Highway police say they found more than 200 large pieces of meteorites hidden under the seats of a truck which they had stopped in a random check.
Three Argentines and a Paraguayan were arrested.
The province of Chaco is world famous for meteorites, which are protected under Argentine law.
Chaco contains an area known as "Campo del Cielo", or the "Field of Heaven".
It spreads out over an area of 1,300 sq km (500 sq miles) and is littered with meteorites which fell around 4,000 years ago.
The largest, named El Chaco, was discovered with a metal detector in 1967 and weighs 37 tonnes.
El Chaco is the second-biggest meteorite ever found - and it too aroused avarice among speculators and collectors.
In 1990, an Argentine highway police officer foiled a plot to steal it for sale to a private US collector.

Gylfi Sigurdsson's neat finish into the bottom corner was enough to settle a cagey, low quality match.
Nathan Redmond shot wide late on for the visitors but Swansea, whose head coach Francesco Guidolin missed the game through illness, held on to win.
Norwich remain in the relegation zone and are without a win in 10 matches in all competitions.
Alex Neil's side are now one point from safety after Sunderland picked up a draw against Southampton.
Swansea have now secured back-to-back league victories after their shock win over Arsenal on Wednesday.
Except for a low Cameron Jerome effort from range that was palmed away by Lukasz Fabianski, neither goalkeeper was tested in an uneventful first half.
But Iceland midfielder Sigurdsson opened the game up shortly after the break with a calm finish that gave Swansea what was, in the end, a deserved win.
He was also denied a second goal from a curling free kick late on by John Ruddy's finger-tip save.
Norwich lacked urgency until the closing stages and pressed late on in the game, but Dieumerci Mbokani could not keep a header down and substitute Patrick Bamford saw a low effort saved.
The Canaries remain without an away win since beating Manchester United in December.
The second-half introduction of former Norwich midfielder Leroy Fer, signed by Swansea in the January transfer window, gave the hosts a fresh impetus in attack.
It was his square ball that found Sigurdsson in space for the winning goal and, having impressed at the Emirates against Arsenal on Wednesday, he went on to put in a lively performance for the Swans.
Swansea boss Guidolin picked the team from his hospital bed for a second consecutive game, as he continues to recover from a chest infection.
Coach Alan Curtis, who has taken on first-team duties in his absence, confirmed Guidolin is due to return to work this week and said picking up six points from two games would no doubt aid his recovery.
"I know he's delighted and has sent his best wishes," said Curtis. "He'll probably be relaxing now and it's a huge boost for him.
"He's due to leave hospital on Monday. We won't see him for a couple of days, but I expect him to be at the Bournemouth game next Saturday."
Media playback is not supported on this device
Swansea coach Alan Curtis: "It was a strange game. The first half was poor from both teams but we upped our game and we got the goal. We were hanging on a bit at the end.
"When it's two teams who need the points it affects it. It was one of the worst games of the season.
"We felt like we had to make changes in the second half and everyone played their part and we're delighted. It gives us breathing space."
Norwich manager Alex Neil: "It was edgy but I don't think there was a team that was clear. You hope you've got the players to make the difference.
Media playback is not supported on this device
"Swansea opened up in a 10-minute spell and got the goal.
"We need to win games to stay in this league. We've got to stay positive and we've got to believe we can win these remaining games. The other teams may determine out fate."
Swansea travel to Bournemouth on 12 March, while Norwich host Manchester City at lunchtime on the same day.
Police in Argentina have arrested four men who appear to have been trying to steal more than a tonne of meteorites in the northern province of Chaco.
[NEXT_CONCEPT]
Swansea City moved nine points clear of the Premier League relegation zone as Norwich slipped further into danger.