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对塔里木盆地北部肖尔布拉克寒武系露头剖面中 8.8m厚的黑色页岩夹硅质岩组合中的硅质岩的系统采样分析表明 ,该硅质岩具有深源成因特征。其低的Th/U和Rb/Sr比也证明了其沉积时所具有的深部物源和热水注入迹象。硅质岩的稀土元素经北美页岩标准化后的Ce/Ce 从 0 .4 2到 0 .79,平均 0 .5 7。Ce的负异常明显。这些稀土元素的参数特征与加利福尼亚弗朗希斯科杂岩 (FranciscanComplex)中沉积在大洋海底硅质岩的稀土元素特征十分相似。北美页岩标准化后的Eu/Eu 值从 8.0 5下降到 1.0 3。其相对较高的Eu/Eu 值很有可能反映了热水的注入。Eu/Eu 值从剖面底部到顶部的系统降低反映了剖面底部的热水作用最强烈 ,向上热水作用逐渐减弱。上述一系列的地球化学标志指示该硅质岩应沉积在离洋中脊不远的、具有深源物质 /热水注入的远洋盆地背景中。结合区域地质和伴生黑色页岩地球化学的综合分析认为 ,该套硅质岩的形成与上升洋流的影响有关。上升洋流将形成于大洋盆地背景中的物质带到大陆边缘陆棚环境中发生沉积 ,造成了沉积在陆棚环境中的硅质岩 ,在地球化学组成上保留了其大洋盆地背景的特征
Systematic sampling of the cherts in the 8.8-m-thick black shale-chert chert in the Cambrao outcrop section of the Shoballac Cambrian outcrop in the northern part of the Tarim Basin shows that the chert is characterized by its deep source. Its low Th / U and Rb / Sr ratios also demonstrate evidence of deep source and hot water injection during its deposition. The Ce / Ce of the rare earth elements of the chert is normalized from North American shale from 0.42 to 0.79, averaging 0.57. The negative anomaly of Ce is obvious. The characteristics of these rare earth elements are very similar to the characteristics of rare earth elements deposited in oceanic seafloor chert in the Franciscan Complex of California. The standardized Eu / Eu value of North American shale decreased from 8.05 to 1.03. Its relatively high Eu / Eu value is likely to reflect the hot water injection. The systematic reduction of Eu / Eu values from the bottom to the top of the profile reflects that the hot water at the bottom of the section is most strongly affected and the upward hot water is gradually weakened. The above series of geochemical markers indicate that the chert should be deposited in the background of the oceanic basin with deep source / hot water injection not far from mid-ocean ridges. According to the comprehensive analysis of regional geology and associated black shale geochemistry, the formation of this set of chert is related to the influence of rising ocean currents. The upwelling ocean currents deposited the material formed in the background of the oceanic basin into the marginal continental margin of the continental margin, resulting in the chert of the sedimentary environment in the shelf environment, retaining the characteristics of its oceanic background in the geochemical composition