东昆仑野马泉地区景忍花岗岩锆石SHRIMPU-Pb定年及其地质意义

Zircon SHRIMP U-Pb dating of the Jingren granite,Yemaquan region of the east Kunlun and its geological significance.

东昆仑西段(祁曼塔格)的野马泉地区,是青海省内一个重要的多金属成矿区。该区以往的工作程度较低,与花岗岩有关的铁、铜、多金属矿床多是近几年地质大调查中新发现的。本文报道了野马泉地区与铁、铜、多金属矿床密切相关的景忍中细粒正长花岗宕的地球化学特征和锆石 SHRIMP U-Pb 定年数据,并对其地质意义进行了讨论。研究表明,景忍正长花岗岩具有造山晚期花岗岩类的岩石地球化学特征,其形成年龄为204.1±2.6Ma,属印支末期。因此东昆仑西段与东段一样,主要的构造岩浆旋回也应是晚古生代一早中生代构造岩浆旋回(华力西-印支旋回)。根据景忍花岗岩锆石 SHRIMP 定年结果,我们推测在祁曼塔格地区与景忍花岗岩有关的铁、铜、多金属的主要成矿期也应为印支期这一结论与该区迄今己发表的关于成矿岩体与蚀变岩的高精度同位素年龄数据均为印支期相吻合因此今后该区的区域找矿方向,应该重点放在寻找与印支期花岗岩岩株有关的铁、铜、多金属矿床。

Yemaquan region in western part of the East Kunlun Range （ the Qimantage） is one of the most important metallogenic districts in Qinghai Province. Many granitoid-related iron, copper and polymetallic deposits have recently been discovered during regional geological investigations. This paper presents new zircon SHRIMP U-Pb dating and geochemical data of Jingren syenogranite, which shows a close relationship to polymetallic mineralization and geochemical affinity with late-post orogenic granites. The SHRIMP U-Pb dating yields an age of 204.1 ± 2.6Ma for the syenogranite intrusion. This age tells us that the major tectonomagmatic epoch for western part of the East Kunlun Orogenic Belt is of late Paleozoic early Mesozoic （Variscian-Indochina） epoch, which is similar to the eastern part of the East Kunlun Orogenic Belt. Furthermore, the SHRIMP U-Pb dating of Jingren syenogranite, together with other updated isotope geochronology data indicate that the major epoch of iron, copper and polymetallic mineralization is of the late Indo Chinese epoch, namely, the late stage of the major tectonomagmatic cycle, for western part of the East Kunlun. Therefore, the potential prospecting targets in this region should be the late Indo-Chinese granite plutons and related polymetallic mineralization.