地球学报2016，Vol.37Issue(4)：493-516,24.DOI:10.3975/cagsb.2016.04.11
柴北缘乌兰地区花岗岩锆石SHRIMP定年及其成因
Zircon SHRIMP Dating and Genesis of Granites in Wulan Area of Northern Qaidam
摘要
Abstract
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 (0.7108) and Nd model age (T2DM=2.10 Ga) of the early granite are both higher than those of the late granite (0.7076~0.7107,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.关键词
花岗岩/锆石SHRIMP定年/欧龙布鲁克陆块/宗雾隆构造带/乌兰Key words
granite/zircon SHRIMP dating/Oulongbuluke block/Zongwulong tectonic zone/Wulan分类
天文与地球科学引用本文复制引用
吴才来,雷敏,吴迪,李天啸..柴北缘乌兰地区花岗岩锆石SHRIMP定年及其成因[J].地球学报,2016,37(4):493-516,24.基金项目
本文由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)和国家专项(编号: Sino Probe 05-05)联合资助. This study was supported by China Geological Survey (Nos. 121201102000150005-06, 12120115027001 and 12120114079901), National Natural Science Foundation of China (Nos.41472063, 40921001, 40472034 and 40672049), and the Science and Technology Project (No. Sino Probe 05-05). （编号: Sino Probe 05-05）
