| 粤南海宴A型花岗岩与镁铁质包体的成因及意义 |
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| 引用本文： | 贾小辉,谢国刚,孟德磊,万乐,吴俊,卜建军,吴富强,曾海良,卢加文,詹瑞华.粤南海宴A型花岗岩与镁铁质包体的成因及意义[J].地球科学,2018,43(7):2294-2309. |
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| 作者姓名： | 贾小辉 谢国刚 孟德磊 万乐 吴俊 卜建军 吴富强 曾海良 卢加文 詹瑞华 |
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| 作者单位： | 1.中国地质调查局武汉地质调查中心, 湖北武汉 430223 |
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| 基金项目： | 中国地质调查局项目DD20160064-01国家自然科学基金项目41302046 |
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| 摘 要： | 华南晚中生代花岗岩及其形成的构造背景是目前研究的热点之一，通过对粤南地区A型花岗岩与镁铁质包体的年代学和地球化学组成的研究，探讨其岩石成因及构造意义.LA-ICP-MS锆石U-Pb测年结果显示，广东海宴花岗岩与镁铁质暗色微粒包体形成于早白垩世（分别为144.0±1.7 Ma和141.1±2.5 Ma）.花岗岩具有典型的A型花岗岩特征:富硅、碱、铁而贫镁、钙，具有高的10 000×Ga/A1比值和Zr+Nb+Ce+Y含量等.包体具有钾玄质岩的特征:富碱更富钾、低钛、高铝及强烈富集大离子亲石元素和轻稀土元素等.花岗岩的ISr=0.706 6~0.712 2，εNd（t）=-7.01~-2.03，镁铁质包体则显示了稍低的ISr（0.708 5~0.711 1）和稍高的εNd（t）（-6.99~-2.23）.元素及Sr-Nd同位素结果显示，花岗岩可能是中元古代地壳岩石部分熔融的产物，而钾玄质包体的初始岩浆可能源自俯冲沉积物交代的富集地幔.海宴A型花岗岩及其钾玄质包体的发现，暗示着区域早白垩世处于伸展的构造背景，不同于东南沿海地区的挤压构造应力环境.
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| 关 键 词： | 早白垩世 A型花岗岩 钾玄质岩 伸展作用 华南 年代学 |
| 收稿时间： | 2017-11-23 |
Petrogenesis and Implications of the Haiyan A-Type Granites and Mafic Microgranule Enclaves in Southern Guangdong Province |
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| Abstract: | The study of the late Mesozoic granites in South China and its tectonic setting is a hotspot issue. In this paper, new zircon U-Pb ages and geochemical data of the Haiyan A-type granites and mafic microgranule enclaves (MMEs) in southern Guangdong are reported, and the petrogenesis and implications of these rocks are discussed. We present new zircon LA-ICP-MS U-Pb ages of the Haiyan granites and its MMEs, and the results of the age analyzing show that the granites and MMEs were generated in Early Cretaceous (144.0±1.7 Ma and 141.1±2.5 Ma, respectively). The Haiyan granites have the typical features of A-type granites, they are characterized by enrichment in silicon, alkali and iron contents, and depletion in magnesium and calcium contents, with high 10 000×Ga/A1 values and Zr+Nb+Ce+Y components. Small amounts of MMEs occur in the Haiyan granites, and they are characterized by enrichment in alkali and more enrichment in potassium contents, high aluminum and low titanium, strong enrichment in the large ion lithophile elements and light rare earth elements, belonging to shoshonitic rocks. Granites have ISr values of 0.706 6-0.712 2, εNd(t) values of -7.01——2.03. While MMES have relatively lower ISr values (0.708 5-0.711 1) and higher εNd(t) values (-6.99——2.23). Combining with geochemical and Sr-Nd isotopic compositions, we suggest that the Haiyan granites were likely generated by partial melting of the Mesoproterozoic crustal rocks, and the primitive compositions of shoshonitic MMEs likely originated from enriched mantle source somatized by subducted oceanic sediments. The findings of the Haiyan A-type granites and shoshonitic mafic enclaves suggest that the regional tectonic setting during the Early Cretaceous was in extension, and different from southeast coastal areas with compressive tectonic regime. |
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