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| 苏门答腊岛北部Takengon早志留世S型花岗片麻岩年代学、地球化学特征及构造意义 | |
| 引用本文： | 徐畅,王岳军,钱鑫,张玉芝,余小清. 苏门答腊岛北部Takengon早志留世S型花岗片麻岩年代学、地球化学特征及构造意义[J]. 地球科学, 2020, 45(6): 2077-2090. DOI: 10.3799/dqkx.2020.030 |
| 作者姓名： | 徐畅 王岳军 钱鑫 张玉芝 余小清 |
| 作者单位： | 1.中山大学地球科学与工程学院, 广东省地球动力作用与地质灾害重点实验室, 广东广州 510275 |
| 基金项目： | 国家自然科学基金项目41830211国家自然科学基金项目U1701641国家重点研发计划项目2016YFC0600303广东省基础与应用基础研究基金2018B030312007广东省基础与应用基础研究基金2019B1515120019 |
| 摘 要： | 苏门答腊岛位于巽他大陆西南缘，被中苏门答腊构造带分隔为东、西苏门答腊两地体.其中东苏门答腊地体的基底年龄和构造归属均未得到很好地约束.在东苏门答腊北部Takengon地区新识别出的花岗片麻岩进行了锆石U-Pb年代学、原位Hf同位素和全岩地球化学研究.年代学结果表明该套花岗片麻岩的206Pb/238U加权平均年龄为442 ±5 Ma（MSWD=1.03），代表其结晶年龄.锆石的εHf（t）介于-1.3至-7.8之间.地球化学研究表明，样品富SiO2（69.97%~74.30%）和Al2O3（13.90%~15.93%），相对贫TiO2（0.48%~0.61%）、MgO（0.54%~0.93%）和CaO（0.11%~0.25%）.样品具高的A/CNK值（2.58~3.06）和CIPW刚玉体积百分含量（10.0%~11.4%），具有S型花岗岩的特征.其轻重稀土分异明显，富集LILE（Rb、Th、U），亏损HFSE（Nb、Ta、Ti）.地球化学研究表明Takengon花岗片麻岩是变沉积岩部分熔融形成的.该套花岗片麻岩的发现证实了在东苏门答腊地块发育有前志留世基底岩石，其形成与原特提斯洋的演化有关. |
| 关 键 词： | 花岗片麻岩 早志留世 苏门答腊 原特提斯 锆石年代学 锆石Hf同位素 地球化学 |
| 收稿时间： | 2019-12-21 |
Geochronological and Geochemical Characteristics of Early Silurian S-Type Granitic Gneiss in Takengon Area of Northern Sumatra and Its Tectonic Implications |
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| Abstract: | Sumatra Island is located in the southwestern margin of the Sundaland, and is divided into East/West Sumatra by the Medial Sumatran Zone. While East Sumatran basement affinity and tectonic evolution are not well defined. The Early Paleozoic granitic gneisses have been identified from the East Sumatra Terrane, with providing zircon U-Pb age, in-situ Hf isotopic and geochemical results. Geochronological result yields a 206Pb/238U mean age of 442 ±5 Ma (MSWD = 1.03), representing the crystalline age. Zircon εHf (t) values range from -1.3 to -7.8. The whole-rock geochemical characteristics show that our samples are characterized by high SiO2 (69.97%-74.30%) and Al2O3 (13.90%-15.93%), but poor in TiO2 (0.48%-0.61%), MgO (0.54%-0.93%) and CaO (0.11%-0.25%). These samples have high A/CNK (2.58-3.06) and CIPW-normalized corundum (10.0%-11.4%), similar to those of the S-type granite. They have obvious fractionation between LREEs and HREEs. These samples are characterized by enrichment in LILEs (Rb, Th, U) and depletion in HFSEs (Nb, Ta, Ti). The geochemical results indicate that the Takengon granitic gneisses are originated from the partial melting of the meta-sediments during the evolution of the Prototethyan Ocean. This study confirms the existing of Early Silurian basement rocks in the East Sumatra Terrane, which were related to the Prototethyan evolution. |
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