上黑龙江盆地中侏罗统绣峰组的沉积环境与大地构造背景

对上黑龙江盆地中侏罗统绣峰组的岩石学特征、砂岩类主要化学成分、微量元素、稀土元素及C、O同位素的定量分析表明,其主要化学成分具有K2O/Na2O、SiO2较高和SiO2/Al2O3、Fe2O3 MgO较低的特征,显示了活动大陆边缘的性质;微量元素中B、Sr/Ba值较低,Fe/Mn值高,C、O同位素Z值低,显示了内陆淡水沉积的特点;稀土元素具有轻稀土富集、分馏好、Eu弱亏损的特点,与活动大陆边缘及上黑龙江盆地南缘古生代花岗岩的稀土模式相似。综合分析绣峰组岩石学及岩石地球化学特征,认为绣峰组沉积于淡水河流环境,物质主要来源于蒙克山以南晚石炭世塔林超单元及中元古界—下寒武统大网子岩组;上黑龙江盆地的形成与蒙古-鄂霍次克造山作用有关,属活动大陆边缘盆地。

Sedimentary environment and tectonic setting of the Middle Jurassic Xiufeng Formation in the Upper Heilongjiang River basin

The petrological characteristics and major element,trace element,REE and C and O isotope quantitative analyses of sandstones of the Middle Jurassic Xiufeng Formation in the Upper Heilongjiang River basin indicate that:the major elements are characterized by higher K2O/Na2O and SiO2 and lower SiO2/Al2O3 and Fe2O3 MgO,showing the nature of the active continental margin;the trace elements are featured by lower B and Sr/Ba,higher Fe/Mn and lower Z values of C and O isotopes,indicating the features of inland fresh-water sediments;and REE are characterized by enrichment in LREE,good fractionation and weak Eu depletion and the REE patterns are similar to those of the active continental margin and Paleozoic granites on the southern margin of the Upper Heilongjiang River basin.An integrated analysis of the petrological and geochemical characteristics of the Xiufeng Formation suggests that Xiufeng Formation formed in a fresh-water river environment and that its materials mainly came from the Late Carboniferous Talin superunit and Mesoproterozoic-Lower Cambrian Dawangzi Formation-complex.The formation of the Upper Heilongjiang River basin is related to the Mongolia-Okhotsk orogeny,and this basin is an active continental-margin basin.