鄂尔多斯盆地南部铜川组碎屑岩地球化学特征及其对物源的制约

Geochemical Features of the Detrital Rocks of Tongchuan Formation in the Southern Ordos Basin and Its Constrains on Provenance

通过主量元素、微量元素及稀土元素等地球化学分析手段,结合前人的研究成果,对鄂尔多斯盆地南部铜川组物源进行研究。碎屑岩地球化学特征分析结果表明,研究区碎屑岩主要为杂砂岩和岩屑砂岩。稀土元素标准化配分曲线呈轻稀土明显富集、重稀土平坦和弱Eu异常特征。沉积物源岩的原始物质应来自上地壳,以长英质岩石为主。常量和微量元素构造判别图显示物源区构造背景为活动大陆边缘和大陆岛弧。结合前人碎屑锆石研究成果,鄂尔多斯盆地南部铜川组碎屑物质主要来自早期沉积再循环,其初始沉积物质来自华北北缘,秦岭没有为鄂尔多斯盆地南缘铜川组沉积期提供物源。

Based on the analysis of major previous results, the source of Tongchuan elements,trace elements and rare earth elements （REE）, combined with Formation in the southern Ordos Basin has been investigated. Geochemi cal analysis shows that sandstones consist mainly greywacke and lithic arenite. The rare earth element （REE） patterns are characterized by enriched light rare earth element （LREE）, flat heavy light element （HREE） and poor negative Eu anomalies. The primary materials of sedimentary rocks should come from the upper continental crust, and are mainly composed of felsic rocks. According to the structure discriminant figure, the tectonic settings of source rock area for Tongchuan Formation sandstones in the southern Ordos Basin belong to active continental margin and continental island arc. In combination with previous data of the detrital zircons, we suggest that the source of the Tongchuan Formation is most likely recycled from previous sedimentary rocks from the North China Block. The initial source for the Tongchuan Formation is the northern margin of the North China Block. The Qinling orogen did not provide source for the Tongchuan Formation.