CAJ | 학술논문

华北南缘中元古代熊耳群之上中–新元古代官道口群高山河组和汝阳群云梦山组中发育疑似火山岩的“夹层”,前人试图确定这套地层的年代,但一直没有取得实质性进展。本文研究发现这套“火山岩”与围岩并非沉积接触,而是侵入基底变质岩系的次火山岩。运用LA-ICP-MS法进行锆石U-Pb同位素定年,首次获得了栾川地区侵入高山河组的次粗安岩的206Pb/238U年龄为162±1 Ma,舞钢地区侵入云梦山组的次玄武安山岩的206Pb/238U年龄为165±2 Ma。这些结果表明这些中–晚侏罗世次火山岩应从官道口群高山河组和汝阳群云梦山组地层中解体出来,为华北南缘中–晚侏罗世构造岩浆作用的产物,而非古老的中–新元古代官道口群和汝阳群的沉积地层。同时为确立华北南缘存在燕山早期的火山岩浆活动,及其相关的陆内伸展构造事件提供了关键的年代学制约。
화북남연중원고대웅이군지상중–신원고대관도구군고산하조화여양군운몽산조중발육의사화산암적“협층”,전인시도학정저투지층적년대,단일직몰유취득실질성진전。본문연구발현저투“화산암”여위암병비침적접촉,이시침입기저변질암계적차화산암。운용LA-ICP-MS법진행고석U-Pb동위소정년,수차획득료란천지구침입고산하조적차조안암적206Pb/238U년령위162±1 Ma,무강지구침입운몽산조적차현무안산암적206Pb/238U년령위165±2 Ma。저사결과표명저사중–만주라세차화산암응종관도구군고산하조화여양군운몽산조지층중해체출래,위화북남연중–만주라세구조암장작용적산물,이비고로적중–신원고대관도구군화여양군적침적지층。동시위학립화북남연존재연산조기적화산암장활동,급기상관적륙내신전구조사건제공료관건적년대학제약。
No isotopic dating results have been reported yet on the volcanic interlayers in the Mesoproterozoic Gaoshanhe and Yunmengshan Formations overlying the Mesoproterozoic Xiong’er Group in the southern margin of the North China Craton. Our field survey shows that the “volcanic rocks” are actually intrusive, sub-volcanic rocks. LA-ICP-MS U-Pb dating of zircon from the sub-potassic trachyandesite, which intruded the Gaoshanhe Formation in the Luanchuan area, was emplaced at 162±1 Ma, whereas the sub-basaltic andesite intruded the Yunmengshan Formation in the Wugang area was formed at 165±2 Ma. It is therefore inferred that, these volcanic rocks are not members of the Gaoshanhe Formation of the Guandaokou Group and the Yunmengshan Formation of the Ruyang Group, but the result of the Middle-Late Jurassic tectonics and magmatism in the southern margin of the North China Craton. In addition, the presence of the early Yanshanian volcanic activities in the southern margin of the North China Craton provides key chronological constraints for exploring the extensional tectonic event of the southern margin of the North China Craton.