| 东昆仑花石峡北部上二叠统格曲组源区特征:来自碎屑组成和岩石地球化学的证据 |
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| 引用本文： | 黄晓宏,张海军,王训练,王勋,沈智军,黄宇飞.东昆仑花石峡北部上二叠统格曲组源区特征:来自碎屑组成和岩石地球化学的证据[J].沉积学报,2016,34(6):1133-1146. |
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| 作者姓名： | 黄晓宏 张海军 王训练 王勋 沈智军 黄宇飞 |
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| 作者单位： | 1.中国地质大学(北京)地球科学与资源学院 北京 100083; |
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| 基金项目： | 中国地质调查局(12120113028800;1212011121258)，中央高校基本科研业务费专项资金(2652014005)[China Geological Survey Project |
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| 摘 要： | 东昆仑南缘上二叠统（乐平统）格曲组为一套由砾岩、砂岩和钙质泥岩构成的扇三角洲-浅海碳酸盐台地相沉积组合，记录了东昆仑造山带海西-印支过渡期构造演化过程，是解析该构造演化过程的理想对象。通过分析花石峡北坦地克借地区格曲组碎屑岩的碎屑组成与主量、微量和稀土元素特征，探讨了其物源区属性。结果显示，砂岩类型为长石砂岩和岩屑长石砂岩，石英、长石和岩屑平均含量分别为50.9%、36.8%、12.4%，长石以钾长石为主，岩屑和砾石成分复杂。砂岩的SiO2、Al2O3、TiO2、TFe2O3、MgO、K2O和Na2O平均百分含量分别为62.06%、13.26%、0.44%、4.53%、3.02%、2.42%和3.18%；微量元素比值Th/Sc和Th/U较高，平均为1.06和7.71；稀土元素总量∑REE平均120.43×10-6，LREE/HREE和（La/Yb）N均值分别为9.34和12，轻稀土相对富集，δEu平均为0.96，Eu异常不明显，REE特征与大陆岛弧背景区杂砂岩相似，与东昆仑地体加里东期俯冲-碰撞型火山弧花岗岩具有亲缘性。碎屑组分和主量、微量元素特征与判别图解揭示，格曲组砂岩物源区为海西旋回早期从东昆仑地体裂离的东昆南微地块，源岩以花岗岩为主，变质岩、沉积岩和酸性-基性火山岩较少，其中花岗岩形成构造背景为加里东期的大陆岛弧。结合区域地质和前人研究成果，认为格曲组为前陆盆地系统的隆后盆地沉积。
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| 关 键 词： | 上二叠统格曲组 东昆仑 物源分析 构造演化 |
| 收稿时间： | 2016-01-08 |
Provenance of the Upper Permian Gequ Formation in the Southern Margin of the East Kunlun Mountains: Constraints from Detrital Composition and Geochemistry |
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| HUANG XiaoHong,ZHANG HaiJun,WANG XunLian,WANG Xun,SHEN ZhiJun,HUANG YuFei.Provenance of the Upper Permian Gequ Formation in the Southern Margin of the East Kunlun Mountains: Constraints from Detrital Composition and Geochemistry[J].Acta Sedimentologica Sinica,2016,34(6):1133-1146. |
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| Authors: | HUANG XiaoHong ZHANG HaiJun WANG XunLian WANG Xun SHEN ZhiJun HUANG YuFei |
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| Institution: | 1.School of Earth Sciences and Resources, China University of Geosciences(Beijing), Beijing 100083, China;2.9th Gold Team of Chinese People's Armed Police, Haikou 571127, China;3.3rd Gold Team of Chinese People's Armed Police, Mudanjiang, Heilongjiang 157000, China |
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| Abstract: | The Upper Permian (Lopingian) Gequ Formation in the southern margin of the East Kunlun Mountains is composed of conglomerates, sandstones and calcareous mudstones of fan delta-sea carbonate plateau. It recorded the tectonic evolution of the East Kunlun orogenic belt during Late Hercynian-Early Indosinian. This paper studies the detrital modes and the compositions of major, trace and rare earth elements for sandstones of the Gequ Formation in Tandikejie area, north of Huashixia, and investigates the tectonic attributes and provenance types. Sandstone detrital modes show that the Gequ Formation consists of arkose and lithic arkose. The QtFL averages of sandstones are Qt 50.9%, F 36.8%, L 12.4%, feldspars are mainly K-feldspar, the composition of gravel and lithic is complex. Geochemistry analysis shows that average concentrations of SiO2, Al2O3, TiO2, TFe2O3, MgO, K2O and Na2O are 62.06%, 13.26%, 0.44%, 4.53%, 3.02%, 2.42% and 3.18%, respectively. Trace elements ratios such as Th/Sc, Th/U have high averages of 1.06, 7.71. The Gequ Formation sandstones have REE gross of 120.43×10-6. In the sandstones, LREE is relatively rich, the LREE/HREE ratio is 9.34, the (La/Yb)N ratio is 12, δEu is 0.96 and the anomaly of δEu is not obvious. According to the REE features, the Gequ Formation show similarities to the greywackes from continental island arc and affinity to the Caledonian subduction-collision arc type granites of the East Kunlun terrane. Based on the features and discriminant diagrams of clastic composition, major elements and trace elements, the provenance of the Gequ Formation sandstones came from the south microblock of East Kunlun, which was rifted from the East Kunlun terrane during Early Hercynian. The source rocks consisted of mainly granites and little sedimentary rocks, metamorphic rocks and acid-basic volcanic rocks, and the granites belong to the Caledonian continental island arc. Combined with regional geological background and previous basin studies, the Gequ Formation formed in back-bulge of foreland basin system. |
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| Keywords: | Upper Permian Gequ Formation East Kunlun Mountains provenance tectonic evolution |
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