QuarkXPress 10 as a whole is a 32 bit application, only the new Xenon Graphic Engine is 64 bit.
Graphics look stunning in QuarkXPress 10; thanks to the native and deep understanding of image and vector files. Pan and zoom to see graphics come to life.
For more information please refer: http://forums.quark.com/p/32640/121310.aspx#121310
And for information on Xenon Graphics Engine refer: http://www.quark.com/Products/QuarkXPress/Default.aspx#xenon-graphics-engine