豫西栾川地区大红口组、鱼库组的特征及其大地构造背景

本文在构造变形分析的基础上,厘定了大红口组和鱼库组的地层层序及上下关系。火山岩岩石化学特征、稀土元素及微量元素特征的研究表明,大红口组火山岩应属大陆边缘裂陷槽环境下的偏碱性粗面岩。晚元古代青白口纪与震旦纪之交,由于南部秦岭洋壳开始向华北地台俯冲,在原秦岭地块的部位发育了岛弧。岛孤以北的弧后盆地发育了以二郎坪群下部为代表的火山-碎屑沉积组合。受弧后扩张影响,更北的华北地台南缘则出现了边缘裂陷槽。大红口组和鱼库组以及其上的三岔口组,就是这种构造环境下发育的火山-沉积岩组合。

CHARACTERISTICS OF DAHONGKOU FORMATION AND YUKU FORMATION AND THEIR TECTONIC ENVIRONMENT IN LUANCHUAN AREA, HENAN PROVINCE

This paper discusses the stratigraphic sequence,geochemical feature and tectonic envi- ronment of Dahongkou Formation and Yuku Formation,Luanchuan area, Henan province. Based on the analysis of regional structural modeI and the data of isotopic time, Dahongk- ou Formation and Yuku Formation should be put under to the Sinian Period. The feature of rock chemistry, trace and rare elements distribution of Dahongkou Formation suggest that the volcanic rock is an alkali --trachyte formed in a continental margin rift. ln early Sinian period (800--700Ma), the north part of East QinIing underwent such a tectonic de- velopment history,i. e. from a passive continental margin to an active continental margin.