Combine the salt and 1 teaspoon of the ground chipotle in a small shallow dish. Dip the rims of four margarita glasses in water, then coat in the chipotle salt. Set aside.
In a blender, combine the pineapple chunks, lime juice, tequila, triple sec and the remaining teaspoon ground chipotle. Add 1 tablespoon of the agave and blend until smooth. Taste and adjust the sweetness with more agave, as needed. Pour into a pitcher.
Add ice to the rimmed glasses and pour the margarita mixture over. Serve garnished with pineapple chunks and lemon wedges.