Extracting .app in runtime (Mac Issue)

I am using Windows. I have no issues making a build for mac. We can archive a .app file in windows (zip, tar, or tar.gzip), and manually open that archive on mac without a problem. However, when we try to extract the .app on run time, opening outputs the following: "You can't open the application (name of application) because PowerPC applications are no longer supported."

The extraction code i am trying to use works for just about any other file on both Windows and Mac, but seems to fail when extracting a .app.

Extraction code snippet below:

            using (Stream fs = new FileStream(gzipFileName, FileMode.Open, FileAccess.Read)) {
                 using (var gzipStream = new GZipInputStream(fs)) {
                     String fnOut = Path.Combine(targetDir, Path.GetFileNameWithoutExtension(gzipFileName));
                     using (FileStream fsOut = File.Create(fnOut)) {
                         var dataBuffer = new byte[4096];
                         StreamUtils.Copy(gzipStream, fsOut, dataBuffer);
                     }
                 }
             }

This code uses ICSharpCode.SharpZipLib.dll