改则格列戈阿尔辉长岩侵入于羌塘地体南缘木嘎岗日群,为研究班公湖—怒江缝合带在改则地区的演化提供新的强有力的约束。本文对辉长岩进行了LA-ICP-MS锆石U-Pb定年,结果显示格列戈阿尔辉长岩锆石UPb年龄加权平均值为122.9±1.6Ma,表明该辉长岩体形成时代为早白垩世中晚期。岩石地球化学研究表明,该区早白垩世辉长岩具有高Al_2O_3(15.39%~16.83%)、低Ti O_2(0.78%~0.92%)、贫P2O5(0.09%~0.17%)和低碱(Na_2O+K_2O=3.93%~4.41%)的特点。稀土元素总量(ΣREE)为63.37×10-6~73.76×10-6,平均为68.84×10-6,稀土元素配分曲线呈右倾型,(La/Yb)N介于2.43~3.09之间,δEu=0.89~1.03,表现弱的负铕异常,具有明显的轻稀土富集,重稀土亏损特征。岩石微量元素总体上富集大离子亲石元素(LILE)Rb、Ba、Th、U等,显著亏损高场强元素(HFES)Nb、Ta、P、Ti等,Nb/Ta、Zr/Hf比值接近或略低于原始地幔组成。根据地球化学特征和微量元素构造判别图结果表明,该辉长岩源区为被俯冲改造的岩石圈地幔源岩浆,岩浆在演化过程中遭受了上地壳物质的同化混染,并经历一定程度的结晶分异作用。格列戈阿尔辉长岩形成于班公湖—怒江洋向北俯冲构造环境下的岛弧环境,表明至少在122.9±1.6Ma期间班公—怒江洋盆正在向北俯冲。结合区域资料,研究区班公—怒江洋盆闭合时间应介于110~85Ma之间。 Instead, the Gregorian gabbros intruded into the Mugagang on the southern margin of the Qiangtang terrane, providing new and powerful constraints for the study of the evolution of the Banghong-Nujiang suture in the Gazian area. In this paper, LA-ICP-MS zircon U-Pb dating of gabbro has been performed. The results show that the UPb age of the zircons from the Gregorian gabbro is 122.9 ± 1.6Ma, indicating that the gabbro body was Late Cretaceous. Petrological and geochemical studies show that the Early Cretaceous gabbro in this area has high contents of Al 2 O 3 (15.39% ~ 16.83%), low Ti O 2 (0.78% ~ 0.92%), poor P 2 O 5 (0.09% ~ 0.17%) and low alkali + K_2O = 3.93% ~ 4.41%) of the characteristics. The total REE contents (ΣREE) ranged from 63.37 × 10-6 to 73.76 × 10-6 with an average of 68.84 × 10-6. The REE distribution curve showed a right-tilting type with (La / Yb) N ranging from 2.43 to 3.09. δEu = 0.89 ~ 1.03, showing weak negative europium anomaly, with obvious characteristics of light rare earth enrichment and heavy rare earth loss. The trace elements in rocks generally enrich LILEs such as Rb, Ba, Th and U, and significantly deplete Nb, Ta, P, Ti, etc. in high field strength elements (HFES) Near or slightly below the original mantle composition. According to geochemical characteristics and trace elements, the result shows that the gabbro source area is subducted lithospheric mantle source magmatism, and the magma underwent assimilation and contamination of the upper crust in the evolution process and experienced a certain degree of Crystallization differentiation. The Gregorian gabbros formed in the island arc environment under the subduction tectonic setting of the Bangong-Nujiang Ocean, indicating that the Bangong-Nujiang oceanic basin is subducting northward for at least 122.9 ± 1.6Ma. According to the regional data, the closure time of the Bangong-Nujiang oceanic basins in the study area should be between 110 ~ 85Ma.