祁漫塔格中部元古代高钾(变质)侵入岩体的发现及其地质意义

The Discovery and Geological Significance of Proterozoic Intrusive Rock with High-K in the Central of Qimantage Area

通过1∶5万矿产远景调查在祁漫塔格中部圈定出5个大小不等的元古代中酸性高钾(变质)侵入岩体,岩性为灰-浅肉红色眼球状二长片麻岩,分布在角闪岩相的火山-沉积岩系中,原岩恢复为二长花岗岩类。锆石U-Pb表面年龄加权平均值为832±12Ma,是区内已知最早一期中酸性岩浆侵入活动的产物。岩石具高K2O(4.92～5.76×10-2),贫FeO、MgO、CaO的特点。岩石为高钾钙碱性S型高演化的花岗岩,形成地壳厚度约34.7km,反映同碰撞挤压构造背景。研究表明Rodinia大陆在东昆仑地区830Ma左右碰撞闭合,此后到早古生代中期,中酸性岩浆活动进入了一个相对不活动的时间段,为Rodinia解体时期,也是板块从低纬度向中高纬度漂移的时期。这一发现对认识东昆仑早古生代构造演化具有重要意义。

Five metamorphic intermediate-acid intrusive rock bodies in Proterozoic have been identified in the central Qimantage by the 1 ： 50000 mineral prospect survey. The intermediateacid intrusive rock bodies located in amphibolite facies the volcanic-sedimentary rocks are graypale flesh red two-feldspar gneiss with eye-shaped. The two-feldspar granites are their original rocks. Zircon U-Pb age is of 832±12 Ma on average, which are known the oldest intermediateacid intrusive magma products. Geochemistry of rocks is as follows： high K20 （4. 92--5.76 × 10-2）, poor FeO, MgO, and CaO. Rocks with high-K are talc-alkaline S-type high-evolution granites that were formed about 34. 7 km in crustal thickness. Tectonic setting is shown syscollision by R1-R2 discriminant diagrams. Rodinia continent closed at about 830 Ma in the East Kunlun. Intermediate-acid magma action reproduced in early Paleozoie. In this process Rodinia breakup and plates in low latitudes moved＇to high-latitude. The discovery is important to know the structure evolution of early Paleozoic in East Kunlun.