赣东北晚白垩世橄榄玄粗岩(Shoshonite)系列火山岩厘定的地质证据  

Shoshonite Series Volcanic Rocks in Northern Jiangxi Province

作　　者：项媛馨[1,2] 巫建华[1,2] 余达淦[1,2] 刘帅[1,2] 

机构地区：[1]东华理工大学核资源与环境省部共建国家重点实验室培育基地,江西南昌330013 [2]东华理工大学地球科学学院,江西抚州344000

出　　处：《东华理工大学学报（自然科学版）》2012年第1期43-53,共11页Journal of East China University of Technology(Natural Science)

基　　金：中国核工业地质项目"中国中;新生代铀成矿作用"

摘　　要：赣东北广泛发育晚白垩世红色沉积盆地,并常伴有镁铁质火山活动。位于东乡-广丰断裂带南侧的广丰盆地产有上、下两套镁铁质火山岩,而位于该断裂带北侧的玉山盆地产有一套镁铁质火山岩。研究表明,广丰盆地上部的镁铁质火山岩和玉山盆地的镁铁质火山岩均呈块状构造,多气孔,气孔内常充填硅质、碳酸盐、绿泥石;斑晶矿物含量为15%左右,以斜长石和单斜辉石为主,并有少量橄榄石和斜方辉石,斜长石斑晶常见钾长石环边;基质为似粗面结构,斜长石定向排列,也具有钾长石环边;岩石SiO2含量为49.8%～53.6%(平均51.7%),富碱(Na2O+K2O为5.00%～6.94%,平均6.35%)、富钾(K2O为2.40%～3.99%,平均2.98%)、K2O/Na2O(0.68～1.08,平均0.79)比值高,在SiO2-(Na2O+K2O)图解上落入碱性系列范围,在SiO2-K2O和SiO2-K2O/Na2O图解上均落入橄榄玄粗岩范围;全铁含量(7.10%～9.99%,平均8.26%)低,但具有高的Fe2O3/FeO比值,在AFM图解中具有钙碱性系列特征,在MgO-∑Fe图解上落入钙碱性系列趋势范围内,且大多数位于Lesser Antilles(CA-1)和Cascades(CA-2)两钙碱性趋势线之间,表现出亲钙碱性特征;其地球化学总体特征与典型橄榄玄粗岩系列一致。本文通过对矿物学和地球化学这两方面特征的总结,厘定其为橄榄玄粗岩系列火山岩。The red sedimentary basin was appeared extensively with large scare of mafic volcanic rocks in Late Cretaceous.Guangfeng basin has two sets of mafic volcanic rocks,which located in the south of Dongxiang-Guangfeng fault line.Yushan basin has one set of mafic volcanic rocks,which located in the north of Dongxiang-Guangfeng fault line.Results show that the mafic volcanic rocks are lump structure,and filled silicious,carbonate and chlorite in many blowholes in Guangfeng and Yushan basins.The content of its phenocrysts is about 15%,the main phenocrysts are lagioclase and linopyroxene,the other phenocrysts olivine and orthopyroxene.The lagioclase has the K-feldspar shell.The hole rocks has the SiO2 of 49.8%～53.6% with a mean of 51.72%,Na2O＋K2O of 5.00～6.94% with a mean of 6.35%.The K2O is approximately 2.40～3.33% with a mean of 2.79%,K2O/Na2O of 0.68～1.08 with a mean of 0.79.The data is plotted within the alkaline series in the TAS diagram.It should be the shoshonite series of SiO2-K2O and SiO2-K2O/Na2O.The low Fe2O3＋FeO of 7.10～9.99% has a mean of 8.26%,and high Fe2O3/FeO ratio.The plotted points fall in calcalkaline series in AFM diagram.They plotted in calcalkaline series in MgO-∑Fe diagram.Most of them are located between Lesser Antilles（CA-1） and Cascades（CA-2）,which show calc-alkaline feature.The geochemical compositions are same with the typical shoshonite series.In this study,we conclude that the mafic volcanic rocks are shoshonite series volcanic rocks.

关 键 词：橄榄玄粗岩系列 岩相学 地球化学 广丰盆地和玉山盆地 江西 

分 类 号：P59[天文地球—地球化学]