中国地质2016，Vol.43Issue(6)：1932-1946,15.DOI:10.12029/gc20160606
内蒙古西乌旗地区晚石炭世石英闪长岩的岩石成因及构造意义
Petrogenesis and tectonic significance of Late Carboniferous quartz diorite in Xi Ujimqin Banner, Inner Mongolia
摘要
Abstract
Late Carboniferous quartz diorites are distributed in the Xi Ujimqin Banner of Inner Mongolia. The results of LA-ICP-MS zircon U-Pb dating of the quartz diorite samples indicate ages of 304.64 ± 0.82 Ma and 309.84 ± 0.86 Ma. In addition, new geochemical data from six quartz diorite samples are presented. All six samples show high Al2O3 values but low TiO2 values, and are thus classified as calc-alkali basalt series. These samples are characterized by low REE abundance and slight LREE enrichment. They also show LILE enrichment, HFSE depletion and distinctly negative Nb and Ta anomalies. All of these characteristics resemble those of arc magmatic rocks. Furthermore, as shown in the correlation plots of La/Ba versus La/Nb, Ba/La versus Ce/Pb, and Nb/Y versus La/Yb, the magma source has experienced contamination and metasomatism from the subduction fluid. According to the Zr/Nb, La/Nb, La/Ta ratios and the diagram of Sm/Yb versus La/Sm, the magma was derived from the shallow lithospheric mantle and formed by moderate (10%-20%) partial melting of spinel-garnet lherzolites. Based on geochemical characteristics of these samples in this study, combined with regional geological data and previous research results, the authors hold that, in the late Early-Carboniferous, there was a new limited ocean basin under an intensely extensional rift setting. Consequently, as the newly formed ocean basin was still immature or experienced subduction-related contamination and metasomatism, the Late Carboniferous quartz diorites of Xi Ujimqin Banner exhibited the continental margin-arc-like enriched signatures.关键词
石英闪长岩/锆石年龄/地球化学/拉张环境,晚石炭世/西乌旗Key words
quartz diorite/zircon U-Pb dating/geochemistry/extensional setting/late Carboniferous/Xi Ujimqin Banner分类
天文与地球科学引用本文复制引用
马士委,周志广,柳长峰,李瑞杰,来林,张学斌,孟元库..内蒙古西乌旗地区晚石炭世石英闪长岩的岩石成因及构造意义[J].中国地质,2016,43(6):1932-1946,15.基金项目
国家自然科学基金委创新群体项目(40921001)、国土资源部公益性行业基金项目(201511022、201211093)、中国地质调查局项目(12120115026801、1212011120700、1212011220465、12120114093901)联合资助。 （40921001）
