吉林省中部晚古生代SSZ型蛇绿岩

The SSZ Ophiolite Late Paieozoic in the Central Part of Jilin Province

本文通过5幅1:5区域地质调查与新取各类岩石样品22件,《吉林省新编地质志》(2017)的20件及其他同行做的21件,计63件岩石样品做了岩石学、地球化学研究;新做5件岩石及磨拉石建造的8层70粒锆石的U-Pb同位素年代学研究。获得蛇绿岩(套)形成地质时代、组成岩石单元、地质构造环境及西伯利亚板块与华北板块碰撞闭合时限的准确信息,为认识区内蛇绿岩、中亚造山带(吉林段)及古亚洲洋构造域向滨太平洋构造域转换提供时空地质记录的实证。结果证实:区内头道沟-芹菜沟、小绥河镁铁-超镁铁岩块与其时空相联系的细碧角斑岩,构成“吉林省中部SSZ型蛇绿岩”。组成它的岩石单元(上至下):海相碳酸岩-硅质岩上覆岩系;细碧角斑岩-玄武安山岩(玻安岩或高镁安山岩)岩石单元,属E-MORB或P-MORB,成于弧前环境,峰期年龄300Ma-265Ma;堆晶岩和脉岩岩石单元(橄榄辉石岩、辉长岩和辉绿岩),年龄297Ma-265Ma;变质辉石橄榄岩和变质橄榄岩岩石单元,源自弱亏损至弱交代富集地幔,年龄317Ma-270Ma。各岩石单元时空谐合。查出的特征显示是较典型的SSZ型蛇绿岩,时代为晚古生代。其独有的时空特征证实:板块碰撞俯冲起始于石炭纪,峰期317Ma-265Ma;古亚洲洋闭合期(250Ma-243Ma);盖层为丰满砾岩和蒋家砾岩(250Ma-243Ma)。

This paper conducted petrological and geochemical studies on rock samples obtained from 5 1: 50 000 regional geological survey 22 newly collected rock samples, including 20 items from the new geological of Jilin Province (2017) and others 21 items were completed by peers and 63 rock samples were analyzed for petrology and geochemistry study; U-Pb isotope geochronology study of new made 5 pieces of rock and millstone construction of 8 layers of 70 zircons. Obtain accurate information on the geological age, constituent rock units, geological structural environment, and the time limit of the collision and closure between the Siberian Plate and the North China Plate of serpentinite (suite) , providing empirical evidence of spatiotemporal geological records for understanding the transformation of serpentinite, Central Asian orogenic belt (Jilin section) , and ancient Asian oceanic tectonic domain to the coastal Pacific tectonic domain in the region. The results confirm that the Toudaogou Celery Gully and Xiaosuihe Magnesium Iron Super Magnesium Iron rock blocks in the area, which are temporally and spatially related, constitute the "SSZ type ophiolite in central Jilin Province". The rock units that make up it (from top to bottom) are: marine carbonate rock siliceous rock overlying rock series; spirille hornblende basaltic andesite (boehmite or high magnesium andesite) volcanic rock unit, belonging to E-MORB or P-MORB, formed in a pre arc environment, with a peak age of 300 Ma-265 Ma; cumulate and vein rock units (olivine pyroxene rock, gabbro and diabase) , with an age of 297 Ma-265 Ma. The metamorphic pyroxene peridotite and metamorphic peridotite rock units originate from weakly depleted to weakly metasomatized enriched mantle, with ages ranging from 317 Ma to 270 Ma. The temporal and spatial coordination of each rock unit indicates a typical SSZ type serpentinite, dating back to the Late Paleozoic era. Its unique spatiotemporal characteristics confirm that plate collision and subduction began in the Carboniferous period, with a peak period of 317 Ma-265 Ma; The closure period of the ancient Asian Ocean (250 Ma-243 Ma) ; The cover layer consists of plump conglomerate and Jiangjia conglomerate (250 Ma-243 Ma) .