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| 深部过程对埃达克质岩石成分的制约 | |
| 引用本文： | 肖龙 RobertPRAPP 许继峰.深部过程对埃达克质岩石成分的制约[J].岩石学报,2004,20(2):219-228. |
| 作者姓名： | 肖龙 RobertPRAPP 许继峰 |
| 作者单位： | 1. 中国地质大学地球科学学院,武汉,430074 2. Department of Geosciences, Center for High Pressure Research and Mineral Physics Institute, State University of New York, Stony Brook, NY 111794, USA 3. 中国科学院广州地球化学研究所,广州,510640 |
| 基金项目： | 国家自然科学基金(40272040),中国科学院知识创新工程项目(KZCX3-SW-122),973项目2002CB412601资助研究成果. |
| 摘 要： | 埃达克岩、太古宙TTG和中国东部广泛出露的燕山期埃达克质中酸性火山-侵入岩在岩石地球化学特征方面有许多相似之处,也有一些显著的差异。与典型的埃达克岩相比,太古宙TTG具有相对高Si和低Mg^#的特点：中国东部埃达克质岩石多表现为低Mg^#贫A120,和高K特征。埃达克岩相对高Mg^#是由于俯冲洋壳部分熔融产生的原生埃达克岩熔体受到了地幔橄榄岩的混染,太古宙TTG多无明显的地幔混染印记,反映其可能主要形成于下地壳底侵玄武岩的部分熔融,而与洋壳俯冲没有直接联系。中国东部埃达克质岩石相对低Mg^#畜K,暗示其可能是下地壳底侵玄武岩部分熔融或拆沉-熔融的产物,而幔源富钾熔体的混合、壳内分异和混染过程都有可能影响其成分特征中国东部部分地区的高镁埃达克质岩石可能揭示了下地壳拆沉一熔融和地幔混染过程。钾质埃达克岩的源区可能是被小比例软流圈熔体交代富集的底侵玄武岩层(增厚的下地壳)。结合燕山期岩浆作用和构造转换的特点来看,埃达克岩的形成是中国东部晚中生代岩石圈强烈减薄和大规模岩浆作用产物的一部分,这一重大构造体制的转换可能与地幔柱上涌对岩石圈的侵蚀和导致的伸展作用有关。 |
| 关 键 词： | 埃达克岩 太古代TTG 加厚地壳 地壳拆沉-熔融 深部过程 地幔柱 |
| 文章编号： | 1000-0569/2004/020(02)-0219-28 |
| 修稿时间： | 2003年7月22日 |
The role of deep processes controls on variation of compositions of adakitic rocks |
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| Robert P RAPP XIAO Long,Robert P RAPP and XU JiFeng Faculty of Earth Sciences,China University of Geosciences Wuhan,China.The role of deep processes controls on variation of compositions of adakitic rocks[J].Acta Petrologica Sinica,2004,20(2):219-228. | |
| Authors: | Robert P RAPP XIAO Long Robert P RAPP and XU JiFeng Faculty of Earth Sciences China University of Geosciences Wuhan China |
| Institution: | Robert P RAPP XIAO Long,Robert P RAPP and XU JiFeng Faculty of Earth Sciences,China University of Geosciences Wuhan,ChinaDepartment of Geosciences,Center for High Pressure Research and Mineral Physics Institute,State University of New York,Stony Brook,NY,USA Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou,China |
| Abstract: | There are many geochemical similarities and significant dissimilarities among Adakite, early Archaean TTG suites and Yanshanian intermediate-acid magamtic rocks (" adakitic rocks" or potassic adakite) in eastern China. Simple geochemical parameters, such as silica content, Mg# and K2O content, show that TTG and "adakitic rocks" from eastern China are distinct from adakite, suggesting that they experienced different deep processes. Comparing with slab-melting generated adakite, the early Archaean TTG suites have higher SiO2 and lower Mg# and, potassic adakite from eastern China show lower Mg# and higher K2O. The higher-Mg# adakites imply that the ocean slab melting generated pristine adakite melts interacted with the mantle wedge. There is little convincing evidence for a direct mantle component in TTG, implying that accommodate TTG production through melting of hydrous basaltic material at the base of thickened crust, without modern-style subduction processes. The potassic adakite from eastern China may predominately experienced partial melting of underplated basaltic rocks (lower Mg# potassic adakite) , or delimitation-melting of lower crust and interacted with mantle peridotite ( higher Mg# potassic adakite), and followed assimilation and contamination of crustal intermediate-acid rocks. Potassic adakite might be generated from a basaltic underplated layer that was metasomated by small melt fractions from asthenosphere mantle. Adakitic magmatism is then an accompanying product of Yanshannian lithosphere thinning and magmatism, which may be related to a upwelling of mantle plume. |
| Keywords: | Adakite Archean TTG Thickened crust Crust delaminating and melting Deep processes Mantle plume |
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