| 海拉尔盆地火山岩的锆石U-Pb年龄及其地质意义 |
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| 引用本文： | 陈崇阳,高有峰,吴海波,瞿雪姣,刘志文,白雪峰,王璞珺.海拉尔盆地火山岩的锆石U-Pb年龄及其地质意义[J].地球科学,2016,41(8):1259-1274. |
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| 作者姓名： | 陈崇阳 高有峰 吴海波 瞿雪姣 刘志文 白雪峰 王璞珺 |
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| 作者单位： | 1.辽宁石油化工大学石油天然气工程学院，辽宁抚顺 113000 |
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| 基金项目： | 国家重点基础研究发展计划(973计划)项目2012CB822002国家自然科学基金项目41202072 |
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| 摘 要： | 海拉尔盆地位于大兴安岭西侧，盆内存在多套火山-沉积岩组合.通过对海拉尔盆地Chu8井等4处火山岩样品进行的锆石LA-ICP-MS U-Pb年代学研究，探讨了海拉尔盆地火山岩的形成时代和构造背景，为盆内和邻区地层对比以及大兴安岭地区构造演化提供了依据.研究区4个火山岩样品的锆石均呈自形-半自形晶，显示出典型的岩浆生长环带，结合其高的Th/U比值(0.22~1.50)，说明其属于岩浆成因.测年结果表明，海拉尔盆地布达特群确实存在时代为晚三叠世-早侏罗世(214.4±4.3 Ma)的火山岩，结合前人研究，可将盆内火山作用划分为4期:分别为中-晚石炭世基底岩浆岩(320~290 Ma)；晚三叠世-早侏罗世早期布特达特群火山碎屑岩组(224~197 Ma)；晚侏罗世-早白垩世早期塔木兰沟组(152~138 Ma)；早白垩世晚期铜钵庙组(128~117 Ma).大兴安岭地区各期岩浆作用的地球化学特征、时空分布特征以及盆地地震剖面特征表明，中-晚石炭世基底岩浆岩(320~290 Ma)是额尔古纳-兴安地块和松嫩地块碰撞造山后的伸展背景下形成的；晚三叠世-早侏罗世早期火山岩(224~197 Ma)是古亚洲洋闭合后的伸展背景下形成的，该期火山岩的发现说明古亚洲洋构造域对大兴安岭地区的影响至少延续到早侏罗世早期(197 Ma)，而该区域蒙古-鄂霍茨克洋的俯冲碰撞最早可能开始于早侏罗世以后；晚侏罗世-早白垩世早期(152~138 Ma)和早白垩世晚期(128~117 Ma)火山岩的形成均与蒙古-鄂霍茨克洋碰撞闭合后的伸展作用有关.盆内部分火山岩样品中存在古元古代-新元古代捕获的锆石，这表明额尔古纳地块和兴安地块很可能存在着元古代结晶基底.
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| 关 键 词： | 年代学 海拉尔盆地 火山岩 兴安岭群 布达特群 构造演化 岩石学 |
| 收稿时间： | 2016-03-01 |
Zircon U-Pb Chronology of Volcanic Rocks in the Hailaer Basin,NE China and Its Geological Implications |
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| Abstract: | The Hailaer basin is located in the west of the Great Xing'an Range, and there are many sets of volcanic sedimentary rocks in the basin. Determining the age of the formation of volcanic rocks can provide reliable evidence for the stratigraphic correlation of the basin and the Great Xing'an Range, and the tectonic evolution in Northeast China as well. LA-ICP-MS zircon U-Pb dating for 4 volcanic rock samples from coring well in the Hailaer basin (HB) is presented in this paper. Their formation time and tectonic setting focusing on the intra-/inter-basinal stratigraphic correlation are discussed. The dating results show that volcanic rocks with ages of Late Triassic-early Early Jurassic (214.4±4.3 Ma) do exist in the HB. And the whole volcanic succession in the region can be subdivided into 4 stages of eruption including Middle-Late Carboniferous (320-290 Ma), Late Triassic-early Early Jurassic (224-197 Ma), Late Jurassic-early Early Cretaceous (152-138 Ma), and late Early Cretaceous (128-117 Ma). Combined with geochemical characteristics, temporal and spatial distribution characteristics of the magma in the Great Xing'an Range area, as well as the characteristics of the seismic profile of the basin, it is suggested that the Middle-Late Carboniferous magmatic rocks (320-290 Ma) were probably formed in a post-collision extensional setting related to the collision and merging of the Songnen and Ergun-Xing'an blocks. The Late Triassic-early Early Jurassic volcanic rocks (224-197 Ma) were probably formed in a post-collision extensional setting related to the closure of Paleo-Asian Ocean, which indicates Paleo-Asian Ocean tectonic domain affects the Great Xing'an Range area extended to the early Early Jurassic at least and the collision of the Mongolia Okhotsk Ocean possibly started in the early Jurassic at the earliest. The Late Jurassic-early Early Cretaceous (152-138 Ma) and the Late Early Cretaceous (128-117 Ma) volcanic rocks were probably formed in a post-collision extensional setting related to the closure of Mongolia Okhotsk Ocean. Some ages of Paleoproterozoic-Neoproterozoic zircon dating are obtained, which might have been captured from some crystal rocks of Proterozoic crystalline basement in the blocks underneath the HB. |
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