| 山东灵山岛莱阳群粉砂岩地球化学特征及意义 |
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| 引用本文： | 张振凯,周瑶琪,彭甜明,于珊珊,岳会雯,周腾飞,刘加召.山东灵山岛莱阳群粉砂岩地球化学特征及意义[J].地球科学,2017,42(3):357-377. |
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| 作者姓名： | 张振凯 周瑶琪 彭甜明 于珊珊 岳会雯 周腾飞 刘加召 |
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| 作者单位： | 1.中国石油大学地球科学与技术学院，山东青岛 266580 |
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| 基金项目： | 中央高校基本科研业务费专项资金项目15CX06011A国家自然科学基金项目41272123 |
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| 摘 要： | 灵山岛下部莱阳群重力流沉积地层以其巨厚的沉积规模，独特的沉积特征受到国内外地质学界越来越多的重视.但目前，该套地层的源区风化程度、物源性质、物源区构造背景及沉积环境尚不明确，通过对灵山岛下部莱阳群粉砂岩进行岩相学分析、主量元素XRF测试、稀土及微量元素ICP-MS测试，结果显示:粉砂岩SiO2含量较低 (平均51.78%)，Fe2O3T含量较高 (平均5.73%)，Na2O平均含量为2.74%，K2O平均含量为2.79%；通过主量元素投图分析，样品归类为杂砂岩及岩屑砂岩；样品ΣREE为153.00×10-6~254.38×10-6，平均为201.65×10-6，高于PAAS及UCC，富集轻稀土元素，贫重稀土元素，具有中等程度Eu负异常，弱Ce负异常；相对于UCC，样品富集大离子亲石元素，弱富集高场强元素，亏损过渡组元素.样品ICV值高 (＞0.84)、为初次循环沉积，CIA值低 (＜65) 表明源区风化强度低，物源为长英质物质及少量古地壳再旋回物质，物源区大地构造背景为大陆岛弧与活动大陆边缘，沉积环境为海相还原环境且莱阳期为干热气候.此外，应用对REE元素进行归类统计的方法来推测物源区，分析表明样品物源区最有可能为胶南群与蓬莱群地层.
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| 关 键 词： | 灵山岛 莱阳群 地球化学 沉积环境 |
| 收稿时间： | 2016-09-05 |
Geochemical Characteristics and Signatures of Siltstones from Laiyang Group at Lingshan Island,Qingdao, Shandong |
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| Abstract: | Gravity flow deposits of Laiyang Group at the lower part of Lingshan island attract an increasing attention of geologists at home and abroad because of its huge thickness and unique sedimentary features. However, its weathering degree, characteristics and structural setting of provenance, and depositional environment stillremain in dispute. In this study, major elements, rare earth elements and trace elements contents of the siltstones from Laiyang Group at Lingshan Island were examined by XRF and ICP-MS. It is found that siltstones are characterized by relatively low contents of SiO2 (avg. 51.78%) and high contents of Fe2O3T (avg. 51.78%); average contents of Na2O and K2O of siltstones are 2.74% and 2.79%, respectively, the siltstones are classified as litharenites and greywackes; ΣREE contents of the samples are 153.00×10-6-254.38×10-6 (avg. 201.65×10-6), which are higher than those of UCC and PAAS; the pattern of REE is characterized by LREE enrichment, HREE depletion, moderately negative Eu abnormity and weakly negative Ce abnormity; compared with UCC, samples are enriched in LILEs, weakly enriched in HFSEs and depleted in transitional elements. Index of Compositional Variability (ICV) values of siltstones in Lingshan Island are high, which indicates the source materials are mainly primary cycle sediments, Chemical Index of Alteration (CIA) values are relatively low, which suggests that the weathering intensity of provenance is low. Element analysis indicates that felsic rocks serve as the main source rocks, including small amounts of contributions from recycled orogenic belt materials; tectonic settings of provenance belong to active continental margin and continental island arc; sedimentary environment is reducing marine environment and paleoclimate of Laiyang Period was arid. It is original for the authors to apply the statistical analysis method to determine the provenance regions more precisely according to the features of REEs, and it is concluded that the source rocks are most likely from Jiaonan Group and Penglai Group. |
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