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 IntrusiveRock with High-K in the Central of Qimantage Area
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摘要: 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±12 Ma,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(4.92～5.76×102),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830 Ma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。
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关键词:
- 祁漫塔格 /
- 东昆仑 /
- 元古宙 /
- 高钾 (变质)侵入岩体 /
- 地球化学
Abstract: Five metamorphic intermediate-acid intrusive rock bodies in Proterozoic have beenidentified in the central Qimantage by the 1∶50000 mineral prospect survey. The intermediate-acid intrusive rock bodies located in amphibolite facies the volcanic-sedimentary rocks are gray-pale 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 intermediate-acid intrusive magma products. Geochemistry of rocks is as follows:high K2O(4.92—5.76 ×102), poor FeO, MgO, and CaO. Rocks with high-K are calc-alkaline S-type high-evolution granites that were formed about 34.7 km in crustal thickness. Tectonic setting is shown sys-collision by R1-R2 discriminant diagrams. Rodinia continent closed at about 830 Ma in the East Kunlun. Intermediate-acid magma action reproduced in early Paleozoic. In this process Rodiniabreakup and plates in low latitudes moved to high-latitude.The discovery is important to know the structure evolution of early Paleozoic in East Kunlun.-
Keywords:
- Qimantage /
- East Kunlun /
- Proterozoic /
- intrusive rock bodies with high-K /
- geochem-istry
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