东秦岭地区宽坪群的时代及其意义

<正> 宽坪群分布于华北地台南缘,是北秦岭造山带的重要组成部分。宽坪群的时代及其形成时的构造背景一直存在很大争议。对于这一问题的深入研究,将为华北地台南缘和北秦岭元古代的构造格架、岩浆活动提供重要的依据和信息,无疑对秦岭造山带的研究也具有深远的意义。本文通过对宽坪群的地质特征、同位素年代的综合研究,认为宽坪群不是一般的地层单元,而是一套中元古代俯冲杂岩,其形成时代为1850—1000Ma;宽坪

Age of the Kuanping Group in the eastern Qinling area and its significa-nce

In the light of geological features and isotopic geochronology of igneous and metamor-phic rocks in the Kuanping Group, we regard that the Kuanping Group is not a general st-ratigraphic unit, but a suit of subduction complex in the Middle Proterozoic Era is between 1 850 and 1000Ma B. P., During the formation of this complex, there was a global tectono-thermal event which was reflected in the KGSC formation. KGSC ended about 1 000Ma B.P., which marks the collision of the Qinling old land with North China block, and disappearance of the North Qinling ocean. The effect of tectono-thermal event in East Qinling, South China and the other parts of the world about 1 000Ma B.P., has also been discussed in this paper.