摘要
前人曾测得西秦岭酒刺梁花岗岩岩体中白云母的Ｋ－Ａｒ年龄为４２４．４Ｍａ；笔者利用单颗粒锆石法测得锆石年龄为５８０Ｍａ±８Ｍａ，认为代表岩体形成年龄，且是目前为止西秦岭地区测得最老的花岗岩．其地质意义有：①西秦岭地区存在前寒武纪的花岗岩，②前人在该区所划分的秦岭群是正确的，目前，张维吉等人所划分的李子围群仍然是一个构造地层地体，其中仍含有时代大于５８０Ｍａ±８Ｍａ、甚至更老的地质体；③白云母Ｋ－Ａｒ年龄证实了在４４０Ｍａ±１０Ｍａ时地质构造事件的存在，
The age of Jiuciliang granite in West Qinling mountains is 424. 4 Ma, which is previously measured by K-Ar radioactive method for muscovites, but it becomes 580 Ma±Ma by using the method of single grained zircon in this syudy. The authors believe that the latter represents the rock-forming age of the body and therefore the granite is the oldest one measured so far in West Qinling. As in the following are their geologic significances. ① There exists in west Qinling area the pre-cambrian granite; ②It is correct that Qinling Group is formerly divided in this area. The Liziyuan Group divided by Zhang Weiji and others is still a tectostratigraphic terrane which may contain the geologic bodies of which the ages are greater or even much greater than 580 Ma±Ma. ③The K-Ar dating of muscovites confirmed that there exists a geologic tectonic event at 440 Ma 10 Ma. ④The forming age of Jiuciliang granite is about 580 Ma±8 Ma. This age evidence for the existence of the 540 Ma±50 Ma intrusion event in this region is proposed by Zhang Weiji et al. (1994).
出处
《西北地质科学》
1996年第2期6-10,共5页
Northwest Geoscience
基金
地矿部秦巴重点片"八.五"地质找矿科技攻关项目
