| 辽东黄花甸地区古元古代花岗质岩浆作用及其地质意义 |
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| 引用本文： | 王鹏森,董永胜,李富强,高铂森,甘宜成,陈木森,许王.辽东黄花甸地区古元古代花岗质岩浆作用及其地质意义[J].岩石学报,2017,33(9):2708-2724. |
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| 作者姓名： | 王鹏森 董永胜 李富强 高铂森 甘宜成 陈木森 许王 |
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| 作者单位： | 吉林大学地球科学学院, 长春 130061,吉林大学地球科学学院, 长春 130061,吉林大学地球科学学院, 长春 130061,吉林大学地球科学学院, 长春 130061,吉林大学地球科学学院, 长春 130061,吉林大学地球科学学院, 长春 130061,中国地质科学院地质研究所, 北京 100037 |
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| 基金项目： | 本文受国家自然科学基金重点项目（41430210）和中国地质调查局地质调查项目（DD20160121）联合资助. |
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| 摘 要： | 胶-辽-吉古元古代造山/活动带的辽东黄花甸地区出露大量古元古代花岗质岩石,前人将该区的花岗质岩石统称为花岗质混杂岩。本文通过详细的野外地质调查和室内综合研究,将该套花岗质混杂岩解体为时代及性质完全不同的两类花岗岩——黑云母二长花岗岩和花岗闪长岩。其中黑云母二长花岗岩具有块状、条痕状、片麻状的不同构造类型,均显示富SiO_2(72.37%~77.44%)、贫Al_2O_3(11.69%~13.21%)、富K_2O(3.97%~5.11%)的特征,Na_2O/K_2O=0.64~1.08,TiO_2含量在0.18%~0.34%之间,MnO、MgO和P_2O_5的含量较低,分别为0.01%~0.07%、0.12%~0.32%和0.01%~0.06%,铝饱和指数A/CNK集中分布在1.33~1.45之间,A/NK在1.49~2.60之间,属于过铝质高钾钙碱性系列;微量元素Sr、Ba、Ti、P强烈亏损,具有明显的Eu负异常,具有A型花岗岩的特征。黑云母二长花岗岩的锆石大部分为具有清晰震荡环带结构的岩浆锆石,从3个样品获得LA-ICP-MS锆石U-Pb谐和年龄分别为2185±29Ma、2183±13Ma、2166±10Ma,据目前所获得南辽河群碎屑锆石年龄(1.95~2.15Ga),本文认为黑云母二长花岗岩的侵位时代要早于南辽河群地层沉积的时间,构成了南辽河群地层沉积的基底。花岗闪长岩呈岩枝状侵入黑云母二长花岗岩和里尔峪组地层中,富SiO_2(72.54%~74.31%)、Al_2O_3(15.01%~16.17%),全碱(K_2O+Na_2O)平均7.77%,相对富钠(Na_2O/K_2O=1.27~2.82),贫钙、镁,MgO平均为0.26%,CaO平均为1.59%,Mg#值平均为54.0,铝饱和指数A/CNK集中分布在1.61~1.78之间,A/NK在1.49~2.60之间,属于过铝质钙碱性系列,具明显的Eu正异常,Y/Yb低,Sr/Y高,而且强烈亏损Th、Ta、Nb、Ti等高场强元素,富集Ba、K、Rb、Sr等低场强元素,具有埃达克质花岗岩的特征。花岗闪长岩的锆石大部分为具有清晰震荡环带结构的岩浆锆石,从2个样品获得LAICP-MS锆石U-Pb年龄分别为1995±18Ma、1995±13Ma。可以推断花岗闪长岩的侵位时代为2.0Ga左右。本文认为具有A型特征的黑云二长花岗岩是陆块内部拉伸减薄-裂解过程中下部地壳部分熔融的产物,具有埃达克质特征的花岗闪长岩是俯冲过程中所形成火山弧或活动大陆边缘岩浆活动的产物。以上研究表明胶-辽-吉古元古代造山/活动带可能经历了在2.2~2.15Ga左右的拉伸裂解过程和2.0Ga左右俯冲挤压的构造演化过程。
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| 关 键 词： | 胶-辽-吉造山带 A型花岗岩 埃达克质花岗岩 活动大陆边缘 辽东黄花甸 |
| 收稿时间： | 2017/4/12 0:00:00 |
| 修稿时间： | 2017/7/15 0:00:00 |
Paleoproterozoic granitic magmatism and geological significance in Huanghuadian area, eastern Liaoning Province |
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| WANG PengSen,DONG YongSheng,LI FuQiang,GAO BoSen,GAN YiCheng,CHEN MuSen and XU Wang.Paleoproterozoic granitic magmatism and geological significance in Huanghuadian area, eastern Liaoning Province[J].Acta Petrologica Sinica,2017,33(9):2708-2724. |
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| Authors: | WANG PengSen DONG YongSheng LI FuQiang GAO BoSen GAN YiCheng CHEN MuSen and XU Wang |
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| Institution: | College of Earth Science, Jilin University, Changchun 130061, China,College of Earth Science, Jilin University, Changchun 130061, China,College of Earth Science, Jilin University, Changchun 130061, China,College of Earth Science, Jilin University, Changchun 130061, China,College of Earth Science, Jilin University, Changchun 130061, China,College of Earth Science, Jilin University, Changchun 130061, China and Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China |
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| Abstract: | Paleoproterozoic granites are widely distributed in the Huanghuadian area of the eastern Liaoning Province, which belongs to the central part of Jiao-Liao-Ji orogenic/activities belts. In the past, some granitic plutons were considered as granitic melange in this area. In this paper, we divide the granitic melange into two types, biotite monzogranites and granodiorites on the basis of comprehensive studies of field observation, petrography, geochemistry and isotope chronology. The biotite monzogranites yield massive, gneissic and striate in structure, which are characterized by high SiO2 (72.37%~77.44%) and K2O (3.97%~5.11%) and low Al2O3 (11.69%~13.21%) contents, with Na2O/K2O=0.64~1.08; Their TiO2 content are between 0.18%~0.34%, MnO, MgO and P2O5 contents are 0.01%~0.07%, 0.12%~0.32% and 0.01%~0.06%, respectively. The saturation index A/CNK is between 1.33 and 1.45 and A/NK between 1.49 and 2.60, which suggest that the biotite monzogranites should belong to the peraluminum high potassium calcium alkaline series. Some trace elements, e.g. Sr, Ba, Ti and P are strongly depleted, with an obvious anomaly of negative Eu. All the geochemical characteristics suggest that they should be A-type granites, most zircon grains of the biotite monzogranite show clear oscillating zoning structures. LA-ICP-MS zircon U-Pb harmonic ages from three samples are 2185±29Ma,2183±13Ma, 2166±10Ma. Combined with the ages of detrial zircons in South Liaohe Group (1.95~2.15Ga), it was inferred that the biotite monzogranites are the basement of the South Liaohe Group. Granodiorites, occurring as apophyses, intrusted into the biotite monzogranites and the Li''eryu Formation. They characterized by high SiO2 (72.54%~74.31%) and Al2O3 (15.01%~16.17%)contents, with Na2O/K2O=1.27~2.82 and the total alkali (K2O+Na2O) in average of 7.77%; The average value of Mg# is 54.0 and the average contents of MgO and CaO is 0.26% and 1.59%, respectively. The saturation index A/CNK is between 1.61 and 1.78 and A/NK between 1.49 and 2.60, which suggest that the granodiorites should belong to the peraluminum calcium alkaline series. Granodiorites have obviously positive Eu anomalies. Besides, they are low in Y/Yb, high in Sr/Y and high field strength elements Th, Ta, Nb, Ti have strong depletion while large ion lithophile elements Ba, K, Rb, Sr are abundant. All the geochemical characteristics are similar to the feature of adakitic granite. Most zircons grains of the granodiorites show clear oscillating zoning structures. LA-ICP-MS zircon U-Pb ages from two samples are 1995±18Ma, 1995±13Ma. We infer that the emplacement age of granodiorites is about 2.0Ga. This paper considers that the biotite monzogranites with A-type characteristics are products of partial melting of the lower crust during the process of the internal thinning of the continental crust and the granodiorites which have characteristics of adakitic granite are products of magmatic activity formed by volcanic arc or active continental margin during subduction. The studies above indicate that Jiao-Liao-Ji orogenic/activities belts experienced stretching period at 2.2~2.15Ga; Then there is a process of subduction and compression around 2.0Ga. |
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| Keywords: | Jiao-Liao-Ji Paleoproterozoic orogenic belt/activities A-type granite Adakite-like granite Active continental margin Huanghuadian area eastern Liaoning Province |
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