辽西地区晚古生代火山事件沉积地球化学特征及物源区分析

Geochemistry and Provenance Analysis of Late Paleozoic Volcanic Event Deposits in the West Liaoning

近年来，在华北板块北缘许多地区晚古生代地层中先后发现了多层火山事件沉积，而火山碎屑物质的物源区方向一直为地质界所关注。通过对辽宁西部南票矿区晚石炭世－ 早二叠世火山事件沉积与兴蒙槽区同期火山岩岩石化学及地球化学资料分析和研究，并采用多种判别图解进行了对比，令人信服地证明本区火山碎屑物质来自兴蒙槽区中酸性、钙碱性岛弧型火山喷发。这一研究结果对进一步探讨晚古生代火山喷发的古构造背景及火山事件沉积的时空展布规律具有重要的理论和实际意义。

In recent years, volcanic event deposits have been discovered in Late-Paleozoic strata from the areas on the northern edge of North China Plate.Their origin has always been paid attention to by geological circle Based on the analysis and study of the data on petro geochemistry of volcanic event deposits of late Carboniferous-Earlier Permian strata from Nanpiao mining area,west Liaoning and synchronous volcanic rocks from Xing Mong geosynclinal area, their correlation shown in the judgement diagrams,a satisfactory result has been obtained. By making total chemical analysis of 6 volcaniclastic samples of volcanic event layers from this area and several synchronous volcanic rock samples from Xing Mong geosynclinal area,converting them into Jensen,Rittmann,Wright and the other parameters,and projecting them respectively on Al-(<Fe>+Ti) Mg diagram,SiO 2 K 2O diagram ,SiO 2 AR diagram and lgδ lgτ diagram ,It is found that all the volcanic-clastics and volcanic rocks fall onto medium-acidic calc-alkaline island-arc or active continent margin areas. Using the ICP-MS method to make the rare earth and trace relements quantitative analysis of the samples mentioned above,and standarizing them,we respectively draw REE distrbution pattern ,ration spidergram of trace elements ,Hf/3 Th Ta judgement diagram and Rb (Y+Nb) digram,illustrating that they all belong to medium acidic,calc alkaline,island arc eruption patterns,whether they are volcanic event deposits in this area or volcanic rocks in Xing Mong geosynclinal area. As a result of the study of petro-geochemitry above,it is fully proved that the volcanic event deposits in Late Paleozoic strata of North China,Nangpiao in the west of Liaoning,came from medium-acidic,calc alkaline,island arc volcanic eruption at the same period from Xing Mong geosynclinal area. The result will be of great value both in theory and practice for further resarch into the paleo tectonic background of volcanic eruptions and distribution law of volcanic event deposits.