Those sources don't mention Spanish settlements in Rio Grande do Sul because... *gasp*... there weren't Spanish settlements in Rio Grande do Sul. 

 And your asides about other subjects don't help. Nobody is discussing Serra Gaúcha here. Gaúchos aren't as mixed as Amazonian caboclos; you are again ignorantly confusing MtDNA with genetic ancestry as a whole. And anyway, what has this to do with "Brazilians of Spanish ancestry"?    

 You still have absolutely no source supporting the existence of Spanish settlements in Rio Grande do Sul, months after the beggining of this discussion. And you will likely never have. So stop being stubborn; if your "genetic study" is right, it completely demolishes all established knowledge about Rio Grande do Sul's demography; history will have to be rewritten. If true, this is a breaktrough, not a confirmation of what we already know. Perhaps it is so; but what you can't do is to pretend that the "findings" of that study are in accordance with historic knowledge. 

 And of course Azoreans did move hundred miles from the coast and ended up on the border with Argentina. Where do you think the "Dornelles" in "Getúlio Dornelles Vargas" came from? Have you ever heard of "sesmarias"? Dont't you know that the Portuguese distributed sesmarias in Rio Grande do Sul to attract people there?