厄立特里亚西部新元古代岛弧花岗岩对东非造山带构造演化的指示意义
The Augaro Arc-type Granite in the Nubia Shield,Western Eritrea:Petrogenesis and Implications for Neoproterozoic Geodynamic Evolution of the East African Orogen
曾国平 1王建雄 1向文帅 2张紫程 3姜军胜 1向鹏1
作者信息
- 1. 中国地质调查局武汉地质调查中心 / 中南地质科技创新中心,湖北 武汉 430205
- 2. 中国地质调查局武汉地质调查中心 / 中南地质科技创新中心,湖北 武汉 430205;中国地质大学(北京)地球科学与资源学院,北京 100083
- 3. 中国地质矿业有限公司,北京 100029
- 折叠
摘要
东非造山带是东西冈瓦纳大陆的拼合带,详细解剖其形成演化过程对深入理解超大陆旋回具有重要意义.笔者报道了厄立特里亚西部Augaro地区Meraf花岗岩的锆石U-Pb年龄、全岩地球化学和Sr-Nd-Hf同位素组成,以研究其成因及其对东非造山带新元古代构造演化的指示意义.LA-ICPMS锆石U-Pb定年结果为(875±6)Ma,形成于新元古代拉伸纪.Meraf花岗岩具有高硅、钙碱性、过铝质特征,稀土元素配分曲线总体右倾,LREE富集,HREE相对亏损,弱Eu负异常(δEu=0.70～0.91),富集Ba、Rb、K等大离子亲石元素,相对亏损Ta、Nb、Ti等高场强元素,属于岛弧性质I型花岗岩.εHf(t)值为正(7.7～9.9),ISr值较低(0.702 00～0.702 73),εNd(t)值为 4.85～6.06.结合微量元素特征,说明Meraf花岗岩为俯冲洋壳板片脱水交代上覆地幔楔并使其部分熔融的产物,指示区内大陆裂解和莫桑比克洋形成早于875 Ma.
Abstract
The East African orogen is a collisional collage belt of East Gondwana and West Gondwana.A deep study of the evolution of the orogenic belt is of great significance for understanding the supercontinent cycles.Zircon LA-ICP MS U-Pb ages and Hf isotopic compositions,whole rock major and trace elements and Sr-Nd isotopic compositions of the Meraf granite within the Augaro,west Eritrea,are reported in this paper to study the petrogenesis and implications for the Neoproterozoic tectonic evolution of the East African orogenic belt.LA-ICPMS zircon U-Pb dating of the Meraf granite yields magmatic crystallization age of(875±6)Ma.The Meraf granite has geochemistry patterns resembling those of Arc-type granite,with high-SiO2,calc-alkaline and peralu-minous,and enriched in LREE and LILE such as Ba,Rb,K,relatively depleted in HREE and HFSE such as Ta,Nb,Ti,with weak Eu negative anomalies(δEu= 0.70-0.91).Combined with the positive εHf(t)(7.7～9.9),low initial 87Sr/86Sr(0.702 00～0.702 73),and remarkable εNd(t)values(4.85～6.06),the Meraf granite is supposed to be the product of partial melting of the mantle wedge triggered by dehydration of the subducting oceanic plate.Together with widespread Neoproterozoic arc-type granites in the East African orogen,the break-up of Super-continent and formation of Mozambique oceanic are believed to predate the 875Ma.
关键词
地球化学/岛弧花岗岩/锆石U-Pb定年/新元古代/东北非造山带Key words
geochemistry/arc-type granite/zircon U-Pb dating/Neoproterozoic/east african orogen引用本文复制引用
基金项目
中国地质调查局项目(D20230126)
湖北省自然科学基金项目(2022CFB850)
出版年
2024
国家科技期刊平台
NSTL
万方数据