There is only one file type that uses the .XCARCHIVE extension:
Application archive created by Xcode, Apple's development IDE for Mac OS X and iOS applications; stores all application files in a format that can be submitted to the App Store for review; contains a digital signature identifying the developer.
Xcode archives are created by choosingfrom the application menu with an open project. The archives can be viewed in the Xcode Organizer window by choosing the Archives tab. From this view, you can click the button to submit the archive for review.
XCARCHIVE files are saved to the ~/Library/Developer/Xcode/Archives/ directory.
Updated: December 3, 2015