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现有地质资料分析,把发育于香山群第三亚群辉绿岩时代下限定为早古生代。辉绿岩主元素以高钠、镁,低钾、钛为特征。稀土总量(∑REE)较低,轻、重稀土分馏作用不明显;基本不显示Eu异常,球粒陨石标准化配分曲线具有平缓的特征。与原始地幔相比,微量元素值约是原始地幔标准值的2~10倍,大离子亲石元素(LILE)相对亏损,高场强元素(HFSE)分布平坦且不分异;N-MORB标准化蛛网图上,呈现大离子亲石元素(LILE)富集特征。地球化学特征表明:辉绿岩属于大洋拉斑玄武岩系列,显示了伸展作用的构造背景。另外,结合岩石学、沉积背景和同构造期岩套特征分析,再次验证了在中晚寒武世,阿拉善地块南缘与鄂尔多斯地块西南缘具离散型大陆边缘性质。
According to the analysis of the existing geological data, the lower limit of the diabase age developed in the third sub-group of Xiangshan Group is defined as the Paleozoic. The main elements of diabase are characterized by high sodium, magnesium, low potassium and titanium. The total REREE (ΣREE) is low, and the fractionation of light and heavy rare earths is not obvious. The Eu anomalies are basically absent, and the normalized distribution curve of chondrite melatonites has a gentle feature. Compared with the original mantle, the trace element value is about 2 ~ 10 times of the standard value of the original mantle. The LILE is relatively depleted and the HFSE distribution is flat and undifferentiated. The N-MORB normalization On the cobweb, LILE enriched features were shown. Geochemical characteristics indicate that diabase belongs to the oceanic basalt series and shows the tectonic setting of extension. In addition, with the analysis of petrology, sedimentary background and the characteristics of the rock mass at the same tectonic stage, it is verified again that there are discrete continental margins in the middle and late Cambrian with the south margin of Alxa Block and the southwestern Ordos block.