(中南大学 地球科学与信息物理学院，长沙 410083)
摘 要: 西秦岭天水—党川地区的马家坪二长花岗岩和牛头河群黑云母变粒岩的元素地球化学的研究表明，马家坪二长花岗岩显示强烈的轻、重稀土元素分馏(∑LREE/∑HREE=11.62，w(La)N/w(Yb)N=46.2)，极度亏损重稀土元素以及具有极高的Sr(579×10-6~1 120×10-6)及Ba(2 350×10-6~2 470×10-6)，极低的Y(7.86×10-6~10.2×10-6)及Yb(0.72×10-6~0.98×10-6)，极高的w(Sr)/w(Y)(64.10~132.32)和w(La)/w(Yb)(56.33~75.19)的特点，其地球化学特征同Ⅱ型埃达克岩(C型)相类似，岩浆源于增厚的下地壳部分熔融，与晚三叠世陆内运动有关。而牛头河群黑云母变粒岩的地球化学特征则类似于大陆碰撞型花岗岩，其原岩为造山过程中因地壳部分熔融形成的S型花岗岩，是陆陆碰撞过程中的产物，与早古生代中秦岭和北秦岭与华北克拉通的碰撞密切相关。
关键字: 西秦岭造山带；花岗岩；埃达克质岩；大陆碰撞型花岗岩
（College of Geosciences and Info-Physics, Central South University, Changsha 410083, China）
Abstract:The study of the geochemical features of monzogranite in Majiaping and biotite leptynite in Niutouhe Group suggested that these two kinds of granites were formed in different tectonic environments. The monzogranite in Majiaping had strongly fractionated REE, high contents in Sr (579×10-6-1 120×10-6) and Ba (2 350×10-6-2 470×10-6), low contents in Y (7.86×10-6-10.2×10-6) and Yb (0.72×10-6-0.98×10-6), high w(Sr)/w(Y) (64.10-132.32) and w(La)/w(Yb) (56.33-75.19). The geochemical features show that the monzogranite in Majiaping is similar to C-type adakitic rock. It is formed by melting of basaltic lower crust under thickened setting. It is related to intracontinental tectonic movement in Triassic. The geochemical features of biotite leptynite in Niutouhe Group are similar to continental collision granites. Its protolith is S-type granites, which is formed by the melting of the crust in the process of orogenic. It is related to the collision of Middle Qinling and North Qinling terrane and North China Craton.
Key words: West Qinling orogenic belt; granite; adakitic; continental collision granites
