| 太行山-大兴安岭东麓晚中生代碱性侵入岩岩石地球化学特征及其意义 |
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| 关键词:lithogeochemical characteristics alkaline intrusive rocks late Mesozoic east foot of the Taihang-Da Hinggan Mountains |
| 基金项目:国土资源部直管局项目和国家教委博士点基金项目(编号:99000141) |
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| The Late Mesozoic Alkaline Intrusive Rocks at the East Foot of the Taihang-Da Hinggan Mountains: Lithogeochemical Characteristics and Their Implications |
| The Late Mesozoic alkaline intrusive belt at the east foot of the Taihang-Da Hinggan Mountains, which consists of more than twenty alkaline intrusives, passes through two tectonic units, namely, the North China Craton (NCC) and the Inner Mongolian Orogenic Zone (IMOZ). The authors made for the first time a systematic lithogeochemical study of seven typical complexes along the belt. The results indicate that the alkaline intrusives in different tectonic units have obviously different characteristics, which can be used to reveal their tectonic settings, different source region features and depths. According to the bulk compositions, these rocks belong to acid igneous protoliths with over-saturated aluminum, characterized by the enrichment of alkaline, high K, and low Ca, Fe and Mg content, which reflects the rising acidity and alkalinity and the decreasing Al, Ca, Fe and Mg content of rocks from south to north. The tectonic environment of the late Mesozoic rocks in this belt is mainly of the extensional type. According to REE characteristics, the rocks in the NCC are all characterized by strongly depleted heavy rare elements (HREE), those in south Taihang area are noted for the absence of Eu anomalies, representing a deep magma source, and those in north Taihang area have clear negative Eu anomalies. The rocks in the IMOZ are characterized by weakly fractionated REE and distinct negative Eu anomalies. The δEu values in the belt gradually decrease from south to north, which shows that the source region in the north section is shallower than that in the south one. As for the trace element features, the alkaline intrusives in the NCC are characterized by high Sr, high Ba, low Rb, and relative depletion of the high field strength elements such as Nb, Ta, Zr and Hf, but things are just the opposite for those in the IMOZ, suggesting that the alkaline magma source in the NCC is related to the enriched mantle. |
| CAI Jian-hui,YAN Guo-han,XU bao-liang,WANG Guan-yu,MOU Bao-lei,ZHAO Yong-chao.2006.The Late Mesozoic Alkaline Intrusive Rocks at the East Foot of the Taihang-Da Hinggan Mountains: Lithogeochemical Characteristics and Their Implications[J].Acta Geoscientica Sinica,27(5):447-459. |
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