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柴达木盆地北缘之全吉地块花岗质岩体大量发育,具多期次多阶段特征。通过对全吉地块金泉山—化石沟一带古生代花岗质岩体岩石学、岩石化学特征及单颗粒锆石U-Pb同位素定年,发现该区花岗岩有4次侵入,侵入时代分别为早奥陶世(471~476Ma)、中奥陶世(459±5Ma)、早志留世(423±4Ma)和中泥盆世(366±2Ma)。岩石地球化学研究显示,该4期花岗岩均具典型的钙碱性特征,轻稀土富集、重稀土轻度亏损、Eu轻微负异常—正异常,大离子亲石元素K2O、Rb、Ba、Th等相对强烈富集,高场强元素Nb、Ta、Hf、Zr及Yb明显亏损,除第4期岩体即具I型,又具S花岗岩特征外,其它各期次均属I型花岗岩,总体显示岩体具壳源特征,为板块碰撞前消减地区花岗岩,研究推测,金泉山—化石沟一带古生代花岗质岩体第1、2组年龄为全吉地块与柴达木陆块碰撞的时代,第3组年龄反映了深俯冲地下的板块由于拆沉而折返的时代,第4组年龄为碰撞隆起后造山带伸展、滑塌的时代。
The granitic rocks of the Quanji block in the northern margin of the Qaidam Basin have been extensively developed with multi-stage and multi-stage features. Through the petrology and petrochemical characteristics of the Paleozoic granitic rocks and the dating of U-Pb isotopes of single-grain zircon in the Jinquan Shan-Hsijigou area of the Quanji block, the granite has been invaded 4 times by intrusions. Taozhu (471 ~ 476Ma), Middle Ordovician (459 ± 5Ma), Early Silurian (423 ± 4Ma) and Middle Devonian (366 ± 2Ma). Petrological and geochemical studies show that these four phases of granite are characterized by typical calc-alkaline features such as light rare earth enrichment, slight heavy rare earth loss, slight negative anomalies of Eu, positive anomalies, large ion lithophile elements such as K2O, Rb, Ba, Th Nb, Ta, Hf, Zr and Yb of high-field-strength elements obviously lose. Except that No. 4 rock body has I-type and S-granite features, the other phases belong to I-type granite. Generally, the crust-source characteristics of the rock mass are shown, and the granite is reduced in the area before the plate collision. According to the study, the Paleozoic granitic rocks in the Jinquan-Fagal area belong to the first and the second group ages, which are the collision between the Ji-Kyu block and the Qaidam block The age of Group 3 reflects the era of subduction of subterranean plate due to delamination. The age of Group 4 is the age when the orogenic belt extended and collapsed after the collision and uplift.