大兴安岭北段诺教河第四纪火山24座,分布于诺敏河及其支流毕拉河和甘河支流奎勒河,火山岩分布面积约600km2.诺敏河火山岩均属于钾质系列火山岩(K2O含量2％～4％,且K2O＞ Na2o-2％),类似于邻区五大连池-科洛钾质火山岩,具有来自类似的富钾地幔源区.但诺敏河火山岩的K2O含量明显低于五大连池-科洛火山岩的K2O含量(一般4％～6％).东北地区和内蒙东部处于中亚造山带东段,从古生代到新生代,多重构造-岩浆活动导致火山岩源区地球化学非均一性和火山岩的多样性.根据本文提出的火山岩K-Ar年龄(2.3 ～0.128Ma)及火山地质特征,可将诺敏河第四纪火山岩分为四期.早期(早更新世)火山活动主要沿诺敏河和奎勒河流域分布,火山产物多被晚期沉积物或火山产物所覆盖.中更新世保留的火山锥体及熔岩流是诺敏河第四纪火山产物的主体,表明是第四纪火山活动的高潮期.晚更新世-全新世火山活动限于毕拉河流域,典型的四方山火山和马鞍山火山是该时期火山活动的代表作,保留了较完好的火山地质地貌特征.从火山产物的时空展布,推测诺敏河第四纪火山活动有从东向西发展的趋势.%24 Quaternary volcanoes are distributed along IVnomin river and Kuile river area volcanic field ( NK for short) in the north of the Great Xing' an Range. With an area of 600 square kilometers, the volcanic rocks are characterized by potassic series (K2O =2% -4% , K2O > Na2O -2% ), which are similar with rocks in Wudalianchi-Keluo volcanic field (WK for short). Although NK and WK share the alike mantle source, volcanic rocks from NK are low in K2O than that from WK ( K2O = 4% ~6% ). During the Paleozoic and the Cenozoic, multiple tectonic and magmatic activities resulted in the heterogenous geochemistry in the magma source, and thus varied volcanic rocks were generated. Based on K-Ar dating (2.3 ~ 0. 128Ma) and volcanic field characteristics, it is identified that the volcanism in NK occurred in four periods ?Early Pleistocene, Middle Pleistocene, Late Pleistocene, and Holocene. Volcanic products of Early Pleistocene, mostly mantled by the later volcanic rocks, are distributed along the valleys of Nuorain river and Kuile river. Middle Pleistocene volcanism formed most of the volcanoes and lava spreading in NK. In Late Pleistocene and Holocene Period, volcanic activities were confined in Bila river area, and well kept Sifangshan volcano and Maanshan volcano exemplify volcanism in this period. According to the distribution of volcanoes in four periods, it is inferred that the volcanism have the tendency to develop from the east to the west of NK.
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