Shanghai (AFP) - Brooke Henderson aced the par-three second hole on Friday to ignite an eight-under round of 64 and take a two-stroke lead into the weekend at the Buick LPGA Shanghai.
The Canadian world number six shot the lowest round in the field so far to reach the halfway mark at 11 strokes under par, with American Jessica Korda two back at nine-under.
But last year's champion Danielle Kang of the USA was in the mix at eight-under for the tournament as she tries to go 2-for-2 in the $2.1 million tournament, now in its second year.
Kang eagled the par-5 ninth and added four birdies for a 69 on the day.
Marina Alex of the USA and Amy Yang of South Korea were next on six-under at the par-72 Qizhong Garden Golf Club.
The world's top-ranked woman golfer, Ko Jin-young of South Korea, will need some help in the final 36 holes if she wants to take the title.
Ko has won two of the last four tournaments she has played and has won two Majors this year.
But she was left nine shots behind Henderson after managing only a 70 in the second round following an even-par 72 on the opening day.
First-round joint leader Nasa Hataoka, the world number four, saw her chances dive after she bogeyed the 15th hole, following that up with a double-bogey on the next, a short par-three.
Meanwhile, the troubles of New Zealand's former world number one Lydia Ko continued, as she failed to break par with a two-over 74 and was just 1-under for the tournament.
Ko, now 22, was the youngest world number one as a 17-year-old and was widely expected to be a dominant force for years to come.
But she has slumped to number 31, rarely making a tournament top-ten this year and missing the cut at the British Women's Open in August by a whopping 10 strokes.