深层火山岩地球化学特征及沉积古环境--以松辽盆地北部徐家围子断陷兴城地区为例

Deep buried igneous rock geochemical characteristics and sedimentary paleoenvironment:a case study of the Xingcheng Area in deep Xujiaweizi Fault Depression,Northern Songliao Basin

以松辽盆地北部徐家围子断陷兴城地区深层火山岩为研究对象,考虑埋藏成岩、后期蚀变、风化淋滤作用等影响因素,分析10件样品的岩石学和地球化学特征,判别火山岩堆积、保存时的古地理环境。结果表明:研究区火山岩岩石类型丰富,从基性玄武岩到中性安山岩和粗面岩,再到酸性流纹岩、霏细岩,以及熔结火山碎屑岩和正常火山碎屑岩均有发育。稀土元素配分模式图解曲线呈右倾斜特征,轻、重稀土分异程度较大,轻稀土相对富集。火山岩微量元素V/(V+Ni)、V/Cr、Sr/Ba、V/Zr纵向演化趋势较为相似,火山岩堆积、保存时的地理环境复杂,整体以陆上喷发陆上沉积成因为主,水下喷发水下沉积及频繁水陆过渡相复杂成因环境火山岩也发育。该结果为火山岩地层岩石成因环境及岩相古地理研究提供地球化学依据。

Fully considering the influence of burial,alteration and weathering,we take Xingcheng Area igneous rocks in Xujiaweizi Fault Depression of Northern Songliao Basin as an example,using petrological and geochemical characteristics of 10 volcanic rock samples to identify the deposition and preservation environment.The result shows that the deep buried igneous rocks of the area have rich and diverse types,including basic basalt,neutral andesite and trachyte,acidic rhyolite,felsite,lava pyroclastic and normal pyroclastic rocks.Curves on the diagram of rare earth element distribution patterns are right inclined and indicate that the degree of differentiation of light and heavy rare earth is large and the light rare earth is relatively more enriched.The trend of V/(V+Ni),V/Cr,Sr/Ba and V/Zr is relatively stable and consistent on the longitudinal evolution.The result reveals that deposition and preservation environment of this area is complex,which is mainly onshore environment,but also underwater and frequent transition environment.The study provides geochemical basis for the study of petrogenetic environment and lithofacies paleogeography of igneous rocks.