| 摘要点击次数: 0 全文下载次数: 0 查看全文 查看/发表评论 下载PDF阅读器 |
| 基金项目：广东省地质勘查与城市地质专项“广东东源地区1∶5万区域地质调查”（2022-17）、“广东1∶5万双江圩、义合圩、河源县、柏埔圩幅区域地质调查”（2023-16）、“广东1∶5万蓝塘、观音阁区域地质调查”（2023-19） |
|
| 摘要： |
| 通过LA-ICP-MS锆石U-Pb测年、锆石Lu-Hf同位素测试以及岩石主微量元素分析，揭示了广东东源地区青溪复式岩体的两种主要岩性：中细粒（斑状）黑云母二长花岗岩（J31cηγ）、粗中粒黑云母二长花岗岩（K13bηγ），其加权平均年龄分别为（158.2±1.3）、（112.8±2.9）～（116.1±1.7）Ma，表明青溪复式岩体形成于晚侏罗—早白垩世。该岩体的地球化学特征表现为高硅（SiO2质量分数为74.32%～78.73%）、准铝质—过铝质（A/CNK为0.97～1.08）、高分异（DI为92.55～94.78，Zr/Hf比为17.9～26.3），且富集Rb、Th、U、La、Nd、Sm、Lu和LREE等元素，亏损Ba、Nb、Sr、P和Ti等元素。此外，两期侵入体的Eu值呈明显负异常（δEu分别为0.1、0.1～0.2）,Ga/Al比较高（104Ga/Al比分别为2.68～2.79、2.90～3.79）,岩体地球化学特征指示应属高分异铝质A2型花岗岩。εHf(t)为-8.6～6.9，绝大部分为-6.7～-0.3，相应TDMC为0.73～1.76 Ga。综合分析表明，青溪复式岩体形成于燕山晚期古太平洋板块俯冲后撤、地壳减薄的伸展构造环境中,在高温热流的作用下，由地幔与古老的下地壳岩石部分熔融混合形成。 |
| 关键词：高分异A2型花岗岩 同位素年龄 地球化学特征 青溪复式岩体 成因 广东东源 |
|
| Abstract: |
| By means of LA-ICP-MS zircon U-Pb dating, zircon Lu Hf isotope testing, and major and trace element analysis, it is revealed that two main lithologic types of the Qingxi complex pluton in Dongyuan area, Guangdong are medium fine grained (porphyritic) biotite monzonite granite (J31cηγ) and coarse medium grained biotite monzonite granite (K13bηγ), whose weighted average ages are (158.2±1.3)Ma and (112.8±2.9)-(116.1±1.7)Ma, respectively, indicating that the Qingxi complex pluton was formed in the Late Jurassic and the Early Cretaceous. Their geochemical characteristics are high silica (SiO2 mass fraction is 74.32%-78.73%), quasi-aluminous-peraluminous (A/CNK is 0.97-1.08), high differentiation (DI is 92.55-94.78 and Zr/Hf is 17.9-26.3). They are enriched in Rb, Th, U, La, Nd, Sm, Lu and LREE, and deficient in Ba, Nb, Sr, P and Ti. The Eu values of the two intrusions are obviously negative (δEu is 0.1, 0.1-0.2 respectively), and the 104Ga/Al is high (104Ga/Al is 2.68-2.79, 2.90-3.79). The geochemical characteristics indicate that the Qingxi complex pluton belongs to aluminous A2 type granite with high differentiation.εHf(t) values range from -8.6 to 6.9, with most values ranging from -6.7 to -0.3 and corresponding TDMC ranging from 0.73 to 1.76 Ga. Comprehensive analysis shows that the Qingxi complex pluton was formed in the extensional tectonic environment of the late Yan shan period when the paleo Pacific plate subducted and the crust thinned. The Qingxi complex pluton was the product of partial melting of the ancient lower crust and the mantle rock under the high temperature heat flow. |
| Keywords:A2 type granite with high differentiation isotopic age geochemical characteristic Qingxi complex pluton genesis Dongyuan in Guangdong |
| 叶升明，尼玛央金，郭永山，等.广东东源地区青溪复式岩体年代学、地球化学及成因[J].地质学刊,2024,48(2):125-139 |
|
|
|
|
|