【摘要】 内蒙古北山甜水井地区龙脊山—神蛇岭岩体,总体呈北西向长椭圆状,面积大于100km2。按岩石谱系单位划分为一单元含斑细粒黑云母二长花岗岩、二单元含斑中细粒黑云母二长花岗岩和三单元中细粒花岗岩,归并为—龙脊山序列。岩石富硅碱,ALK在7.23%～8.37%,AKI小于1,A/CNK=1.01～1.07;OX较高,在0.47～0.83。相对富集大离子亲石元素、轻稀土元素,亏损Ba、Nb、Sr、Zr、Ti,稀土配分曲线呈现显著的"V"字型。副矿物组合为Mt-Ap-Zi型。由早单元到晚单元,向酸碱性增强方向演化,显示深源浅成铝质A型(A2型)花岗岩特征。各类构造环境判别图解投点,具造山后或后造山特征。同位素测年(锆石U-Pb法)为267.1Ma。反映本区中二叠世碰撞造山作用的存在,中二叠晚期已转入稳定的陆内发展环境。更多还原

【Abstract】 Intrusive rocks of Longjishan-Shensheling, which distributed in Tianshuijing region in west of Inner Mongolia, have an elliptic shape toward northwest. Its area is more than 100 km~2. They were named Longjishan Series, and included three units. The first unit is phenocryst bearing fine-grained biotite adamellite, the second is phenocryst bearing middle-fine grained biotite adamellite and the third is middle-fine grained granit. Granitoids enrich in SiO2 and Alk, contents of Alk vary between 7.23% and 8.37%, AKI are less than 1, ratios of A/CNK range from 1.01 to 1.07, and OX values vary between 0.47 and 0.83. The rocks enrich in LILE and LREE, and deplete Ba, Nb, Sr, Zr and Ti relatively. REE patterns have distinct "V" type. Accessory mineral assemblages are Mt-Ap-Zi. Granitoids evolve toward acidity and alkalinity from early unit to late unit, display the characteristics of aluminous A-type granite (A2-type) and have the characteristic of post-orogeny in some tectonic setting distinguish diagram. U-Pb age of Zircon is 267.1 Ma. All of those indicated that the orogenic process occurred in Middle Permian, might end in late of Middle Permian and the tectonic setting might be shifted to the setting of interior plate in Late Permian.更多还原