The Magnetic and Opaque Petrological Response of Basalts to Regional Hydrothermal Alteration

摘要: Summary The alteration state of basalt lavas is shown to be largely the result combined action two processes, deuteric oxidation and regional hydrothermal alteration. The former process well described in literature while latter here another widespread source lava environment hydro-thermal that zeolite metamorphic facies, with temperatures up 300 °C, abundant groundwater being major elements. Independent rapid spatial variation processes results wide range observed properties. Microscopically undetectable titanomagnetite alteration, indicated by steady rise strong field Curie point, first response a non-deuterically oxidized With more extreme titanohematite etc. seen pseudomorph grains. Ilmenite also shows very distinctive mineralogical changes. Initially, high specimens appear immune magnetically moderate but these too eventually succumb when conditions are enough for formation prehnite rock. The geophysical implications this post eruption discussed. We conclude it probably possible obtain information on original TRM basalts at least many cases potassium-argon dating need serious investigation.