Characteristics and Petrogenesis of Zoned Amphiboles in Wengeqi Mafic-Ultramafic Complex, Inner Mongolia
详细信息
- 责任者：Liu Fei (State Key Laboratory of Continental Tectonics and Dynamics ; Institute of Geology ; Chinese Academy of Geological Sciences ; Beijing 100037 ; China) ; Su Shangguo
- 刊名：Earth Science Frontiers
- 出版年：2013
- 卷期：20(1)
- 关键词：角闪石岩 ; hornblendite ; 矿物学 ; mineralogy ; 内蒙古 ; Inner Mongolia
- 页码：p.206-222
- 图表：illus., 5 tables, 43 refs.
- 分类号：0700
- issnNo：ISSN1005-2321
- isbnNo：CN11-3370/P
摘要
Wengeqi mafic-ultramafic complex is composed of pyroxenite and hornblendite.Hornblendite,enclosed by pyroxenite and biotite pyroxenite,is mainly consisted of amphibole(more than 95%) and apatite(3%-5%),and is characterized by zoned amphibole,pegmatitic texture,and occurred in the southern part of the complex.The major element and trace element contents from the two zoned amphibole sections are analyzed by Electron Probe Microanalysis and LA-ICP-MS respectively.The zoned amphiboles show pargasitic cores rimmed by ferropargasite.From core to rim,zoned amphiboles have progressively lower composition of SiO2,MgO,Na2O and higher Al2O3,TiO2,FeOT,K2O,alkali metals(Na2O+K2O).The maximum composition of Sc,middle and high rare earth elements are situated in the core,and the minimum is in the rim;but the maximum composition of light rare earth elements,LILE,HFSE lies in the rim,and the minimum is located in the core.The core was higher in oxygen fugacity,but lower in temperature and pressure.and the rim is vice versa.The characteristics of main and trace elements above attribute to the crystallization of two magmas with different composition and oxygen fugacity,and with different temperature and pressure.The crystallization temperature of the zoned amphibole is below 950 ℃ with hot rim(mean 770 ℃) and cool core(mean 730 ℃).The zoned amphiboles are crystallized within 13 kilometers under the 272 MPa.The tectonic settings,compositions and petrogenesis of Wengeqi complex are similar to the middle Devonian mafic-ultramafic rocks in the northern margin of North China Block,suggesting that the primary magma of hornblendite was derived from enriched lithospheric mantle.The evolution of zoned amphiboles resembles to that of the mineralization of platinum group elements in Wengeqi.
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