广西十万大山盆地扶隆坳组地球化学特征及其地质意义

Geochemical Characteristics and Geological Significance of Fulongao Formation of Shiwandashan Basin in Guangxi Province

为了探究广西十万大山盆地扶隆坳组地球化学特征及其地质意义,在显微镜下对研究区砂岩进行了系统鉴定、碎屑颗粒组分统计,并利用ICP-MS对该区泥岩样品进行了微量元素和稀土元素分析,结果显示扶隆坳组砂岩碎屑颗粒组分石英颗粒含量较高,长石含量较少,岩屑以浅变质岩屑为主,Dickinson图解显示物源区为再旋回造山带;泥岩样品的REE受成岩作用改造微弱,且主要来自陆源碎屑矿物,源岩主要为沉积岩及花岗岩岩石;稀土元素和微量元素相关参数显示晚三叠世扶隆坳沉积时期气候相对湿热,沉积了一套以陆相沉积环境为主的碎屑岩。综合前述认识,结合本区构造演化史,推断扶隆坳组物源供给主要来自晚泥盆世-早石炭世钦防海槽沉积的硅质岩、硅质页岩及泥岩,源区构造背景兼有活动大陆边缘和被动大陆边缘的性质。

In this research,microscopic examination,clastic particles statistics,and ICP-MS method were used to determine the petrologic characteristics and geological significance of the Fulongao Formation in Shiwandashan basin of Guangxi province.Clastic particles statistics showed that the sandstone in Fulongao Formation had high quartz content but low feldspar content,and it was mainly characterized as epimetamorphic rock debris.Dickinson figure revealed that the source area was recycled orogen.The content of REE in mudstone samples was slightly influenced by diagenesis and mainly from terrigenous detrital minerals which rock source was sedimentary rock and granitic rock.The correlation between REE and trace element indicated that the weather was warm and wet during the period Fulongao came into formation.Moreover,the depositional environment was continental environment.Based on the results shown above and the history of tectonic evolution,this paper concluded that the material source of Fulongao Formation was mainly composed of siliceous rock,siliceous shale,and mudstone;the tectonic background was a combination of active continental margin and passive continental margin.