Ages, Origin and Geological Implications of the Amuguleng Composite Granite in East Ujimqin Banner, Inner Mongolia
详细信息
- 责任者：He Fubing (Beijing Institute of Geological Survey ; Beijing 100195 ; China) ; Xu Jixiang
- 刊名：Geological Review
- 出版年：2013
- 卷期：59(6)
- 关键词：花岗岩 ; granite ; 铀—铅计时 ; U-Pb dating ; 内蒙古 ; Inner Mongolia
- 页码：p.1150-1164
- 图表：13 illus., 2 tables, 40 refs.
- 分类号：0801
- issnNo：ISSN0371-5736
- isbnNo：CN11-1952/P
摘要
Amuguleng granite is located at the north of East Ujimqin Banner( Dong Ujimqin Qi)Administration Center in Inner Mongolia. Geological investigation indicates that the granite composing of 2 intrusive rocks: gray-yellow medium—fine,medium—coarse grained adamellite containing huge phenocryst and gray-white fine adamellite. Zircon U-Pb age of the granite dated as 314. 2 ± 2. 2Ma and 167. 1 ± 1. 3Ma,suggesting that they were products of magmatic evolution during Late Carboniferous and Middle Late Jurassic respectively. Accessory minerals of both the two granites are rich in magnetite,monazite,and sphene,and there is fluorite in the Mid-Late Jurassic granite. Compositon of the rocks indicates that these two kinds of granites have similar geochemical characteristics: major element are characterized by enrichment of Si,higher DI and NK / A,Fe2O / FeO ratios. The race element spider diagram indicates that granites are relatively rich in Rb,Th,U,Pb,slightly enriched in the light rare earth elements La,Ce,and depleted in high field strength elements such as Nb,Ba and Sr,Ti; While the distribution model of REE is right oblique,which is relatively LREE-enriched and HREE- depleted,and the HREE curve is flat. Based on the results,these two kinds of granites are attributed to high differentiated metaluminous—weakly peraluminous high-K calc-alkaline series,which are the typical I-type granites. The source materials might come from younger crustal felsic rocks with high K and normal water content,And the source material of felsic continental rocks of late Carboniferous granite unit is mixed with mantle-derived basaltic components. The Middle Late Jurassic granitic magma maybe originated from the remelting or the partial remelting of Late Carboniferous granite,at least,it has similar magma source with that of the Late Carboniferous granite. The Late Carboniferous granite unit was formed in compression setting at the late syn-collision stage of Central Asian Orogeny. The Middle Late Jurassic granite unit was formed in the extension environment setting,while the geotectonic background was changing from Mongolia—Ochotsk ocean system into the Paleo-pacific tectonic dynamic systems.