| 海南荔枝沟中三叠世酸性火山岩年代学、地球化学特征及其构造意义 |
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| 引用本文： | 芶琪钰,钱鑫,何慧莹,张玉芝,王岳军.海南荔枝沟中三叠世酸性火山岩年代学、地球化学特征及其构造意义[J].地球科学,2019,44(4):1357-1370. |
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| 作者姓名： | 芶琪钰 钱鑫 何慧莹 张玉芝 王岳军 |
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| 作者单位： | 广东省地球动力作用与地质灾害重点实验室, 中山大学地球科学与工程学院, 广东 广州 510275 |
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| 基金项目： | 国家自然科学基金项目41830211广东省自然科学基金项目2018B030312007中国科学技术部国家重点研发计划课题2016YFC0600303国家自然科学基金项目U1701641国家自然科学基金项目41702230 |
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| 摘 要： | 海南岛位于印支与华南陆块的交界地带，构造演化复杂，因此海南岛的拼合历史和构造属性一直备受争议.在海南岛三亚荔枝沟地区新识别出的酸性火山岩对于探讨海南岛早中生代的构造属性具有重要指示意义.LA-ICP-MS锆石U-Pb定年结果显示该套酸性火山岩中流纹岩的成岩年龄为241±6 Ma（MSWD=0.9）.地球化学特征表明该套火山岩样品的SiO2含量介于72.34%~77.83%，具较高的Al2O3（10.51%~13.53%）、K2O（2.85%~4.85%）、Na2O（1.75%~3.79%）含量和A/CNK比值（0.99~2.07），为过铝质钙碱性酸性火山岩.样品稀土元素含量为∑REE=87×10-6~177×10-6，富集轻稀土元素，显示右倾岛弧型稀土元素配分模式，Eu负异常明显.样品富集大离子亲石元素，亏损高场强元素，εNd（t）变化于-12.1~-11.3之间，可被解释为变沉积物部分熔融后经历分离结晶作用的产物.区域对比研究表明该套酸性火山岩可与三江地区的金沙江-哀牢山-松马构造带的中三叠世岩浆岩进行类比，应形成于印支与华南陆块汇聚的构造背景.
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| 关 键 词： | 中三叠世 酸性火山岩 年代学 地球化学 碰撞后 海南岛 |
| 收稿时间： | 2018-04-03 |
Geochronological and Geochemical Constraints on Lizhigou Middle Triassic Felsic Volcanic Rocks in Hainan and Its Tectonic Implications |
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| Abstract: | Hainan Island, which is located between the Indochina and South China blocks, has undergone multiphased structural overprinting and complex tectonic evolution.However, the Late Paleozoic tectonic regime and amalgamation process of the South China with Indochina blocks are still controversial. The newly-identified felsic volcanic rocks in the Lizhigou area are important for understanding the Early Mesozoic tectonic evolution in Hainan. LA-ICP-MS zircon U-Pb dating results show that the representative rhyolite samples yield a weighted mean 206Pb/238U age of 241±6 Ma (MSWD=0.9). These samples contain SiO2 ranging from 72.34% to 77.83%, Al2O3 from 10.51% to 13.53%, K2O from 2.85% to 4.85% and Na2O from 1.75% to 3.79%.The A/CNK values range from 0.99 to 2.07. These samples have REE concentrations of 87×10-6 to 177×10-6, and Eu/Eu* of 0.49-0.65.They are characterized by subparallel right-sloping REE pattern and enrichment in LREEs and LILEs, and depletion in HFSEs, similar to those of arc volcanics. Their εNd(t) values range from -12.1 to -11.3. These felsic volcanic rocks are the products of partial melting of metasediments with significant fractionation crystallization. In combination with other available data, it is inferred that the Lizhigou felsic volcanic rocks can be compared with the Middle-Late Triassic igneous rocks along the Jinshajiang-Ailaoshan-Songma zone, and formed during the assemblage of the South China with Indochina blocks related to East Paleotethyan consumption. |
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