贵州峨嵋山玄武岩的显微斑状结构及其意义

本文从岩石结构的角度,研究了贵州西部峨嵋山玄武岩。以镜下依据为基础,结合岩石化学特征和其他地质事实,认为贵州西部峨嵋山玄武岩曾经历了埋藏变质作用的改造。本区玄武岩Na_2O偏高,MgO偏低,并非岩石原有特征。这一认识,对今后进一步研究本区玄武岩及其有关矿产,是值得重视的。     

湘中保和堂煤的煤岩学研究

从煤岩学的角度详细地研究了保和堂煤,结果表明,保和堂煤具有独特的煤岩特征,主要表现在下列几个方面:多过渡组分及腐泥基质;渗出沥青体尤为丰富;含有一种具一定形态和结构的腐泥物质,并从煤岩特点出发探讨了保和堂煤的形成环境,认为其形成于具有一定深度覆水的泥炭沼泽,并从腐泥基质及黄铁矿含量探讨了泥炭形成过程中沼泽覆水深度的变化,并籍此探讨了Ⅰ、Ⅱ煤的稳定性,此外,还从过渡组分含量较多及组分形态和排列等特点推测,Ⅰ、Ⅱ煤形成时有相当一部分泥炭来自于经常干涸的岸后泥炭沼泽,潮汐和洪水是搬运营力。图2,表1,参5。     

Laser step-heating ^40Ar/^39Ar dating on young volcanic rocks

An attempt was made to use CO_2 laser step-heating method to date the late Pleistocene basaltic groundmass (DF-2) from Tengchong volcanic field. Among the fourteen heating steps, ten define a good inverse isochron (MSWD = 1.4) with an age of 32.2 ± 7.1 ka (2 σ).The inverse isochron also shows that the initial argon isotopic ratio is 297.1±2.0 (2σ) which is the same as the atmospheric argon at the 2σ error level. Study indicates that it is a useful means to date young volcanic groundmass with low K content by using CO_2 laser step-heating ~(40)Ar/~(39)Ar method.