摘要
北祁连老虎山地区玄武岩与沉积岩呈互层产出 ,玄武岩主要为E MORB ,少数为N MORB ;多数样品具Nb负异常 ,表明很可能形成于弧后盆地环境。玄武岩中的沉积岩夹层主要为浊积岩、硅岩和硅质泥岩 ,有少量含棘皮类和双壳类化石的层状生物碎屑灰岩。浊积砂岩中含有大量陆源石英碎屑 ,硅岩具较高的Al2 O3 Fe2 O3 比值和较低的MnO TiO2 比值 ,不具有明显的Ce负异常。上述特征表明老虎山玄武岩及其中的沉积岩夹层形成于弧后盆地中靠近陆缘的环境。
The basalts from Laohushan, north Qilian, are mainly basalts of E MOEB, with very few N MORB. Most of the basalts are depleted in Nb, indicating a back arc tectonic setting. Layers of sediments, including tubiditic conglomerates, sandstones, cherts and occasionally echinodermata and bivalve bearing limestones, are intercalated with the basalts. The sandstones contain lots of continental quartz clasts, and the cherts have high Al 2O 3/Fe 2O 3, low MnO/TiO 2 ratios and very small Ce negative anomaly. Geochemical characteristics of the basalts and cherts, as well as lithofacies of the sediments, indicate that the Laohushan basalts were formed close to the continental margin in a back arc basin.
出处
《地质科学》
CAS
CSCD
北大核心
2001年第4期444-453,共10页
Chinese Journal of Geology(Scientia Geologica Sinica)
