Whisk together orange marmalade and lime juice in a small microwave-safe bowl. Microwave at HIGH 15 seconds.
Peel and core pineapple, and cut into quarters. Reserve half of pineapple for another use. Halve each of the 2 remaining quarters lengthwise into long spears. Brush with vegetable oil, and toss with marmalade mixture. Sprinkle with salt. Grill pineapple over medium-high heat (400°) for 5 to 7 minutes or until tender, turning occasionally.
Spoon 1 scoop coconut sorbet into each of 4 bowls. Serve with grilled pineapple slices, and sprinkle with mint.