| 柴北缘乌兰地区花岗岩锆石SHRIMP定年及其成因 |
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| 关键词:granite zircon SHRIMP dating Oulongbuluke block Zongwulong tectonic zone Wulan |
| 基金项目:中国地质调查局项目(编号: 121201102000150005-06; 12120115027001; 12120114079901)；国家自然科学基金项目(编号: 41472063; 40921001; 40472034; 40672049)；国家专项(编号: Sino Probe 05-05) |
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| Zircon SHRIMP Dating and Genesis of Granites in Wulan Area of Northern Qaidam |
| Zircon SHRIMP U-Pb dating of granites in Wulan area of northern Qaidam indicates that Hadesengou rock mass was formed at (413±3) Ma, Xugeigou rock mass at (254±3) Ma, Yiluoshan rock mass at (251±1) Ma, hornblende diorite and granite of Chahanruo rock mass at (249±1) Ma and (248±2) Ma, Chahanhe rock mass at (240±2) Ma, granodiorite and granite of Shailekeguo rock mass at (250±1) Ma and (244±3) Ma respectively. These granites have two formation periods: 1) the early period belongs to Early Devonian (413 Ma) with the rock association being adamellite+alkali-feldspar granite; 2) the late period belongs to Late Permian–Early Triassic (254~240 Ma) which can be further divided into three emplacements (254~251 Ma, 250~248 Ma and 244~240 Ma) with the rock association being diorite+granodiorite+granite. Geochemical study indicates that the early granitoids are not only enriched in large ion lithophile elements but also enriched in some high field-strength elements (Zr, Y, Nb etc.), thus belonging to A-type granite; the late granitoids are enriched in large ion lithophile elements and depleted in high field-strength elements, thus belonging to I-type granite. 87Sr/86Sr ratio (0.710 8) and Nd model age (T2DM=2.10 Ga) of the early granite are both higher than those of the late granite (0.707 6~0.710 7, T2DM=1.41~1.58 Ga). Nevertheless, εNd(t) of the late granite (?11.6) is lower than that of the early granite (?4.8 ~ ?6.8). These data show that the early A-type granite might have originated from Paleoproterozoic continental crust, whereas the late I-type granite originated from Mesoproterozoic crust. Combined with regional geological structural characteristics, the authors consider that the formation of early A-type granite was related to the thinning and stretching of north Oulongbuluke block caused by Qilian lithosphere delamination which also marked the beginning of Zongwulong rift, while the formation of late I-type granite was related to the southward subduction of Zongwulong oceanic crust beneath Oulongbuluke block. |
| WU Cai-lai,LEI Min,WU Di,LI Tian-xiao.2016.Zircon SHRIMP Dating and Genesis of Granites in Wulan Area of Northern Qaidam[J].Acta Geoscientica Sinica,37(4):493-516. |
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