东北帕米尔塔什库尔干中新世高钾碱性岩的成因机制与大地构造意义

发布时间：2018-04-30 22:21

本文选题：帕米尔 + 塔什库尔干　；参考：《地质论评》2017年03期

【摘要】：塔什库尔干地区位于青藏高原西北缘,帕米尔高原东北部,是中国境内唯一属于帕米尔弧形构造带的地区。然而,对于东北帕米尔地区新生代岩浆作用的研究相对青藏高原主体的研究薄弱得多。我们对东北帕米尔塔什库尔干地区新生代岩浆岩的锆石U-Pb年代学、地球化学及锆石Hf同位素组成进行了研究。结果表明:塔什库尔干新生代岩体中锆石U-Pb年龄约为10 Ma。所有样品显示高钾、碱性特征:K_2O(4.39%~11.86%)、AR值为3.07~6.36及A/CNK为0.57~0.81,为高钾碱性岩。塔什库尔新生代高钾碱性岩相对亏损Nb、Ta、Zr、Hf、Ti等高场强元素。岩石具有高的Sr/Y比值,Eu异常不明显。富集LREE,(La/Yb)_N=40.26~287.59。这些地球化学特征指示了塔什库尔干高钾碱性岩可能来源于榴辉岩相加厚下地壳。岩石的ε_(Hf)(t)为-0.83~-8.90,范围较大,说明其源岩物质主要来自地壳。推测新生代印度—亚洲大陆碰撞后,印度板块持续向北推进引起帕米尔地壳快速增厚,由于地壳增厚不均以及喀喇昆仑断裂的向北扩展作用,在中新世中期塔什库尔干地区局部范围内岩石圈重力失稳并发生垮塌,下地壳发生部分熔融形成高钾碱性岩浆。
[Abstract]:The Tashkurgan region is located on the northwest margin of the Qinghai-Tibet Plateau and northeast of the Pamir Plateau. It is the only region in China that belongs to the Pamir arc tectonic belt. However, the study of Cenozoic magmatism in Pamirs in Northeast China is much weaker than that in the main body of Qinghai-Tibet Plateau. Zircon U-Pb geochronology, geochemistry and HF isotopic composition of zircon from Cenozoic magmatic rocks in Pamir Tashkorgan area, Northeast China, have been studied. The results show that the U-Pb age of zircon in the Tashkurgan Cenozoic is about 10 Ma. All the samples showed high potassium and alkaline characteristics: K _ 2O 4.39 ~ 11.86 and AR = 3.07 ~ 6.36 and A/CNK = 0.57 ~ 0.81, respectively, which is a high-potassium alkaline rock. The Cenozoic high-potassium alkaline rocks in Tashkur are relatively depleted in high field strength elements such as NB ~ (2 +) ~ (2 +) ~ (2 +) ~ (2 +) ~ (2 +) ~ (2) ~ ( The rocks have high Sr/Y ratio and EU anomaly is not obvious. Enriched LREE / Yb / N 40.26 / 287.59. These geochemical characteristics indicate that the high potassium alkaline rocks in Tashkurgan may have originated from the lower crust thickened by the durgite facies. The range of 蔚 -0.83 ~ 8.90 for the rocks is -0.83 ~ 8.90, indicating that the source rocks are mainly derived from the crust. It is inferred that after the Cenozoic Indo-Asian continental collision, the Indian plate continued to push northward, resulting in rapid thickening of the Pamir crust, due to uneven crustal thickening and the northward expansion of the Karakoram fault. In the middle Miocene Tashkurgan area, the lithospheric gravity instability occurred and collapsed, and the lower crust partially melted to form high potassium alkaline magma.
【作者单位】：中国地质大学(北京)能源学院;中国地质科学院地质研究所;南京大学地球科学与工程学院;
【基金】：国家自然科学基金资助项目(编号:41302166;41472198及41430212) 中国地质调查局项目(编号:1211302108022;12120115027001及12120115002101)的成果~~
【分类号】：P588.15

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