【摘要】 广西德保泥盆系硅岩在沉积特征上具有热水沉积的环状“眼式”分布结构、准同生沉积期的热水蚀变、喷发角砾岩、底板被硅化等特征。常量元素、微量元素和REE均表现出热水沉积的特征。更多还原

【Abstract】 There is a basin in Debao, Guangxi, Chna, which belongs to the "Nandan"-type basins (Middle-Early to Late-Middle Devonian). In the basin occur cherts spotted in shape. The spotted cherts show a gradational relationship with marl and micrite beds. It exhibits hydrothermal "eye" structure in plane. There are some hydrothermal eruptive breccias and three synsedimentary hydrothermal alterations. (1) network-filling fine-microcrystalline quartz; (2) silicified fossil; and (3) recrystallization-fading related to the quartz network in origin in the Debao cherts. Mu-dstone beneath the chert beds has been silicified by hydrothermal solutions.The geochemical features of cherts in Debao show that they possess the compositions of hydrothermal cherts. Fe/Ti>20, Al/(Al + Fe+Mn)<0.35 and U/Th> 4.0 are all indicative of hydrothermal-sedimentary features of the Debao cherts. All the data points of the Debao cherts fall into the hydrothermalsedimentary fields as shown in Fe-Mn-(Cu + Co + Ni) ×10 diagram and logU-logTh plot. The REE patterns (North American Shale-normalized) in the Debao cherts display a significant negative Ce anomaly (Ce= 0.45 - 0.60) and a positive Eu anomaly (δEu = 1.05 -2.4), which are similar to those of hydrothermal deposits, but different from those of hydrogenous deposits and diatoms.更多还原