准噶尔盆地东北缘卡拉麦里组物源区特征:碎屑岩地球化学及锆石U-Pb年代学的制约

准噶尔盆地东北缘广泛发育泥盆纪卡拉麦里组，其形成时代与构造背景一直备受争议.对卡拉麦里组碎屑岩开展岩石学、地球化学和同位素年代学研究，结果显示:卡拉麦里组形成于斜坡-半深海沉积环境，具浊积岩特征.砂岩样品SiO₂含量高，Al₂O₃/SiO₂比值低，K₂O/Na₂O比值高，REE配分曲线总体表现为右倾，ΣLREE/ΣHREE=4.81~8.03，δEu=0.59~0.80，Eu具有弱负异常，构造环境判别图解揭示卡拉麦里组砂岩物源区构造背景为被动大陆边缘.砂岩LA-ICP-MS锆石U-Pb年龄测定表明，锆石年龄分为2期，主要为393~524 Ma，其次是823~3 077 Ma，表明卡拉麦里组物源区地质体时代主要为早古生代和前寒武纪，分别对应于准噶尔盆地周缘早古生代造山带和前寒武纪结晶基底.综合分析认为，卡拉麦里组形成时代为早-中泥盆世，沉积于准噶尔地块东北缘被动陆缘一侧.中泥盆世开始，卡拉麦里古生代洋盆持续向北俯冲消减，形成了野马泉岛弧及其弧前沉积体系，最终闭合于早石炭世之前. 

Provenance Characteristics of Kalamaili Formation in Northeastern Margin of Junggar Basin: Constraints of Geochemistry and Detrital Zircon U-Pb Geochronology

The Devonian Kalamaili Formation is widely exposed in the northeastern margin of Junggar basin, while its depositional age and tectonic setting are still in debate. In this study, an integrated analysis of petrology, geochemistry and isotope chronology for the Kalamaili Formation was carried out. The results show that the Kalamaili Formation, characterized by turbidite features, was mainly deposited in the slope and semi-deep ocean. Geochemically, the Kalamaili Formation sandstone is characterized by high SiO₂, low Al₂O₃/SiO₂ and high K₂O/Na₂O. The REE distributing patterns show rightward incline and weaker negative Eu anomaly (ΣLREE/ΣHREE=4.81-8.03, δEu=0.59-0.80). Tectonic-setting discrimination diagrams of the Kalamaili Formation sandstone indicate a passive-margin tectonic setting. The detrital zircon age spectrum of the Kalamaili Formation sandstone was composed of two age groups, including 393-524 Ma and 823-3 077 Ma, which correspond to the Early Paleozoic orogenic belt and Precambrian crystalline basement of Junggar basin, respectively. It is concluded that the Kalamaili Formation was deposited in a passive-margin of the northeastern Junggar block during the Early-Middle Devonian.Since the Middle Devonian, the Paleozoic Kalamaili Ocean subducted northward continuously, and then formed the Yemaquan island arc and related forearc sedimentary system, and finally the Kalamaili Ocean closed prior to the Early Carboniferous.