Koreans Mi Jung Hur and Sei Young Kim accounted for their respective opponents comfortably on day four but the games between Ariya Jutanugarn and Cristie Kerr and Michelle Wie and Angel Yin both required extra time to decide an outcome.
Jutanugarn eventually prevailed at the 19th hole in a match where she was 3up though 13 before Kerr fought back with three birdies in a four hole stretch to square the ledger.
Both players made bogey at the par-4 18th with Jutanugarn’s par at the 19th, the course’s first, enough to take the match.
Yin and Wie also fought an epic battle, the talented Yin putting on a display of power golf that took her to a 4up lead when she got to 5-under through the first seven holes.
But Wie, a rejuvenated player in 2017, fought back to go to the turn 3 down before turning the tables on Yin on the inward nine.
Winning four holes from the 12th to the 16th she put the pair back on level terms then they swapped the lead at 17 and 18 before heading to extra time.
In a match that saw just three holes halved in 18 holes, the 19th was again squared with pars despite Yin hitting her tee shot almost 30 metres past Wie.
But at the second it was the youngster who made the fatal mistake, her second flying the green at the par-4 and her third from the back bunker also unable to find the putting surface.
Wie also missed the green but a regulation chip and putt from pin high left saw her advance to the semi-finals.
That result means Wie will now meet Jutanugarn in the semi-final, a match which will likely hog the limelight tomorrow.
Jutangarn might be the longest hitter in the women’s game and Wie is among the most high profile ensuring the match will attract plenty of attention.
There was less excitement in the other two matches of the day where Mi Jung Hur accounted for Shanshan Feng 1up and Sei Young Kim demolished France’s Karine Icher 5&4.
Feng and Hur squared the first 12 holes before Feng got her nose in front with a birdie at the 13th.
A dropped shot at 15, though, saw her fall back to all square and Hur capitalised with a birdie at 17 to go 1up.
A half at the last was enough to see the result go her way and she will now meet Sei Young Kim, who easily accounted for Karine Icher in the last match of the day, in the semi-finals tomorrow morning.
Icher was in uncharacteristically poor form and failed to make a single birdie in the 14 holes played as Kim took the match 5&4.
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