The 33-year-old, who started the second round two off the lead, had moved into a share of top spot with Swede Alexander Bjork after carding a seven-under 65.
It was Jamieson’s best round of the season and his lowest effort since posting the same course in the second round of the British Masters at The Grove last October.
“I was very solid again from tee to green, like yesterday, and I’m delighted with that,” said the Scot, whose sole European Tour success so far came in South Africa when winning the 2013 Nelson Mandela Championship.
“I struggled a bit tee to green last week, but it seems to have clicked this week and hopefully I can hole a few more putts over the weekend.”
Jamieson, who has finished 106th and 107th in the Race to Dubai over the last two seasons, is determined to avoid a third successive close card shave.
He’s made a promising star to the current campaign, making the cut in four out of five events, and was in impressive form as he moved to 10-under-par at the halfway stage this week.
“I hit 16 greens in regulation yesterday and it was probably something similar today. Hopefully If I can keep that up,” he added.
“If you hit 16 greens, you are bound to have a couple of birdies in there, but I hit a couple of really nice shots as well and hopefully I can keep doing that.”
Bjork, who’d shared the overnight lead with Gregory Havret and Haydn Porteous, backed up an opening 65 with an equally impressie 67 to set the clubhouse target along with Jamieson.
The pair sit a shot ahead of Thomas Aiken, who catapulted himself through the field with a second-round 62 that contained 10 birdies.
Another South African, Peter Karmis, is also sitting on nine-under after he fired a second 67.
Scott Henry, the other Scottish player out in the morning wave, started alongside Jamieson after an opening 67 but ended his round facing a seventh successive missed cut.
The 30-year-old slumped to a disappointing 76, which included two double-bogeys, to sit one-over, one outside the projected cut.
Duncan Stewart, who opened with a 66, was among the afternoon starters, as were Richie Ramsay, Marc Warren and David Drysdale.