安徽霍山陈家湾岩体地球化学特征、年代学及其地质意义

Geochronological and Geochemical characteristics of Chenjiawan granitoid intrusion in Huoshan, Anhui Province and its geological significance

安徽霍山陈家湾岩体位于北淮阳东段,侵位于古生代佛子岭岩群中。文章对陈家湾岩体进行了地质特征、年代学和地球化学研究。年代学分析结果显示,陈家湾岩体形成于(124.5±2.7)Ma,属于大别造山带北淮阳地区130~125Ma阶段岩浆活动的产物。地球化学特征显示,陈家湾岩体SiO2、Al2O3及碱质含量中等,具有高钾钙碱性系列岩石特征。该岩体的稀土元素质量分数较低,w(Rb)/w(Sr)和∑LREE/∑HREE比值均较高,呈较轻微的Eu异常,岩浆源于有少量地幔物质混入的地壳源区,在上升过程中经历了较显著的结晶分离作用。区域成岩成矿综合分析结果表明,陈家湾岩体是在早白垩世古太平洋西向俯冲背景下岩浆作用的产物。

The Chenjiawan granitoid intrusion is located in the eastern sector of Northern Huaiyang district,Dabie orogenic belt,Anhui Province. The granitoid intrusion intruded into the Precambrian Foziling metamorphic group. The laser ablation inductively coupled plasma mass spectrometry(LA-ICPMS) zircon U-Pb dating of the Chenjiawan intrusion is (124.5±2.7) Ma,corresponding to the magmatism during late Yanshanian stage(130 125 Ma). The whole geochemical results of the Chenjiawan granitoid intrusion show that its SiO 2,Al 2O 3 and alkaline contents are plotted into the high K calc-alkaline series zone. The granitoid intrusion has low rare earth element(REE) concentrations,whereas high w (Rb)/ w (Sr) and ∑LREE/∑HREE ratios with visible negative Eu anomaly,indicating that the magma was derived from crustal source with minor mantle materials added,and experienced obvious fractional crystallization during its emplacement. Combined with the regional petrological analysis,the Early Cretaceous Chenjiawan granitoid intrusion is product of Paleo-Pacific westward subduction-related magmatism.