Deformation, Metamorphism and Mineralization of the Mengku Iron Deposit, Altay, Xinjiang
详细信息
- 责任者：Lin Longhua (Department of Resource Engineering ; University of Science and Technology Beijing ; Beijing 100083 ; China) ; Xu Jiuhua
- 刊名：Acta Petrologica Sinica
- 出版年：2010
- 卷期：26(8)
- 关键词：铁矿 ; iron ores ; 变质成矿作用 ; metamorphic metallization ; 新疆 ; Xinjiang
- 页码：p.2399-2412
- 图表：9 illus., 1 table, 44 refs.
- 分类号：1001
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
The Mengku iron deposit,located in south margin of Altay orogenic belt,occurs in metamorphosed volcanic sedimentary rocks of the Lower Kangbutiebao Subgroup of Lower Devonian age. The ore bodies of the deposit are controlled by the Tiemuxiaergun syncline within the Kangbutiebao Group. The authors’ study shows that the deposit has experienced three mineralizing periods,which are marine volcanic sedimentary mineralizing period,regional metamorphic mineralizing period and hydrothermal metasomatic mineralizing period. Among them, regional metamorphic mineralizing period is the most important one,with banded or massive magnetite formed by pressure-solution and enrichment. Skarn-like rocks were generated by metasomatic hydrothermal fluid flowing through silicon-rich and calcium-rich rocks and posterior to the formation of massive magnetite. The later copper mineralization was a hydrothermal metasomatic mineralizing event. Homogenization temperatures of primary fluid inclusions in metamorphic layer quartz veins ( Q2 ) are 235～511 ℃,and those of secondary are 157～326 ℃ for lateral fluid inclusions. Homogenization temperature of fluid inclusions in the later quartz veins ( Q3 ) varies between 122～337 ℃ . The authors got trapping pressures of coexisting pure CO2 and H2O-NaCl fluid inclusions in Q2 by isochore crossing method,which are 73～90 MPa. The oxygen isotope data on magnetite show a range of - 2‰ ～ + 1. 28‰ in δ18OSMOW with the average of - 0. 15‰,which is similar to those of volcanic sedimentary-metamorphic iron deposits in other areas. Decrepitate curves of magnetite also clearly shows the features of multi-stage metamorphism superimposing. It could be presumed that the Mengku iron deposit was finally formed by enrichment of regional metamorphism and hydrothermal metasomatism during Altay Orogeny.