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骑田岭花岗岩体位于南岭中段,湖南省南部,总出露面积约520km2.根据本文已获得的25个及其他作者已发表的7个有效和相互协调的单颗粒锆石U-Pb定年数据,结合地质学、岩石学和空间分布等特征,认为骑田岭岩体是一个燕山早期多阶段形成的复式岩基,主要可分成3个侵入阶段:第一阶段,侵位于163～160Ma,峰值在161Ma左右,主要为角闪石黑云母二长花岗岩,有时为黑云母二长花岗岩,出露面积约占45%,分布在岩体东部、北部和西部的靠边缘部位,可进一步分解为菜岭、江口、竹枧水、蒋家洞和安源等岩体;第二阶段,侵位于157～153Ma,峰值在157～156Ma,主要为黑云母花岗岩,有时含不同数量角闪石,出露面积约占40%,主要分布在岩体的中部和南部,可进一步分解为芙蓉、将军寨、廖家洞和将军石等岩体;第三阶段,侵位于150～146Ma,峰值在149Ma左右,主要为细粒(有时含斑)黑云母花岗岩,出露面积约占12%,分布在岩体的中南部位,可进一步分解为荒塘岭、大山里和仙鹤抱蛋等岩体.其中前两个阶段花岗岩构成岩基的主侵入相,第三阶段花岗岩为补充侵入相.另有一些侵入到第一阶段和第二阶段岩体中的细粒花岗岩岩瘤(如回头湾、龙渡岭、屋场坪)和岩脉,出露面积约占3%,在岩基范围内零散分布,其侵位年龄主要在第二阶段花岗岩的范围内,他们是侵入到早些时间已固结岩石裂隙空间的晚阶段侵入相.根据不同阶段花岗岩结晶年龄的时间差和他们之间明显的侵入接触关系和冷凝-烘烤现象,可以认为,从骑田岭花岗岩基侵位、冷却、结晶、固结到产生裂隙的时间,不会超过2~6Ma.中晚侏罗世在骑田岭及其周边的南岭地区,广泛发育同时代的花岗质和中基性岩浆活动,反映了燕山早期是本区岩浆活动的高峰期,此时本区处于大陆内部岩石圈伸展、减薄的构造环境,壳幔相互作用对本区花岗岩的形成有至关重要的影响.
The Qitianling granite body is located in the middle of Nanling and southern Hunan Province, with a total exposed area of about 520 km 2. Based on the 25 available and other authors published 7 effective and coordinated single-grain zircon U-Pb dating data Based on the characteristics of geology, petrology and spatial distribution, it is considered that the Qitianling pluton is a complex rock foundation formed in the early Yanshanian multi-stage and can be divided into three intrusive stages: In the first stage, the intrusion ranged from 163 to 160 Ma, with a peak About 161Ma, mainly hornblende biotite monzogranite, sometimes biotite monzogranite, the exposed area of about 45%, located in the eastern, northern and western parts of the rock can be further decomposed into vegetables Lingjiang, Jiangkou, Zhuangshui, Jiangjiadong and Anyuan rocks. In the second stage, the intrusion ranged from 157 to 153 Ma with a peak value of 157 to 156 Ma, mainly composed of biotite granites, sometimes containing different amounts of hornblende, with an area of about Accounting for 40%, mainly distributed in the central and southern parts of the rock mass, and can be further decomposed into rock masses such as Furong, Jiangjunzhai, Liaojiadong and Generalslites; in the third stage, the invasion is located at 150 ~ 146Ma with a peak value of 149Ma, (Sometimes spotted) biotite granite, out Dew area of about 12%, located in the central and southern parts of the rock mass, can be further broken down into desert pond Ridge, the mountain and cranes nest egg and other rocks.The first two stages of granite constitute the main intrusion of rock, the third stage Granite is the complement of the intrusion facies, and some of the fine-grained granite rocks (such as Huitouwan, Longduling, Yepingchangping) intruded into the first and second stages of rock mass have an area of about 3 %, Scattered within the rock foundation, the emplacement age is mainly in the second stage of granite, they are intrusive into the early stage of consolidation of rock fracture space late phase intrusion phase.According to the different stages of granite crystallization age Time difference and their obvious relationship between invaded contact and condensation - baking, it can be considered, from Qitianling granite base emplacement, cooling, crystallization, consolidation time to produce cracks will not exceed 2 ~ 6Ma. The Jurassic extensively developed contemporaneous granitic and mafic magmatic activities in Quntianling and its surrounding Nanling area, reflecting the early peak of the Yanshanian magmatic activity in this area, when the area was in the interior of the mainland Lithosphere extension, thinning of the tectonic environment, Crust-mantle interaction plays an important role in granite formation in this area.