| 辽东半岛隆昌地区~2 113 Ma变辉长岩地球化学与Hf同位素研究:对胶辽吉造山带构造演化的制约 |
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| 引用本文： | 赵岩,寇林林,张朋,毕中伟,李东涛,陈聪.辽东半岛隆昌地区~2 113 Ma变辉长岩地球化学与Hf同位素研究:对胶辽吉造山带构造演化的制约[J].地球科学,2019,44(10):3333-3345. |
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| 作者姓名： | 赵岩 寇林林 张朋 毕中伟 李东涛 陈聪 |
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| 作者单位： | 1.中国地质调查局沈阳地质调查中心, 辽宁沈阳 110034 |
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| 基金项目： | 中国地质调查局项目DD20190042-03国家重点研发计划项目2016YFC0600108中国地质调查局项目DD20190156国家重点研发计划项目2018YFC0603804 |
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| 摘 要： | 辉长岩的成岩时代、成因等研究对限定胶辽吉造山带构造背景等关键问题具有重要意义.对其开展详细的岩石地球化学分析、全岩Nd同位素和锆石U-Pb测年及原位Hf同位素分析，结果显示样品受蚀变影响不大，TiO2含量较低（< 1.31%），FeOT（11.91%~14.25%）、MgO（6.88%~7.62%）含量不高，K2O含量中等偏高（0.85%~1.23%），属钙碱性-高钾钙碱性岩浆系列，岩石轻重稀土分馏不明显，富集Rb、Ba、K等大离子亲石元素，亏损高场强元素P、Hf等，岩石相对富集Nd同位素，εNd（t）值介于-1.6~2.6，（176Hf/177Hf）i比值变化于0.281 497~0.281 612之间，εHf（t）值变化于2.2~6.3之间，模式年龄tDM1（Hf）值介于2.25~2.33 Ga.多种特征元素地球化学图解显示辉长岩具有E-MORB特征，与裂谷构造环境中产出的MORB和OIB不同.研究认为胶辽吉造山带在~2.1 Ga已存在洋壳俯冲，并可能已存在古岛弧，造山带演化过程中存在弧陆碰撞.
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| 关 键 词： | 华北克拉通 胶辽吉造山带 隆昌地区 古元古代 变质辉长岩 地球化学 |
| 收稿时间： | 2019-07-29 |
Characteristics of Geochemistry and Hf Isotope from Meta-Gabbro in Longchang Area,Liaodong Peninsula: Implications on Evolution of the Jiao-Liao-Ji Paleoproterozoic Orogenic Belt |
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| Abstract: | The meta-gabbro, distributed in the Longchang area, eastern part of the North China craton, yields a zircon U-Pb age of 2 113±15 Ma by LA-ICP-MS. Detailed geochemistry analyses, whole rock Nd isotope and zircon U-Pb and in-situ Hf isotope analyses were made to confine tectonic settings of the Jiao-Liao-Ji orogenic belt and other crucial problems. The gabbro samples studied show calc-alkaline to high potassic alkaline series features with weak alteration and also low content of TiO2(< 1.31%), moderate content of MgO (6.88%-7.62%), FeOT(11.91%-14.25%) and K2O (0.85%-1.23%). The studied samples are characterized with low REE content and show weak REE fractionation and depletion in high field strength elements like P and Hf. The samples also show enrichment in large ion lithophile elements like Rb, Ba and K, and enrichment in Nd isotope content, with εNd(t) values of -1.6 to 2.6. (176Hf/177Hf)i of zircon from the meta-gabbro samples ranging from 0.281 497 to 0.281 612, and the calculated εHf(t) values ranging from 2.2 to 6.3. The calculated Hf modal ages are 2.25 to 2.33 Ga. Several crucial diagrams from meta-gabbro sample analysis results show far distance from MORB or OIB both of which are typical basalts distributed in a rift geological setting. E-MORB with continental crust component mixed in may be the exact origin of the meta-basalts in the Longchang area. It can be concluded that there was ocean crust subduction in~2.1 Ga within the Jiao-Liao-Ji orogenic belt, with possible paleo-arc and the evolution model of the Jiao-Liao-Ji orogenic belt is more like an arc-continental collision model. |
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