Spieth exited Amen Corner with a birdie at the par-five 13th after punching out off the pine straw and wedging to birdie-range to keep his charge going.
The 21-year-old Spieth began the hot, humid day with a three-shot lead after a sizzling opening round of eight-under-par 64 and picked up where he left off at Augusta National.
He followed a flawless front nine that featured three birdies with a birdie at 10 and then 13 and was on pace to match or exceed the Masters' 36-hole record of 13-under 131 set by Raymond Floyd in 1976.
A distant second on the leaderboard was fellow American Charley Hoffman, who was two-under at the turn to stand seven under par for the championship.
Next best was four-times major winner Ernie Els of South Africa, who shot a level par 72 to hold third place on the leaderboard with a five-under-par total of 139.
Australian Jason Day and England's Justin Rose both began the day at five-under but both lost a stroke to par and were four-under through 10 and two holes, respectively.
Looking forward, other Masters scoring records could be within reach of the precocious Spieth.
Tiger Woods won his first of four Masters in 1997 with a record total of 18-under-par 270 for a record 12-shot victory margin - both possible targets for Spieth.
One Woods record at the Masters was safe from Spieth, who would be the second youngest player to wear the green jacket behind Tiger should the Texan go on to win his first major.
Woods, meanwhile, was moving up the leaderboard after opening with a one-over 73 on Thursday in his return to competition after a two-month absence.
The four-time champion was three-under for the day through 12 holes and tied for 13th at two under par after finishing the first round tied for 41st.
Spieth has made a big splash before. As a 19 year old in 2013, he triumphed in a playoff to win the John Deere Classic and become the youngest winner on the PGA Tour in 82 years since Ralph Guldahl claimed the Santa Monica Open in 1931.
Original source: Spieth makes run at Masters records