黄陵花岗岩基的成因

黄陵花岗岩基位于扬子地台北缘，它连同汉南和鲤鱼寨岩基一起构成扬子地台北缘的低钾花岗岩等，形成于晋宁晚期扬子地台北侧的“秦岭洋”壳向南俯冲导致的大陆边缘造山运动过程中。黄陵花岗岩基可解体为三斗坪、黄陵庙、大老岭、晓峰4个岩套和14个单元，侵位于832－750Ma之间。三斗坪和黄陵庙两个岩套主要由英云闪长岩、奥长花岗岩花岗闪地组成，是在近南北向区域挤压下于约16km深部塑性域定位的同构造花岗岩，前者主要依靠岩浆在构造弱面逐次强力楔入创造定位空间，后者主要在处于活动状态的韧性拉张剪切带内定位。钙碱性系列的大老岭和晓峰岩套则是在本区地壳迅速隆起过程中分别在5km和＜1．5km深度的脆性域定位的构造晚期花岗岩。根据岩石化学和同位素组成推断，三斗坪岩套的源岩主要是晚太古代大陆拉斑玄武岩，母岩浆相当于英安质，岩套内的成分变化主要受角闪石分离结晶作用控制；黄陵庙岩套除受分离结晶作用影响外，成分变化主要与英安质母岩浆和某种长英质岩浆的混合有关；大老岭岩套的源岩亦为早前寒武纪火山岩。

The origin of Huangling granite batholith

Huangling granite batholith, along with Hannan and Liyuzhai granite batholith, constructs a low_K granite belt in the northern periphery of Yangtze Platform. It is disintegrated into Sandouping, Huanglingmiao, Dalaoling and Xiaofeng suites, comprising 14 units, whose emplacement ages are between 832 and 750 Ma. Sandouping and Huanglingmiao suites consist mainly of tonalite, trondjemite and granodolerite, being syntectonic granitoids emplaced at the ductile domain 16 km deep under the action of SN_strikingregional compression. Dalaoling and Xiaofeng suites, belonging to calc_alkaline series, are late_tectonic granitoids emplaced at the brittle domain (5 and <1.5 km in depth respectively) formed during rapid uplift of the crust. Based on major and trace elements and isotope geochemical data, it is inferred that Sandouding suite is formed by magma melting of Late Archeozoic continent tholeiite source, and its geochemical variation is controlled by hornblende fractional crystallization. Besides fractional crystallization, the geochemical variation of Huanglingmiao suite is related to the mixing between dacitic magma and felsic magma. Dalaoling suite is probably derived from early Precambrian volcanics.