The phrase "after approximately a" is correct and usable in written English.
It can be used when indicating a time frame or duration that is not exact but is close to a specific point in time.
Example: "After approximately a week of waiting, I finally received a response to my application."
Alternatives: "following about a" or "after roughly a".
Whereas source memory in rats is sustained for at least a week, spatial memory degraded after approximately a day.
The silver coating of the louvers is removed after approximately a hundred cycles whilst, to the contrary, damage to the CuCrZr louvers is relatively low.
Conclusively, sludge treatment wetlands can be successfully used, not only to dewater, but also to stabilize and mature wastewater sludge after approximately a four-month resting phase.
Trailing much of the field after approximately a half mile, Flip Sal, according to Murray's account, "snapped a whole bunch of bones in his leg and went flopping around the track like a bird with one wing gone".
The absolute error values are initially very low, but after approximately a day period they indicate an increase over time.
The total petroleum hydrocarbon concentrations slowly increased from about 0.05 mg/L after approximately a five-year to peak at 1 mg/L at about 50 years, in monitoring bore P-19 (Fig. 4).
Once electrolysis started the carbon cathodes expanded rapidly, but slowed down after approximately an hour.
After approximately an hour, the meeting broke up, with two of the spies leaving the Oval Office and the third remaining behind.
After approximately an hour at the site, the operators re-boarded the Black Hawks, and were back in the "neighboring country" by sunrise.
UPDATE, 2 54PM: After approximately an hour live on CelebBoutique's Twitter account, the tweet has now been deleted.
After approximately an hour of shooting, the German battleships sent Glorious to the bottom.
