南太行山平顺闪长岩体斜长石捕虏晶特征及其对壳幔岩浆混合过程的记录  

Characteristics of Plagioclase Xenocrysts from Pingshun Diorite in Southern Taihang Mountains:Record of Crust-Mantle Magma Mixing

作　　者：张海东[1] 刘建朝[1] 彭素霞[2] 张苏楠[1] 王得权[1] 

机构地区：[1]长安大学地球科学与资源学院,西安710054 [2]中国地质调查局西安地质调查中心,西安710054

出　　处：《吉林大学学报（地球科学版）》2014年第2期566-573,共8页Journal of Jilin University：Earth Science Edition

基　　金：国家自然科学基金项目(41040020;41073027);中国地质调查局工作项目(1212011121076);中央高校基金基本科研业务费专项资金项目(CHD2011ZY005;CHD2011JC168)

摘　　要：在南太行山平顺闪长岩体中偶见具有特殊环带结构的斜长石,其核部为钙含量高的基性斜长石(An>63),幔部为富钠的斜长石,二者之间存在由绢云母和绿帘石组成的溶蚀带,且核、幔An值变化截然不同。根据斜长石的环带构造特征和成分分析,认为本区岩浆混合过程大致如下:起源于EMI型富集地幔的幔源岩浆底侵作用于下地壳,在高温下结晶出钙含量高的基性斜长石,且所携带的热使下地壳开始熔融形成壳源岩浆;壳、幔两种岩浆沿着太行山深大断裂快速上升侵位于地壳浅部,发生岩浆混合;与此同时,早期形成的基性斜长石由于压力突然减小发生溶蚀,形成形态不规则的溶蚀带;壳幔混合岩浆在基性斜长石基础上结晶生长富钠斜长石,形成具有特殊环带结构的斜长石。这为研究区内存在岩浆混合作用提供了最直接的证据。Plagioclases with special zonal structure were seen occasionally in diorite intrusion in Pingshun,southern Taihang Mountains.The plagioclases is characterized by high Ca-riched basic plagioclases（An63）in the core and Na-riched in the rim,and a corrosion zone formed between the core and the rim that composed epidote and sericite.In addition there are distinctive compositional differences between core and rim of the plagioclase xenocrysts.Based on the evidences from the components and textures of the plagioclause,the following scenario about the magma evolution is tentatively suggested. Mantle magma originating from the EMI underplated to lower crust andcrystallized Ca-riched basic plagioclases under high temperature.Crustal source magma originated by melting of lower crust with the help of heat-carrying mantle magma.Mantle magma and crustal magma ascended quickly along Taihang deep fault,intruded into shallow crust,and mixed.Meanwhile,earlyformed basic plagioclases dissoluted because of sudden reduced pressure and formed corrosion zone with irregular shape.The crust-mantle magma crystallized Na-riched plagioclases on the basis of Ca-riched basic plagioclases and formed plagioclases with special zonal structure,providing the most direct evidence to magma mixing in the study area.

关 键 词：平顺闪长岩 捕虏晶 斜长石环带结构 壳幔岩浆混合 

分 类 号：P588.121[天文地球—岩石学]