How to Make It
In each of 2 large resealable plastic bags, combine 2 tablespoons of the orange juice, 1 tablespoon of brown sugar, 1 tablespoon of olive oil, 1 teaspoon of chile powder and 1/2 teaspoon of cumin. Seal the bags and shake to mix. Add 4 pork chops to each bag, seal and shake again to coat the chops. Refrigerate for at least 4 hours.
Light a grill. In a large saucepan, combine the remaining 1 quart of orange juice with the ketchup, garlic, jalapeños, vinegar and fennel seeds and bring to a boil, stirring once or twice. Simmer over moderate heat, stirring occasionally, until reduced to 2 cups, about 30 minutes. Season the barbecue sauce with salt.
Season the pork chops with salt and grill over a medium-hot fire until nicely charred and just pink in the center, about 12 minutes per side. Brush a thick layer of barbecue sauce on each chop, cover the grill and cook until the pork is nicely glazed, about 3 minutes. Top each chop with an orange slice and serve.