First of all have you done any analysis on these three specializaitons like

1. The type of work you will doing after completing (may be you can look at your seniors and get some idea)
2. Which type of jobs does the three specializations provide (field work / lab research etc..)
3. The amount of job opportunities available in the market. If there are few opportunities and less scope for career development then existing professionals look for stability and don't often move. Hence finding new opportunities become difficult.

The above points may seem relevant after you complete engineering but will surely help you in your decision making process.

I would have given a clear picture has any of the specialization is related to IT. I don't know any career devleopment platform for geology or metallurgy sciences like www.MyTechLogy.com, which provides career insights, skills in demand and job trends.

All the best in your career.

Cheers.