FAIRFAX, VA. — Charlotte-based Grubb Properties has acquired Argon Plaza, a 275,000-square-foot office building in Fairfax, for $38.8 million. The property is located within the Fair Lakes master-planned community, roughly 19 miles west of Washington, D.C. The mixed-use development is home to a Hyatt Regency hotel and more than 1 million square feet of retail and restaurant space. C-III Asset Management sold Argon Plaza, and HFF and NAI Global arranged the transaction. Grubb Properties plans to make capital improvements to the building that will upgrade its tenant amenities. The property’s anchor tenant, a defense contractor specializing in military technology and intelligence, occupies more than half of the building and recently signed a five-year lease renewal.