Translation of "Petardas"
What does petardas translate to in "Las jóvenes de la cantera estadounidense del mundillo de petardas ricas."
It means "kitschy". As in "garish", "showy", or "overly flashly" (e.g. a diamond-studded hot pink private jet). "Kitschy riches". Since cantera is "quarry" it's talking about "the girls in the quarry/pit/mine". The whole thing is probably a statement on how these "girls of the quarry" feel about the "world of kitschy riches", but there's no verb in that sentence, so one might change the connotations around. It might also be something symbolic or metaphorical, not literal.
Taking @djrudov answer, the best example of "petarda rica" is Paris Hilton. About "quarry", I don't know if in English it's used in the same way we use it in Spanish. Here figuratively is used as "pool", like in a pool of sportsplayers, professionals... so, the "cantera" (pool) here probably is Hollywood.