摘要
目的对扬子地块西北缘后龙门山地区轿子顶穹窿构造核部的花岗岩类进行年代学研究。方法利用锆石SHRIMP U—Pb年代学对其形成时代进行约束。结果轿子顶花岗岩体中变形花岗岩和块状花岗岩中锆石均发育岩浆韵律环带结构，具有较高的TIVU比值（0．52—1．23、0．32～1．16），为岩浆成因锆石。对变形花岗岩和块状花岗岩中岩浆锆石的SHRIMP U-Pb定年结果分别为793±11Ma和792-1-11Ma，表明它们的形成时代完全一致，均为新元古代晚期南华纪早期。结论轿子项岩体具有后碰撞岩浆活动特征，是新元古代扬子地块西北缘活动大陆边缘俯冲以及弧陆碰撞造山作用导致的地壳增厚下地壳部分熔融的产物，形成于同碰撞（挤压环境）向碰撞后（伸展环境）转化阶段，即后造山期，是Rodinia超大陆初始裂解阶段产物。
Aim To sdudy the granite of Jiaoziding dome core located in back-Longmenshan area of the northwest margin of Yangtze block. Methods The objectives of study with zircon SHRIMP U-Pb geochronology are constraints of its formation age. Results The results show that the zircons of the samples in dormative granite and mssive granite of the Jiaoziding granites have internal oscillatory zoning, zircons of the Jiaoziding granites have higher TICU ratios （0. 52 - 1.23, 0. 32 - 1.16） and are igneous in origin. The zircon SHRIMP U-Pb dating for dormatire granite and mssive granite results were （793 ± 11 ） Ma and （792± 11 ） Ma, which indicates that the granite intrusions were formed in the Nanhuan of late Neoproterezoie, and formation of their time is fully consistent. Conclusion The Jiaoziding granite shows post-collisional granite characteristics, and were regarded as post-orogenic granites. Thus the granite intrusions are interpreted as syn-collisional granites resulted from the crustal thickening caused by active continental margin subduction and arc-continent collision orogeny during the Neoproterozoic in the Northwest Margin of Yangtze block. The granitic intrusion was formed in a transitional environment from syn-（ compressional environment） to post-collision （extensional environment）, and was the products of Rodinia supercontinent initial break-up.
出处
《西北大学学报（自然科学版）》
CAS
CSCD
北大核心
2009年第3期425-433,共9页
Journal of Northwest University（Natural Science Edition）
基金
国家自然科学基金资助项目(40572121
40234041)
