CAJ | 학술논문

运用LA-ICP-MS锆石U-Pb测年获得华北地块北缘内蒙古赤峰莲花山地区朝吐沟组2件流纹质熔结凝灰岩的形成时代，分别为366Ma±2Ma和364Ma±2Ma。测年结果表明，莲花山朝吐沟组火山岩形成于泥盆纪晚期，而不是早石炭世。同时，这一结果也将赤峰地区朝吐沟组的时代限定为泥盆纪晚期，而非早石炭世。莲花山泥盆纪晚期火山岩总体上以富硅、碱、铝，贫铁、镁、钙、钛及过铝质为特征，与本区晚石炭世-二叠纪钙碱性火山岩（如青凤山组或大石寨组火山岩）的特征明显不同。华北地块北缘泥盆纪晚期火山岩的形成可能与早古生代末期-晚古生代初期白乃庙岛弧和华北克拉通北缘弧-陆碰撞后的伸展环境有关。这一构造环境与华北地块北缘泥盆纪碱性岩及基性-超基性岩侵位背景相似。
운용LA-ICP-MS고석U-Pb측년획득화북지괴북연내몽고적봉연화산지구조토구조2건류문질용결응회암적형성시대，분별위366Ma±2Ma화364Ma±2Ma。측년결과표명，연화산조토구조화산암형성우니분기만기，이불시조석탄세。동시，저일결과야장적봉지구조토구조적시대한정위니분기만기，이비조석탄세。연화산니분기만기화산암총체상이부규、감、려，빈철、미、개、태급과려질위특정，여본구만석탄세-이첩기개감성화산암（여청봉산조혹대석채조화산암）적특정명현불동。화북지괴북연니분기만기화산암적형성가능여조고생대말기-만고생대초기백내묘도호화화북극랍통북연호-륙팽당후적신전배경유관。저일구조배경여화북지괴북연니분기감성암급기성-초기성암침위배경상사。
LA-ICP-MS zircon U-Pb dating of two rhyolitic tuff samples from the Chaotugou Formation in Lianhuashan area of Chifeng on the northern margin of the North China block yielded weighted mean 206Pb/238U ages of 366Ma±2Ma and 364Ma±2Ma, respectively. The new geochronological results indicate that the Lianhuashan volcanic rocks were erupted during the latest Devonian instead of the Early Carboniferous as previously considered. Because the volcanic rocks are located within the Chaotugou Formation which was previously considered to be Early Carboniferous in age, the age of the Chaotugou Formation should evidently be latest De-vonian. The Lianhuashan latest Devonian volcanic rocks are characterized by high content of SiO 2, Na2O+K2O, Al2O3, low content of T Fe2O3(0.36%~0.70%), MgO, CaO, TiO2 and A/CNK>1.1, quite different from the geochemical characteristics of the Late Car-boniferous-Permian calc-alkaline volcanic rocks on the northern margin of the North China block.