The company has reported a highlight of 20m at 8.18g/t gold and 22.6g/t silver from 20m, among final assays from expansion drilling.
President and CEO Warren Rehn said the programme had extended the high-grade mineralisation to the north and south of the openpit and discovered a zone of disseminated gold-silver mineralisation surrounding the high-grade core.
"We are modelling the data now and will update our resource model and our mine plan as warranted once we have understood the extent of the possible additions to the mineralised material," he said.
Rodeo, which started production in January, had a remaining mine life estimated last week of 2.25 years.
It produced 4,777 payable gold ounces and 12,196oz payable silver in the September quarter, leading to Golden Minerals' "first-ever profitable quarter from mining operations based on continuing strong results from gold-silver production at Rodeo".
The company processes Rodeo material at its Velardena plant, about 115km away, where it's aiming to make a development decision on a mine restart in the first quarter of 2022.
Its other projects include El Quevar in Argentina where Barrick Gold signed an earn-in agreement last year.
Golden Minerals started the quarter with US$8.8 million in cash and equivalents.
Its shares jumped 7.5% to close at C57c, a level similar to 12 months ago, capitalising it at $92.8 million (US$55.3 million).