Is it ok to have a paper with no academic citation but just think tank and investigative journalism?
If your research concerns a specific subject for which all presently published material comes from think-tanks and news articles, then it is perfectly legitimate to cite those sources as your main source of literature.  However, while this may be true of the specific issue you are investigating, it would be extremely unusual for that issue to be so unique that it cannot be put into any broader scholarly context in any field of academic inquiry.

For example, suppose you take some extremely specific topic -- e.g., you want to investigate the effect of fluctuating prices of bananas on the eating habits of rural families in Peru.  Perhaps there is not yet any academic literature on that topic, but there might be news articles from time to time that talk about farmers when banana prices go up or down.  Even so, if you were writing about that topic, you would probably discuss the specifics within a broader academic context with some economic theory, social science, etc.  So you might augment your discussion of the specific topic by noting that shortages of bananas in other parts of the world cause consumer prices to increase, and this increases profits to banana growers, which gives them more disposable income, etc.  There would be plenty of general academic literature (e.g., general economics literature) on those phenomena that are not specific to banana-growing in Peru.  By citing literature on these general phenomena you would augment your specific topic by placing it in a broader context.

If you are unable to find any scholarly literature that could put your issue into an academic context, you are implicitly telling your reader that your issue falls outside the scope of all historic scientific and academic inquiry, and there is no avenue of academic research that could shed any light on your topic.  Are you sure that is the case?