What occurs at plate boundaries associated with sea-floor spreading?
Sea floor spreading is a tensional environment associated with rifting. On the sea floor the rifting is accompanied by upwelling magma which is expelled as submarine lavas. The magmatism is also accompanied by exhalative activity, with black smokers being one manifestation of this. Precipitation of base metal sulphides and manganese oxides would be expected, and siliceous iron and manganese rich chemical sediments would precipitate near the mid ocean ridge volcanism. Transverse faulting is also present in these settings. This is a structure formed by the complex movement near the spreading centre. The magmas which erupt from the spreading centre rift build up on the walls and flanks of the rift and record the magnetic field of the time in their magnetic mineral components. As the earth’s magnetic field changes over millions of years the crystalline lavas have recorded this as lines of similar magnetic characteristics which parallel the spreading centre. These are commonly referred to a
