赣东北晚白垩世橄榄玄粗岩系列火山岩中单斜辉石矿物化学及其地质意义  

Mineral chemistry of clinopyroxenes from the Late Cretaceous shoshonitic volcanic rocks in Northern Jiangxi Province and its geological significance

作　　者：王佳玲[1] 巫建华[2] 

机构地区：[1]东华理工大学核资源与环境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,江西南昌330013

出　　处：《岩石矿物学杂志》2014年第1期163-173,共11页Acta Petrologica et Mineralogica

摘　　要：利用电子探针对广丰-玉山盆地晚白垩世橄榄玄粗岩中单斜辉石进行了详细的矿物学研究,结果表明,所有的单斜辉石都属于普通辉石,表现出低Al,高Ti、Na含量的特征,具有碱性系列特征;单斜辉石斑晶的结晶温度为1 151～1 202℃,压力为0.12～0.58 GPa,可能是相对原始的岩浆上升到浅部(相当于上地壳位置)发生结晶分异作用形成。单斜辉石指示板内构造环境,与寄主岩石指示的构造环境一致。单斜辉石的矿物化学特征与碱性橄榄玄武岩中在浅源结晶的单斜辉石斑晶特征一致,而与碱性橄榄玄武岩中在深源处结晶的单斜辉石斑晶特征存在差异,且明显区别于拉斑玄武岩中单斜辉石斑晶的特征。In this paper, the authors investigated in detail chemical composition of clinopyroxene from the Late Cretaceous shoshonite in Guangfeng and Yushan basins on the basis of electron microprobe analyses. The results show that all clinopyroxenes are composed of augite,which contains relatively low Al2O3 （2.34%～4.13%）, high TiO2 （1.19%～2.78%） and Na2O （0.35%～0.49%）, showing a typical alkaline series. The crystallization temperature and pressure of clinopyroxenes from the Late Cretaceous shoshonite in Guangfeng and Yushan basins are estimated by the formula that p（0.1 GPa）=-7.538 3＋83.169 2（Al）, t（℃）=1 056.898 6＋902.797 8 （Al） from Thompson et al. （1974）. The results show that the crystallization temperatures and pressures of clinopyroxenes are 1 151～1 202℃ and 0.12～0.58 GPa respectively. The clinopyroxenes resulted probably from fractional crystallization of relatively primitive magma in shallow magma chambers, equivalent to the upper crust. These clinopyroxenes were identical with clinopyroxenes in alkaline olivine basalt in the shallow source in such aspects as mineral chemical characteristics and formation environment but slightly different from clinopyroxene phenocrysts in the alkali olivine basalt in the deep source. They are evidently different from the tholeiite in mineral chemical characteristics. In addition, the compositions of the clinopyroxenes are consistent with those in intraplate basalt.

关 键 词：橄榄玄粗岩 晚白垩世 单斜辉石 广丰盆地与玉山盆地 江西 

分 类 号：P578.954[天文地球—矿物学] P588.143[天文地球—地质学]