CAJ | 학술논문

东秦岭丹凤县东部的郭家沟是丹凤蛇绿混杂岩的典型出露区,作为其重要组成部分的沉积岩主要由夹有少量硅质岩的泥质粉砂岩构成,目前已变为角闪石英片岩和少量黑云石英片岩.这些变泥质粉砂岩显示了活动陆缘岛弧物源区沉积物高CaO、MgO、MnO、Sr、Ba,低K_2O/Al_2O_3,比值,轻稀土元素中等富集,Eu异常微弱的地球化学特征.其中,占主体的角闪石英片岩高Co/Th、低La/Sc和Th/Sc比值:黑云石英片岩低Co/Th、高La/Sc和Th/Sc比值,反映其源区以基性物质为主,花岗质物质的供给有限.根据与变泥质粉砂岩共生的硅质岩形成于奥陶纪-志留纪推断,这套沉积岩形成于北秦岭区活动大陆边缘岛弧演化早期弧前沉积盆地环境.
동진령단봉현동부적곽가구시단봉사록혼잡암적전형출로구,작위기중요조성부분적침적암주요유협유소량규질암적니질분사암구성,목전이변위각섬석영편암화소량흑운석영편암.저사변니질분사암현시료활동륙연도호물원구침적물고CaO、MgO、MnO、Sr、Ba,저K_2O/Al_2O_3,비치,경희토원소중등부집,Eu이상미약적지구화학특정.기중,점주체적각섬석영편암고Co/Th、저La/Sc화Th/Sc비치:흑운석영편암저Co/Th、고La/Sc화Th/Sc비치,반영기원구이기성물질위주,화강질물질적공급유한.근거여변니질분사암공생적규질암형성우오도기-지류기추단,저투침적암형성우북진령구활동대륙변연도호연화조기호전침적분지배경.
The Danfeng ophiolites outcrop in Guojiagou area east of Danfeng County, eastern Qinling. Being an important part of the ophiolites, the mud siltstones are closely associated with cherts, which have been metamorphosed to hornblende quart schists with minor biotite quart schists. They are featured by high CaO, MgO, MnO, Sr, Ba and low K_2O/Al_2O_3 ratios, moderate LREE enrichment and slight Eu anomalies, geochemically similar to those of sedimentary rocks occurred in island-arc areas in an active continental margin. Furthermore, hornblende quartz schists have high Co/Th and low La/Sc, Th/Sc ratios, while biotite quartz schists have relatively low Co/Th and high La/Sc, Th/Sc ratios, indicating that they mainly derived from basic materials with limited granite material supply. Based on the fact that the siliceous rocks associated with meta-mud siltstones are formed during Ordovician to Silurian, this sedimentary set should be formed in a fore-arc basin of an active continental margin during early islandarc of north Qinling in early Paleozoic.