| 丁磊磊,李伟,袁鑫,姜玉龙.新疆东天山三叠纪岩浆记录的年代学、地球化学及其成因研究[J].矿产勘查,2021,12(4):868-882 |
| 新疆东天山三叠纪岩浆记录的年代学、地球化学及其成因研究 |
| Geochronology, Geochemistry and Petrogenesis of Triassic magmatism in Eastern Tianshan, Xinjiang Province |
| 投稿时间：2021-01-15 |
| DOI： |
| 中文关键词: 东天山 三叠纪 埃达克岩 地壳加厚 拆沉 |
| 英文关键词: eastern Tianshan Triassic adakite delamination thickened continental crust |
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| 中文摘要: |
| 东天山在古生代—早中生代经历了一系列的增生造山过程，近年来区域上陆续有三叠纪的岩石记录报道，但三叠纪岩浆作用的成因和构造背景仍不明确。本文以博格达 -大南湖岛弧带的双岔沟花岗岩和雅满苏-中天山岛弧带的流纹岩为研究对象，进行了全岩地球化学、 Sr-Nd同位素、锆石年代学及 Hf同位素特征分析。双岔沟浅肉红色花岗岩和灰褐色黑云母花岗闪长岩分别形成于 247.3±1.0 Ma和 248.3± 1.2 Ma，雅满苏灰白色流纹岩形成于 249.5±1.4 Ma。双岔沟花岗岩类岩石具有埃达克质岩石特征:富硅( SiO2>68.81%)、富铝( Al2O3=15.04%~15.38%)、高 Sr( 398×10-6~416×10-6)、低 Y( 8.9×10-6~14.2× 10-6)和 Yb( 0.81×10-6~1.38×10-6)，轻重稀土发生明显分馏(( La/Yb) N = 21.7~26.5)。 87Sr/86Sr初始值为0.703984~0.704203，ε Nd(t)值为 +1.4~+2.8。雅满苏流纹岩为 I型花岗岩特征，低镁( Mg#=42~45)、低 Cr( 16×10-6)，ε Nd(t)值为 +4.5，它们的源区都是新生的下地壳物质。早三叠纪东天山地区的岩浆作用是地壳加厚拆沉作用的产物，形成于增生造山作用结束后构造单元之间的汇聚作用过程。 |
| 英文摘要: |
| Eastern Tianshan is a typical accretionary orogeny during the Paleozoic to early Mesozoic. Recently, increasing Triassic magmatic records were found. However, their genesis and tectonic setting are still poorly constrained. In this study, Shuangchagou granitoids of the Bogda-Dananhu Arc and Yamansu rhyolites of the Yamansu-Central Tianshan Arc were collected. We carried out whole rock element, Sr-Nd isotope, zircon geochronology and in-situ Hf analysis for these samples. The Shuangchagou granitoid are dated at 247.3± 1.0 Ma and 248.3±1.2 Ma, separately. For the Yamansu white rhyolite, the weight mean age is 249.5± 1.4 Ma. The Shuangchagou Granite are adakite-like, with high content of SiO2(>68.81%), Al2O3(15.04%~15.38%), Sr(398×10-6~416×10-6), but lower in Y(8.9×10-6~14.2×10-6) and Yb(0.81×10-6~1.38×10-6). Their HREEs and LREEs are strongly fractionated((La/Yb)N = 21.7~26.5).The initial Sr vale are 0.703984 to 0.704203, and the εNd(t) values are between +1.4 and +2.8. Moreover, the Yamansu rhyolite is I type, owning low Mg# value(42~45)and Cr content(16×10-6). The εNd(t) value is +4.5. Early Triassic magmatism may be attributed to delamination of thickened continental crust, which was resulted from continuous convergence of amalgamated blocks within the accretionary orogeny. |
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