CAJ | 학술논문

北祁连地区早古生代海相火山岩十分发育。笔者对大岔—大坂一带奥陶纪海相火山岩中细碧角斑岩化过程 Na 元素的来源与地质意义进行了研究。认为细碧角斑岩比正常火山岩富Na2 O,是海水参与的结果；判别角斑质岩石的原始岩浆系列及构造环境类型时不宜采用涉及 Na的图解作为判别依据,应选取惰性元素作为判别依据；同时提出采用 Na2 O-SiO2图解展示岩石细碧角斑岩化。细碧角斑岩类与正常海相火山岩界线为一条微上凸的曲线,该界线 Na2 O 含量为3.5%~4%；大岔—大坂一带海相火山岩的成分点多落在该界线之上的细碧角斑岩类分布区,可反映该区奥陶纪弧后和岛弧扩张脊火山喷发间歇期,海底热卤水对流循环活动强烈,成矿条件非常有利。
북기련지구조고생대해상화산암십분발육。필자대대차—대판일대오도기해상화산암중세벽각반암화과정 Na 원소적래원여지질의의진행료연구。인위세벽각반암비정상화산암부Na2 O,시해수삼여적결과；판별각반질암석적원시암장계렬급구조배경류형시불의채용섭급 Na적도해작위판별의거,응선취타성원소작위판별의거；동시제출채용 Na2 O-SiO2도해전시암석세벽각반암화。세벽각반암류여정상해상화산암계선위일조미상철적곡선,해계선 Na2 O 함량위3.5%~4%；대차—대판일대해상화산암적성분점다락재해계선지상적세벽각반암류분포구,가반영해구오도기호후화도호확장척화산분발간헐기,해저열서수대류순배활동강렬,성광조건비상유리。
Early Paleozoic marine volcanic rocks were well developed in the North Qilian Mountains. The paper focuses on discussing the formation process and origin of Na element for Ordovician marine volcanic rocks during the process of spilite-keratophyre alteration. There is more Na2 O in spilite-keratophyre than normal volcanic rock,because of the basaltic magma react with seawater. Therefore,the discrimination diagram involved with Na element cannot be used as the discrimination criteria for distinguishing the original magma series of keratophyre and related geotectonic setting,but the immobile elements can be used as distinguishing basis. Meanwhile, the Na2 O-SiO2 diagram is proposed for reflecting the degree of spilite-keratophyre alteration. In this graphic,the boundary line for the percentage of Na element between spilite-keratophyre and normal volcanic rock is a slightly up-convex,which is stand for the content of Na element ranging from 3.5% to 4%. For the marine volcanic rocks in Dacha-Daban area,most of them fall into the distribution region of spilite-keratophyre,suggesting that the convection of seafloor hot brine was very strong at Ordovician back-arc and island-arc spreading ridge during intervolcanic eruption stage,and this area provides very favorableconditions for mineralization.