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高温实验研究火成岩成因的意义

周珣若 白志民   

  1. 中国地质大学材料科学系
  • 收稿日期:1999-03-20 修回日期:1999-03-20 出版日期:1999-03-20 发布日期:1999-03-20

GENETIC SIGNIFICANCE OFHIGH-TEMPERATURE EXPERIMENTS ON IGNEOUS ROCKS

Zhou Xun-ruo, Bai Zhi-min   

  1. China University of Geosciences,Beijing 100083
  • Received:1999-03-20 Revised:1999-03-20 Online:1999-03-20 Published:1999-03-20

摘要: 通过对球粒陨石晚壳的分层及玻璃质的研究,探讨了类地行星的层圈构造划分及地球早期玄武岩与月岩形成的机理。论述了高温实验结果对火山岩、侵入岩、陨石及含水暗色矿物等有关成因研究的意义。根据酸性火山岩干熔与湿熔实验中矿物熔融顺序的不同,分析了花岗闻风而动 浆侵入酸度演经及浅色麻粒岩的 ,讨论了岩石熔点与酸度、结构的关系。根据玄武岩加花岗岩的熔融实验结果,排队了玄武岩浆同化花岗岩形成 白榴玄武岩的可能,并提出了高铝玄武岩浆与碱性苦橄岩浆分离结晶形成拉斑玄武系列岩石及出现跨越趋势的可能。通过不同酸度、不同温度熔体粘度的计算.阐述了同一温度下熔浆酸度愈大粘度增大率愈大的特点及其与火山相、喷发及火山类型的关系。通过轻度钠化、变质、风化的玄武岩熔融结晶实验与新鲜玄武岩的对比,指出具原岩显微结构的岩石.其化学成分仍可作为火山岩分类命名、系列划分的依据。通过玄武岩熔融结晶实验,研究了熔浆过冷度、成桉密度、晶体生长速度与矿物结晶程度的关系,并指出了白榴苦橄岩熔体在降温过程中,晶出矿物的共生组合、演化顺序及其意义。根据含水暗色矿物的升温研究,阐明了它们氧化、脱水与热光性的变化过程及其暗化、分解、熔融的变化阶段,阐述了它们在地质温度计、划分岩浆岩相等方面的作用,并由玄武岩的熔融结晶实验结果,研究了富钙单斜辉石在压力效应、淬火效应中Ti 与Al2含量的不同,还指出可能有“等温效应 的存在。

Abstract: This paper puts emphasis on the genetic significance of some high-temperature experiments with volcanic rocks, intrusive rocks, meteorites and dark hydrous minerals as initial experimental materials.On the basis of layering of the melting crust of chondrite and the glass,a discussion is made on the layer structure of terrestrial planet and the forming mechanism of volcanic rocks during the early period of the earth and moon rocks.On the basis of the melting sequence of minerals from acidic volcanic rocks during dry melting and wet melting,an analysis is made on the acidity evolution of granitic magma during intrusion and the genesis of light-colored granulite.In addition,a discussion is also ma de on the relation of melting point,acidity and structure of rocks.According to the melting experiments of basalt with added granite,the authors exclude the possibility of formation of leucite basalt through assimilation of basaltic magma by granitic magma,and suggest the possibility of forming tholeiitic series rocks with Large straddle trend through fractional crystallization of high-aluminium basaltic magma and alkali picritic magma.By calculating the viscosity of melt at different acidities and different temperatures,the authors illustrate the relationship between the acidity, viscosity of melt and volcanic phase,eruption and volcano types,and point out that at the same temperature,the larger the acidity,the higher the viscosity increasing rate. The correlation is made between the melting experiments of fresh basalt and basalt with weak spilitization, metamorphism and weathering. It proves that the compositions of these rocks,as long as their original microstructures are preserved, can be taken as the criteria for rock type and series classification and rock nomenclature. By using the method of basalt melting-crystallization experiments, the relationship is studied between the course of mineral crystallization,the degree of supercooling, the nucleation of melt and the growth rate of crystals. The mineral assemblage and evlution sequence as well as their significance are investigated during the cooling course of leucite picritic melt. According to the heating experiments of dark hydrous minerals,an interpretation is given to the course of their changes such as oxidation,dehydration and thermo-optical characteristics, and to their stages of changes such as darking, resolution and melting. A discussion is made on the application of these results to geothermometer and phased division of igneous rocks. The pressure effect and quenching effect of calcium-rich clinopyroxene is also studied especially its changes in TiO2 and A1203 contents. The authors point out that isothermal effect may exist for calcium-rich clinopyroxene.