中国地质2018，Vol.45Issue(3)：469-482,14.DOI:10.12029/gc20180304
新疆阿尔泰山西段喀纳斯地区奥陶纪火山岩锆石U-Pb年龄和地球化学特征
Zircon U-Pb age and geochemical characteristics of Ordovician volcanic rocks from Kanasi area in Western Altay Mountains, Xinjiang
摘要
Abstract
There is a suite of volcanic-sedimentary strata comprising Dongxileke Formation in Kanasi area; nevertheless, there is no accurate ages and geochemical study for these rocks. The genesis and geodynamical background are in controversy for a long time. To tackle these problems, the authors chose a layered mylonitic dacite in this area as the study object. LA-ICP-MS zircon U-Pb ages of(445.4±3.1)Ma and(445.7±3.7)Ma from two mylonitic dacite samples suggest that these volcanic rocks erupted in late Ordovician and that Dongxileke Formation was formed in late Ordovician. The mylonitic dacite is characterized by SiO2 content from 53.99%to 71.04%, high Al2O3(13.83%-16.27%) and low MgO (1.09%-3.53%),with K2O between 1.11%and 3.83%, 2.84% on average, suggesting high alkline volcanic rock series. The mylonitic dacite forms a LREE-enriched distribution pattern with the existence of negative Eu anomaly (δEu=0.65-0.82). Geochemical characteristics of mylonitic dacite suggest island-arc volcanic features characterized by enrichment of LILE such as Rb, Th and Ce and depletion of HFSE such as K, Nb and Ta. Combined with regional data and the results obtained by this study, the authors consider that the volcanic rocks were generated during syn-collision of the late stage subduction in an active continental margin arc. The background was the conversion from the northward subduction of Paleo-Asia Ocean under the Siberia plate to Altay micro landmass land, which resulted in the formation of late Ordovician volcanic rocks in an active continental margin arc of Kanasi area.关键词
阿尔泰山/喀纳斯地区/LA-MC-ICP-MS锆石U-Pb年龄/地球化学/活动大陆边缘Key words
Altay Mountains/Kanasi area/LA-ICP-MS zircon U-Pb age/geochemical characteristics分类
天文与地球科学引用本文复制引用
朱彦菲,木合塔尔·扎日,赵同阳,韩琼,郑加行..新疆阿尔泰山西段喀纳斯地区奥陶纪火山岩锆石U-Pb年龄和地球化学特征[J].中国地质,2018,45(3):469-482,14.基金项目
中国地质调查局项目"新疆阿尔泰1:5万M45E021013等四幅区域地质矿产调查"(12120114040701)资助.Supported by China Geological Survey Program (No. 12120114040701). （12120114040701）
