论文部分内容阅读
黔东晚震旦世—早寒武世留茶坡组硅质岩,具有展布广、层位稳、厚度大等特征,并具有热水沉积的岩石学证据。代表性剖面硅质岩主量元素分析结果显示,w(SiO2)为93.41%～96.32%,均值95.23%,表示其为化学成分纯净的硅质岩;TFeO、MnO相对富集,Al2O3、TiO2、MgO含量相对较低,与热水沉积物相似,表明具有热水沉积特征;研究区硅质岩的Ba/Sr和U/Th等比值均大于1,以及稀土总量偏低(∑REE为9.22×10-6～24.04×10–6),Ce负异常(0.44～0.76),重稀土富集等特征,表现出热水沉积岩的元素地球化学特征;而其Al/(Al+Fe+Mn)、K2O/Na2O、CaO/(CaO+Fe)和MgO/Al2O3等比值的均值分别为0.46,1.86,0.33和0.19,也暗示出研究区热水沉积硅质岩受到一定程度陆源物质的影响。综合研究表明,典型剖面硅质岩形成于大洋盆地向大陆边缘台地过渡环境。
Late Sinian - Early Cambrian Oligocene siliceous rocks in eastern Guizhou Province are characterized by wide distribution, stable bedding and large thickness, and have petrological evidence of hydrothermal sedimentation. The main elemental analysis results of the representative section siliceous rocks show that the content of w (SiO2) is 93.41% ~ 96.32% with an average of 95.23%, which indicates that it is pure siliceous rocks with chemical composition; the relative enrichment of TFeO and MnO, The MgO content is relatively low, similar to that of hot-water sediments, indicating that it has hot-water sedimentary characteristics. The ratios of Ba / Sr and U / Th of cherts in the study area are both greater than 1 and the total REEs are low (ΣREE 9.22 × 10-6 ~ 24.04 × 10-6), Ce negative anomaly (0.44-0.76), heavy rare earth enrichment and other characteristics, showing the element geochemical characteristics of hydrothermal sedimentary rocks; and its Al / (Al + Fe + Mn) , K2O / Na2O, CaO / (CaO + Fe) and MgO / Al2O3 ratios are 0.46, 1.86, 0.33 and 0.19, respectively. It is also suggested that the hydrothermal sedimentary cherts in the study area are affected by some terrestrial sources. Comprehensive studies show that the typical profile of chert is formed in the transitional environment from the oceanic platform to the continental marginal platform.