The choice to open something in a new tab should almost always be left to the user. The only exceptions are when leaving the current page would cause data loss and the link they are clicking is related but you expect them back (for example help links when filling out forms).
All mobile browsers that I am aware of that support tabs or any form of windows already have a way for the user to open the links in a new tab on their own. For touch screen phones this is usually reached via long-pressing a link, but there are lots of variations on the theme. The user is expected to know the functions of their own phone and browser, every individual site on the web is not responsible for making these decisions on their users behalf.