摘要
本文根据核爆炸岩石熔融玻璃的地球化学研究结果,与超速陨石撞击坑的熔岩进行比较,获得在远离热力学平衡条件下,各种玻璃和熔岩在化学成分上分布十分均匀的重要结论。岩石玻璃和熔岩是由基岩各组成岩石按一定比例混合熔融形成的。它们的主量元素和痕量元素丰度受基岩元素背景值制约。文中根据熔体和靶岩的化学成分,计算了熔岩各组成岩石的百分比。玻璃陨石是地壳岩石受撞击熔融形成的。同一撒布区的玻璃陨石化学成分相近,说明起源于同一源坑;而玻璃陨石化学成分的不同,则说明母岩组成分量的差异。因此,文中通过模拟计算,得出各玻璃陨石的组成源岩。澳大利亚撒布区的玻璃陨石,Al_2O_3,K_2O 和Na_2O 与 SiO_2及 K_2O/Na_2O 比值不完全相同,说明澳大利亚撒布区存在着几个不同的源岩和源坑,至少有印支、爪哇、菲律宾和澳大利亚四个相应撞击坑。
The geochemical characterization of melt glasses formed from rocks by nuclear explesion is made in this paper, and the composition of melt rocks from the hypervelocity meteorite tnpact carters was obtained. Under the conditions far from thermodynamic equilibrium the chemical composition of various glasses and melt rocks is quite homogeneous. They were formed by mixing-melting of bedrocks close to the point of impact (and/or nuclear explosion) in a certain proportion. The concentrations of major and trace elements in the melts are restricted by the background values of target rocks.By high-temperature turbulant flow the material is shown to be mixed melts which chemically is extremely homogeneous during hypervelocity impact. Thus, we can calculate the percentage of components of target rocks on the basis of chemical composition of the melt rocks.The tektite was formed from the upper crust rocks by impact melting. The formation mechanism of tektite is similar to that of glasses by nuclear explosion and melt rocks by impact. Tektites from same strewn field show their chemical composition very approximate to that of their crater bedrocks, but different chemical compositions of tektites are usually attributed tc different combinations of parent rocks. Therefore, we can calculate source rock's components of tektite. The different ratios A12O3, K2O and Na2O to SiO2 in tektites from the Australasiantektite strewnfield indicate the existance of several craters in the Austalian strewnfield--atleast the Indochinites, Javaites, philippinites and Australites source craters were defined.
出处
《地质科学》
CAS
CSCD
北大核心
1991年第2期148-158,共11页
Chinese Journal of Geology(Scientia Geologica Sinica)
关键词
撞击坑
熔岩
玻璃陨石
击变玻璃
impact crater, melt rock, diaplectic glass, tektite, turbulent flow
