代浊积岩源区风化特征和源岩性质的沉积地球化学记录

对扬子地台南缘元古代浊积岩的常量元素和微量元素地球化学研究表明，源区遭受了中等程度的风化作用影响，这种影响记录在碱金属和碱土金属元素的丰度与分布型式、蚀变化学指数(CIA)以及Th／U比值等方面。稀土元素的组成和配分型式、Th／Sc和La／Sc比值以及其他常量和微量元素之间的关系表明，沉积岩不具备成熟的再旋回沉积物的特征，其源岩主要为由酸性岩浆岩等长英质组分构成的古老上地壳，源岩曾受到了显著的壳内分异作用的影响。中元古界冷家溪群地层的源岩较新元古界板溪群合有较高的Co，Cr，Ni，Sc，V等基性组分，且基性的铁镁质成分主要反映在粘土级组分的沉积记录中。

SEDIMENTARY GEOCHEMICAL RECORDS FOR THE SOURCE AREA WEATHERING AND NATURE OF SOURCE ROCKS OF THE PROTEROZOIC TURBIDITES FROM THE SOUTHERN MARGIN OF THE YANGTZE BLOCK

Studies on the major and trace element geochemistry of the Proterozoic turbidites from the southern margin of the Yangtze block indicate that the source area was affected by a moderate weathering regime, as recorded by the contents and distribution patterns of alkali and alkaline earth elements, the Chemical Index of Alteration (CIA), and Th/U ratios. Rare earth element compositions and chondrite normalized patterns, Th/Sc and La/Sc ratios, as well as the relationship among other major and trace elements indicate that the turbidites do not exhibit characteristics of recycled metasediments and were derived from an old continental crust dominated chiefly by felsic rocks of magmatic origin. The source rocks were significantly affected by intracrustal differentiation. The source rocks of the Mesoproterozoic Lengjiaxi Group contain more mafic materials like Co, Cr, Ni, Sc, and V compared to those of the Neoproterozoic Banxi Group, and the incorporation of these mafic components is mainly concentrated in clay size fraction.