摘要
陕南山阳地区中晚泥盆世刘岭群位于秦岭造山带的商丹断裂带与山阳断裂之间。由于所处的特殊位置,刘岭群沉积特点及其盆地形成时期构造背景的确定,可以为秦岭地区古生代以来构造演化提供有价值的信息。岩石地球化学分析表明,刘岭群砂岩主要氧化物特征以SiO2和K2O含量较高为特点,具有较高的化学成熟度,反映出其碎屑物质可能来源于相对稳定的大陆源区或更老的沉积岩再旋回的沉积产物。砂岩的稀土元素LREE/HREE比值为3.61,属轻稀土中等富集;Eu/Eu值为0.77,属亏损型,与后太古代大陆地壳沉积岩总体演化特点相一致。主量元素氧化物、稀土元素及微量元素的多种图解和多种参数交叉分析,表明刘岭群沉积不具备前陆盆地堆积的特征。根据砂岩岩石地球化学的构造背景判别和物源区判别,结合沉积序列和沉积岩石学等分析,指示中晚泥盆世刘岭群碎屑岩应属于被动大陆边缘盆地沉积。
The Middle-Late Devonian Liuling Group in Shanyang region, Shaanxi Province, located in between the Shang-Dan Fault and Shanyang Fault of the Qinling orogenic belt. Determination of nature of the Liuling Group sediments and basin tectonic setting could offer important information for processes of tectonic evolution in the Qinling area due to the special spatio-temporal distribution of the Liuling Group in geological evolution since Paleozoic. Analyses of rock geochemistry showed that high contents of SiO2 and K2O among the oxides of major elements of the Liuling Group sandstones were mainly characterized and reflected generally higher chemical maturity of sandstones, whose clastics derived from relative stable continent provenance or older recycled sedimentary rocks. The average LREE/HREE value was 5.27 and average Eu/ Eu^＊ ratio （0.77） was a depleted type in the sandstones from the group, which was approximately consistent with the Eu evolution feature of post-Archean sedimentary rocks. According to multi-analysis of oxides of major elements, rare earth elements and trace elements in plot diagrams and parameters, the results showed that the sediments of the Liuling Group were not representative as accumulation of a foreland basin. The clastic rocks of the Liuling Group were regarded as deposited products of a Middle-Late Devonian passive continental margin based on discriminations of tectonic setting and provenance from sandstones geochemistry, synthesized with the researches on sedimentary succession and petrology.
出处
《地质科学》
CAS
CSCD
北大核心
2005年第4期594-607,共14页
Chinese Journal of Geology(Scientia Geologica Sinica)
基金
中国地质调查局项目(编号:200210000009)资助。
关键词
刘岭群
被动大陆边缘
砂岩岩石地球化学
中-晚泥盆世
秦岭造山带
陕南山
阳地区
The Liuling Group, Passive continental margin, Sandstones geochemistry,Middle-Late Devonian, The Qinling orogen, Shanyang region in southern Shaanxi
