| 中生代河北、内蒙古基性岩墙及酸性岩年代学和地球化学研究 | |
| 唐亮 | |
| Thesis Advisor | 刘燊 |
| 2013 | |
| Degree Grantor | 中国科学院研究生院 |
| Place of Conferral | 北京 |
| Degree Name | 硕士 |
| Degree Discipline | 矿物学、岩石学、矿床学 |
| Keyword | 基性岩墙 流纹岩 年代学 华北克拉通 兴蒙造山带 |
| Abstract | 河北省北部及内蒙古赤峰地区位于中亚造山带的东部，是中国构造演化最复杂的地区之一，也是中国地质学家提出“燕山运动”理论的研究区。以内蒙古赤峰西拉木伦缝合带为界，缝合带以南属华北克拉通北缘，本文研究的河北杨树沟和新房子基性岩墙侵位于该区。西拉木伦缝合带以北到索伦-贺根山缝合带地区是一个过渡地块，属兴蒙造山带的范围，本文研究的内蒙古赤峰市巴林左旗中心屯流纹岩就出露该区，中心屯地区同时属于大兴安岭花岗岩带南缘。 基性岩墙是研究大陆伸展裂解的理想证据，华北克拉通北缘在晚中生代发生了显著的拉伸作用，基性岩墙广泛出露，河北省北部杨树沟基性岩墙就是其中的代表。锆石U-Pb年龄显示，基性岩墙的形成时代约为134.9?9.2Ma，为早白垩世中期岩浆作用的产物。在岩石化学组成上，SiO2=52.02-57.79wt.%，位于碱性和亚碱性过渡区，另外，基性岩墙的Na2O（3.77-5.26wt.%）大于K2O（2.17-3.32wt.%），MgO（1.88-3.46wt.%）含量较低，富集轻稀土元素（LREE）和大离子亲石元素（LILEs，Rb，Ba和Sr）和弱的Eu正异常（δEu=0.98-1.19，平均1.08），亏损高场强元素（HFSEs，Nb和Ta）及重稀土元素（HREE）。地球化学系统研究表明，研究区基性岩墙来源于富集岩石圈地幔的部分熔融作用，岩浆上侵过程中存在橄榄石、尖晶石、榴辉岩和角闪岩相的残余，基性岩墙的形成可能与造山后伸展作用有密切的联系。 河北北部新房子基性岩墙锆石U-Pb年龄显示，该基性岩墙形成于142.9±7.9Ma，为早白垩世早期岩浆事件的产物。在岩石化学组成上，SiO2=50.01-51.78wt.%，落在了亚碱性范围内，靠近碱性和亚碱性过渡线。基性岩墙的Na2O（3.02%-3.79%）含量大于K2O（1.06-1.32wt.%）；较高的MgO（5.18-6.02wt.%）含量此外，富集轻稀土及大离子亲石元素（Ba、K、Sr等），亏损重稀土元素（LREE/HREE=6.13-6.37），Yb、Lu含量较低，Eu显轻微的正异常（δEu=1.06-1.11）；不具有高场强元素（Nb，Ta，Zr、Hf）的异常。εSr(t)=1.14-2.70，εNd(t)=2.69-2.89。地球化学系统研究表明，研究区基性岩墙来源于亏损地幔的部分熔融作用，源区存在榴辉岩相的残余，同时，基性岩墙的形成可能与造山后伸展作用有密切联系。 内蒙古中心屯流纹岩锆石U-Pb年龄显示，该流纹岩喷发于136.3±2.3Ma，是早白垩世中期岩浆活动的产物。在岩石化学性质方面，该花岗岩的SiO2=69.71-77.31wt.%，有较低的Fe2O3和MgO以及CaO含量，K2O大于Na2O。Cr与Ni以及Sr含量变化较大。较高的Ba、Zr、Th以及U含量；稀土元素球粒陨石标准化图解呈典型的右倾型，富集轻稀土，亏损重稀土（LREE/HREE=6.0-10.6），Eu显示负异常（δEu=0.08-0.77）；富集大离子亲石元素Rb、Zr、Hf、La、Ce等，亏损高场强元素（Nb、Ta、Ti）以及Sr、P等。系统研究认为，岩浆形成过程中，钾长石无明显结晶分离作用；存在斜长石、橄榄石、单斜辉石、尖晶石、榍石和金红石等矿物的结晶分离作用；该流纹岩形成于拉伸环境，地球化学性质与A型花岗岩的特征类似，是下地壳部分熔融作用的产物。 |
| Other Abstract | Northern Hebei province and Chifeng in Inner Mongolia are located in the east part of Central Asia orogene belt, are the most special areas in China, and the study areas for the investigation of Yanshan activity. The North China Craton (NCC) is situated in the south of the Xilamulun suture. The Mafic dykes from Yangshugou and Xinfangzi in Hebei Peovince were found in these areas. In addition, there is a transitional plate between Xilamulun suture and Soker-Hegengshan suture; there the rhyolites in Chifeng were studied here. As the direct result of lithospheric extension, late Mesozoic mafic dykes are widespread in Northern NNCC. The zircon U-Pb age of the Yangshuigou mafic dykes is 134.9?9.2Ma, indicating that these mafic dykes are the result of earlier Cretaceous magmatism. The SiO2 contents of the rocks range from 52.02wt. % to 57.79 wt. %, and straddle in the field of alkaline and sub-alkaline series. In addition, the mafic dykes are characterized by higher Na2O (3.77-5.26wt.%) than K2O(2.17-3.32wt.%), depleted in MgO(1.88-3.46 wt.%), enrichment in light rare earth elements(LREEs) and large ion lithophile elements(LILEs , Rb, Ba, and Sr)and weak positive Eu anomalies(δEu =0.98-1.19, average in 1.08), as well as depletion in heavy rare earth elements(HREEs)and high field strength elements(HFSEs, Nb and Ta). Systemic geochemistry research indicates that these mafic dykes, in this study, were derived from partial melting of an enriched lithospheric mantle, however, there were remnant of olivine、Cr-spinel、 eclogite and amphibolite faces in the source. In summary, the origins of the studied dykes were related to post-collision extension of Xing-Meng Orogene. The zircon U-Pb age of Xinfangzi mafic dykes is 142.9±7.9Ma, the result of earlier Cretaceous magmatism. The SiO2 =50.01-51.78 wt. %, and located in the field of sub-alkaline series but also near alkaline series. In addition, the mafic dykes are characterized by higher Na2O (3.02-3.79 wt.%) than K2O (1.06-1.32 wt.%), enrichment in MgO (5.18-6.05 wt.%), LREE and lLILEs(Rb, K, and Sr)and weak positive Eu anomalies(δEu =1.06-1.11), depletion in HREEs and much lower Yb and Lu,and HFSEs(Nb、Ta、Zr and Hf)are normal in this mafic dykes. εSr(t)=1.14-2.70,εNd(t)=2.69-2.89. Systemic geochemistry investigation indicates that these mafic dykes were derived from partial melting of depleted mantle; however, there were remnant of eclogite face in the source. Based on the above interpretations, the origins of the dykes were related to post-collision extension of Xing-Meng Orogene blet. The zircon U-Pb age of Zhongxintun rhyolites is 136.3±2.39 Ma, the result of middle earlier Cretaceous magmatism. The SiO2 = 69.71-77.31wt. %, located in the dacite and rhyolite series, have a lower contents of Fe2O3, MgO and CaO, but K2O is much richer than Na2O. And have a wide range of Cr, Ni and Sr, the studied rhyolites are characterized by enrichment in LREE, LILEs(Rb, Zr, Hf, La and Ce), depletion HFSEs(Nb, Ta and Ti), Sr and P. Systemic geochemistry researches show that the magma experienced the fraction of plagioclase, olivine, clinopyroxene, spinel, titanite and rutile. In addition, these rhyolites were formed in an extentional setting, and lower crust partial melting may contribute to the magma formation. |
| Subject Area | 矿床地球化学 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.gyig.ac.cn/handle/352002/5868 |
| Collection | 研究生_研究生_学位论文 |
| Recommended Citation GB/T 7714 | 唐亮. 中生代河北、内蒙古基性岩墙及酸性岩年代学和地球化学研究[D]. 北京. 中国科学院研究生院,2013. |
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