Given that "Schatz" is a masculine word, I would use masculine modifiers with it, such as "der".
But suppose I were using "Schatz" to refer to a woman I was dating.
Would I then refer to "mein Schatz" because "Schatz" is masculine?
Would I say "meine Schatz" because my date is feminine?
Or should I refrain from using masculine words to refer to female dates?