(中南大學(xué) 地球科學(xué)與信息物理學(xué)院，長(zhǎng)沙 410083)
摘 要: 西秦嶺天水—黨川地區(qū)的馬家坪二長(zhǎng)花崗巖和牛頭河群黑云母變粒巖的元素地球化學(xué)的研究表明，馬家坪二長(zhǎng)花崗巖顯示強(qiáng)烈的輕、重稀土元素分餾(∑LREE/∑HREE=11.62，w(La)N/w(Yb)N=46.2)，極度虧損重稀土元素以及具有極高的Sr(579×10-6~1 120×10-6)及Ba(2 350×10-6~2 470×10-6)，極低的Y(7.86×10-6~10.2×10-6)及Yb(0.72×10-6~0.98×10-6)，極高的w(Sr)/w(Y)(64.10~132.32)和w(La)/w(Yb)(56.33~75.19)的特點(diǎn)，其地球化學(xué)特征同Ⅱ型埃達(dá)克巖(C型)相類似，巖漿源于增厚的下地殼部分熔融，與晚三疊世陸內(nèi)運(yùn)動(dòng)有關(guān)。而牛頭河群黑云母變粒巖的地球化學(xué)特征則類似于大陸碰撞型花崗巖，其原巖為造山過程中因地殼部分熔融形成的S型花崗巖，是陸陸碰撞過程中的產(chǎn)物，與早古生代中秦嶺和北秦嶺與華北克拉通的碰撞密切相關(guān)。
關(guān)鍵字: 西秦嶺造山帶；花崗巖；埃達(dá)克質(zhì)巖；大陸碰撞型花崗巖
（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
